Role of superfine grinding in purple-whole-wheat flour. Part Ⅰ: Impacts of size reduction on anthocyanin profile, physicochemical and antioxidant properties

While purple wheat has garnered attention for its rich and complex anthocyanin profile, its coarse bran may pose challenges for its further utilization in bakery products. Superfine grinding is a promising size-reduction technique to enhance the practicability of purple-whole-wheat flour (PWWF) as a functional food ingredient. In this study, purple wheat was ground into flours of three different particle sizes (Q50 = 214.8 μm, 55.6 μm and 31.3 μm, respectively), followed by characterising their micro-morphology, physicochemical and antioxidant capacity properties, as well as identifying and quantifying anthocyanin compositions. Three antioxidant capacity assays - TPC, ABTS and ORAC - suggest that superfine PWWF exhibited an antioxidant capacity up to 1.6 times greater than that of original PWWF. Triple quadrupole mass spectrometric results indicate that the content of individual anthocyanin compounds increased with size reduction. The anthocyanin profile of purple wheat was complex, comprising 26 species of which 12 were acylated. Among them, cyanidin 3-glucoside, peonidin 3-glucoside, malvidin 3-glucoside, delphinidin 3-glucoside and malvidin 3-rutinoside accounted for over 80% of the total content. Altogether, these results highlight the unique functionality of superfine ground PWWF and lay the groundwork for further utilization into bakery products with enhanced health benefits.