The traditional application of correct temperature and relative humidity management to harvested fresh fruits and vegetables has been thoroughly explored. When combined with handling and marketing practices that reduce injuries, stress and exposure to disease - while fostering rapid handling - these technologies deliver a cornucopia of fresh fruits and vegetables at reasonable prices and excellent quality. Additional improvements using these traditional techniques will be incremental and will involve working with agricultural engineers and economists to optimize wholesale and retail marketing.
As with many other areas of biology, revolutionary changes promise to come from a better understanding of the basic process that controls the maturation, ripening and senescence of fruits and vegetables. Once identified, specific enzymes or pathways can be modified to produce the desired change. However, most researchers are involved in breeding crops for characteristics such as disease resistance and yield; or in formulating cultural practices that involve optimizing fertilizer and pesticide use; or in designing harvesting, processing, and marketing of the primary product. They may not be as interested in how their modifications affect material that is presently considered waste and which requires a recovery process to capture anything of value. In addition, consumer reluctance to accept some practices (such as genetically altered food) may limit the implementation of the more innovative changes and force reliance on the traditional repertoire of postharvest techniques (e.g. low temperatures, high humidity, sanitation, minimized injuries and ethylene exposure, altered gaseous environments and rapid marketing and use).
The major constraints limiting the implementation and usefulness of these postharvest techniques to maintain the quality of products diverted from the usual marketing chain because of defects or as waste from processing are their low economic value, their increased disease susceptibility and their enhanced metabolism. Because of the wounds inflicted during harvest, handling and processing, these commodities are the very ones in need of the most effective postharvest techniques; yet their low economic value precludes the use of the more expensive technologies.
The appropriate postharvest technology not only depends on the value of the commodity, but also on the duration of storage, and the use to which the product will be put. For example, the texture of waste fruits and vegetables destined for canning is often degraded if first frozen, while the extraction of juice, sugar, pigments, flavors and aroma compounds can be facilitated by freezing. The packing shed or processing plants that generate these waste products are often working at maximum capacity, so any co-product recovery must wait until some of that capacity becomes available and is reconfigured, or until an alternative co-processing line becomes operational. Storage techniques are therefore necessary that quickly arrest deleterious changes and can handle the large amounts of material that are rapidly produced. Short-term storage may be needed if the material is to be transported in bulk to a local processing facility, while prolonged storage may be necessary if it is to last until the end of the current season. In either case large amounts of material must be rapidly treated in a relatively short time at minimal expense. Techniques employed in under-developed counties may be better suited to these requirements than are the energy-intensive technologies used to maintain the quality of the primary products in the industrialized West.
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