Effect of Okara Inclusion on Starch Digestibility and Phenolic-Related Health-Promoting Properties of Sorghum-Based Instant Porridges

This study investigated the effect of okara incorporation on modulating starch digestibility and phenolic-related bioactivity in sorghum-based instant porridges. Fermented and unfermented formulations were prepared using sorghum, okara, and their composite blends. Okara substitution at 50% reduced rapidly digestible starch by 37% and increased resistant starch by 368%. Antioxidant indicators such as 2,2-Diphenyl-1-picrylhydrazyl (DPPH) (60.22 µmol TE/g), 2,2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (68.33 µmol TE/g), and Ferric Reducing Antioxidant Power (FRAP) (66.09 µmol TE/g) of the 50:50 fermented composite porridge were significantly higher compared with the sorghum-only porridge. All porridges demonstrated DNA protective properties, while the HPLC profile revealed increased phenolic acids (e.g., 312.90 µg/g in fermented okara porridge) and flavonoids (e.g., 1384.21 µg/g in fermented sorghum porridge), with bioconversion of glycosylated isoflavones into aglycones. Overall, the findings highlight the synergistic benefits of incorporating okara and fermenting it in sorghum-based porridges, offering valuable insights for developing functional cereal-based products.