Impact of Cooking on the Antioxidant and Functional Properties of Milling Fractions from Cold-Adapted Dutch Sorghum

Sorghum is increasingly recognized for its nutritional and functional benefits, yet its application in temperate regions remains limited. This study examined the effects of cooking at 100 °C for 30 min on total phenolic content (TPC), total anthocyanin content (TAC), and antioxidant activity across whole grain, decorticated grain, and bran fractions from four cold-adapted Dutch sorghum genotypes (Dusormil HD7, HD19, HD100, and HD101). Black-grained genotypes (HD100 and HD101) exhibited the highest TPC and TAC, with uncooked HD100 bran reaching 39.49 mg FAE/g (TPC) and 151.10 mg LUE/L (TAC). Cooking led to a 64% increase in TPC in HD19 bran, while decorticated samples showed TPC reductions up to 70%. TAC consistently decreased post-cooking, with declines up to 39% in HD100 bran and 30% in whole grain. Antioxidant capacity, as measured by ABTS, decreased in most fractions after cooking, notably by 28% in HD100 bran from 1175.49 ± 24.2 mg TE/g to 845.81 ± 44.13 mg TE/g. HPLC analysis tentatively identified luteolinidin and apigeninidin as the predominant anthocyanins, with concentrations generally decreasing after cooking and being highest in bran. Cellular antioxidant activity (CAA) assays revealed that bran and decorticated samples, particularly HD19 at 400 μg/mL (42.91 ± 2.66 Units), maintained the highest post-cooking values, while the lowest was observed in decorticated HD100 at 200 μg/mL (5.54 ± 0.50 Units). These results emphasize the critical influence of genotype and processing on sorghum phytochemical retention, supporting the development of functional foods for temperate climates.