A SKYROCKET increase in the human population, changes in dietary habits especially in the developing countries towards high quality foods, decrease in the per-capita crop land availability, and poor management are the major implications for food security. Addition to this a large portion of all fresh produce is lost worldwide after harvest due to physiological (wilting, shriveling, chilling injury etc.), pathological (decay due to fungi and bacteria) and physical factors (mechanical injury); among these many are interrelated, i.e. mechanical injury can lead to postharvest decay in many cases.
Farmers in the developing countries lose about 20-40% of their crops compared with 10-15% in the developed countries. In case of fruits and vegetables; losses after harvest are particularly severe due to their highly perishable nature. The wholesale value of fruits is estimated at around 40 billion EUR, and a similar figure for vegetables. In European Union alone millions of euros lost due to postharvest losses and reduced quality of fruits. Similar losses occur in other developed OECD countries.
Following are some of the evidences of crop losses worldwide:
• About 10-20% of the total grain harvest is lost each year due to inappropriate storage and management, according to Archer Daniels-Midland´s co-chairman Patricia Woertz (Davos, 2010).
• Rice losses after harvest in Southeast Asia are estimated between 10-37% (FAO, 1999).
• Potato postharvest losses in Asia are estimated around 23-27% (FAO 2009).
• Postharvest losses of tomatoes in Egypt account for 27-43%, depending on the source (University of California, 2009).
• Vegetable (tomato, cucumber, pepper, beans) postharvest losses in Southeast Asia range between 13-20%.
• Mango postharvest losses in several tropical countries (Benin, Brazil, Costa Rica, and Pakistan) range between 15% in the dry season and 70% in the rainy season mostly due to poor storage and anthracnose (University of California 2009).
• In India and China, countries with a combined population of 2.4 billion inhabitants postharvest losses for citrus and mango 15-25%, cabbage 20-25% and tomato 20-35% (Kumar et al. 2004) (Feng, 2001).
In order to reduce these losses in the distribution chain especially in fruits, producers tend to harvest green, immature crop that resulted a poor tasting and visual quality. Postharvest chemicals offer protection against decay after harvest. However in many countries like European there is a very high sensitivity in retail to residue issues not only when MRLs (maximum residue levels) are exceeded, also some retailers in Europe favor a zero-residue policy.
An integrated approach from “seed to supermarket shelf” will be required to decrease the postharvest losses will require since many pre-harvest factors do influence postharvest behavior and losses.
Generally growers and shippers try to reduce postharvest losses through earlier harvesting and shipping greener fruit. Often this fruit has not reached the maturity levels necessary for good eating quality (sugars, taste and color development). This change in harvest criteria results in less losses in transit, but is a major cause of rejection, dissatisfaction by consumers that leads to sales reduction. Fruits maturing rooms are used usually for some crops, such as bananas, but are seldom used for others, such as mango and avocado. For citrus, degreening rooms have been used to remove chlorophyll, the green pigment and expose carotenes, the orange pigment characteristic of citrus. When fruits are harvested at the proper maturity stage, ripening systems can improve significantly the eating quality of many fruits (stone fruits, pears, mango and avocado) at retail. These systems have to be well planned, managed and controlled; so that they improve eating and visual quality without damaging internal quality and/or reducing shelf life of the fruits and vegetables.
In the past times breeding has been done for shelf life and productivity at the expense of taste for seed vegetable business. However in some crops like tomato and melon, the trend was reverted in variety development with the introduction of tastier varieties. Still the majority of the vegetable varieties being sold today is selected for productivity, disease resistance and extended shelf life.
Application of postharvest chemicals has been usually the responsibility of fruit producers and handlers. Mistakes in dosage, application, equipment calibration and coverage can result in excess deposition in certain fruit parts or whole lots. Good deposition, correct concentration and dosage per fruit are keys. Unfortunately, in many production areas, postharvest application methods are deficient. Additionally, there exists the environmental problem of the disposal of excess chemical residue in the packing station after fruit or vegetable spraying in an environmentally. Zero spillage chemical application systems have been developed, such as the one developed by Citrosol in Spain (Citrosol zero spillage®), but only starting to be implemented.