Effect of cooking water in a broad pH from acidic to alkaline condition on the quality of cooked rice

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K02226
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 08030:Family and consumer sciences, and culture and living-related
• Research Institution: Wayo Women's University
• Principal Investigator: Ohishi Kyoko 和洋女子大学, 家政学部, 准教授 (40372908)
• Co-Investigator(Kenkyū-buntansha): 香西 みどり お茶の水女子大学, 基幹研究院, 教授 (10262354)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 米 / 炊飯 / pH / 老化 / 物性

Outline of Final Research Achievements

We prepared cooking water by adjusting the pH to 3, 5, 7, and 9 to investigate the influence of pH on the physical properties and staling of cooked rice. Rice cooked in pH 3 and pH 9 buffers showed a significant increase in adhesiveness, which demonstrates a staling control effect under refrigeration. These samples also showed the highest abundance of solid components and proteins that cover the rice grain surface. SDS-PAGE analysis indicated protein degradation by aspartic proteinase under acidic conditions, and protein solubilization by disulphide bond reduction under alkaline conditions. These results suggest that such property changes promote water absorption and starch swelling under acidic and alkaline conditions, contributing to an increased solid content adhering to the grain surface. However, protein solubilization is limited, and both starch swelling and gelatinization are obstructed at pH 5, suggesting that this condition can accelerate staling.

Free Research Field

調理学

Academic Significance and Societal Importance of the Research Achievements

これまで広範囲のpHの炊飯液を用いて米飯を調製し，これらの飯の物性や老化に伴う経時変化を比較検討した報告はない。本研究の結果，酸性および弱アルカリ性においては米飯の物性向上が認められ，弱酸性では老化が促進された。炊飯液のpHにより米のタンパク質に与える影響が異なり，これらの違いが澱粉の膨潤，糊化に影響を及ぼしていることが考えられた。炊飯液に調味料や酸味料が添加されることが多い加工米飯において，本研究で明らかにしたことは米飯の調製および販売過程における品質低下を抑える視点からも有用であると考える。