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 QUENCHER ABTS (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. This assay is able to measure both soluble and insoluble antioxidants, that simultaneously come into contact with ABTS •+ molecules by either 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 wheat varieties, characterized by three different particle sizes: a smaller one, ≤0.2 mm (control, WF 0.2 ), and two larger ones, ≤0.5 mm and ≤1 mm (WF 0.5 and WF 1 , 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 QUENCHER ABTS procedure provided for WF 0.2 an AC value of 42.0±2.7 mmol eq. Trolox/g d.w. A similar result was obtained for WF 0.5 (38.3±0.9 mmol eq. Trolox/g d.w.), thus indicating that these large particles may be analyzed by the QUENCHER ABTS assay provided that the "slope" calculation procedure is used. On the contrary, WF 1 showed about half AC (20.3±0.2 mmol eq. Trolox/g d.w.), thus showing that very large particles cannot be used even adopting the "slope" calculation.

Antioxidant capacity (AC) of quinoa (Chenopodium quinoa Willd. cv. Real) seeds and sprouts obtained after 4 days of seed germination at 20°C and 70% humidity was evaluated using trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays, able to highlight reducing activity and peroxyl radical scavenging capacity, respectively; phenolic content (PC) was also measured. Both TEAC and ORAC assays revealed a significantly higher (about 2-and 2.8-fold, respectively) AC of 4-day-old sprouts compared to seeds; consistently, also PC values of sprouts resulted about 2.6 times higher than seeds. In order to investigate the influence of storage on AC and PC, as well as on vitamin C content (VCC), 4-day-old sprouts were subjected for 7 days at 5°C to three different conditions of controlled atmosphere storage (CAS) compared with air. Interestingly, whatever the CAS conditions, storage of quinoa sprouts up to 7 days induced an increase of AC evaluated in terms of reducing activity by TEAC assay. Consistently, an increase of PC and VCC was measured during storage, positively correlated to TEAC values. Moreover, a decrease of peroxyl radical scavenging activity, measured by ORAC, was observed after 7 days of storage, in accordance with a shift of AC towards the reducing activity component. Overall, these findings indicate that sprouting approach using quinoa may provide highly antioxidant-enriched seedlings that may improve nutritional quality of diet or of functional foods. Interestingly, antioxidant properties of quinoa sprouts may be deeply influenced by storage, able to increase reducing activity by increasing phenols and vitamin C.