pH-dependent pasting and texture properties of rice flour subjected to limited protein hydrolysis

• Published in: Food hydrocolloids 2021-08, Vol.117, p.106754, Article 106754
• Main Authors: Park, Jiwoon, Sung, Jung Min, Choi, Yun-Sang, Park, Jong-Dae
• Format: Article
• Language: English
• Subjects: Gel properties; Gluten-free; Non-covalent interaction; Physicochemical properties; Protease-treated rice flour; Protein–starch interaction
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2021.106754

We investigated the physicochemical and functional properties of rice flour modified by partial protein hydrolysis and the further effects of pH. Protease treatment changed the molecular composition, surface hydrophobicity, and protein solubility, thereby altering the surface charge, water absorption capacity, and solubility of rice flour. The pasting viscosity of rice flour at neutral or basic pH decreased as the extent of protein hydrolysis increased. However, at pH 3, a significant increase in pasting viscosity was observed despite extensive protein hydrolysis. The solution pH also affected the gel hardness properties. Protease treatment reduced overall gel hardness at neutral pH, but increased gel hardness slightly at acidic pH (pH 3–5); at pH 3, hardness increased even when the rice flour was subjected to extensive protein hydrolysis. Protein–protein and starch–protein interactions were affected by pH; in particular, electrostatic and hydrophobic interactions synergistically increased gel hardness at acidic pH. Our findings indicate that fortified gel texture can be achieved via limited protein hydrolysis of rice flour followed by pH adjustment. [Display omitted] •The solubility of protease-treated rice flour increased and its water absorption capacity decreased.•The pasting properties of protease-treated rice flour were more greatly affected at low pH.•The gel hardness of protease-treated rice flour increased at low pH and decreased at high pH.•Ionic bonds and hydrophobic interactions contributed to form a strengthened gel at low pH.