【作者】 谢宏；

【导师】 李新华；

【作者基本信息】 沈阳农业大学 ， 食品科学， 2007， 博士

【摘要】 稻米是我国第一粮食作物，其生产和储藏情况直接关系到国家粮食供应体系的安全。目前我国的稻米库存量约占全年总产量的40％，长时间的储藏必然导致稻米的品质劣变。陈米相对新米而言，食用品质明显下降。随着人们生活水平的提高，对稻米品质提出了更高要求，陈米食用品质下降是阻碍其进入正常流通的主要原因。研究稻米陈化机理，制定有效的调控措施，解决陈米食用品质降低问题，对满足人们的生活需要，减少储藏中的损失，提高农民收入具有重要意义。稻米发生陈化的内在因素有自身细胞结构损伤和化学成分改变两方面，其中化学成分的改变是导致细胞结构损伤以及一系列生理变化的根本原因。本论文在前人取得的研究成果基础上，研究了陈化过程中稻米脂质、蛋白质、淀粉等主要化学成分的改变，探讨了化学成分变化对淀粉糊化特性、米饭质地等的影响，利用扫描电镜观察了糊化前后米粒胚乳的变化，研究了在糙米萌发过程中淀粉酶和抗氧化酶活性的变化，旨在进一步补充和完善稻米的陈化机理。本文还全面的探讨了N₂与CO₂对调控糙米和大米的储藏品质的作用效果。研究表明：在稻米储藏过程中，支链淀粉在脱支酶作用下的降解是导致淀粉各组分变化的主要原因。直链淀粉增加、支链淀粉下降使淀粉分子的排列有序化，凝沉倾向增强，导致稻米淀粉的RVA谱的糊化温度升高；储藏过程中长链部分的比率增高限制了淀粉粒的潜在膨胀能力，是RVA谱的峰值粘度下降的原因。在稻米储藏过程中，粗脂肪含量下降，脂肪酸值增加。随储藏时间延长，各种脂肪酸含量均有上升。非淀粉脂（NSL）的脂肪酸组成与变化基本同于糙米脂肪；淀粉脂（SL）中脂肪酸组基本保持不变。脂类酸增加与淀粉形成的附和体提高了淀粉糊化的热焓值（ΔH），并对淀粉糊的热稳定性有较大影响，促进陈米饭的老化回生。随储藏时间延长，脂类的变化及与淀粉的协同作用增加了米饭的硬性、粘附性下降。在稻米储藏过程中，蛋白质总量及谷蛋白含量基本保持不变，谷蛋白的巯基减少，二硫键增加，低分子蛋白质通过二硫键的交联作用生成了高分子蛋白。增加的高分子蛋白质强化了蛋白质的基质作用，与二硫键的增加共同提高了糊化的温度范围和热焓值（ΔH），提高了淀粉糊的粘度。随储藏时间延长，蛋白的变化及与淀粉的协同作用使米饭粘弹性逐渐减弱，硬性逐渐增加。蛋白使米饭松弛性明显增加，凝聚性显著下降。利用扫描电镜观察糊化后米粒胚乳结构变化可以直观描述陈化对稻米食用品质的影响。陈米在沸水煮沸10min后，胚乳中部不糊化的区域比新米大。煮饭过程中新米较陈米吸水快，细胞破裂内容物溶出多。陈米淀粉呈现相互融合的倾向，形成板块结构。随储藏时间延长，糙米发芽率降低，淀粉酶活性、抗氧化酶活性下降。萌发过程中新鲜糙米的过氧化氢酶（CAT）、超氧物歧化酶（SOD）活性不断下降，陈米中活性则基本保持不变。过氧化物酶（POD）活性在不同储藏时间稻米的萌发进程中表现出上升趋势，并与幼芽生长量快速升高表现一致，说明POD可能与糙米幼芽生长有关。充N₂气调储藏有利于保持糙米品质，在低温条件下效果更加显著。CO₂与N₂对糙米的品质保持效果基本相同，但在高温条件下小包装大米气调保藏CO₂的作用效果最好，N₂与真空包装次之，大米水分含量高作用效果更明显。更多还原

【Abstract】 Rice is the first yield crop in china, Production and storage of rice related to the state’s food supply system security directly. The rice stock of the year’s total is about 40% in china now, Long time will inevitably lead to the storage of rice quality deterioration Compared with aging rice with fresh rice,edible quality decreased obviously. With the improvement of people’s living, the quality of rice and a higher requirement the main reason of impeding their access to normal flow is aging rice edible quality fell to.Research on ageing mechanism, development of effective control measures to solve aging rice lower edible quality, to meet people’s needs, reducing the storage losses and increase farmer’s income is of great significance.The internal factors of rice aging have tow facts their own cell structure and chemical composition injury, The chemical composition of which is to change the structure of cell injury and a series of physiological changes as the fundamental reasons. The research based on predecessors resultsin this pape, studies of the aging process rice lipid, protein, starch, and other major changes in chemical composition, explored changes in the chemical composition of the starch properties, the texture of the rice, Using scanning electron microscope to observe before and after the pasting office endosperm,In a study of brown rice germination process amylase and antioxidant enzymes activity to further improve the rice and add the aging mechanism, The paper also study on the gas storage environment conditions on rice storage effect preliminary.Research indicate:in the rice stored process, the main reasons of changing composition of starch is amylopectin debranching in the role of debranching enzyme.Amylose and amylopectin content decline made starch molecules arranged in an orderly, tend to strengthen aggregation, made rice starch RVA spectrum have the highest peak value,breakdown value decreased setback value increased, starch paste is not easy. With the extension of storage time, change of starch make rice hardness and sediment increases gradually.In the storing rice process, crude fat content decrease, fatty acid values increase. With the extension of storage time longer, various fatty acid content increased, the fatty acid composition and changes of NSL is same with brown fat basicly.Fatty acid group of SL remained unchanged basically. Lipid acid increased and the echoed bodies of starch formation enhance the starch paste the enthalpy value （△H）, and have bigger impact on paste thermal stability of starch Promote aging rice to setback. With the storage time longer, the changes in lipid and starch synergy made the rice rigid increase, and adhesion reduce.In the rice storage process, total protein and cereal protein content remained unchanged, the glutenin sulfhydryl reduced, disulfide band increase, low molecular weight protein change to high molecular weight protein by disulfide-through in the crosslinking role formation.High molecular weight increase in the protein matrix and raising the temperature range of paste and enthalpy value （△H）, improve the starch paste viscosity. With the storage time longer, the changes in protein and starch synergies made rice viscoelastic gradually weaken, rigid increase gradually. Protein make rice relaxation increased markedly, cohesion dropped significantlyUsing scanning electron microscope observate rice endosperm structural changesafter paste can described impact on aging rice rice edible quality directly. After aging rice 10minutes’ boiling, the bright region is extending slowly compared with the fresh rice, The new rice absorbs water fast, whose cell breaks and the content comes out more during cooking, the old rice has the tendency of melting and forms the platy structure owing holes.With the storage time extension longer, brown germination rate lower, the amylase activity and antioxidant enzyme activity decrease, of CAT and SOD of fresh brown rice activity decreased during germination, the basic activity of aging rice remained unchanged, in the rice germination storage process, activity POD of show an upward trend, as the same as rapid increase performance of bud growth shows POD may be related to the growth of the brown bud.Fill N₂ gas adjustment preserve is advantageous to the brown rice quality maintenance, under low temperature condition, the effect is more remarkable. Under atmospheric pressure condition, filling N₂, CO₂ has same effect to the brown ricequality maintenance. However, in high temperature conditions undersmall-conditioning packaged rice storage of CO₂ have the best effect, N₂ and vacuum packaging followed, high moisture content in rice effect is even more evident.更多还原