Báo cáo Nghiên cứu khoa học Mango Postharvest Manual

i Mango Postharvest Manual CARD Project 050/04VIE Version 1 APRIL 2007 By Dr. Roberto Marques, Dr. Peter Hofman, Robert Nissen QDPI&F Ministry of Agriculture & Rural Development ii â The State of Queensland, Department of Primary Industries and Fisheries [2007]. Copyright protects this work. Except as permitted by the Copyright Act 1968 (Cth), reproduction by any means (photocopying, electronic, mechanical, recording or otherwise), making available online, electronic transmission or other publication of this work is prohibited without the prior written permission of The Department of Primary Industries and Fisheries, Queensland. Inquiries should be addressed to copyright@dpi.qld.gov.au (Ph: +61 7 3404 6999). iii CARD VIETNAM 2006 MANGO POSTHARVEST TRAINING MANUAL 1 Introduction................................................................................................1 2 Key production practices affecting postharvest quality .............................2 3 Know your mango (postharvest biology)...................................................3 3.1 Fruit ripening and quality loss ..........................................................3 3.1.1 Respiration rate................................................................................3 3.1.2 Ethylene production .........................................................................4 3.1.3 Loss of water (transpiration) ............................................................4 3.1.4 Fruit changes during ripening ..........................................................5 3.2 Main causes of quality loss after harvest.........................................5 3.2.1 Inadequate temperature control.......................................................5 3.2.2 Mechanical damage .........................................................................5 3.2.3 Sapburn and skin browning .............................................................6 3.2.4 Postharvest diseases and physiological disorders ..........................7 3.2.5 Treatment injuries ............................................................................7 4 Take care of your mango (postharvest technology)..................................9 4.1 Harvesting and field handling...........................................................9 4.1.1 When to harvest your mango...........................................................9 4.1.2 How to recognise when mango fruit are mature: maturity indices...9 4.1.3 How to harvest your mango ...........................................................10 4.1.4 Desapping ......................................................................................11 4.1.5 Field packing and transport............................................................13 4.2 Packhouse operations and practices.............................................13 4.2.1 How to sort/grade your mango.......................................................13 4.2.2 How to pack and label your mango................................................15 4.2.3 Postharvest treatment to control rots .............................................16 4.2.4 General recommendations for the packing shed...........................16 4.3 Ripening and storage of your mango.............................................17 4.3.1 Temperature management ............................................................17 4.3.2 Pre-cooling and transport...............................................................18 4.3.3 Forced-air cooling ..........................................................................18 4.3.4 Guidelines for temperature management ......................................19 4.3.5 Controlled ripening .........................................................................21 4.4 How to transport your mango to the retailer ..................................21 4.5 Know your market (customer requirements)..................................21 iv 5 Causes and solutions of the main postharvest defects of your mango ..23 5.1 Anthracnose ...................................................................................23 5.1.1 Treating fruit with a hot dip.............................................................24 5.1.2 Treating fruit with a flood spray......................................................25 5.1.3 Sanitation .......................................................................................25 5.2 Stem end rot...................................................................................26 5.3 Bacterial black spot ........................................................................27 5.4 Sapburn..........................................................................................28 5.5 Skin browning.................................................................................29 5.6 Sunburn..........................................................................................30 5.7 Abrasion damage ...........................................................................31 5.8 Pressure damage...........................................................................32 5.9 Impact damage ..............................................................................33 5.10 Rhizopus rot ...................................................................................34 5.11 Black mould....................................................................................35 5.12 Alternaria-rot...................................................................................36 5.13 Stemphylium rot .............................................................................37 5.14 Sooty mould ...................................................................................38 5.15 Grey mold.......................................................................................39 5.16 Blue mold .......................................................................................40 5.17 Mucor rot .......................................................................................41 5.18 Cytosphaera rot..............................................................................42 5.19 Lenticel spotting .............................................................................43 5.20 Abnormal ripening ..........................................................................44 5.21 Jelly seed .......................................................................................45 5.22 Stem end cavity..............................................................................46 5.23 Internal breakdown.........................................................................47 5.24 Chilling injury..................................................................................48 5.25 Heat injury ......................................................................................49 5.26 Failure of skin to yellow..................................................................50 5.27 Fumigant injury...............................................................................51 5.28 Fruit fly damage .............................................................................52 5.29 Mango seed weevil damage ..........................................................53 CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 1 1 Introduction The successful marketing of fresh fruit requires careful attention to detail during production to produce a quality fruit, and also during postharvest to reduce loss of quality of the harvested fruit. After spending a lot of time, effort and money on crop production, it is logical also to spend resources to protect the value of the product after harvest. Fresh mango fruit are highly perishable, especially in tropical environments because of high temperatures. Care needs to be taken during harvesting, handling, transport, and distribution to ensure that the fruit reaches the consumer in good condition. Growers, collectors, traders, and retailers should receive appropriate instruction on how to use the most appropriate postharvest practices, based on the characteristics of the product, needs of the customer, cost of technology, and market conditions. This manual presents the basic principles of postharvest biology that affect fruit quality, as well as the key postharvest practices that should be used to ensure quality mango are marketed. Commercial practices were organised in a sequence aimed at maximising costumer satisfaction, highlighting the benefits and providing practical recommendations for each step from harvest to customer. The causes and solutions of most postharvest defects of mango are presented. This document is not intended to be an exhaustive book on mango postharvest, but will summarise the key issues as they relate to improving existing supply chains in Vietnam. More detailed information is available in the Vietnamese translation of the Queensland DPI&F Agrilink Mango Information Kit. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 2 2 Key production practices affecting postharvest quality Although good postharvest practices are essential to reduce quality loss during handling and distribution, they cannot improve fruit quality beyond that achieved at harvest. The application of good crop management practices is essential to ensure good quality at harvest. Major postharvest problems relating to disease, insects, and fruit appearance can be reduced by good production practices. Some of the main production practices that affect mango fruit quality are: • Use of appropriate cultural practices that allow healthy tree and fruit development, including a balanced fertilisation program (especially nitrogen and calcium), proper irrigation (if necessary), and tree canopy management to ensure that pest and diseases can be managed well, and harvesting is efficient. • Orchard hygiene to reduce fungal infections that start on the fruit on the tree, and insect damage. These practices include removing fruit left over on the trees or on the orchard floor, removing dead branches that can contain fungal spores, and cleaning bins or containers that have been in contact with soil. • Disease management (especially anthracnose) through an effective spray program aimed at reducing infection of flowers and fruit. • Integrated pest management (IPM) to monitor and control orchard pests such as fruit flies, seed weevils, scales and other pests that cause skin defects that reduce fruit quality. The above is a very brief summary of the importance of good production practices in producing quality fruit. More detailed information on these practices can be obtained from the Vietnamese translation of the Queensland DPI&F Agrilink Mango Information Kit. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 3 3 Know your mango (postharvest biology) 3.1 Fruit ripening and quality loss There are many reasons for quality loss after harvest. Some of these are the result of the normal processes of the fruit as it "moves" from the unripe to the ripe, then to the senescent or decayed state. These processes cannot be stopped, but we can use practices to minimise or slow down these processes to extend the life of the product. Others factors that reduce quality are the result of external practices which adversely affect the produce, and which need to be minimised or managed appropriately. Figure 1. Maturity and ripening in relation to other stages of the fruit growing process. The major factors that affect quality after harvest are: 3.1.1 Respiration rate Fruit are alive and continue to have active biological processes operating after harvest. The process of senescence (aging leading to death) commences immediately after harvest. This process of deterioration has to be managed to reduce quality loss. Common symptoms of senescence are excessive softening, tissue breakdown, diseases, loss of colour, loss of flavour, and off-flavours. Controlling respiration rate is the main way of controlling fruit shelf life. • The mango fruit continue to use oxygen and produce carbon dioxide after harvest, a process called respiration. • During respiration, heat is also produced. • Mango has a moderate respiration rate and undergoes a burst of respiration that coincides with the start of fruit ripening (called climacteric respiration, see Figure 2). • After reaching a peak, respiration falls again. • The rate of fruit deterioration relates largely to their respiration rate. Growth maturation mature ripening senescence Fruit development CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 4 • The higher the air temperature, the higher the respiration rate. • Control of temperature is crucial to minimising loss of quality because it slows down respiration and delays senescence. • There are other ways of slowing down respiration, for example by controlling the concentrations of oxygen and carbon dioxide. This is referred to as controlled atmosphere or modified atmosphere storage, but strict control of temperature is required for these practices to be effective. Figure 2. Respiratory patterns of fruit during ripening. 3.1.2 Ethylene production Ethylene is a natural plant hormone that is involved in plant growth, development, ripening and senescence. • Ethylene is a key component of ripening in climacteric fruit such as mango. In these fruit ethylene production rates increase during ripening, and added ethylene can stimulate ripening. • Ethylene in the air around produce can have both a positive and negative effect. o The positive effect is when ethylene is used to control the ripening of climacteric fruit, so that the ripening of the fruit is more predictable and makes marketing easier. o However if unwanted ethylene builds up in the air around sensitive produce, it can speed up ripening, so that the fruit ripen is too quickly and can spoil before being consumed. • Fruit ethylene production rates increases with higher air temperatures, fruit physical injuries (called wound ethylene), and rots. 3.1.3 Loss of water (transpiration) All plants lose water through a process called transpiration. • Transpiration continues after harvest. • It results not only in direct weight loss (reduces the saleable weight), but also reduces appearance and textural quality (shrivelling, softening, etc). Time CO2 output Heat output O2 Consumption Respiration rate Climacteric (ripening fruit) Eg. Mango Non-climacteric Eg. Orange CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 5 • Water loss increases with higher air temperatures, lower relative humidity of the air, more air movement across the fruit surface, and fruit surface injuries. 3.1.4 Fruit changes during ripening Ripening is the combination of processes involving changes in fruit quality attributes that leads to good eating quality. Both chemical and sensory qualities of the mango fruit change as they ripen (see Figure 3). The main changes are: • Texture: firmness decreases (softening of the flesh due to changes in the cell walls). • Colour: generally (depending on the cultivar) skin colour changes from green to yellow (mostly because of destruction of the green pigment), and the flesh from a pale yellow to a darker yellow. • Flavour: sugars increase (due to conversion of starch to sugars) and acidity decreases (due to breakdown of acids) in the flesh. Figure 3. Main changes in mango fruit during ripening. 3.2 Main causes of quality loss after harvest 3.2.1 Inadequate temperature control Temperature is the environmental factor that most affect the deterioration rate of fruit after harvest. • The higher the temperatures, the higher the respiration rate, ethylene production, transpiration, spore germination, and growth rate of pathogens. • The rate of deterioration of fruit typically increases 2-3 times for each increase of 10 oC above the optimum. 3.2.2 Mechanical damage • Can cause loss of appearance. Eating ripe Time R el at iv e ch an ge Firmness Skin colour Sugars Acidity CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 6 • Can also increase water loss, increase respiration and ethylene production, and allow entry of disease organisms. • Symptoms of mechanical injuries can appear externally (cuts etc) or internally (bruising and cracking of the flesh). • They may be visible almost as soon as they occur, or they may only become visible at some later time. • Injuries can occur at any stage of harvesting, packing, transport and marketing. The major types of mechanical injury are: Bruising • May not be obvious quickly, and only appear as an area susceptible to breakdown (discoloured) as the product is marketed. • Can be caused by impact or pressure damage. • Impact damage can occur from dropping of individual produce or packages, or from hard knocks on equipment and during transport. • Pressure damage can occur in product stacked too high or packed in a package unable to support the required weight. Abrasion injury (rubbing) • Leads to rupture of cells, loss of water, and cell death, resulting in dry black or brown areas on the surface. • May be visible immediately, but frequently takes several days to become visible. • Common causes are rubbing of produce against dirty or rough surfaces of containers and equipment, and rubbing of loosely packed produce during transport. Cracking and splitting • Caused by heavy impacts to hard products. • Can occur when a single fruit is dropped on to a hard surface, a container of fruit is dropped or loose fruit bounce against each other during transport. 3.2.3 Sapburn and skin browning Sapburn • Mango fruit spurt a highly caustic sap when the stem is first removed from the fruit (spurt sap), which causes severe injury to the fruit skin (dark spots, blotches or streaks around the stem end of the fruit and down the cheeks). • Sap is then released more slowly over about 1 hour (ooze sap), causing mild injury (light-brown discolouration to the skin). • The amount of sap exuded by fruit varies with cultivar, maturity (less mature fruit has more sap) and time of day (more sap in the morning). Skin browning CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 7 • Several different skin blemishes appear on mangoes during postharvest handling, causing brown markings on the skin (light- to dark-brown etching, staining, or spotting). • The damage can be similar to that caused by abrasion, brushing, or heat treatments for disease on insect control. • Possible causes include rough handling, fruit sitting in water and detergent, or sap left on the skin (from picking containers or equipment). Damage from sapburn and skin browning is not visible immediately and symptoms develop 1 to 2 days after injury. 3.2.4 Postharvest diseases and physiological disorders Diseases • The main problems in mango are rots caused by the anthracnose and stem-end rots fungi (refer to sections 5.1 and 5.2 for detailed information on symptoms and control measures). • Bacterial black spot can also be a significant problem in some cultivars and seasons (refer to section for 5.3 more details). • Infection by rots generally occurs in the field during growth, mainly from fungal spores remaining on old fruit and dead branches. The infection remains very small and inactive (dormant) on green fruit until it begins to ripen. Good orchard hygiene and disease control during fruit growth is essential to minimise diseases after harvest. • Symptoms may range from small surface lesions that reduce appearance, to severe infections causing external and internal breakdown of most of the fruit. • Symptoms of moderate severity commonly appear as areas of excessive softness, off-colour or off-flavour. • Disease development is usually higher with increased air temperatures (especially above 25 oC) and humidity, in fruit with mechanical injuries, and in very mature and over-ripe fruit. • Spoilage organisms are spread in wash water, particularly where the water is not changed frequently enough or treated to control organisms. Physiological disorders • Include flesh defects such as jelly seed, soft nose, internal breakdown, stem end cavity (refer to section 5 for detailed information on symptoms and control measures). • Causes are not well known, but are usually related to factors such as genetics, fruit minerals (for example high N and low Ca), low crop load, and fruit maturity. 3.2.5 Treatment injuries Temperature, gas, and chemical injuries may develop as a result of postharvest treatments, including: • Cold (chilling) injury: caused by storage of fruit at temperatures below their chilling threshold (see section 5.24 for details). CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 8 • Heat injury: caused by excessive high temperatures during hot water or fungicide treatments for disease control, and heat treatments (water and air) for insect disinfestation (see section 5.25 for details). • Ethylene: over exposure can cause premature initiation of ripening on-farm or in transit, causing fruit to arrive at the market too ripe for sale, as well as increase problems with rots and mechanical damage. • Fumigant injury: caused by fumigants used for insect disinfestation (see section 5.27 for details). CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 9 4 Take care of your mango (postharvest technology) 4.1 Harvesting and field handling 4.1.1 When to harvest your mango The characteristics of the fruit at harvest determine the quality of the ripe fruit. Thus, harvesting at the right stage of maturity is critical to achieve good ripe fruit quality. Harvesting at the proper maturity stage of the fruit can: • Allow good flavour and texture of the fruit when ripe. • Improve fruit external appearance when ripe due to proper loss of the green skin colour. • Reduce problems with diseases and physiological disorders. • Allow more uniform fruit with more consistent quality, thus improving consumer confidence and return to the grower over time. Mangoes are usually harvested in a hard green mature state so that it can be packed and delivered to market before it ripens and becomes too soft. • If produce is harvested too early, the fruit will have an acceptable flavour and texture, due to insufficient starch and other reserves. In addition, other essential changes associated with ripening, for example softening and loss of the green skin colour may not occur if the fruit is harvested too early • If produce is harvested too mature, senescence may occur before the fruit reaches the consumer. Also, physiological disorders such as jelly seed and soft nose are usually more severe in very mature fruit • Not all mangoes on a tree mature at the same time. Usually 3 to 4 selective picks may be needed (1-2 weeks apart) to ensure more uniform maturity at harvest and good fruit quality. • Avoid harvesting soon after rain (it tends to increase disease problems and the skin is often more sensitive to mechanical damage). • Do not harvest if fruit have not reached maturity (even if the market price is high), as this will damage customer and consumer confidence in the product, and result in reduced returns to the grower over time. 4.1.2 How to recognise when mango fruit are mature: maturity indices Maturity is the single most important manageable factor affecting fruit physiology. It affects shelf life, ripening behaviour, responses to postharvest treatments, susceptibility to diseases and physiological disorders, and final eating quality of the fruit. Table 1 lists some of the effects maturity has on fruit quality. Table 1. Maturity effects on different aspects of mango quality. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 10 Parameter Immature Mature Green life longer shorter Skin/flesh colour patchy, pale uniform, bright Shrivelling higher lower Aroma faint full Internal disorders lower higher Chilling injury higher lower There are different ways of measuring or predicting maturity (known as maturity indices). These can be used individually, but it is more accurate to use several maturity indices together. The most common ones for mango are: • Days from flowering to harvest (in Vietnam about 81-85 days depending on cultivar and climate). Variable flowering times within tree – strip harvesting not good – mixed maturity. Need to do on fruit shape/colour if possible, or later harvest to make sure that most fruit are mature. • Fruit size and shape. For example, depending on cultivar fruit can be mature when shoulders and beak (or stylar end of the fruit) are full and there is no visible line running down the centre of the fruit. • Skin colour changes (depending on the cultivar, for example from a darker green to a light green). • The colour of the flesh at harvest. The flesh colour changes from light yellow to darker yellow as fruit mature. Colour charts have been developed in several countries to rate the flesh colour at harvest. The maturity standards should be developed for each cultivar and for each major climatic region. Several maturity standards should be developed to increase the accuracy of when to start picking. For example, in Australia, Kensington Pride mango fruit is considered mature when: • Flesh has a minimum of 14% dry matter. • Flesh colour of Kensington Pride fruit is showing yellowing as described for Stage 3 in the DPI’s Mango Picking Guide. • Beak-end of the fruit fills out and feels smooth, and the shoulders of the fruit lose any wrinkling. • Background colour of the fruit changes from distinct green to pale green • Blush colour of the fruit brightens. • Fruit separates easily from the stalk, and at advanced maturity exudes less sap. Pickers need to be trained to recognise the proper maturity stage of the fruit. 4.1.3 How to harvest your mango • Plan your harvest: what equipment, materials, facilities and labour are needed. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 11 • Train personnel in the proper way to harvest to reduce damage and waste during harvesting (for example emptying picking bags and/or baskets with care, and avoiding dumping or throwing fruit). • Harvest early in the morning because of the cooler temperature. • Harvest fruit from a low of parts of the tree using secateurs or clipping poles. • For high fruit, preferably use picking poles with scissors with a soft cloth bag attached to catch the fruit and reduce sapburn and mechanical damage (Figure 4), rather than the picking pole with cutter blade with a net to catch fruit, or picking poles with a looped wire. Alternatively, place fruit in a basket that is lifted into the tree by rope. • Harvest the fruit with long stems and remove the sap (see section 4.1.4). • Do not pick up fruit that has fallen onto the ground and avoid laying picked fruit on bare soil. These fruit will often have more disease. • Containers used should be clean, smooth (free of rough edges), vented, not too large. • Always place harvested fruit in the shade to prevent heat and sunburn. • Do not stack containers on top of each other unless they are designed to spread the weight and avoid mechanical damage. • Regularly clean/disinfect all tools and equipment used during harvest, including soft bags to avoid contamination and build-up of sap. Figure 4. Harvesting system using scissors to cut the fruit from the tree with a long stem caught in a cloth bag suspended underneath. 4.1.4 Desapping There are two main systems to reduce sapburn caused by sap contact with the fruit: Desapping in the field o Harvest the fruit with at least 2 cm long stems. o Hold fruit with the stem end down as the stem is pulled off to direct the sap away from the fruit and the desapper’s hands. o Place the fruit upside down on desapping racks (Figure 5). Make sure the fruit does not contact any sap on the racks or contact the CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 12 soil. Leave the fruit on the desapping rack for at least 1-2 hours to allow most of the sap to drain from the fruit. Figure 5. Mango being desapped on racks in the field. o Caution: the sap can burn the skin and sappy hands will cause skin browning on the fruit. Wash hands regularly. o Fruit can then be wrapped individually in paper and sent to cooperative, collector or wholesaler. o Keep fruit and containers in the shade as much as possible. • Desapping in the packing shed (Figure 6). o Pick fruit with stems (about 15 cm). Place carefully into containers, making sure that no stems are broken off in the process. Carefully transport them to the packing shed. o Dip or spray fruit with a solution of detergent before destemming by hand. o Proceed as per field desapping. Figure 6. Desapping of mango in the packing shed. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 13 4.1.5 Field packing and transport • Preferably use plastic crates. If using rough packages such as baskets and wooden crates, line them with paper or cardboard inserts to reduce damage to the fruit skin. Place paper inside baskets between each layer of fruit to protect fruit from sapburn or rub marks. • If baskets are hoisted into the trees via ropes slung over branches during harvesting, lower them to the ground when they are half full. • Keep fruit packages covered whilst in the field. • Secure field boxes well during transport, but do not overfill. • Do not pack fruit either too tightly or too loosely. • Grade roads between the field and the packinghouse, keeping them free from large ruts, bumps and holes. 4.2 Packhouse operations and practices 4.2.1 How to sort/grade your mango Grading for defects is the most important operation in the packing shed, and requires knowledge and experience as well some training. The quality of individual fruit is very important, but if the good quality fruit is sold with lower quality fruit, the value of the higher quality fruit is not realised. Therefore, sorting of fruit into quality grades is essential to maximise returns. Often the increased returns from grading the fruit is greater than selling the fruit without grading. Good sorting/grading can: • Improve fruit presentation and uniformity • Reduce fruit quality loss • Increase returns Typically buyers require the produce to be uniform within the saleable unit (in terms of fruit size/weight, colour, shape, and skin appearance). This is achieved by grading the fruit (Figure 7). Before grading After grading Figure 7. Basket of mango fruit before and after grading. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 14 • The characteristics of the fruit that are used for grading (grading standards) must be agreed to between the grower and the customer, or the cooperative and its customers (e.g. the retailers they supply to). This is essential to prevent misunderstandings between the growers and their customers in relation to quality requirements. In Australia, the grading standards are based on skin damage and fruit size, and there are usually several grades (e.g. grade 1 and 2) for each fruit size category. • Develop a poster or similar showing pictures of the various defects and acceptable limits, and display in an obvious place in the sorting/grading area. • We recommend that grading occurs at packing on the farm (see Figure 8) or at the cooperative. Re-grading later increases the risk of mechanical damage to the fruit because of too much handling. Figure 8. Grading of mangoes in a packing shed. • Good training is required, with regular re-training, to ensure consistency in grading to meet customer requirements. The main criteria used for mango fruit grading are: • Size/weight • External defects • Maturity stage (based in skin colour and fruit shape) Possible grade standards are summarised on Table 2. Table 2. Possible grade standards for mango fruit Criteria for mango fruit grading Grades Weight (g) External defects Maturity stage Class 1 A > 420 No Acceptable Class 1 B > 420 Yes (minor) Acceptable Class 2 A 300 – 420 No Acceptable Class 2 B 300 – 420 Yes (minor) Acceptable Class 3 < 300 Yes (major) Too immature or too mature CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 15 Minor defects: affects only the appearance of the fruit in a small area, without affecting eating quality. Examples are small blemishes and mild abrasion damage (Figure 9). Major defects: affect the soundness of the fruit, such as wounds and fruit rots, or affects the appearance of the fruit severely and in large areas (Figure 9). Minor defects Major defects Figure 9. Examples of minor and major defects in mango fruit. 4.2.2 How to pack and label your mango Fruit quality is important, but the way the fruit are packed, and the packing material used, can have a big effect on general appearance of the whole package, and customer reactions. Good packaging can: • Significantly reduce fruit damage, especially if fruit containers are stacked on each other during transport and holding. • Help slow down ripening by allowing good air movement around the fruit through holes in the packaging. This will reduce the risk of temperature increases during holding and transport. • Improve the appearance of the fruit. • Allow labelling. • For higher quality fruit, consider using packaging materials such as a single layer fibreboard carton tray (Figure 10), add plastic or fibreboard inserts with cups to help with fruit placement and protection. This will help get a higher price for these better quality fruit, eliminate repacking and allow the logo or farm name to be labelled on the tray. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 16 Figure 10. Mango fruit being packed into single layer carton trays (left picture) and then stacked on a pallet (right picture). • Consider using plastic crates rather than rougher materials such as bamboo baskets. • If using baskets, add layers of paper or liners between several layers of fruit to prevent sapburn and abrasion damage between fruit. • Pack securely to immobilise produce, but do not overfill or under-fill packages. • Do not block the ventilation of packages with fillers or liners. • Label containers with your logo or farm to improve marketing. Inexpensive papers labels or stickers can be used. • Do not stack containers on top of each other to avoid mechanical damage. • Good truck loading patterns and ideally refrigerated transport is recommended, especially for long distances. 4.2.3 Postharvest treatment to control rots Refer to Section 5.1. 4.2.4 General recommendations for the packing shed • Provide shade for harvested fruit waiting to be sorted and packed. • Avoid locating the packhouse directly next to an unpaved, dusty road. Otherwise the fruit will become dusty and more likely to develop abrasion and rub marks. • Reduce mechanical damage: avoid drops, throwing and rough handling at all stages. Do not use large containers because this increases the risk of containers being handled roughly. • Provide good lighting to help sorters identify the defects. • Display the grading standards in an obvious place for the sorters to refer to when required. • Keep the packing line clean and as simple as possible. • Provide enough ventilation in the shed to avoid heat build up. • Provide comfortable work stations, which increase worker efficiency and help to reduce fatigue. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 17 • Practice good shed hygiene, including regular removal of reject fruit from the shed and regular cleaning of all equipment. • Provide clean sanitary conditions for all supplies, including containers storage. 4.3 Ripening and storage of your mango Managing ripening and fruit temperature can provide valuable control over the marketing period and shelf life of the fruit. Retail customers usually want to buy mangoes at a specified stage of ripeness (for example, n Australia this is usually close to eating ripe). This section gives recommendations of ripening and storage condition adopted in Australia for ‘Kensington Pride’ mangoes. These may also be suitable for the common Vietnamese cultivars, but should be tested. 4.3.1 Temperature management Temperature management is the most important factor in the ripening, storage and transport of mangoes. • Fruit will begin to ripen as soon as it is harvested. • Controlling the fruit temperature will give some control over the time it takes for fruit to reach eating ripe. • The conditions at which fruit is stored will also determine the shelf life, final quality and appearance. • The best temperature management strategy will depend on the expected marketing period from harvest to consumer. • You will need to know whether the fruit is to be sold immediately or whether the wholesale agent will store it. Once this is determined, temperature management can be used to give some control over the marketing period and shelf life of the consignment. There are three stages of postharvest life and each stage has different temperature tolerances. (a) Mature green. Green fruit can tolerate temperatures between 10 and 13°C. Holding fruit at these temperatures will delay the onset of ripening. Storing fruit below these temperatures leads to chilling injury. The lower the temperature and the longer the storage time, the more severe the injury symptoms will become. Green fruit can be held for up to two weeks before the ripening process starts. Keep an eye on the fruit at all times. If it starts to ripen it must be brought up to 20°C. (b) Ripening. As soon as the fruit begins to ripen the storage temperature must be maintained between 18° and 22°C. At temperatures below 18°C, skin colour development is slow and flavour development poor. At temperatures above 22°C, the flesh will soften but the skin colour will remain green or develop an unattractive green-yellow mottle. Postharvest diseases also develop more quickly at temperatures above 22°C. (c) Eating ripe. When the fruit is close to eating ripe the fruit will tolerate cooler storage temperatures again. The best storage temperatures are between 10 and 13°C but the fruit will tolerate a short period at lower temperatures. At this CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 18 stage shelf life is limited but it can be extended for another three or four days by storing at 7° to 10°C. Do not store ripe mangoes below 5°C. Always maintain a relative humidity between 85 and 95% while in storage. 4.3.2 Pre-cooling and transport The first step in the cool chain is pre-cooling. Field heat should be removed from the fruit as soon as possible after harvest and the fruit kept cool from then on. However, simply placing pallets into a cool room does not achieve fast effective cooling throughout the pallet. Neither is refrigerated transport sufficient to bring fruit down to storage temperatures. Transport will only maintain fruit at the loading temperature in the upper rows. • If fruit arrive at the market above the optimum ripening temperature, there is a greater risk that fruit will prematurely ripen. The outcome will be green ripe fruit and reduced saleability. • High ripening temperatures have a compounding effect. Mangoes that are ripening produce heat, resulting in hotter fruit if they are not effectively cooled. The hotter the fruit, the more heat they produce. Fruit at 25°C produce twice as much heat as at 20°C. • Even when fruit arrive at the market at the optimum ripening temperature, ripening heat must be removed to maintain the optimum ripening conditions. • For effective cooling, mangoes must be placed into a cool room at 18° to 22°C and the pallets either placed under a forced-air system or air stacked onto other pallets. • The temperature for pre-cooling and transport depends on whether the fruit is to be sold immediately or stored by the wholesale agent. For immediate sale, pre-cool and transport fruit at 18° to 20°C. If fruit is to be stored, a lower temperature of 10° to 13°C should be used. To the consumer in less than 10 days If fruit is to be sold in less than 10 days it should be pre-cooled and transported at 18° to 22°C. Ripening can be initiated at the farm or at the markets. To the consumer in more than 10 days If you need more than 10 days some storage or transport at lower temperatures is needed. This fruit must be carefully monitored. If there are any signs of the fruit beginning to ripen, it should be removed from cool storage and allowed to ripen at 18° to 22°C. When fruit are close to eating ripe they can be placed back into 7° to 10°C. 4.3.3 Forced-air cooling Forced-air cooling involves forcing cold air through containers or past individual pieces of fruit to rapidly cool the fruit. A forced-air system can be set up inside existing cool rooms and can cool fruit to the correct ripening temperature within 12 hours. A forced-air system uses a fan to create a chamber of low pressure on one side of the pallet that subsequently causes cold air to flow through the container from the high to the low-pressure side. A blind or cover is normally used to ensure that the airflow is through all the packages and does not short-circuit the system. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 19 Two cooling techniques can be used: Tunnel cooling. A row of pallets is placed either side of an air channel. The same number of pallets must be placed in each row. A blind is then run over the top and down the end of the air channel. Air is then pulled through the trays into the air channel and back through the auxiliary fan and cooling unit. This technique can use either a freestanding fan or a permanent wall mounted system to pull air though the pallets (Figure 11). Figure 11. An example of a tunnel forced air system. Single pallet cooling. The best design for cooling single pallets is the cold wall system. In this system the pallets are placed against openings of similar width in a plenum. Openings must be closed if not in use. Air is pulled through the containers into the plenum and back through the auxiliary fan to the cooling unit. A technique for small operations where floor space is restricted involves placing an individual fan over the central chamber of each pallet, pulling air through trays into this central chamber. The bottom of the central chamber should be covered so air does not pass through the bottom of the pallet. 4.3.4 Guidelines for temperature management The handling requirements for mangoes will depend on the ripening stage of the fruit and whether it is to be stored or ripened. The customer will determine the stage of ripeness for delivery. Following is a guide on how to handle mangoes through the supply chain to achieve the stage of ripeness required by the customer. The information is based on the current knowledge of the physiology and postharvest characteristics of Kensington Pride but can also be used for handling other varieties. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 20 Hard green fruit To ripen (18-22°C) To store (10-13°C)  Hold fruit at 18-22°C and 80- 90% relative humidity  Forced air cool or air stack to maintain temperature  Vent room regularly to prevent build-up of carbon dioxide  Gas with ethylene for 1-3 days for faster and more even ripening  Fruit will take from 6-9 days to reach eating ripe from start of ethylene treatment  Store fruit at 10-13°C and 80- 90% relative humidity for a maximum of 7 days  Pre-cool with forced-air cooling to ensure uniform fruit temperatures through pallet  Vent room regularly to prevent build-up of carbon dioxide  Check fruit inside pallet daily for any sign of softening  Raise temperature to 18-22°C at first sign of softening or colouring  Ethylene from nearby ripening rooms or other produce will trigger ripening Ripening fruit (up to 40% yellow) To ripen (18-22°C) To store (10-13°C)  Hold fruit at 18-22°C and 80- 90% relative humidity  Forced air cool or air stack to maintain temperature  Vent room regularly to prevent build-up of carbon dioxide  Gassing with ethylene is not needed if fruit is already softening and yellowing  Fruit will take up to 6 days to reach eating ripe from first sign of yellowing  Do not store ripening fruit at low temperatures as skin yellowing and flavour is reduced Near-ripe to ripe fruit (more than 40% yellow) To ripen (18-22°C) To store (10-13°C)  Hold fruit at 18-22°C and 80- 90% relative humidity  Forced air cool or air stack to maintain temperature  Vent room regularly to prevent build-up of carbon dioxide  Check ripeness daily to avoid fruit being too ripe for sale  Store near-ripe to ripe fruit at 10-13°C to slow further ripening  Check ripeness daily to avoid fruit being too ripe for sale  The risk of over-ripeness increases with storage times above 4 days CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 21 4.3.5 Controlled ripening Depending on the fruit conditions and market requirements, this postharvest practice may be recommended. • Provides more even ripening of fruit in the batch, thereby improving appearance in the tray/basket. • If not done properly, fruit may become overripe causing increased losses. • Traditionally a carbide stick is placed in the bottom of each crate and covered with paper. The carbide combines with water to release acetylene. • Ethylene gas is far more effective, but is harder to obtain. • Dipping fruit in a water solution with ethephon (for example the commercial formulation Ethrelđ), which liberates ethylene can be a suitable alternative, and probably provides more uniform ripening than carbide. 4.4 How to transport your mango to the retailer • Do not overload vehicles. • Be careful about stacking the fruit containers on top of each other. Considerable fruit damage can occur if the packaging is unsuitable (insufficient strength to support the load above, or over-packaging within each container). • Train workers in correct methods for loading and stacking vehicles, so as to avoid rough handling during loading and unloading. • Transport fruit without delay to the destination. • Cover containers during transport to reduce moisture loss and exposure to the sun. • Do not use rope or ties in ways that may damage fruit. • Temperature control during transport: very important for long distances (refer to section 4.3.2 for recommended temperatures). 4.5 Know your market (customer requirements) Your immediate customer - the person you sell your fruit to - can have a major effect on your profitability. It is important that you understand his requirements for quality and volumes. Give them what they want. That’s the key to successful marketing. • Regular supplies of consistent quality mangoes are required to satisfy domestic and export markets. • Consistency and reliability build a strong brand reputation, which improves buyer loyalty and maximises returns There are basic quality expectations that consumers may consider when buying fruit, including: • Free of major injury, spoilage, or blemish likely to affect quality. • Free of dirt, dust, unacceptable chemical residues and other foreign matter. • Not overripe, soft, or shrivelled. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 22 • In a condition that is acceptable to eat. • Free of foreign odours and taste. Consumer lifestyle changes and social trends are occurring in countries around the world, creating a shift in retailing to: • Greater convenience and longer opening hours. • More one stop shopping (growth of supermarkets). • A wider range of foods and more choice. • A more healthy, hygienic and cleaner shopping environment. • Higher demand by retailers for food that is safe and the right quality. Lifestyle changes in South East Asia can impact on customer requirements. These lifestyle changes are following the trends of other parts of the world as income increases: • Higher proportion of smaller families and one-person households. • Changed preferences in shopping, food, cooking and eating habits due to exposure to western influences. • People are becoming more aware of nutritional value and food safety in their diet (due to higher education levels). • Due to more tourism, changes in retailing are occurring to cater for western tastes and provide food that is safe and of good quality. • Asians are travelling more, being exposed to modern retailing, a wider range of products and the availability of fresh produce out-of-season. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 23 5 Causes and solutions of the main postharvest defects of your mango MAJOR DEFECTS 5.1 Anthracnose Cause In Australia, the fungus Colletotrichum gloeosporioides, and occasionally the fungus Colletotrichum acutatum. Symptoms • Small, dark specks enlarging to irregular, dark-brown to black areas. In a moist atmosphere, pink spore masses appear towards the centre of these areas. • The damage usually does not extend to more than 10 mm beneath the skin. Anthracnose may also develop at wound sites. • Surface staining or russeting of fruit may result from spores being washed over the fruit from diseased twigs or flower stalks. Occurrence • The most important fungal disease of mangoes, with major losses occurring from flowering to fruit set and again after harvest, specially in areas of high rainfall. It is most severe following periods of wet weather. • Spores of the fungus are produced on dead twigs, branches and leaves and spread by water splash. Infection of young fruit may cause fruit drop. • Disease development after harvest results from fruit infection before harvest; the fungus may remain dormant or latent in unharvested green fruit for many weeks. • Develops most rapidly after harvest because the fruit loses its natural resistance during ripening. Post-harvest spread is unlikely. Early anthracnose Advanced anthracnose CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 24 Control The best control of these diseases is through a combination of preharvest and postharvest fungicide application, orchard hygiene (removal all dead fruit and wood from the tree and the orchard floor to reduce the number of fungal spores in the orchard), and postharvest temperature management during ripening and storage. The postharvest treatment will not replace lack of care in the field. In Australia, there are three main postharvest fungicide treatments available. 1. Heated dip using carbendazim (Spinflođ) 2. Non-recirculated flood spray with prochloraz (Sportakđ) 3. Sanitation using chlorine or ammonium solutions The choice of treatment will depend on the level of disease in the orchard (ie. the cleanliness) and the incidence of the major fungi such as stem-end rot (ie. the age of trees). If stem-end rot is not a problem, you can treat with prochloraz alone; if it is a problem, you will need to use a hot carbendazim dip. However, these treatments need to be tested under Vietnamese conditions. 5.1.1 Treating fruit with a hot dip For stem-end rot and anthracnose control, fruit must be immersed for five minutes in a heated solution of carbendazim at 52°C. This is done in a specially designed tank in the packing line. The tank is heated by gas or electricity and the contents are kept agitated with a powerful recirculating pump. This agitation keeps the fungicide evenly mixed and helps to distribute heat from the heating element. The size of the tank should be big enough to allow 3 L of dip to each kilogram of fruit, so there is no appreciable drop in temperature in the tank when the fruit is added. If done correctly this treatment will provide effective control of postharvest diseases. During the day the volume of the dip will drop and the chemical will be stripped as fruit passes through. This means that the dip must be topped up during the day. To top up add an extra one-third of the original quantity of chemical into the dip at the halfway point of the day. There are three points to note when dipping fruit: • Timing: the total dipping time should be five minutes. Fruit should be dipped within 24 hours of harvest but no sooner than four hours after harvest. If treatment is delayed for more than 24 hours, control is not as effective. Fruit that has just been harvested is more susceptible to heat injury. • Temperature: fruit must be treated at 52°C. This temperature must be carefully controlled. If the temperature is lowered the treatment will not be as effective and if the temperature is higher there is a greater risk of fruit damage from scalding. During wet weather fruit becomes more susceptible to heat damage. In this case the temperature may be reduced to 50°C, but this will also reduce disease control. • Dip cleanliness: as fruit passes through the dip the water will become contaminated with sap and dirt, even if fruit has been desapped and washed. It is advisable to replace the dip every two or three days or after every 4000 trays. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 25 5.1.2 Treating fruit with a flood spray An alternative treatment for the control of anthracnose alone, is a low volume spray with prochloraz at ambient temperatures. The rate of decline in concentration of prochloraz has been determined so for the best control the spray should be not be recirculated. Fruit should be sprayed for between 30 second and 1 minute. Complete coverage of the fruit is essential for effective control. Prochloraz is not effective against stem-end rot, so you should only choose to use this treatment if you know that stem-end rot is not a problem in your orchard. It is best to apply both treatments for fruit that is going to be cool-stored or transported for long distances. 5.1.3 Sanitation Equipment used in the picking, dipping, packing and storage of mangoes can be sources of disease infection. Cleaning and sterilising all equipment before and at the end of the season can help to minimise disease presence particularly storage rots. Sanitisers should be used once the equipment has been cleaned. Sterilisation and sanitation may also be required during the packing season if equipment becomes contaminated (eg. with Transit rot or Aspergillus). There are two main chemical used to sanitise equipment: (a) Chlorine solutions • A 200 milligram per litre (mg/L or ppm) chlorine solution should be used to sanitise equipment. Sodium hypochlorite is available as a liquid containing between 4 to 12.5% chlorine. To make a 200 mg/L chlorine solution mix 160 ml of 12.5% sodium hypochlorite or 500 ml of 4% sodium hypochlorite in 100 litres of water. • Since chlorine in solution dissipates quickly, the solution should be freshly prepared immediately before use. The chlorine level can then be checked using a swimming pool test kit. Either sodium or calcium hypochlorite can be used to prepare wash solutions. • Chlorine may corrode steel and some rubber compounds if used continuously, but 2 or 3 sprays a week should not cause problems. • Calcium hypochlorite (Hypochlor, Activ 8), chlorine dioxide (Oxine) and bromochlorodimethylhydantoin (Nylate) are alternatives to sodium hypochlorite. (b) Quaternary ammonium compounds • Products (eg. Applied 3-300*) used as sanitisers in the dairy industry to sterilise milking machines and storage bins are also suitable for sterilising mango picking and packing equipment. Follow the label directions given for each particular product. • These products have a residual effect allowing sterilisation to remain effective for a longer time. Quaternary ammonium compounds are non-corrosive. • Most sanitising products are hazardous if they are inhaled or the concentrated solution comes in contact with the skin. Always read the warning label and wear the applicable protective clothing when handling these chemicals. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 26 5.2 Stem end rot Cause Several fungi, including Dothiorella dominicana, Dothiorella mangiferae, Lasiodiplodia theobromae, Phomopsis mangiferae, and Pestalotiopsis mangiferae. Symptoms • As the fruit ripen, a brown, soft decay starts at the stem end, and rapidly spreads through the whole fruit, which may split open as they collapse. • A straw-coloured fluid drains from the stem end or from splits in the side of the fruit. Steel-grey mycelium may cover the surface of fruit. • Lesions may occur away from the stem end, particularly if the fruit has been injured. • The disease may spread to healthy fruit that are touching diseased fruit. Occurrence • The fungi occur as natural inhabitants of mature branches. Colonisation proceeds into new growth flushes as they mature, reaching the stem ends of fruit midway between flowering and harvest. The fungi do not develop in healthy fruit until after harvest. • Fruiting bodies of the fungi also occur on tree litter beneath the tree and, in humid conditions, on the bark of the tree. • The disease builds up in an orchard as trees become older. • Water stress may favour twig dieback and branch canker caused by the same fungi • Fruit may also be infected if they are placed on the ground for sap bleeding. Control • Field sprays and fruit treatments (as per anthracnose). • Orchard hygiene, including removal of leaf litter and prunings, and strategic pruning after flowering to force new growth. • If desapping in the field, do not place fruit on the ground directly. • Avoid unnecessary long storage of fruit. Stem end rot of mango fruit Stem end rot : section of fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 27 5.3 Bacterial black spot Cause The bacterium Xanthomonas campestris pv. mangiferae indicae. Symptoms • Appear initially around the lenticels as small, irregular, water-soaked specks on which a bead of bacterial ooze may develop, resembling fruit fly stings. • Raised black spots with greasy margins develop later. Cracks, from which sap laden with bacteria may ooze, can also develop. • Anthracnose and secondary rots commonly develop in bacterial black spot lesions as the fruit matures, causing deep, extensive decay. • Bacteria from fruit lesions may infect the fruit in a tear-stain pattern. Lesions can also occur on fruit and flower stalks. The symptoms are visible on fruit at harvest. Occurrence • Severe in windy areas that lack windbreaks and in trees that lack vigour. • The disease can be prevalent in both low and high rainfall areas. • Infected nursery trees can be major cause of spread of bacterial spot into new orchards. • Bacteria from diseased tissue are dispersed by wind-driven rain, splashing, insects, and mechanical transfer on infected planting material. • Bacteria enter through natural openings on leaves (stomates) and fruit (lenticels), or through abrasions. • More on exposed and abraded leaf and fruit surfaces or where fruit touch each other. Control • Pre-harvest control measures, including the use of disease-free plant material (rootstock and scion wood), resistant cultivars (e.g. Sensation, Carabao, Nam Dok Mai, Early Gold), and windbreaks around the orchard. • Preventative sprays of bactericide, fortnightly during wet weather, monthly at other times. Avoid applications during flowering. Bacterial black spot of mango fruit (tear stain pattern infection on fruit) Bacterial black spot of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 28 5.4 Sapburn Cause • Mango sap (latex) exudes from the cut stems of harvested green mature fruit. If this sap flows onto the fruit skin during harvesting and post-harvest handling, the skin is damaged. There are two types of sap: o Spurt sap, which is released rapidly within 10 seconds of removing the stem, causing severe injury to the fruit skin. o Ooze sap, which is released more slowly over about 1 hour after removing the stem, causing mild injury to the skin. Symptoms • Spurt sap injury: dark spots, blotches or streaks around the stem end of the fruit and down the cheeks. • Ooze sap injury: light-brown discolouration. It can also remain as a clear, sticky fluid on the skin, detracting from the fruit's appearance. This sap slowly collects in a pool either between fruit, or between fruit and the carton. Occurrence • The amount of sap exuded by fruit varies according to: o Maturity (the less mature the fruit, the more sap it will exude). o Time of the day (greater sap flow early in the morning than later during the day). o Cultivar. • The blemish does not appear for about 24 hours after sap has been in contact with the skin. Fruit may be free of blemish in the packhouse, but appear blemished by the time it reaches the wholesaler or retailer. Control Desapping either in the field or in the packhouse (refer to section 0 for details). Sapburn of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 29 5.5 Skin browning Cause Free moisture, low concentration of sap on the skin for extended periods, or rough fruit handling. Symptoms • Several different skin blemishes that appear on mangoes during postharvest handling, causing brown markings on the skin (light- to dark-brown etching, staining, or spotting of the skin. • The damage is similar to that caused by abrasion, brushing, or heat. Occurrence • Damage occur from: o Moisture (fruit are handled during wet weather, fruit left to sit in water, or packed wet). o Sap left on the skin (from picking containers, harvest tools, and postharvest equipment). o Abrasion caused by contact with dirty or rough surfaces. o Scalding by hot air or water. • Damage is usually not visible immediately, and symptoms develop 1-2 days after injury. Control • Clean picking containers, harvest tools, racks, packing equipment, hands (or gloves) regularly to avoid dirt and build up of sap. • If washing fruit, replace solutions in detergent/lime baths, and dipping tanks frequently. • Avoid picking mangoes in wet weather. Do not pack wet fruit. • Train staff in handling and transport procedures to minimise mechanical damage. Skin browning of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 30 5.6 Sunburn Cause Overexposure of fruit to high levels of solar radiation during growth and development damages the skin, especially if associated with high skin temperatures. Symptoms • Skin becomes discoloured, which may range from yellow through red and brown to black as the disorder develops. A combination of colours, with the darkest in the centre, is common. • Slight sunburn produces bleached or yellow patches on the skin. In severe cases, there are leathery, yellow-brown to black, slightly depressed patches on the skin. Occurrence • Fruit exposed to the sun and which are not shaded by leaves are most susceptible, especially in growing areas with high irradiance levels. • Damage can result if fruit is suddenly exposed to sunlight when branches are broken, or if harvested fruit is left in direct sun. • Late-maturing fruit are more prone to sunburn than those maturing early in the season. • Fruit on water stressed trees will sunburn more easily. Control • A healthy foliage canopy is the best protection against sunburn. • Avoid any tree damage that may expose fruit to the sun. • Keep trees well watered during fruit filling. • Do not leave fruit in direct sunlight after harvest. Severe sunburn of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 31 5.7 Abrasion damage Cause Fruit being scratched on dirty containers or equipment, rough handling, and excessive vibration during transport from loose packing. Symptoms • Fine brown scratches on the skin, sometimes with smear. • Symptoms are similar to those of heat damage and skin browning. Occurrence • Damage can occur at any stage during harvesting, handling, and transport of fruit. • Risk of damage increases during wet weather. Control • Careful handling of fruit during harvesting and postharvest operations. • Keep field containers and packing line equipment clean. • Cover loads during delivery to the packhouse to avoid dust collecting in field containers. • Pack fruit tightly to prevent them from moving around during transport. Abrasion damage on mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 32 5.8 Pressure damage Cause Over-packing, excessive package depth, package collapse, and sagging of package bottom. Package collapse may be due to insufficient stacking strength or poor handling. Symptoms • Flattened areas on the fruit. • The flesh below the flattened areas is usually not damaged and it ripens normally. • The skin in these areas, however, may fail to colour as the fruit ripen. Occurrence • Damage is usually apparent after fruit have been transported to the market. • Mangoes become more susceptible to pressure damage as they ripen. • Hard green mangoes can be handled in bulk bins, but ripe fruit will suffer damage if stacked or packed more than three fruit high. Control • Choose packages with sufficient stacking strength for the handling system. • Extra strength is required when packages are held under refrigeration. • Ensure pallet loads are adequately secured. • For single-layer packs, use an internal package depth of 105 mm and leave a 3 mm gap between the top of the fruit and the lid. This avoids overpacking and allows for carton sag. For very large fruit (less than 10 fruit per carton), a deeper package may be required. • Include Vietnam examples Pressure damage of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 33 5.9 Impact damage Cause Dropping fruit or packages during handling and by shocks during transport. Symptoms • There are usually no external symptoms. • Green mature fruit crack internally when dropped, and the damage shows as firm, white strands or patches in the flesh when the fruit ripens. • When softening fruit are dropped, damage shows as a pale, firm area in the flesh between the seed and skin. • In ripe fruit, damage extends from the seed to the skin and the flesh is watery due to cell collapse. Occurrence • At any stage during harvesting, handling and transport, such as: o Fruit are dropped onto hard surfaces in the packhouse. o Packages are dropped during restacking at wholesale markets. o Packages fall off pallets during transport. Control • Avoid dropping fruit or packages. Hard fruit will be damaged if dropped more than 300 mm, while softening and ripe fruit will be damaged if dropped from lower heights. • Reduce manual handling by palletising loads. Choose packages which stack effectively on the pallet. Secure pallet loads properly during transport. • All handling operations should be thoroughly supervised. Impact damage of green mango fruit Impact damage of ripe mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 34 MINOR DEFECTS 5.10 Rhizopus rot Cause The fungus Rhizopus stolonifer. Symptoms Rhizopus rot begins as small, pale spots in the skin, spreading rapidly as a watery rot, within both skin and flesh. The rotted tissue is soft but generally not discoloured. Damaged tissue splits readily, and under humid conditions black spore bodies form on white, whiskery fungal threads. Occurrence Rhizopus rot causes sporadic, serious losses in fruit after harvest, when moisture has condensed on the skin. One or more fruit in a carton may be affected. The fungus is widely distributed in soil and in decaying organic matter where spores form under moist conditions. It can be present on wood wool used for fruit packing. The fungus also attacks many other fruit. Spores are dispersed in the air or in water and infect through small wounds. Spore germination occurs in condensate formed on the fruit after removal from coolrooms. Infection may also occur by direct contact with the growing fungus. The disease can spread from fruit to fruit after harvest. Control Remove from the packinghouse reject fruit which may harbour Rhizopus fungi. Clean the packing equipment and the shed using steam or high-pressure hot water, and then spray with a sanitising agent. If fruit is to be cooled, do not use wood wool as a packing material. No fungicides are approved for control of rhizopus rot in mangoes. Early Rhizopus rot of mango fruit Rhizopus rot of packed mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 35 5.11 Black mould Cause The fungus Aspergillus niger. Symptoms The disease black mould begins as a yellowing of the affected areas, spreading rapidly to produce soft, light-brown lesions. The centre of the lesion may become sunken, and black fruiting structures may appear. Symptoms can appear at the stem end, or on the sides of fruit. Occurrence Black mould occurs occasionally in consignments of early season and immature fruit. It is a minor disease affecting individual fruit in a carton. The fungus is widely distributed in soil or in decaying organic matter where spores form under moist conditions. The fungus is common on mouldy hay, grain and decaying foodstuffs. Spores are both air-borne and soil-borne. Infection occurs through natural openings in the skin, wounds, or areas of the skin where sapburn has occurred. Overheating during harvest and transport may favour development of symptoms. Control Do not harvest immature fruit. Follow procedures to minimise sapburn. Do not place fruit on the ground while bleeding sap from fruit. Observe the hygiene recommendations for the control of rhizopus rot. No fungicides are approved for control of black mould in mangoes. Black mould of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 36 5.12 Alternaria-rot Cause The fungus Alternaria altemata. Symptoms Small brown spots with diffuse margins expand into extensive dark-brown lesions at the stem end or on the sides of fruit affected by alternaria rot. A white to grey fungal growth may cover the surface of the lesions. Occurrence Alternaria rot is slow to develop and is likely to be serious only after prolonged storage, e.g. in the conditions recommended for controlled atmosphere storage (5% 02, 2% C02, 13°C) for 3 or more weeks, when fruit have ripened slowly and are reaching the end of their storage life. Usually, the disease is seen only when anthracnose and stem end rot, which would normally develop earlier in the ripening process, have been well controlled. This fungus has a wide host range, and causes leaf spots and fruit lesions on a number of crops (e.g. tomatoes). The spores are air-borne. Infection can occur before or after harvest, but symptoms do not begin to develop until the fruit have ripened. Control The pre-harvest and post-harvest fungicide sprays applied to control anthracnose will also reduce alternaria rot. The disease is unlikely to cause losses in fruit consumed within 2 weeks of harvest. Early alternaria rot of mango fruit Advanced alternaria rot of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 37 5.13 Stemphylium rot Cause The fungus Stemphylium vesicarium. Symptoms Dark-brown or black lesions develop on the sides of fruit affected by stemphylium rot. A dark-brown fungal growth may cover the surface of lesions. Symptoms can resemble those of alternaria rot. Occurrence Stemphylium rot may occur sporadically on fruit in controlled atmosphere storage (5% 02, 2% C02, 13°C) for 3 or more weeks, when fruit are reaching the end of their storage life. Usually, the disease is observed only when anthracnose and stem end rot have been well controlled. The fungus has a wide host range, and causes leaf spots and fruit lesions on a number of crops (e.g. tomatoes). The spores are air-borne. Infection occurs before harvest, but symptom development is delayed until the fruit have ripened. Control There are no fungicides approved for the control of stemphylium rot. Hot water and fungicide treatments (applied to control anthracnose before controlled atmosphere storage) will provide some control of stemphylium rot. The disease is unlikely to cause losses in fruit consumed within 2 weeks of harvest. Stemphlyium rot of mango CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 38 5.14 Sooty mould Cause Principally fungi in the order Dothideales and their anamorphs. Symptoms The large group of fungi that cause sooty mould form dense, dark mats of mycelium on living leaves, stems and fruit. This covering is superficial, and can be rubbed away to reveal undamaged tissue beneath. Occurrence While sooty moulds do not cause disease lesions, their dark growth makes the fruit surface unsightly, impairing market quality. The growth of these fungi is associated with infestation by scale insects. The fungi use nutrients on the plant surface and in the excreta of the insects. They are a more serious problem in humid growing conditions. Control Control scale insects. Remove mould by washing and brushing fruit after harvest. Sooty mould of mango CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 39 5.15 Grey mold Cause The fungus Botrytis cinerea. Symptoms A brown, firm decay develops from the stem end or from wounds, affecting a large portion of the fruit. The affected surface becomes covered with grey or brown fungal growth containing a mass of spores. Occurrence Grey mould is favoured by cool storage conditions (13-20°C) and occasionally affect fruit during controlled atmosphere storage (5% 02, 2% C02) at 13°C). Infection can occur via wounds, damage tissue, or the remains of flowers. Spores may carry over from other hosts (e.g. tomatoes, strawberries) previously stored in the coy tamer or coolroom. The spores are air-borne Control Maintain good hygiene in the packinghous4 and storage facilities. There are no fungicides approved for control of grey mould on mangoes. The hot water-fungicide dip applied for anthracnose will control strains of B. cinerea that are not resistant to benzimidazole fungicides. Grey mould of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 40 5.16 Blue mold Cause The fungus Penicillium expansurrz. Symptoms A soft, pale-brown decay of the skin and flesh develops at the stem end or in wounds, and may spread through the entire fruit. White, powdery spore masses, which become blue when mature, may develop on the stem end, at wound sites or in internal cavities at the stem end. Occurrence Blue mould is likely to occur only in the final weeks of long-term storage in controlled atmospheres (5% 02, 2% C02, 13°C) when anthracnose and stem end rot have been well controlled. The fungus is widely distributed in soil, in decaying organic matter and facilities used for storing citrus, where spores form under moist conditions. Spores are air-borne. The fungus is a weak pathogen and infection can occur only through wounds. Secondary spread may occur during storage. Control Observe hygiene recommendations for control of rhizopus rot. Avoid wounding fruit. Specific fungicides have not been approved for the control of blue mould of mangoes. Hot water and fungicide treatments applied for anthracnose control during controlled atmosphere storage will provide some control of blue mould. Blue mould on mango fruit. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 41 5.17 Mucor rot Cause The fungus Mucor circinelloides. Symptoms A pale, grey-brown, watery rot of the skin and flesh develops at the stem end as the fruit ripens, and may spread through the entire fruit. Occurrence Mucor rot is likely to be serious only in the final weeks of long-term storage in controlled atmospheres (5%02, 2% C02, 13°C). The fungus is widely distributed in soil and in decaying organic matter. Infection occurs via wounds or damaged tissue. Mucor rot is favoured by cool storage (13-20°C). Secondary spread may occur during storage. Control Follow hygiene recommendations for the control of rhizopus rot. Avoid wounding fruit. No fungicides are registered for control of this rot in mangoes. Do not place fruit on the ground while bleeding sap from them. Mucor rot of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 42 5.18 Cytosphaera rot Cause The fungus Cytosphaera mangzferae. Symptoms Symptoms of cytosphaera rot appear as the fruit ripens. A slow-spreading, sunken, tan lesion extends from the stem end. Fruiting bodies (pycnidia) may appear on the surface of established lesions, followed by a collar of white mycelium at the stem end. Occurrence Cytosphaera rot is rarely seen. Its presence may sometimes be masked by other more aggressive stem end rot fungi. Before the appearance of fruiting bodies the symptoms resemble lesions caused by Aspergillus niger. Control Measures recommended for stem end rot are effective. Cytosphaera rot of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 43 5.19 Lenticel spotting Cause Certain growing conditions and post-harvest handling procedures can damage the lenticels on the fruit surface. Symptoms The corky tissue in lenticels on the skin swell and becomes pronounced. The lenticel then darken making the fruit look spotty This becomes more obvious as the ripening fruit changes colour from green to yellow On ripe fruit, damage appears similar to chilling injury. Occurrence Lenticels are the breathing pores on the surface of mango fruit. Conditions that damage the lenticels promote lenticel spotting. For example, the disorder can occur when fruit have been held too long in washing water or in dips, particularly if detergents have been added. Fruit that have been on the tree during heavy rain sometimes show milder symptoms. Control Do not exceed a dipping time of 5 minutes in the recommended hot water/fungicide dip. Avoid immersing the fruit in water for more than 15 minutes during post-harvest handling. Lenticel spotting of mango fruit Lenticel spotting of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 44 5.20 Abnormal ripening Cause When mango fruit start to ripen, their respiration rate rises dramatically. If fruit respiration is disrupted, abnormal ripening may occur. Symptoms Fruit in poorly regulated controlled atmosphere (CA) storage may develop unpleasant odours and unpleasant flavours. Fruit coated with waxes or other materials may fail to ripen or may develop unpleasant odours and unpleasant flavours. Occurrence CA storage can extend storage life of mangoes by 1 or 2 weeks. However, precise control of the atmosphere is essential. Oxygen levels below 1 % and carbon dioxide above 12% will cause abnormal ripening. Coating the fruit skin with wax or other materials can restrict the movement of gases between the air and the fruit. Lack of oxygen, and build-up of carbon dioxide and other by-products of metabolism within the fruit can cause abnormal ripening or failure to ripen. Control In controlled atmosphere storage, precise control of the atmosphere is essential. The storage atmosphere should contain at least 1% oxygen and not more than 8% carbon dioxide. Do not coat the fruit with waxes or other materials that excessively restrict gas exchange. External appearance “skin is green and mango fruit soft eating ripe” Internal appearance “skin is green and mango fruit soft eating ripe” CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 45 5.21 Jelly seed Cause The cause of jelly seed is unknown. Symptoms Watery translucent tissue spreads out from around the seed. The disorder can also develop in the pulp away from the seed, and areas of affected flesh expand and coalesce around the seed. Affected flesh has a foul taste which has been described as “acidic and overripe” Occurrence The disorder is normally evident at harvest, but worsens as the fruit ripen. There are marked differences in cultivar susceptibility: Kensington Pride is not susceptible; Facel is slightly susceptible; Tommy Atkins is highly susceptible. Control The incidence of jelly seed may be reduced by harvesting fruit as early as practicable but not so early that they are immature. Internal jelly seed symptom of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 46 5.22 Stem end cavity Cause The cause of this disorder has not yet been clearly established. Symptoms Internal: affected fruit have a distinct cavity in the flesh at the stem end between the seed and the stem attachment. The flesh surrounding the cavity may show a grey-brown discolouration and have an abnormal, open texture. Irregular tissue strands may be found within the cavity. In ripe fruit, soft, sour- smelling flesh may extend from the cavity down and around the seed. These symptoms may also be associated with internal cracks surrounded by white tissue. External: visible external symptoms appear only in severe cases when the cavity reaches to the under-surface of the skin. A grey-brown sunken area then develops in the skin of the fruit near the stem attachment. If no visible external symptoms are apparent, the disorder may be detected in ripening or ripe fruit by pressing the tissue next to the stem with the thumb. If the tissue gives easily as pressure is applied, then the stem end cavity is usually present. Fruit with the disorder may fall before harvest. Occurrence Stem end cavity affects Kensington mangoes in particular, as well as some other cultivars. The disorder is more prevalent in fruit harvested late in the season. Fruit maturing late in the season can be more severely affected. Mature, hard, green fruit have a low incidence of stem end cavity, although fruit that do not release sap when the stem is removed after harvest are suspect. T he disorder is rarely seen in small fruit, i.e. smaller than 220 g or count 25. Control Harvest fruit at the green mature stage before they have started to ripen on the tree. If ripening fruit are harvested, check their stem ends for discolouration and a spongy feel before packing. CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 47 5.23 Internal breakdown Cause The cause of this disorder has not been clearly established. Symptoms The disorder typically occurs at the stem end. A watery patch develops in the flesh, often with discoloured strands. In severe cases, the flesh collapses, leaving a cavity where only the fibres remain. External symptoms are a dark-green patch on the skin and premature softening of the cheek. Mild cases of the disorder may show no external symptoms. Occurrence The disorder has occurred in recent years in new mango varieties Keitt and Delta R2E2 in districts throughout Queensland. The disorder has been observed in the following: • fruit harvested late in the season-in most fruit showing symptoms, the seed had begun to germinate • large fruit from trees bearing a light crop • fruit from young trees that had received heavy applications of nitrogen fertiliser • fruit from orchards with high vigour, and growing on soil low in calcium and boron. Control Avoid excessive use of nitrogen, and ensure calcium and boron levels are adequate. Harvest the fruit before they become over-mature. Internal breakdown of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 48 5.24 Chilling injury Cause Storage of mangoes at temperatures below their chilling threshold (10-13°C) leads to tissue damage. The lower the temperature, and the longer the storage period, the more severe are the symptoms. Symptoms Mature green fruit: the skin shows blotchy areas of dull, dark grey discolouration, particularly on areas of blush or sunburn. Surface pitting may occur. Fruit ripen unevenly or may fail to ripen. The skin colour is poor, as are flavour and aroma development. Ripe fruit: ripe fruit injured by chilling show dark spotting of the lenticels and have dull skin. Chilled fruit may have an acid or tart taste. Infection by disease organisms is enhanced by chilling damage. Occurrence Chilling symptoms may not be evident during cool storage, but may become obvious during handling after storage. Ripe fruit are less susceptible to chilling injury than green mature fruit. Control Store most cultivars from most mango growing areas at 10-13°C. In retail outlets where a 10-13°C coldroom is not available, mangoes may be stored for no longer than 3 days at temperatures between 5°C and 10°C. Do not store at temperatures less than 5°C. To ripen fruit to an acceptable colour and flavour, hold them at 20-22°C. Chilling symptoms of ripe mango fruit Chilling symptoms of green mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 49 5.25 Heat injury Cause Excessively high temperatures can injure fruit during hot water/fungicide treatments for disease control and heat treatments (water and air) for insect disinfestation. Symptoms Symptoms are not immediately apparent, and show up only after the fruit have cooled. Damage to the skin shows as a grey or brown irregular scald, and the flesh is no longer firm. In severe cases, the skin can be completely scalded and the fruit fails to ripen normally. Internal damage shows as white spots in the flesh, or a hard, white layer of varying thickness directly under the skin. Cavities can also develop in the flesh and the surface can appear sunken. Occurrence The extent of injury depends on the length of time fruit are exposed to high temperature, as well as on the temperature. Scald develops if either the temperature is too high or the period of exposure is too long. Treatment times can be exceeded if fruit move too slowly through dipping tanks. Fruit can also be scalded if the dip solution is poorly circulated, allowing hot spots to develop in the tank. If fruit are packed hot, the areas where they touch each other can develop scald. Similarly, fruit put on racks to dry after dipping may develop scald where they touch. Fruit are more prone to damage just after harvest. Susceptibility varies between fruit from different districts, and increases greatly during cool, wet weather. Ripening fruit appear more prone to damage than green mature fruit. Control Make sure that equipment used for heat treatment (water or air) is calibrated and the treatment conditions have been correctly set. Allow a minimum of 4 hours (preferably 8 hours) between harvest and treatment. Do not cool-store fruit before treatment. The maximum temperature and time for disease control in Kensington mangoes is 52°C for 5 minutes. Do not exceed either duration of dipping or dip temperature. During cool, wet weather, reduce the temperature to 48-50°C. Agitation of the dip helps distribute heat and prevents `hot spots' in the tank. Using a powerful recirculating pump is preferable to stirring or paddling. Allow fruit to cool freely after treatment and before packing. External heat injury symptom on mango fruit Internal heat injury symptom on mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 50 5.26 Failure of skin to yellow Cause The skin fails to yellow when fruit ripen at temperatures above 25°C. Symptoms Although the mango flesh ripens normally, the skin remains green with blotches of yellow. Occurrence Ripening begins after a mature green mango is harvested, and the fruit gradually becomes edible. The skin colour of varieties such as Kensington changes from green to yellow. The texture of the flesh changes from firm and crisp to soft. The characteristic mango aroma and flavour also develop. However, at temperatures above 25°C, the skin colour does not fully develop, even though the flesh ripens normally. Control Ripening the fruit at a temperature of 2022°C will result in acceptable flavour and skin colour. External appearance “skin is green and mango fruit soft eating ripe” CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 51 5.27 Fumigant injury Cause The fumigants ethylene dibromide (EDB) and methyl bromide (MB), used for insect disinfestation, may injure mango fruit when applied incorrectly. Symptoms Fumigants can cause dark discolouration of the skin of affected fruit. Occurrence EDB and MB are being phased out as disinfestation treatments. However, fruit damage will still be a concern until alternatives are found. Control Do not exceed the recommended concentration, time or temperature for fumigant application. Insect injury Methyl bromide injury of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 52 5.28 Fruit fly damage Cause Fruit flies of the genus Bactrocera, especially B. tryoni, the Queensland fruit fly, and Ceratitis capitata, Mediterranean fruit fly. Symptoms The fruit fly leaves an inconspicuous oviposition site (`sting') on the skin of the fruit when laying eggs. Small white larvae emerge from the eggs and consume the fruit flesh. Occurrence In areas where fruit flies are endemic, they are an occasional problem in backyard mango trees. Fruit fly is mostly well controlled in commercial orchards by pre-harvest spraying. Mature green fruit are generally not susceptible. Control Pre-harvest control includes population management (e.g. release of sterile male fruit flies) and/or insecticide application during the period when fruit are susceptible. Populations can be monitored by trapping. Harvest mature green fruit. Post-harvest disinfestation is by fumigation. Insecticides and heat treatment are possible alternatives. QLD Fruit Fly Qld fruit fly damage of mango fruit CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 Postharvest Physiology Training Manual Page 53 5.29 Mango seed weevil damage Cause The mango seed weevil Sternochetus mangiferae. Symptoms There are no apparent external symptoms. The larvae of the seed weevil are found in the seed of the mango fruit. Occurrence In regions where this pest is endemic, the incidence of infestation can be high. Control Control of the pest in the orchard by using recommended pest management techniques is important. Because of the inaccessibility of the weevil in the seed, post-harvest control is difficult. Currently, there are no effective post-harvest treatments for the control of mango seed weevil. Mango seed weevil