Horticultural crops not only provide human beings with nutritional and healthy foods, but also generate income for growers. These include fruits, vegetables, flowers and ornamental crops.

This article however deals with fruits and vegetables and the related post-harvest damage.

Cultural practices determine the quality of produce at harvest, while proper handling ensures preserved quality until the produce reaches consumer. Quality assurance is a prerequisite for high-value fresh fruits and vegetables.

Post-harvest losses have many different forms but the most common is quantitative loss, such as the reduced weight and partial or total waste of a product due to decay or senescence.

A less discernible is qualitative loss, such as deterioration in texture, flavour or nutritional value. Other forms include loss of viability of propagules and reduction in monetary value due to reduced prices.

Post-harvest losses can occur in field, in packing, in storage, during transportation, and in wholesale or retail markets. Severe losses occur because of poor facilities, lack of know-how, poor management, or simply carelessness by the farmers or workers. Post-harvest losses may also occur at consumers' homes, in the kitchen or on dining tables. The causes of post-harvest losses can be divided into four categories.

Fresh fruits and vegetables are very susceptible to mechanical injury. Poor handling, unsuitable containers, improper packaging and transportation easily causes bruising, cutting, breaking, impact wounding, and other forms of injury.

Fruit and vegetable cells are still alive after harvest, and continue their physiological activity. Physiological disorders may occur due to mineral deficiency, low off- high temperature injury, or undesirable atmospheric conditions, such as high humidity. Physiological deterioration can also occur spontaneously by enzymatic action leading to over ripeness and senescence, a simple aging phenomenon.

High post-harvest losses are caused by the invasion of fungi, bacteria, insects and other organisms. Micro-organisms attack fresh produce easily and spread quickly, because the produce does not have much of a natural defence mechanism, and has plenty of nutrients and moisture to support microbial growth. Post-harvest decay control is becoming a more difficult task, because the number of pesticides available is falling rapidly as consumer concern for food safety increases.

Poor planning or inaccurate production and market information may lead to overproduction of certain fruits or vegetables which cannot be sold in time. This situation occurs most frequently in areas where transportation and storage facilities are inadequate.

Produce may lie rotting in production areas, if farmers are unable to transport it to people who need it in distant locations. It is difficult to know exactly the extent to which harvested fruits and vegetables are lost rather than consumed.

The actual figure changes from one commodity to another or one location to another; it also changes from one season or even one day to another. While periodic surveys may help us understand the severity and major causes of losses in a specific location and time, frequent extensive investigation for loss figures is generally unnecessary. The figures vary so rapidly that their usefulness is short-lived.

In order to solve specific problems in specific areas effectively and economically, a comprehensive knowledge of the nature of post-harvest losses, a grasp of various kinds of technologies and a tactical selection of strategies are necessary.

Post-harvest technologies which greatly influence the level of post-harvest losses and the quality of produce include grading, packaging, pre-cooling, storage and transportation. These are briefly discussed below:

Essentially all fruits and vegetables sold in wholesale markets are graded and sized. Sophisticated marketing systems require precise grading standards for each kind of product. More primitive markets may not use written grade standards, but the products are sorted and sized to some extent.

Typical grading facilities in large packing houses include dumpers and conveyors. Produce is graded by human eyes and hands, while moving along conveyor belts or rollers. "Electric eyes" are sometimes used to sort produce by colour.

In small-scale packing operations, one or a few grading tables may be enough. Dumping, conveying and grasping can cause mechanical injury to some products. Equipment should have a smooth, soft surface, and dumping and grading operations should be gentle, to minimize injuries.

Many products are sized according to their weight. Automated weight sizers of various capacities are used in packing houses. Round or nearly round fruits are sized according to their diameter, using automated chain or roller sizers or hand carried ring sizers. An inefficient sizing operation can also cause significant injuries.

The containers for packing fruits and vegetables should be easy to handle, they provide good protection from mechanical damage, they have adequate ventilation, and they are convenient for merchandizing, i.e., they can easily carry printed information and advertising about the product etc. They should also be inexpensive, and easily degradable or recyclable.

Good temperature management is the most effective way to reduce post-harvest losses and preserve the quality of fruits and vegetables. Desirable storage and transportation temperatures for major fruits and vegetables have been identified and published.

Temperatures which are low, but not low enough to cause chilling-injury, slow down physiological activity and hence the rates of senescence of the products. Low temperatures also reduce microbial growth rates and the rate of decay.

Products harvested from hot fields often carry field heat and have high rates of respiration. Rapid removal of field heat by pre-cooling is so effective in quality preservation that this procedure is widely used for highly perishable fruits and vegetables. Currently used pre-cooling methods include room cooling, forced-air cooling, water-cooling, vacuum cooling, and package icing.

Many horticultural crops have a relatively short harvesting season. Storage is needed to extend the marketing period. Various storage methods have been used on a commercial scale. Air-cooled common storage houses are often used or underground or cave storage using natural cold air. Storage humidity is sometimes regulated by controlled ventilation and dehumidifiers.

Refrigerated storage (cold storage) controls temperature and humidity precisely by mechanical means. Controlled atmosphere (CA) storage controls the concentrations of oxygen and carbon dioxide, in addition to temperature and humidity.

Air Cooled Common Storage is widely used for storing horticultural products, particularly those which have good keeping quality even without a precise low temperature. However, its use is generally limited to cool seasons in temperate and sub-tropical regions or high altitude areas where there are low ambient temperatures at night.

An ideal storage room is adequately insulated and has a good ventilation control system which pulls cool air in at night and keeps warm air out, during the day. For instance, hundreds of thousands of tons of citrus fruits are stored in common storage in Taiwan each winter, but ideal common storage facilities are still at their trial stage.

Lack of technical knowledge and the need for an investment to build new facilities delay the adoption of this new technology. If a country cannot afford to buy expensive equipment, cheaper equipment should be developed.

In order to lower the price, it may be necessary to sacrifice quality in terms of appearance, convenience, mobility, durability and/or user friendliness. Sacrificing one or more of these attributes might be acceptable at the initial stage of development, provided that the equipment still functions well.