A physiologic approach to test the global antioxidant response of foods. The GAR method

Several methods have been applied to measure antioxidants in foods. Extraction methods have previously relied on chemical methods which are non-physiological or based on enzymatic hydrolysis. Whatever the method used, the insoluble fraction is systematically excluded. The global antioxidant response (GAR) method use an in vitro approach with enzymatic digestion, designed to mimic digestion through the gastrointestinal tract, aimed to release antioxidants from foods. A total of 27 samples were analysed using the ABTS and FRAP assays applied to the soluble and insoluble fractions. The GAR method showed a higher antioxidant activity compared with the usual chemical extraction and the Quencher (direct) method. The soluble fraction was more antioxidant than the chemical extracts due to the release of compounds from the hydrolysis of carbohydrates and proteins. In addition, the GAR method allowed the measurement of the antioxidant activity in the insoluble fraction, which was important in fibre-rich samples.