A Guide to Post-Harvest Treatment and Handling of Fruits and Vegetables
The post-harvest treatment and handling of fruits and vegetables is a critical step in ensuring that the produce arrives at its destination in the best possible condition.
There are many things to consider when treating and handling fresh produce, from the temperature to the packaging.In this blog post, we will take a look at what goes into post-harvest treatment and handling of fruits and vegetables, and how you can ensure that your produce arrives at its destination in perfect condition!
What is post-harvest treatment and handling of fruits and vegetables?
After harvest, fresh produce needs to be handled with care to maintain freshness, nutrient content, taste and quality. Fruit and vegetables are fragile and perishable, so poor storage post-harvest can result in losses.
The field of post-harvest practices addresses issues of handling, sorting, grading, washing, storing, transportation, and temperature control for crops after harvest.Post-harvest treatment is important in preventing fresh produce losses, maintaining quality, preserving nutrient content, and earning higher market prices.These treatment areas can be grouped into 3 main categories:
Field Operations
Packinghouse Operations
Special Treatments
Field Operations
Harvesting
Most immature fruit vegetables are graded on the basis of size and colour. Immature soft-rind squashes, for example, may be harvested at several sizes or stages of development, depending upon market needs.Fruit that is too developed is of interior internal quality and shows undesirable colour change after harvest. This also applies to other immature fruit vegetables such as cucumbers.
The harvest index for mature fruit vegetables depends on several characteristics, and proper harvest maturity is the key to adequate shelf life and good quality of the ripened fruit.Most fruit vegetables are harvested by hand. Some harvest aids may be used, including pickup machines and conveyors.Immature fruit vegetables generally have very tender skins that are easily damaged in harvest and handling. Special care must be taken in all handling operations to prevent product damage and subsequent decay.
Many of the mature fruit vegetables are hauled to packinghouses, storage, or loading facilities in bulk bins (hard rind squashes, capsicums, pink tomatoes), gondolas (mature green tomatoes and peppers), or bulk field trailers or trucks (muskmelons, hard rind squashes).
Harvesting at night, when products are the coolest, is common for sweet corn and is gaining in use for rock melon. Products reach their lowest temperature near daybreak. Night harvest may reduce the time and costs of cooling products, may result in better and more uniform cooling, and helps maintain product quality.
Field packing
The trend is increasing toward field packing of fruit vegetables. Grading, sorting, sizing, packing, and palletising are carried out in the field. The products are then transported to a central cooling facility.
Mobile packing facilities are commonly towed through the fields for rock melon, honeydew melon, eggplant, cucumber, summer squashes, and capsicums. Field-pack operations entail much less handling of products than in packinghouses.
This reduces product damage and, therefore, increases packout yield of products. In melons, for example, field packing means less rolling, dumping, and dropping and thus helps reduce the "shaker" problem, in which the seed cavity loosens from the pericarp wall.
It also reduces scuffing of the net which reduces subsequent water loss. Handling costs are also reduced in field pack operations. One difficulty with field packing, however, is the need for increased supervision to maintain consistent quality in the packed product.
Field packing is not used for commodities that require a classification for both colour and size, such as tomatoes.
Packinghouse Operations
Receiving
When handling loaded field vehicles transporting produce, it is advisable to park them in shaded areas to prevent product warming and sunburning. The unloading process varies based on the type of produce. Some items, like soft-rind squashes, eggplant, certain muskmelons, cucumber, and watermelon, may be unloaded by hand.
Dry-dumping methods involve unloading onto sloping, padded ramps for rock melons, honeydew melons, capsicum, or onto moving conveyor belts for tomatoes. Wet-dumping is employed for certain produce, such as honeydew melon, tomatoes, and peppers, where items are placed into tanks of moving water to minimize physical injury during the unloading process.
It is important to note that dry-dumping operations can cause significant mechanical damage, leading to issues like bruising, scratching, abrading, and splitting. For tomatoes undergoing wet-dumping, the water temperature in the tanks should be slightly warmer than the product temperature to prevent the absorption of water and the growth of decay-causing organisms within the fruits.
Maintaining the chlorination of the dump tank water is crucial for sanitation. Some operations utilize two tanks with clean water separation via a spray to enhance overall handling sanitation.
Preliminary operations
Presizing
For many commodities, fruit below a certain size is eliminated either manually or mechanically by a presizing belt or chain. Undersized fruit is diverted to a culling conveyor or used for processing.
Sorting or selection
The sorting process eliminates cull, overripe, misshapen, and otherwise defective fruit and separates products by colour, maturity, and ripeness classes (e.g. tomato and muskmelons).
Grading
Fruit are sorted by quality and placed in separate grades. There are different international grading standards for many commodities, but these are not always used.
Waxing
Food grade waxes are commonly applied to cucumber, eggplant, sweet peppers, rock melon, and tomato, and occasionally to some summer squashes.The purpose is to replace some of the natural waxes removed in the washing and cleaning operations, to reduce water loss, and improve appearance.Waxing may be done before or after sizing, and fungicides may be added to the wax. Application of wax and post-harvest fungicides must be indicated on each shipping container.Waxing and fungicides are used only in the packinghouse handling of fruit vegetables.
Sizing
After sorting for defects and colour differences, the fruit vegetables are segregated into several size categories. Sizing is done manually for many of the fruit vegetables, including the legumes, soft and hard rind squashes, cucumber, eggplant, capsicum, okra, pumpkin, muskmelons, and watermelon.Rock melons may be sized by volumetric weights, or diverging roll sizers, capsicums are sized commonly by diverging bar sizers, and tomatoes are sized by diameter with belt sizers or by weight.
Packing
The packing process places the sorted and graded product into containers of specified sizes (e.g. cartons, flats, barrels).For some crops, specialised mechanical harvesters are available that also do preliminary operations such as presizing, sorting, and packing.These packers often have higher initial investment costs than conventional packing lines, but they have lower operating costs and usually pay for themselves within a few years.All other fruit-type vegetables are place-packed into shipping containers by count, bulk bins (hard rind squashes. pumpkin, muskmelons, and watermelon), or bulk trucks (watermelon). Fruit-type vegetables that are place-packed are often sized during the same operation.
Palletising
Packed shipping containers of most fruit vegetables in large-volume operations are palletised for shipment. This is common practice with rock melon, muskmelons, capsicums, and tomatoes.Except for sweet corn, immature fruit vegetables are often handled in low-volume operations, where palletising is not common because of lack of forklifts. In these cases, the products are palletised at a centralised cooling facility or as they are loaded for transport.Palletising is usually done after hydrocooling or package-ice cooling but before forced-air cooling. In field-pack operations, palletising is generally done in the field.
Cooling
Various methods are employed for cooling fruit vegetables, each tailored to specific produce types. Forced-air cooling is a prevalent technique used for beans, rock melons, cucumbers, muskmelons, peas, capsicum, soft-rind squashes, and tomatoes. Forced-air evaporative cooling is applied selectively for chilling-sensitive commodities like squashes, peppers, eggplants, and cherry tomatoes.
Hydrocooling is commonly used before grading, sizing, and packing beans, cantaloupe, sweet corn, and okra. Sorting of defective products occurs both before and after the cooling process. However, hydrocooling cycles might be insufficient, especially during hot weather. To address this, allowing enough time in cold rooms after packing and palletizing can ensure the product is adequately cooled before transport to markets.
Package icing and liquid-icing methods are employed to cool rock melons and supplement hydrocooling for sweet corn. Temporary cold storage is utilized in large-volume operations, where fruit vegetables are placed in cold storage rooms after cooling and before shipment. In smaller farm operations, products are often transported to central cooperatively owned or distributor-owned facilities for cooling and short-term storage.
For transport, some tomatoes, rock melons, and other muskmelons are shipped in refrigerated railcars, but the majority of fruit vegetables are transported in refrigerated trucks or container vans. While some products like cantaloupe and tomatoes are shipped in mixed loads, it's important to note that ethylene-sensitive commodities should be separated. Among immature fruit-type vegetables, cucumber, legumes, bitter melon, and eggplant are sensitive to ethylene exposure. For mature fruit types, watermelon is adversely affected by ethylene, leading to softening, flesh mealiness, and rind separation.
Special Treatments
Ripening
For achieving uniform and controlled ripening, ethylene is commonly applied to mature green tomatoes and occasionally to honeydew, casaba, and Crenshaw melons. Ethylene treatments can be carried out either at the shipping point or the destination, but optimal fruit quality is usually achieved when the treatment is applied at the shipping point soon after harvest.
Satisfactory ripening occurs within the temperature range of 12.5° to 25°C (55° to 77°F), with higher temperatures accelerating the ripening process. However, red color development in tomatoes is inhibited above 30°C (86°F). A typical ethylene concentration of about 100 ppm is used for treatments. Honeydew melons, particularly class 12 melons, are occasionally held in ethylene for up to 24 hours, while tomatoes are typically held at 20°C (68°F) and treated for up to 3 days.
Tomatoes can undergo ethylene treatment either before or after packing, but the majority are treated after packing. Treating before packing has the advantage of favoring the development of any decay-causing pathogens on the fruit in warmer conditions, allowing for the elimination of infected fruit before the final packout. Packing after ethylene treatment also facilitates a more uniform packout. However, since most mature green tomatoes undergo packing and subsequent ethylene treatment, "checkerboarding" may still occur, necessitating repack operations.
Modified atmospheres
Modified atmospheres are seldom used commercially for these commodities, although shipments of melons and tomato under modified atmospheres are being tested for long-distance markets.
Consumer packaging of vine-ripe tomatoes may also involve the use of modified atmospheres. For tomatoes held at recommended temperatures, oxygen levels of 3 to 5 percent slow ripening, with carbon dioxide levels held below 5 percent to avoid injury.
Muskmelons have been less studied, but recommended atmospheres under normal storage conditions are 3 to 5 percent oxygen and 10 to 20 percent carbon dioxide.Recommended storage/transit conditionsFor mature fruit-type vegetables, temperature can effectively control the rate of ripening. Most mature-harvested fruit vegetables are sensitive to chilling injury when held below the recommended storage temperature.
Chilling injury is cumulative, and its severity depends on the temperature and the duration of exposure. In the case of tomatoes, exposure to chilling temperatures below 10°C (50° F) results in a lack of colour development, decreased flavour, and increased decay.
Summary
That’s all for now. We hope you enjoyed this post and learned something new about post-harvest treatment and handling of fruits and vegetables.Be sure to check out our other blogs for more helpful tips, tricks, and information on food waste reduction.And as always, if you have any questions or comments, feel free to reach out to us!