As interest in functional foods and other products with possible health effects is escalating a large number of industrial enterprises are now producing various 'antioxidant' concentrates. Industrial enterprises range from the traditional juice producers and large companies specialising in natural flavours and colours to new companies specialising in health promoting supplements. There is a sparcity of published knowledge available on the molecular composition and the proven health effects of most of these antioxidant concentrates, but many of them are nevertheless claimed and marketed as having potential physiological benefits, or at least to 'supply high amounts of antioxidants'. Some caution in the evaluation of these advertisements is recommended. At the time of writing, the precise action mechanisms of antioxidants and their individual and combined efficiency have not been elucidated in detail. Thus, despite our rather detailed understanding of the various mechanisms by which natural antioxidants may act, it is currently difficult to predict the activities and efficiencies of various plant extracts of mixed composition without knowing the compositional profiles of the preparations. In addition, certain natural antioxidant phenols may act synergistically or even antagonistically, which further complicates predictions of antioxidant effectiveness of mixed concentrates. Therefore, marketing of most natural antioxidant concentrates is based only on empirical knowledge from tests in model systems. In nutrition, only very limited knowledge is available on the potential long-term effect of an elevated intake of natural antioxidants when they are consumed in their concentrated form, even when extracted from natural sources of fruits, berries and vegetables. Much more research is therefore needed on the anti-oxidant effects of natural antioxidant mixtures, on the influence of various types of processing on natural antioxidants and on the possible influence of the natural matrix on the antioxidant and nutritional effects.
For further information, the following review articles and books are recommended:
frankel e n and meyeR a s, 'The problems of using one-dimensional methods to evaluate multifunctional food and biological antioxidants', J Sci FoodAgric, 2000 80 1925-41. Lindsay d and cnFFord m (ed), 'Special issue devoted to critical reviews produced within the EU concerted action 'Nutritional enhancement of plant-based food in European trade' (NEODIET)', J Sci Food Agric, 2000 80 793-1137. pokoRny j, yaniShLieva n and gordon m (ed), Antioxidants in Food. Practical Applications, Cambridge, Woodhead Publishing Ltd., 2001.
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