【作者】 胡碧君；

【导师】 温其标；

【作者基本信息】 华南理工大学 ， 粮食、油脂及植物蛋白工程， 2011， 硕士

【摘要】 电子束辐照技术杀虫防霉具有高效、安全、环保、经济等优点,在粮食贮藏上具有良好的应用前景和经济社会效益。本论文以电子束辐照灭菌、杀虫贮粮技术理论及实践为基础,主要研究不同辐照剂量杀虫、灭菌处理贮备粮对小麦理化性质、加工特性和食用品质的影响,并研究了辐照后小麦淀粉和蛋白质分子及其性质的变化,从分子角度探讨了电子束辐照导致小麦品质改变的原因。结果表明,小麦经过0-5 kGy不同剂量辐照后其主要营养成分变化不大,但能够引起脂肪水解,脂肪酸大幅增加,α-淀粉酶活性显著下降。经5 kGy剂量辐照的比未经辐照的小麦其α-淀粉酶活性下降了41%。因此,对加工品质会有一定程度的影响。且电子束辐照能够导致种子损伤,增加膜透性,对种子活力有一定影响。同时,经过辐照的小麦粉的降落数值、峰值粘度及回生值显著低于对照样品,当辐照剂量达到5 kGy时,降落数值下降了56.2%,峰值粘度下降至42.7%,回生值下降至35.2%。此外,电子束辐照对拉伸特性亦有较大影响,当辐照剂量达到5 kGy时,最大拉伸阻力随剂量增加而逐渐降低,且降幅随着辐照剂量的增大而增大,延伸度却逐渐增大,吸水量略有提高,拉伸曲线面积则先增后减。电子束辐照能显著影响小麦淀粉的流变学特性。随着辐照剂量的增加,小麦淀粉的Brabender峰值黏度显著降低,冷稳定性升高,凝沉性减弱,当辐照剂量达到4.4 kGy时,小麦淀粉的峰值黏度由85 BU减小到42 BU,下降了50.6%,回生值下降了88.2%。当辐照剂量达到4.4 kGy时,小麦淀粉的峰值粘度下降了50.6%,回生值下降了88%。电子束辐照能部分破坏小麦面粉中的淀粉颗粒,且破坏的形式以表观结构破损增加和破损淀粉含量增加来表示。当辐照剂量达到4.4 kGy时,破损淀粉含量增加了38.5%。利用凝胶渗透色谱分析结果显示,辐照后小麦淀粉分子量降低,且当辐照剂量达到4.4 kGy时,分子量降低了一个数量级,说明电子束辐照引起了小麦中淀粉分子的降解,平均分子量减小,导致小麦淀粉流变学特性改变,粘度降低,从而进一步阐释了经电子束辐照的小麦淀粉流变学特性的变化确实与分子结构的改变有关。在本实验剂量条件下,醇溶蛋白大分子发生了部分降解,而辐照过的麦谷蛋白低分子量亚基含量下降较大,剂量越高影响越大。在5.0 kGy时候,减少了一半。电子束辐照的作用破坏了小麦中的低分子量麦谷蛋白,从而也影响了面粉的加工品质。物性测试仪测定结果表明,剂量在1.75 kGy以下时,辐照对馒头的粘附性影响较小,但达到2.75 kGy以上时,馒头的粘附性迅速增大,达到对照样品3倍以上;感官评定结果表明,当小麦所受辐照剂量达到5 kGy时,由其所制作的馒头感官评分低于60分,表明馒头的感官食用品质已显著下降。一定剂量范围内,辐照处理有可能改善和提高曲奇饼的烘焙品质。在较高剂量下,淀粉黏度和面筋弹性的下降,制作的面包、馒头、面条等的品质下降。在高剂量下,辐射对小麦及其制成品造成的不利影响可以通过常规配粉方法加以克服或削弱。更多还原

【Abstract】 Because of high-efficiency, safety, environmental protection and economy, electron-beam irradiation has been broadly used in grain storage, and have good application prospect and economic and social benefits. This paper was based on the storage technology theory and practice of sterilization, insecticidal by electron-beam irradiation, mainly researched on physicochemical property, processing property and edible quality of stored wheat after treated by different doses, and then discussed the changes of starch and protein molecule and their properties, from a molecular perspective, approached the reason of wheat quality changes by electron-beam irradiation.The investigation result demonstrated that the basic nutritive composition of wheat irradiated with doses among 0-5 kGy had not been changed while the fat hydrolysis and the fatty acid value increased greatly,α-amylase activity decreases rapidly. 41% ofα-amylase activity was decreased severely than lack of electron beam irradiation under 5 kGy doses. Thus, there will be certain degree of influence on processing qualities. Besides, electron-beam irradiation led to seed damage, increased membrane permeability, impacted seed vigor. Meanwhile, the falling number, the maximum viscosity and setback were lower than control samples significantly. When it increased to 5 kGy, the falling number reduced by 56.2%, the maximum viscosity and setback reduced to 42.7% and 35.2% separately. Furthermore, effects of electron-beam irradiation on tensile properties were great too. When treated with 5 kGy doses, the water absorption increased slightly; the maximun resistance of dough decreased gradually, the decreasing range enlarged with the increase of irradiation doses, extensibility reduced gradually, while extensograph area increased first and then decreased.Electron beam irradiation can significantly affected the rheological properties of wheat starch. With the increasing of irradiation doses, the Brabender peak viscosity of wheat starches decreased significantly and the cold stability increased, while the retrogradations were weakened. When the irradiation dose reached 4.4 kGy, the peak viscosity reduced from 85 BU to 42 BU, decreased by 50.6%, the setback reduced by 88.2%. The starch granules of wheat flour were damaged by electron-beam irradiation. And the damage was presented with the appearance of increasing surface damages and the contents of damaged starches. The contents of damaged starch increased with increasing dose and the contents raised 38.50% compared with native samples when the dose achieved 4.4 kGy. As determined by HPSEC-MALLS-RI, the molecular masses of wheat starches degraded gradually with increasing irradiation dose, when the irradiation dose upped to 4.4 kGy the molar mass of starch decreased by one order of magnitude. The results indicated that the electron-beam irradiation made wheat starch degradation and lead to the changes of rheological properties and the decrease of viscosity of wheat starches. Furthermore, this explains the relationship between rheological properties and molecular structure changes on wheat starches.In this experiment, gliadin degraded partly, while low molecular weight glutenin decreased significantly with the dose increasing. When it reached 5.0 kGy, low molecular weight glutenin reduced to 50%. Electron-beam irradiation destroyed the low molecular weight glutenin, thus affected the processing quality of wheat flour. TPA test results showed that the adhesiveness was slightly affected when the irradiation doses below 1.75 kGy, but it rose to 3 times of the sample when it above 2.75 kGy; The result of Sensory Evaluation suggested that the quality of Chinese steamed breads made with these flours were decreased significantly when treated with 5 kGy doses, for the score was lower than 60. In some doses, irradiation probably improved baking quality of cookies. In higher doses, starch viscosity and gluten elastic decreased, the quality of bread, steamed bread and noodles made by irradiated wheat flour decreased too. In high doses, the adverse impact of wheat and their products after irradiation can be overcome or weakened by regular flour blending method.更多还原