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

• Published in: Food chemistry 2011-12, Vol.129 (4), p.1926-1932
• Main Authors: Pastoriza, S., Delgado-Andrade, C., Haro, A., Rufián-Henares, J.A.
• Format: Article
• Language: English
• Subjects: ABTS; Biological and medical sciences; Food industries; FRAP; Fundamental and applied biological sciences. Psychology; GAR; In vitro gastrointestinal digestion; QUENCHER; Total antioxidant activity
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2011.06.009

► We determine the total antioxidant capacity (TAC) of fresh or cooked foods. ► We extract antioxidants by application of a gastrointestinal in vitro digestion. ► We measure the antioxidant activity of both the soluble and insoluble fractions. ► The sum of both activities results on the TAC of each foodstuff. ► This method is called the global antioxidant response (GAR) approach. 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.