L-半胱氨酸抑制即食米饭黄变作用机制研究

Inhibition Mechanism of L-Cysteine on Yellow Changing in Instant Rice

本试验研究L-半胱氨酸对即食米饭品质的影响,发现L-半胱氨酸使米饭硬度减小,黏性增大,感官品质改善并显著抑制米饭贮藏过程中的黄变现象。本试验利用电子显微镜、傅里叶红外光谱仪、X射线衍射仪和差示扫描量热仪等仪器分析L-半胱氨酸处理后米饭粉末颗粒的形态、淀粉基团、晶体结构及热力学性质的变化,探究L-半胱氨酸抑制即食米饭黄变作用机制。结果表明:L-半胱氨酸处理后米粒表面部分被侵蚀而变得粗糙甚至出现浅层裂痕,傅里叶红外光谱分析中发现￡-半胱氨酸处理后米饭有新的C-S键生成;吸热焓变大;结晶结构发生了变化。这些现象表明L-半胱氨酸的巯基与米饭中还原糖的羰基可能发生亲核加成反应,进而抑制蛋白质或其他氨基酸与糖类发生美拉德反应。

The effect of L - cysteine on the quality of in instant rice has been studied in the paper. The results showed that L - cysteine decreased hardness of the instant rice, increased viscosity, improved sensory quality and inhibited the yellow changing during storage. Moreover, the particle morphologies, starch groups, crystal structures and thermodynamic properties changes of rice powder were observed by scanning electron microscopy, fourier transform infrared spectroscopy, X - ray diffraction and differential scanning calorimeter to analyze the inhibiting brown mechanism. Starch granule surface of the rice power treated by L- cysteine was eroded partly, leading to rough and even shallow cracks. The FTIR analysis found that there was a new C - S bond formed in the rice treated by L - cysteine. The endothermic enthalpy of the power was lager and the crystalline structure was changed. All these phenomena indicated that the sulfydryl of L - cysteine may react with the carbonyl of reducing sugar in rice. Therefore, Maillard reaction between the amino and carbonyl in rice can be restrained.