The expression "post-harvest losses" means a measurable quantitative and qualitative loss in a given product. These losses can occur during any of the various phases of the post-harvest system. This definition must also take into account cases of product deterioration. However, rather than actual losses, it would be more accurate to call it restriction in the use of the product. The losses in quantity and quality of the products inevitably mean losses of money. In addition to direct economic losses, there are those resulting from poor management of post-harvest systems. They are evidenced by a lack of growth in production and in the income of the farmers.
Production of horticultural crops worldwide has been increasing over many years, partly in response to a rising world population but also due to rising living standards in most countries and active promotion by government health agencies of fruit and vegetable consumption.
Fresh fruit and vegetables have been a part of the human diet since the dawn of history. However their full nutritional importance has only been recognized in recent times. Western societies have tended to value food from animal sources more highly. On the other hand , other societies with diets that are largely or totally vegetarian for religious or economic reasons have had greater dependence on fruit and vegetables for survival.
The status of fresh fruit and vegetables has also benefited from an international trend towards fresh natural foods , which are perceived to be superior to processed foods and contain less chemical additives. This community perception has , however , placed additional pressures on the horticultural industry to retain its fresh natural image by minimizing the use of synthetic chemicals during production and post harvest handling.
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| Stage of the post harvest losses |
The actual causes of postharvest loss are many but can be classified into two main categories. The first of these is physical loss. This can arise from structural damage or microbial wastage, which can leave produce tissue degraded to a stage where it is not acceptable for presentation, fresh consumption or processing. Physical loss can also arise from the evaporation of intercellular water, which leads to a direct loss in weight.
Loss of quality is the second cause of postharvest loss, and this can be due to physiological and compositional changes that alter the appearance, taste or texture. The changes may arise from normal metabolism of produce or abnormal events arising from the postharvest environment.
Improper harvesting, handling, transportation and distribution result in significant losses. These losses include significant economic loss. The reduction of post harvest losses reduces the dependence on imports of the commodity, fertilizers, pesticides and other chemicals. If post harvest losses are minimized or eliminated, the growers will be naturally inclined to produce more. During the present crises of ever increasing burden of population, the importance of reduction in post harvest losses of perishable commodities like horticultural crops is of vital importance to the countries.
Several factors influence the post harvest losses of fruit and vegetables. These include losses due to physical, mechanical conditions. Horticultural crops are characterized by high metabolic activities and short life. Due to these, significant losses occur between harvesting to consumption. Recent developments in post harvest handling and preservation have improved shelf life of crops.
Causes of losses
Inadequate harvesting, transportation, storage and marketing facilities and legislation lead to conditions favorable for causes of losses.
- Mechanical losses.
Besides causing damage, bruising and cracking.
- Physiobiochemical losses.
In fresh fruit and vegetables transpiration and respiration and sprouting.
- Microbial losses.
Like any other food, fruit and vegetable are prone to microbial spoilage caused by fungi, bacteria, yeast and moulds.
- Physical losses
Post harvest technological requirement like refrigerated storage temperature and relative humidity, composition and proportion of gases in controlled atmosphere storage, type of wrapper or packaging and others change with the nature of the fruit and vegetable to be handled.
Control of post harvest losses
The magnitude of post harvest losses in fruit and vegetables can be minimized by proper cultural operations, harvesting, transportation, storage and pre and post harvest treatments.
- Cultural operations
Cultural operations which ensure normal development of fruit and vegetables and avoid infection of decay organisms, help to prolong shelf life.
- Harvesting
Consumer always prefers fresh, and disease, insect free fruits of attractive appearance.
- Pre storage treatments
- Post harvest treatments
-Washing and Grading
- Packaging
- Transportation
Transportation and distribution of fruit and vegetables are the most important areas of post harvest losses. The losses in transportation occur due to physical and mechanical injuries.
- Storage
Low temperature storage most effectively extend shelf life of fruit and vegetables and reduce post harvest losses by arresting metabolic breakdown and fungal deterioration of the commodity.
- Environmental control
Being living entities, fresh vegetables consume O2 for respiration and give out CO2 and emit ethylene. The emitted ethylene further speeds up the ripening. By changing the micro climate around stored fruit and vegetables reducing O2 and increasing CO2 and removing ethylene, there shelf life can be prolonged
- Post harvest treatment of chemicals
Wide range of chemicals have been used to control micro organisms (fungicides), ethylene level (ethylene absorbents), water loss (antitranspirants) and senescence (growth substances) of fresh fruit and vegetables.
- Dehydration
- Processing in to other durable products
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