ABSTRACT
CONTENTS 6.1 Introduction ........................................................................................................................ 111 6.2 Vitamin C............................................................................................................................ 114 6.3 Vitamin A............................................................................................................................ 115 6.4 Phenolic Compounds and Antioxidant Activity........................................................... 116 6.5 Summary............................................................................................................................. 116 6.6 Future Research Needs ..................................................................................................... 117 References.................................................................................................................................... 117
Fruits, nuts, and vegetables play a very essential role in human nutrition and health, especially as sources of vitamins, minerals, dietary fiber, and phytonutrients (phytochemicals). Phytonutrients, which can lower the risk of heart disease, cancer, and other diseases, include carotenoids and flavonoids (anthocyanins, phenolic acids, polyphenols). The antioxidant capacity of fruits is related to their contents of anthocyanins, phenolic compounds, carotenoids, ascorbic acid (AA), and vitamin E. Although antioxidant capacity varies greatly among fruits and vegetables, it is better to consume a variety of commodities rather than limiting consumption to a few with the highest antioxidant capacity. There is increasing evidence that consumption of whole foods is better than isolated food components (such as dietary supplements). Examples of the phytochemicals in fruits and vegetables that have established or pro-
posed positive effects on human health and their important sources are shown in Tables 6.1 and 6.2. Some changes in these tables are likely as the results of additional studies on effects of phytochemicals and their bioavailability on human health become available in the next few years. Meanwhile, it is important to evaluate the validity and dependability of the results of every study before reaching conclusions for the benefit of consumers (Kader et al., 2004). Many pre-and postharvest factors influence the composition and quality of fruits and
nuts. These include genetic factors (selection of cultivars, rootstocks used for fruit species), preharvest environmental factors (climatic conditions and cultural practices), maturity at harvest, harvesting method, postharvest handling procedures, and processing and cooking methods. The selection of the genotype with the highest flavor and nutritional quality for a given
commodity is much more important factor than climatic conditions and cultural practices
TABLE 6.1
Nutritive Constituents of Fruits and Vegetables That Have a Positive Impact on Human Health and Their Sources
in producing the best quality for consumers of that commodity. Producers should use an integrated crop management system to optimize yield and quality of each commodity. Buyers and consumers should be willing to pay more for higher flavor and nutritional quality products because often the producer sacrifices some yield to produce better quality fruits and vegetables. Maturity at harvest has a major impact on quality and postharvest life potential of fruits.
All fruits, with a few exceptions like avocados, bananas, and pears reach their best eating quality stage when fully ripened on the tree. However, since such ripe fruits cannot survive the postharvest handling system, they are usually picked mature but not ripe. It is better to pick fruits partially ripe than mature but not ripe (mature green) to provide the consumer with better flavor and nutritional quality fruits.
