還原劑與界面活性劑於提升米蛋白功能性之應用

Abstract

米蛋白為良好植物性蛋白質來源，具低致敏性、高生物利用價值及成本低廉等優勢。然而米蛋白內部大量的雙硫鍵與疏水性作用力使其形成穩定的球狀結構，造成米蛋白的水溶性、乳化、發泡等功能性均不佳。因此本研究目的為利用食品級還原劑及乳化劑，分別還原米蛋白雙硫鍵及破壞內部疏水性作用力，期盼藉此提升米蛋白之功能性。研究首先以穀胱甘肽 (glutathione, GSH) 與亞硫酸鈉 (sodium sulfite) 兩種食品級還原劑分別對米蛋白進行處理，結果發現此兩種還原劑能提升米蛋白 17~20% 的游離硫氫基數量，但米蛋白在經過處理後的水溶等性質並無明顯改善。若於米蛋白在還原劑處理的過程成中添加 1% (w/v) 的乳酸硬脂酸鈉 (Sodium stearoyl lactylate, SSL)，發現米蛋白中可測得之游離硫氫基數量可提升至 38~41%。最後將其與市售酵素水解米蛋白之進行功能性比較後發現，GSH 及亞硫酸鈉分別與 SSL 共同處理之米蛋白水溶性於 pH 7~10 達 30%，已相當接近市售酵素水解米蛋白之水溶性 (35%)；而亞硫酸鈉與 SSL 處理米蛋白之乳化性為 0.470，和酵素水解米蛋白之乳化性 (0.420) 並無顯著差異。由上述實驗證實，經還原劑及界面活性劑處理後之米蛋白的功能性均有顯著提升，此方法將可應用於食品工業中以提升米蛋白之利用價值。

Rice protein is a good source of vegetable protein due to its hypoallergenicity and high biological value. However, the high insolubility of rice protein with extensive disulfide bonds and interior hydrophobicity resulted in poor performance in functions. Therefore, the aim of this study is to improve rice protein functionality by reducing disulfide bonds and hydrophobicity within rice protein through the application of food-grade reductant and emulsifier. The results suggested that by the treatment with two reductants, glutathione and sodium sulfite, only 17-20% free sulfhydryl groups were increased, and the solubility could not be improved. Nevertheless, adding 1% (w/v) sodium stearoyl lactylate (SSL) during reducing process, the amount of sulfhydryl groups increased to 38-41%. Compare the reductant and surfactant-treated rice protein with a commercially hydrolyzed rice protein, the solubility of rice protein being treated with reductant and surfactant (30%) was close to the commercially hydrolyzed rice protein (35%) at pH 7-10, and the emulsifying activity of sodium sulfite and SSL treated rice protein (0.470) showed no significant difference as compared with hydrolyzed rice protein (0.420). This study demonstrated that reductant and surfactant could be used to improve rice protein functional properties and rice protein application in food industry.