Juice matrix composition and ascorbic acid fortification effects on the phytochemical, antioxidant and pigment stability of acai (Euterpe oleracea Mart.)
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The effects of juice matrix composition on the phytochemical stability of aai (Euterpe oleracea Mart.) were evaluated by contrasting natural clarified juice systems with isolated polyphenolic and anthocyanin fractions, in the presence or absence of ascorbic acid (500 mg/l) under accelerated storage conditions (37 C). Polyphenolic (anthocyanin and non-anthocyanin polyphenolics) and anthocyanin fractions were isolated using C18 Sep-Pak columns and then re-dissolved in the original aqueous juice matrix (unbound fraction) or in a citric acid buffer (pH 3.5). The isolation of anthocyanins from the aai matrix improved their colour stability but a greater retention of non-anthocyanin polyphenolics and antioxidant properties was favoured by the initial juice composition. The presence of non-anthocyanin polyphenolics exerted a protective effect against ascorbic acid oxidation and enhanced polyphenolic and antioxidant stability in isolates fortified with ascorbic acid. However, all isolates obtained from aai experienced significant colour, polyphenolic, and antioxidant losses during storage and this indicated that optimization of early stages of industrial processing, storage and distribution are necessary to retain the functional properties of aai-containing products. 2007 Elsevier Ltd. All rights reserved.