ABSTRACT
I. INTRODUCTION Antioxidants in food are of interest for at least four reasons. First, endogenous or added antioxidants may protect components of the food itself against oxidative damage. For example, spices rich in antioxidants have been used for centuries to delay oxidative deterioration of foods (especially lipid peroxidation and consequent development of off-flavors and rancidity) during storage or cooking. Indeed, dietary supplementation of livestock with vitamin E can improve the keeping properties of their meat (1). The use of synthetic food antioxidant additives such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and propyl gallate is under increasing regulatory scrutiny (2), and so attention is turning to the possibility that “natural” antioxidants may replace them for at least some food applications. Examples include antioxidants from rosemary (3,4), hydroxytyrosol, a phenolic antioxidant from olives (5,6), the tocopherols, tocotrienols, and flavonoids. Most antioxidants in dietary plants are phenols, which act as chain-breaking antioxidants because their −OH group scavenges reactive radicals such as peroxyl radicals (RO2·)
−OH + RO2· → R−O· + ROOH The resulting phenoxyl radical (R−O·) tends to be poorly reactive because of electron delocalization into the aromatic ring, so that the reactive RO2· radical is replaced by one of limited reactivity. Phenols sometimes have additional mechanisms of antioxidant action, e.g., by chelating transition metal ions (7).
