Báo cáo Mango postharvest manual
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
Development
&
Rural
i
© 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).
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CARD VIETNAM 2006
MANGO POSTHARVEST TRAINING MANUAL
Introduction................................................................................................1
Key production practices affecting postharvest quality.............................2
Know your mango (postharvest biology)...................................................3
Fruit ripening and quality loss ..........................................................3
1
2
3
3.1
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
Take care of your mango (postharvest technology)..................................9
4
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
4.5
How to transport your mango to the retailer ..................................21
Know your market (customer requirements)..................................21
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5
Causes and solutions of the main postharvest defects of your mango ..23
Anthracnose...................................................................................23
5.1
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
Bacterial black spot........................................................................27
Sapburn..........................................................................................28
Skin browning.................................................................................29
Sunburn..........................................................................................30
Abrasion damage...........................................................................31
Pressure damage...........................................................................32
Impact damage ..............................................................................33
Rhizopus rot...................................................................................34
Black mould....................................................................................35
Alternaria-rot...................................................................................36
Stemphylium rot .............................................................................37
Sooty mould ...................................................................................38
Grey mold.......................................................................................39
Blue mold .......................................................................................40
Mucor rot .......................................................................................41
Cytosphaera rot..............................................................................42
Lenticel spotting .............................................................................43
Abnormal ripening..........................................................................44
Jelly seed .......................................................................................45
Stem end cavity..............................................................................46
Internal breakdown.........................................................................47
Chilling injury..................................................................................48
Heat injury ......................................................................................49
Failure of skin to yellow..................................................................50
Fumigant injury...............................................................................51
Fruit fly damage .............................................................................52
Mango seed weevil damage ..........................................................53
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
5.20
5.21
5.22
5.23
5.24
5.25
5.26
5.27
5.28
5.29
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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.
Fruit development
Growth
maturation
mature
ripening
senescence
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.
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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.
Climacteric
(ripening fruit)
Respiration rate
Eg. Mango
CO2 output
Heat output
O2
Consumption
Non-climacteric
Eg. Orange
Time
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).
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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.
Eating ripe
Skin colour
Sugars
Firmness
Acidity
Time
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.
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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
Sapburn and skin browning
• 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.
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).
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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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Parameter
Immature
longer
Mature
shorter
uniform, bright
lower
Green life
Skin/flesh colour
Shrivelling
patchy, pale
higher
Aroma
faint
full
Internal disorders
Chilling injury
lower
higher
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.
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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
o
Harvest the fruit with at least 2 cm long stems.
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
o
o
Caution: the sap can burn the skin and sappy hands will cause skin
browning on the fruit. Wash hands regularly.
Fruit can then be wrapped individually in paper and sent to
cooperative, collector or wholesaler.
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
o
Dip or spray fruit with a solution of detergent before destemming by
hand.
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
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.
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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
Acceptable
Acceptable
Acceptable
Acceptable
Class 1 A
Class 1 B
Class 2 A
Class 2 B
> 420
No
> 420
Yes (minor)
No
300 – 420
300 – 420
Yes (minor)
Too immature or
too mature
Class 3
< 300
Yes (major)
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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
To ripen (18-22°C)
To store (10-13°C)
ꢀ Hold fruit at 18-22°C and 80- ꢀ Store fruit at 10-13°C and 80-
90% relative humidity
90% relative humidity for
maximum of 7 days
a
ꢀ Forced air cool or air stack to
maintain temperature
ꢀ Pre-cool with forced-air cooling
to ensure uniform fruit
temperatures through pallet
ꢀ Vent room regularly to prevent
build-up of carbon dioxide
ꢀ Vent room regularly to prevent
ꢀ Gas with ethylene for 1-3 days
for faster and more even
ripening
build-up of carbon dioxide
ꢀ Check fruit inside pallet daily for
any sign of softening
ꢀ Fruit will take from 6-9 days to
reach eating ripe from start of ꢀ Raise temperature to 18-22°C
ethylene treatment
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- ꢀ Do not store ripening fruit at low
90% relative humidity
temperatures as skin yellowing
and flavour is reduced
ꢀ 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
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- ꢀ Store near-ripe to ripe fruit at
90% relative humidity 10-13°C to slow further ripening
ꢀ Forced air cool or air stack to ꢀ Check ripeness daily to avoid
maintain temperature fruit being too ripe for sale
ꢀ Vent room regularly to prevent ꢀ The risk of over-ripeness
build-up of carbon dioxide
increases with storage times
above 4 days
ꢀ Check ripeness daily to avoid
fruit being too ripe for sale
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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 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).
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.
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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
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
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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.
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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.
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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
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