Post-harvest handling

An organic mango orchard may produce its first marketable harvest after 4 to 5 years, depending on the variety and location. The maturity of the fruit is determined by the changes in colour, fullness of fruit and hardened endocarp (fibrous coating of the seed). The fruit is ready for harvest when the colour changes from green/purple to red/yellow/orange and the inside flesh becomes yellow. Since all the fruit do not ripen at the same time, it is necessary to continuously check the change in fruit colour before harvest.

The mango consumed as fresh fruit is harvested by hand using shears or big scissors. If trees are too high, ladders may be used or a long pole with a cloth bag attached at the tip (that can hold two or three fruit). For fresh fruit sales, the fruit should be put in a crate or a basket lined with some leaves. Fruit for processing can be carried in bags, but avoid putting too much fruit in the bags to prevent damage. Injured or damaged fruit should be separated from healthy ones to avoid possible infection with fungi.

Fresh fruit

Harvested fruit should be washed immediately—within12 hours—to remove any sap. Generally, if the mangoes are to be sold as fresh fruit, they must be dipped in a hot water bath (55° C, 3 to 5 minutes) to clean them and then slowly cooled to room temperatures. Afterwards, the mangoes should be left to drip dry, sorted and packed in carton boxes or cushioned wooden boxes ready for delivery.

Dried mangoes

In order to avoid wastage, especially during the peak season, farmers may dry the mangoes so that they can safely store them for a longer time. If there is a market opportunity, then they will earn extra income from the dried mangoes.

Drying is based on the fact that microorganisms will not grow when mangoes are dried to a certain moisture level. However, the quality of the dried mangoes will depend on how the process of drying is done. Many technologies for fruit drying are available, depending on the location, ranging from simple plastic tunnel driers to stainless steel cabinet driers. The farmers should contact the local extension officer for guidance. The process of mango drying is, however, done as follows:

Sorting - After harvesting, the fruit should be sorted to obtain only the fresh, fully ripened and unfermented fruit for drying.

Washing and peeling - Mangoes should be washed in clean water to remove any dirt and infections on the fruit skin.

Slicing and drying - The fruit are cut into similar sized pieces and laid out to dry in thin layers on racks, into the dryers at temperatures between 50 and 60° C.

Sorting and packaging - Before they are packed the fruit are sorted again to remove skin remnants and discoloured fruit.

Discussion on postharvest handling

Inquire among the farmers how they commonly utilize mangoes. Do they sell to the fresh fruit market, dry the fruit or produce pulp or juice? Discuss for all uses what the best harvest time is and how postharvest handling is best managed.

Post-harvest handling of mangoes for fresh fruit market

Mechanical injury is a very common after-harvest source of fruit damage. Poor handling of fruit after harvesting, during sorting and packing, as well as transportation can lead to mechanical injury. Good post-harvest management of mangoes will minimize fruit injuries and contamination, prolong storage life, and ensure freshness and an attractive appearance. It is a requirement that organic fruits must be kept separate from any conventional fruits at the field, farm and subsequent levels of the postharvest chain.

Visit to mango handling facility

Where possible, organize a learning visit to a fresh mango handling facility for participants to observe the fresh mango handling in practice. Share and discuss key
lessons learnt.

Sorting

Immediately after harvesting, while still in the field but under a shade, all immature, overripe, damaged and diseased fruits should be sorted-out and properly disposed.

Washing

Normally, mangoes do not need any treatment for marketing in local markets, except simple washing with water to remove the latex and dust immediately after harvest before the latex dries on the fruit; if the latex has dried off while still on the fruits it becomes practically impossible to remove it afterwards.

To increase shelf-life, however, freshly harvested fruits may be dipped in a hot water bath (55 °C for 3 to a maximum of 5 minutes), to minimize fruit fly damage, anthracnose, and stem-end rot infections, and then slowly cooled to room temperature. Afterwards, the mangoes should be left to drip dry. Care should be taken with the hot water treatment: prolonged dipping in hot water can result in fruit skin damages which may cause more severe postharvest losses. The water used in all processes, including in the packinghouses, should be clean and portable (safe to drink). Equally, the fruit washing facilities and tools should be regularly inspected and cleaned of any debris, dirt or other foreign objects. Regular cleaning reduces the built up of diseases along the handling lines. Only permissible detergents (for organic) should be used to clean and / or sanitize the surfaces, containers and tools. Reference to the regulations of the destination market (domestic and export) ought to be made.

Other treatments

In conventional production, mangoes are commonly dipped in hot water, containing fungicide for the control of diseases, but this is not permitted in organic production. However, naturally derived fruit coating materials, such as pyrethrum and mineral oil, are allowed (refer to Annex II of the EU Reg 889-2008). Equally, the use of chlorinated water is allowed to the extent that at the end of the washing line the residual chlorine content equals that of drinking water (World Health Organization (WHO) recommendations of 10 ppm).

Curing

Mangoes that are planned for the domestic market or processing are usually spread in a cool place, either on the floor in the orchard’s yard, having the cushion materials like leaves or clean washable sheets or on a raised platform for nearly 24 hours, avoiding direct contact of fruits with the soil. This allows the skin to lose some water, becoming harder and less succulent hence less susceptible to damage and to fungal growth. For the export market, proper curing of washed mangoes in crates on a raised platform for 4 to 5 hours is necessary to ensure storage for long periods.

Delivery to packhouse

The fruits should be packed carefully into padded field crates, well-ventilated plastic containers, or picking bags, avoiding overfilling before delivery to the packing house or shed where final packing is done according to the requirements of the target market.

Grading

Mango fruits can be graded according to their size, weight, colour and maturity. It has been observed that bigger size fruits take 2–4 days more time in ripening than smaller ones and may not achieve uniform ripening. Therefore, grading according to size before packaging of the fruits plays an important role to obtain fruits with a uniform ripening period. During grading, any remaining immature, overripe, damaged and diseased fruits should be sorted-out.

According to Codex standards, good quality mango fruits should be; (i) whole, firm, sound and fresh in appearance; (ii) clean, practically free of any visible foreign matter; (iii) free of black necrotic stains or trails; (iv) free of marked bruising; (v) free of abnormal external moisture, excluding condensation following removal from cold storage; (vi) free from damage caused by low / or high temperature; (vii) free of any foreign smell and / or taste; (viii) Free of damage caused by pests; (ix) Sufficiently developed and display satisfactory ripeness; (x) When a peduncle is present, it shall not be any longer than 1.0 cm. (xi) comply with the residue levels of heavy metals, pesticides and other food safety parameters as laid down by the Codex Alimentarius Commission.

Cooling

After curing, fruit for export should be cooled to 12–13 °C, in 85 to 90 per cent relative humidity, as soon as possible after curing until shipping. Cooling removes field heat from harvested fruits, which helps in stabilizing the metabolic process, suppresses enzymatic degradation, slows or inhibits water loss (wilting), slows or inhibits the growth of decay-causing microorganisms (moulds and bacteria) and reduces production of ethylene (a ripening agent).

Different cooling methods are used prior to shipping. Packed and palletized mangoes should be cooled as quickly as possible to their optimum shipping and storage temperature (12 °C [54 °F] for mature green mangoes). Temperatures below 12 °C expose the mangoes to chilling injury.

Room cooling. Rapid cooling requires good contact between the refrigerated air in the postharvest environment and the product in the package. Heat transfer in room cooling is achieved by cold, refrigerated air coming into contact with exposed pallet surfaces, with the heat from the interior of the pallet slowly transferred by conduction to the surface. Thus, room cooling is a relatively slow cooling method that typically requires 24 to 48 hours for palletized mangoes.

Forced-air cooling. It is recommended that mangos be forced-air cooled in order to remove heat from the fruit as rapidly as possible. Forced air (or ‘pressure’) cooling improves heat transfer compared to room cooling by creating a pressure differential from one side of a pallet to the opposite side that pulls the cold, refrigerated air through the ventilation holes in the cartons, directly past the fruit within the pallet. Properly designed forced-air cooling systems are capable of reducing mango flesh temperatures from an initial range of 30 to 40 °C (86 to 104 °F) down to around 12 to 15 °C (54 to 59 °F) within 2 to 4 hours.

Hydrocooling. Hydrocooling involves immersing or drenching the fruits in cold water to remove heat. Although hydrocooling cools faster than forced-air cooling, it is not typically used to cool mangoes prior to shipping due to logistical and sanitization management challenges. Hydrocooling presents several logistical challenges. Water sanitation, e.g with chlorine, is critical to avoid transfer of decay pathogens between fruit. Hydrocooling must either be applied before packing, in which case the fruit must be thoroughly dried prior to packing, or the fruit to be hydrocooled must be packed in water-resistant shipping cartons.

Ripening

Mango fruits may be picked early in the season (premature stage) to capture early market and to allow long transportation, e.g. if by sea. Mangoes which are airfreighted can be picked and transported at a riper stage compared to those exported by sea. Mangoes harvested before ripening are normally subjected to artificial ripening. Under conventional production, many ripening aids are used, for example, ethylene, and acetylene gas or calcium carbide treatments. The spray of calcium in conventional mangoes has been found useful in delaying ripening of mangoes hence extend the shelf life. In organic mango production, however, the use of ripening treatments is restricted, rather fruits are encouraged to be picked at near or peak maturity to allow natural ripening especially for the domestic fresh mango market or processing purposes. Since mangoes intended for export are picked before ripening, artificial ripening with ethylene (ethylene C2H4) is allowed according to the EU Reg. It is important to note that acetylene (ethylene C2H2) is not listed in Annex ll of the EU Regulation and therefore prohibited.

Ripening Protocol:

Before ripening begins, the fruit pulp temperatures should be raised to 68 to 72 °F (20 to 22 °C). Once the fruit pulp temperature stabilizes, apply 100 ppm ethylene for a minimum of 12 hours. Actual time of exposure to ethylene is determined by the maturity of the fruit; a slight change in fruit color indicates that the mangoes are producing ethylene and the external ethylene source is no longer needed.

Humidity is very important and it should be maintained at 90–95 %.

Carbon dioxide will build up during ripening. If no automatic ventilation system is in place, then be sure to vent the room approximately every 12 hours by opening the doors for 20 minutes even while applying ethylene. The actual CO2 level must be kept below 1 % for proper ripening. After ethylene application, keep pulp temperature at 65 to 72 °F (18 to 22 °C) until desired level of ripeness is attained (typically 5–9 days). Then store ripened mangoes at 50 to 55 °F (10 to 13 °C) in a high humidity environment and ship to final destination soon.

Packaging

Packaging is an important component of the postharvest operations for mango. Mango fruits are delicate, especially when they are ripe. They are prone to different types of damage such as compression, skin bruising, and should therefore, be well packaged for proper transportation to the market. Mangoes-for-export are normally packaged in single layers (to avoid compression) in rigid packages made of safe and good quality cardboard material. Exporters have different types of packages – the sizes of packages depend on market / customer specifications. For the local markets, the fruits can be arranged in larger boxes or plastic crates, depending on the market to be supplied.

Mango handling for fresh fruit market

Select two participants – one to describe how he/she handle mangoes for local fresh market, and another for the fresh export market. Sketch the process on the flipchart or blackboard. In a brainstorming session, identify risks to mango quality at every stage and discuss how they can be mitigated. Conclude by agreeing on a preferred handling process agreed upon by all participants.

For large scale operations – sanitation of workers, packinghouse facilities and equipment is important

Note

Check the following publication:

http://ucce.ucdavis.edu/files/datastore/234-1904.pdf for some details.

Packinghouses should conduct regular worker training at the beginning of each harvest season. Workers inspecting and handling mangoes must be trained and must adhere to proper hand-washing and sanitizing procedures. A program of regular training (and retraining, as needed), along with monitoring by supervisors to ensure compliance, is an important management practice to ensure fruit quality and safety. Workers should understand how careless handling of mangoes can cause stress and injuries that can reduce fruit quality during marketing. Workers should also understand how personal and facility cleanliness reduce the risk of fruit contamination, which can have devastating consequences for the business and their own jobs.

Cleaning and sanitizing packing line equipment is critical. Just one source of pathogen introduction, at any point, can potentially inoculate all fruit that passes through the line. Cleaning means physically removing debris, biofilm buildup, and any other residuals on the line. This is done with detergent and physical labor (such as scrubbing or a pressure washer). Sanitation involves using sanitizers like chlorine or quaternary ammonia to kill microbes on clean surfaces. Sanitation is not effective until after a surface has first been cleaned. Regular cleaning and sanitation greatly reduces opportunities for pathogen buildup and inoculation to occur. Many steps can easily be overlooked during cleaning. Here are some key points to remember:

Remove debris accumulation from all surfaces,

Clean all surfaces that fruit or employees may contact, including benches, table tops, drains, walls, cooler coils, ceilings, etc., as appropriate,

Clean using a top-to-bottom method to avoid re-soiling already clean surfaces,

Never put fruit that have fallen from the handling line back into circulation,

Have waste bins available for employee use; regularly empty and clean them.

Post-harvest handling of mangoes for dried fruit market

In most cases, there are harvested fruits which do not meet the fresh mango market requirements due to size or minor bruises, but still useful for processing. To avoid wastage, farmers may dry the mangoes so that they can sell them on the dried fruit market. Fruit drying is a process whereby mangoes are dried to a certain moisture level where they can be stored for a longer time. However, the quality of the dried mangoes will depend on how the process of drying is done. Many technologies for fruit drying are available, ranging from simple plastic tunnel driers to stainless steel cabinet driers.

Mango for drying should be harvested at a more ripe stage than mango for fresh fruit market, that is, when the fruit has started showing visible signs of ripening (¼ to ½ ripe). Mangoes harvested before this stage will not ripen well and the dried product will be whitish, acidic and slightly sweetened. Very ripe mangoes are also very susceptible to damage and fermentation during transport and storage, leading to off-flavours and darkening in colour during drying. The Kent and Amélie varieties are particularly sensitive to damage during transport and storage.

At the processing unit, the mango drying process is done as follows:

Reception and storage

Upon receipt, a first sorting is carried out to separate the mangoes according to the variety and the degree of maturity. Afterwards, depending on their degree of maturity, the mangoes are left, often in crates, but covered with for example a black plastic, to ripen further.

Sorting and washing

Depending on the harvesting stage, mangoes commonly ripen at different rates. Therefore daily sorting of mangoes in stock is done to select sufficiently ripe mangoes for processing – only the fresh, fully ripened and unfermented fruit is good for drying in order to produce the aroma, colour and sweetness desired by the market. Overripe and / or rotten mangoes do not dry well.

The ready-to-dry mangoes are then washed in clean water to remove any dirt and contaminations on the fruit skin. Equally the work space, knives, tables, containers and staff handling the process should be clean, as per the packhouse requirements for fresh mangoes indicated in the slide.

Peeling and slicing

The skin of the fruit is removed manually with a stainless steel knife on tables with holes to directly remove the waste. The peeled fruits are then cut into similar sized pieces and laid out to dry in thin layers on drying racks. The slicing of mangoes is done manually according to the customer’s specifications – in whole patties, slices or pieces. The slices or pieces are made by different people and may not always be homogeneous. There is no other pre-treatment accepted in organic production.

Drying

The racks loaded with fruit slices or pieces are laid into the dryers at temperatures between 50 and 60 °C.

Sorting and packaging

The dried fruit (12–15 % moisture content) is hand-removed from the racks and sorted again to remove skin remnants and discoloured fruit, before they are packed. Well dried fruit should have good colour (yellow to orange depending on the variety), strong flavour and low stickiness. Poorly dried fruit will have irregular colour with brown / black patches, lack of taste, and too dry or hard. Dried mangoes are then packed in bigger bulk packs (1 to 2 kg) and kept in a dry cool store at room temperature, awaiting final pacakging according to customer specifications. Generally, mango fruit drying specifications and packaging will depend on the specific target market.

Mango handling for drying

Select a participant (involved in fruit drying) to describe how he / she handles mangoes for drying. Sketch the process on the flipchart or blackboard. In a brainstorming session, identify risks to mango quality at every stage and discuss how they can be mitigated. Conclude by agreeing on
a preferred handling process agreed upon by all participants.

Post-harvest field management

Immediately after the harvesting season is completed, the mango orchard needs proper cleaning in preparation for the next season. This is done by;

Pruning of old, weak, shading or broken branches and twigs,

Removing all fallen fruits from the ground and taking them to the composting site.

Trimming or slashing of the grass around the trees, which provide good habitats for various pests, including the fruit fly.