Towards an improved global antioxidant response method (GAR+): Physiological-resembling in vitro digestion-fermentation method.

The antioxidant capacity of food influences its shelf life and human health. To determine this parameter, the corresponding antioxidant species must first be extracted. Current methods don't adequately address this issue since they rely on extractions with organic solvents or on in vitro digestion without a subsequent fermentation. We present an improved protocol to determine the global antioxidant response of foods (GAR+) including both in vitro digestion and fermentation. All samples should be fermented with the same fresh faecal inoculum in order to decrease variability. In addition, the use of a pool of faeces from healthy donors is strongly recommended to improve repeatability. Although most antioxidant capacity is achieved after digestion, in some foods fermentation plays a role. Thus, the GAR+ method provides reliable values of the antioxidant capacity of foods that are closer to their in vivo activity by including the effects of gut microbiota over non-digested nutrients.