【作者】 张习军；

【导师】 赵思明；

【作者基本信息】 华中农业大学 ， 农产品加工及贮藏， 2008， 硕士

【摘要】 我国主要是以稻谷的形式储备粮食,然而因陈化变质、仓储害虫及霉变等引起的损失每年约达百亿斤。虽然化学药剂熏蒸和常规技术如低温、气调等可以解决一些问题,然而其受到熏蒸剂污染环境、虫害的抗性以及能源和材料等限制。如何解决稻谷储藏中品质劣变及防虫防霉等问题,目前迫切需要一种高效、安全、环保的方法。微波是一种有效的防虫防霉方法,然而目前缺乏在防虫防霉的微波条件下微波处理对稻谷品质的研究。本课题以稻谷为研究对象,以稻谷的微波防虫防霉条件处理稻谷,研究微波处理后稻谷的加工、食用及储藏品质变化,主要研究结论如下:1.微波对稻谷特性的影响。稻谷经微波处理,随着微波时间延长,温度呈线性上升趋势,随着微波剂量下降,升温速度减小。不同条件的微波处理对稻谷品质的影响有差异,在适宜的微波条件下碎米率,爆腰率变化较小,且该条件利于提高稻谷的出糙率以及整精米率,降低稻谷含水量和游离脂肪酸含量,改善蛋白质和淀粉的水溶性,降低α-淀粉酶、淀粉酶、蛋白酶、脂肪酶、脱支酶活性酶及脱支酶活力,而且提高稻谷的加工性能和储藏性能,改善大米的食用品质。微波处理对稻谷的脂肪酸组成有影响。原料稻谷中以不饱和脂肪酸为主,亚油酸含量为67.00%,棕榈酸含量为17.74%,油酸和硬脂酸含量分别为4.69%和3.41%,其它脂肪酸含量较低。微波处理后的稻谷亚油酸含量降低,为58.86%,而棕榈酸和油酸含量增加,分别为20.83%和12.63%,硬脂酸含量为2.56%,其它脂肪酸含量变化较小。微波对米饭的质构特性影响较小。2.微波对稻谷的储藏稳定性的影响。稻谷在储藏过程中,其出糙率、整精米率、水溶性蛋白质含量、清蛋白、球蛋白和谷蛋白的溶解率、水分含量、稻谷中各种酶活力显著降低,而碘蓝值和游离脂肪酸含量显著增加。稻谷经6个月储藏后亚油酸含量降低,油酸含量和棕榈酸含量增加,而其它脂肪酸变化幅度较小。储藏稻谷制得米饭的硬度增加,粘性和弹性降低。微波处理过的稻谷储藏过程中淀粉酶、蛋白酶、脱支酶均保持较高的活性。微波处理对稻谷的加工特性影响较小,但碘蓝值和游离脂肪酸含量显著高于未处理稻谷。微波处理的稻谷与未处理稻谷相比,不饱和脂肪酸含量稍低,饱和脂肪酸含量稍高,制得米饭的硬度、粘性和弹性与对照差异不明显。3.稻谷的加工品质（出糙率和整精米率）、食用品质（水溶性蛋白质含量和碘蓝值）以及储藏品质（游离脂肪酸含量以及各种酶）之间均存在极显著或显著的相关性。经过6个月储藏的稻谷制得米饭的平衡弹性系数E₀与酶活力呈负相关,衰减弹性系数E₁和松弛时间τ分别与整精米率呈负相关和显著正相关。松弛非线性指数n与整精米率呈极显著正相关,与碘蓝值呈正相关,与脱支酶活力呈负相关。更多还原

【Abstract】 Paddy is one of the main food crops in China. Every year, billions of paddy was damaged by deterioration, pest or mildew during storage. Although chemical fumigation and conventional methods such as low temperature and controlled atmosphere could achieve certain effect, they could result in some environmental problems, insect resistance and so on. In order to resolve this problem an efficient, safety, environmental protection method was required. Microwave treatment shows considerable potential for killing insect and preventing mildew in food. However, few studies have attempted to explain how microwaves influence the quality of paddy. In this study, the effects of microwave treatment on milling quality, edible and storage quality of paddy were investigated. The aim was to provide optimal processing parameters for the industrial application of microwaves to control the growth of pests and mildew in paddy. The results were as follows:1. Microwave could influence the characteristics of paddy. Paddy temperature linearly increased with processing time of microwave treatment. The velocity constant of temperature slowed with decreasing microwave dose. The effects of microwave treatment on paddy qualities depended on treatment conditions, under the optimal microwave conditions, kernel cracking and broken yield were relatively low, which were beneficial for improving brown rice recovery and head yield. Additionally, the optimal microwave treatment reduced the contents of water and free fatty acid, improved the water solubility of protein and starch, and reduced the activity ofα-amylase, amylase, protease, lipase, active debranching enzyme and debranching enzyme. The optimal microwave treatment improved milling and storage qualities of paddy and edible quality of rice.Microwave could influence the composition of fatty acid. The main acid in paddy was unsaturated fatty acid, the contents of octadecadienoic acid, hexadecanoic acid, octadecenoic acid, octadecanoic acid in raw paddy were 67.00%, 17.74%, 4.69% and 3.41% respectively; while they were 58.86%, 20.83%, 12.63% and 2.56% respectively in paddy treated by microwave. The other acids were hardly influenced by microwave. Meanwhile the texture characteristics of rice were hardly influence by microwave.2. Microwave could influence the storage stability. During storage, the significantly decreased indexes were brown rice recovery, head yield, water-soluble protein content, dissolution ratio of albumin, globulin and glutelin, water content and kinds of enzyme activity, and the significantly increased indexes included BV and free fatty acid content. After storage for six months, the content of octadecenoic acid declined, the contents of octadecanoic acid and hexadecanoic acid increased. Cooked rice from storaged paddy owned higher hardness, and lower viscidity and elasticity than cooked rice from raw paddy.Compared with the paddy without microwave treatment, the treated paddy remained higher enzyme activity and lower water content, and higher BV and free fatty acid content. The treated paddy had less unsaturated fatty acid and more saturated fatty acids than untreated paddy. Microwave treatment hardly influenced milling quality of paddy. There was no significant difference in hardness, viscidity and elasticity of cooked rice from treated and untreated paddy.3. There were significant correlations among milled quality （brown rice recovery and head yield）, edible quality （water soluble protein and BV） and storage quality （free fatty acid content and kinds of enzyme activity）. Equilibrium elastic modulus （E₀） of cooked rice from storaged paddy was negatively to enzyme activity in paddy. Smaller retarded elastic modulus （E₁） and higher relaxation time （τ） resulted in higher head yield. Higher nonlinear exponential（n） resulted in higher head yield and BV, and lower activity of debranching enzyme.更多还原