Enzymatic extraction improves functional and phytochemical attributes of rice protein from green and ripe grains

Rice protein, a hypoallergenic and nutritionally balanced plant-based source, was extracted from fully ripe (RR) and green (GR) Khao Dawk Mali 105 rice grains using α-amylase (AA), protease (PT), and their sequential combinations (AA-PT, PT-AA). The GR-PT extract exhibited the highest protein content (11.2 %) compared to RR-control (4.0 %) and GR-control (4.8 %). PT treatment enhanced water-holding capacity (1.7 g/g), while AA-PT improved oil-holding capacity (3.2 g/g) and foam stability (57.5 %). FTIR spectra revealed amide I II and III bands (1650-1240 cm^-1), confirming preserved secondary structures after enzymatic extraction. PT-AA samples showed the highest antioxidant activities (DPPH: 92.7 mg AA/100 g DW; FRAP: 4.08 mg FeSO₄/100 g DW). LC-MS/MS profiling indicated a fourfold increase in arginine in GR-PT-AA. Overall, GR-PT and GR-PT-AA extracts demonstrate superior functional and antioxidant properties, highlighting their potential as antioxidant-rich plant protein ingredients.