Postharvest handling, storage, and processing greatly affect retention and bioavailability of nutrients in horticultural food crops. Although there are a few exceptions, concentrations of most nutrients are reduced by all postharvest operations. Losses of certain nutrients may range from 5% to 100%, depending on their chemical stability, solubility, and postharvest treatment. Therefore, the amount of a particular nutrient in a horticultural food at the time of harvest may not reflect the amount present when the raw or cooked food is consumed. Most vitamins are susceptible to oxidation catalyzed by enzymes, light, pro-oxidant metals, and active oxygen species. Also, nutrient retention and stability are affected by heat, leaching, and certain preservatives, such as sulfites. Physical injuries during handling, processing, and preparation for consumption accelerate vitamin degradation. Therefore, nutrient losses may be very large in minimally processed and food service products that are marketed in peeled, sliced, or shredded forms. Other processing methods, such as dehydration, fermentation, freezing, and canning usually result in significant losses in nutrient concentrations. Although processing generally contributes to loss of nutrient content of foods, certain processing methods improve the bioavailability of some minerals and vitamins, which may increase the actual nutritional value of the food. Methods to reduce inhibitors and antagonists of nutrient availability should receive major emphasis in efforts to improve nutritional value, along with efforts to improve the amount and retention of nutrients in horticultural food crops.
Green revolution: Metabolic engineering of crop plants
