EFFECT OF STORAGE ON NUTRITIVE VALUE OF FOOD

Abstract

With few exceptions, nutrient levels and/or their bioavailability are reduced in foods following harvest, slaughter, or collection. Rate of these losses is usually attenuated by reducing temperature of storage. Initial heat processing to the point of enzyme inactivation, or to the point of microbial sterilization, “stabilizes” the food so that it does not “spoil” but at the same time causes a greater initial reduction in certain nutrients, and a more gradual reduction with extended storage. Initial heat processing and mechanical treatments may also release nutrients so that they become more available, but once released, they are also subject to losses unless stored at low temperatures. Ascorbic acid is undoubtedly the most sensitive to loss and changes to a less active form as the result of time and temperature in storage. In many instances changes in ascorbic acid reflect general changes in quality. Thiamine is the other vitamin which is frequently affected adversely by time and temperature of storage. The A vitamins appear to be lost readily in leafy vegetables, but relatively unchanged in other foods. There is little effect on mineral content of foods, but bioavailability, particularly of iron may be influenced during prolonged storage. Substantial losses in carbohydrates may be encountered as a result of respiratory activity in extended storage at relatively high temperatures. Protein content is rarely affected, but protein availability is readily reduced even in low moisture foods unless they are protected from oxygen and stored at low temperatures. These anticipated changes in nutritive value are of particular significance in nutrient labeling, and must be taken into account when preparing nutrient labels. Copyright © 1977, Wiley Blackwell. All rights reserved