A combined procedure to evaluate the global antioxidant response of bread

Baking is the most representative manufacturing process applied to bread, involving thermal and moisture conditions that facilitate the Maillard reaction (MR) and, at the same time, the destruction-formation of natural-labile and thermally-induced antioxidant compounds respectively. In the present paper, the use of a new approach to measure the Global Antioxidant Response (GAR) of cereal derivatives is proposed: a combination of in vitro digestion - which enables measurement of the bioaccessible fraction - and the QUENCHER, which makes it possible to determine the antioxidant activity of the insoluble fraction, since it is a simple and direct procedure for determining the total antioxidant capacity of solid products. After digestion, the results obtained by the antioxidant assays are up to 20-fold higher than those reported using the standard extraction methods. The non-extractable residue displayed significant antioxidant activity that accounted for up to 17% of the total antioxidant activity. Moreover, the GAR obtained in some of the assays developed was 10-40% higher than the antioxidant activity registered by the QUENCHER procedure in wheat bread, and the difference was even higher in wheat bran bread. Therefore, the use of the GAR approach could avoid underestimation of the antioxidant activity of cereal derivatives. (C) 2010 Elsevier Ltd. All rights reserved.