Antioxidant capacity of durum wheat large flour particles may be evaluated by QUENCHERABTS assay by adopting a proper calculation mode

Assessment of Antioxidant Capacity (AC) of foods is useful to consider cumulative/synergistic action of all dietary antioxidants, thus providing a more integrated information than the simple sum of measurable antioxidants. Among the different AC assays, the QUENCHERABTS (QUick, Easy, New, CHEap and Reproducible)procedure is based on the direct reaction of ABTS•+reagent with fine solid food particles without extraction of antioxidants. Thisassay is able to measure both soluble and insoluble antioxidants, that simultaneously come into contact with ABTS•+ molecules byeither liquid-liquid or solid-liquid interactions,respectively.These interactions may change depending on the particle diameter. Usually, particles having 0.1-0.3 mm size are used. Here, AC was evaluated on whole flour (WF),derived from a mix of grains of ten durum wheatvarieties, characterized by three different particle sizes:a smaller one, <0.2 mm (control, WF0.2), and two larger ones,<0.5 mm and <1 mm (WF0.5 and WF1, respectively). Moreover, a novel AC calculation procedure based on the slope value of the regression line of ABTS•+ response vs flour amount is presented in detail. The classical QUENCHERABTS procedure provided for WF0.2 an AC value of 42.0±2.7 mmol eq. Trolox/g d.w. A similar result was obtained for WF0.5 (38.3±0.9 mmol eq. Trolox/g d.w.), thus indicating that these large particles may be analyzed by the QUENCHERABTS assay provided that the “slope” calculation procedure is used.On the contrary, WF1 showed about half AC (20.3±0.2mmol eq. Trolox/g d.w.), thus showing that very large particles cannot be used even adopting the “slope” calculation.