米饭焖制过程中焦香味及危害物的生成与关联

Generation and Correlation of Scorch Aroma and Hazardous Substances during Rice Stewing

摘要:

传统焦香米饭颇受青睐，但目前尚未有成熟的电饭煲蒸煮程序。采用气-质联用结合气味活度值鉴定得到焦香米饭特征挥发性风味物质为己醛、甲基吡嗪等7种。其中吡嗪类和噻唑类物质贡献了焦香风味，醛类和酚类物质贡献了清香风味。焦香风味物质以及伴生危害物（5-羟甲基糠醛和丙烯酰胺）的质量分数随着焖饭温度的升高和时间的延长而逐步增加。米饭经175 ℃焖制20 min后，吡嗪类物质含量已趋于稳定，5-羟甲基糠醛和丙烯酰胺质量分数仅为1.71、0.08 mg/kg。丙酮醛等二羰基化合物的生成积累促进了焦香特征性风味成分的产生，而Amadori化合物在极端高温（200 ℃以上）更容易转化为有害产物。该研究可为焦香米饭风味的定向调控和电饭煲蒸煮程序的合理设计提供科学依据。

Abstract:

Traditional burnt rice is widely desirable, however, the rice cooker program is not yet mature. Seven characteristic volatile flavor components of burnt rice, i.e., hexanal, methylpyrazine and etc., were identified by gas-mass spectrometry combined with odor activity value. Among them, pyrazines and thiazoles contributed to the burnt flavor, and aldehydes and phenols contributed to the fragrance flavor. The content of scorched flavor substances and associated harmful substances (5-hydroxymethyl-2-furaldehyde and acrylamide) gradually increased with the increase of temperature and time of stewing rice. The pyrazines in rice tended to be stable after heating at 175 ℃ for 20min, while the content of 5-hydroxymethyl-2-furaldehyde and acrylamide in rice were only 1.71 mg/kg and 0.08 mg/kg, respectively. The formation and accumulation of α-dicarbonyl compounds such as methylglyoxal promoted the production of characteristic flavor components of burnt aroma, and Amadori compounds were more likely to be transformed into harmful products at extremely high temperature(above 200 ℃). This study can provide a scientific basis for the directional regulation of the flavor of burnt rice and the reasonable design of cooking procedure of electric rice cooker.