Endosperm rice fiber by-product as source of bioactive phenolic compounds

This study investigated the valorization of rice industrial starch production fiber by-products, as source of valuable antioxidant phenolic compounds. Six enzymes and acid or alkaline solvents were tested. Total phenols yield and antioxidant activity were measured for best treatment selection. Specific phenols were identified by HPLC-DAD. Overall, 2% v/w Celluclast was identified as the best performing enzyme, leading to 436 μg gallic acid eq/gFW phenol yield and increasing the recovery of ferulic and p-coumaric acids with respect to control and other enzymatic treatments. Among chemical treatments, NaOH was more efficient than HCl and H2SO4 and was more specific for ferulic acid release. All digestates showed antioxidant capacity, up to 243 and 502 μg ascorbic acid eq/gFW for 2% v/w Celluclast and 1 M NaOH respectively. Both enzymatic and chemical treatments were successfully applied and, depending on extraction conditions, the release of specific phenolic compounds to obtain enriched digestates was achieved.