Báo cáo nghiên cứu khoa học " Mango Postharvest Manual - Version 1" pptx

CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007 1 Introduction The successful marketing of fresh fruit requires careful attention to

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Mango Postharvest Manual

CARD Project 050/04VIE

Version 1

A PRIL 2007

By Dr Roberto Marques, Dr Peter Hofman,

Robert Nissen QDPI&F

Ministry of Agriculture & Rural

Development

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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)

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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

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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

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CARD Project 05004 VIE Improvement of Vietnamese Postharvest Practices and Supply Chains - July 2007

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

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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

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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

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• 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)

Eg Mango

Non-climacteric

Eg Orange

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• 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

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• 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

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• 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

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• 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)

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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

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Skin/flesh colour patchy, pale uniform, bright

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

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• 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

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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

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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

4.2.1 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)

Figure 7 Basket of mango fruit before and after grading

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• 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

too mature

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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

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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

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• 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

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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

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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

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Hard green fruit

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 90% relative humidity for a maximum of 7 days

80- 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

Ripening fruit (up to 40% yellow)

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%

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

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• 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 Ethrel®), 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)

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

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• 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

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5 Causes and solutions of the main postharvest defects of your mango

• 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

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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 (Spinflo®)

2 Non-recirculated flood spray with prochloraz (Sportak®)

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

Tiêu đề	Mango Postharvest Manual
Tác giả	Dr. Roberto Marques, Dr. Peter Hofman, Robert Nissen
Trường học	Department of Primary Industries and Fisheries
Chuyên ngành	Agriculture
Thể loại	Báo cáo nghiên cứu khoa học
Năm xuất bản	2007
Thành phố	Queensland

Định dạng
Số trang	57
Dung lượng	3,42 MB