微波加速陈化过程中大米理化性质和组织结构的变化

Changes of Physicochemical Properties and Tissue Structure of Rice during Microwave Accelerated Aging

新收获稻米的食用品质不佳,经过自然陈化(3~6个月)可以改善米饭的口感,而采用物理方法不仅能加速稻米陈化还能节省陈化时间,降低仓储成本。本研究采用微波(540 W处理30~50 s)处理稻米,并分析大米糊化性质、质构特性和组织结构的变化。结果显示,微波处理后大米的最终黏度、回生值显著增加,米饭的硬度增加,黏度下降,表明微波处理加速了大米的陈化。组成分析显示,微波处理后大米蛋白质的二硫键增加,同时发现米粒断裂面上的胞间断裂减少,胞内断裂增加,表明微波处理降低了胚乳细胞壁的机械强度。此外,与自然陈化过程中游离脂肪酸含量逐渐上升的变化不同,微波处理后大米中的游离脂肪酸含量降低,可减少哈败味的产生。这说明适度的微波处理可以加速稻米陈化,抑制稻米的哈败味产生,且微波处理的稻米陈化与胚乳细胞壁和二硫键的变化有关。

The newly harvested rice has poor sensory quality which can be improved by natural aging(3-6 months).However,physical methods could accelerate rice aging while save aging time and reduce storage costs.In this study,rice was treated by microwave(540 W treatment for 30-50 seconds),and subsequently the changes of gelatinization,texture and tissue structure were analyzed.After microwave treatment,a significant increase in final viscosity and setback was found.Meanwhile,the hardness of cooked rice was increased and the adhesiveness was decreased.These results indicated that microwave treatment could accelerate rice aging.Tissue structure analysis showed that after microwave treatment,disulfide bond of rice protein was increased,while an increase in intracellular cleavage and decrease in intercellular cleavage was noticed by observing the transverse section of rice grain,which indicated that microwave treatment reduced the mechanical strength of endosperm cell wall.The content of free fatty acids in rice was decreased after microwave treatment,which was different from the trends of increasing in content of free fatty acids during natural aging process,thus reducing the off-flavor of rice.In conclusion,appropriate microwave treatment accelerated the rice aging and reduced the off-flavor of rice.Microwave treated rice aging was related to the changes of endosperm cell wall and disulfide bond.