【作者】 张立；

【导师】 何光源；

【作者基本信息】 华中科技大学 ， 生物化学与分子生物学， 2010， 博士

【摘要】 小麦(Triticum aestivum L.)是世界上最重要的农作物之一,也是世界上消费量和产量最高的作物,在我国,小麦是仅次于水稻的第二大粮食作物。而我国大部分小麦品种的品质与国外优质小麦相比差距较大,主要表现在蛋白质的含量低、储藏蛋白质量差,面筋强度弱。通过遗传育种方式改良小麦品质难度大,耗时长；因此,探索安全、有效的新型小麦粉添加剂以增加面筋强度,已成为小麦粉加工品质改良的一个重要手段；同时,多数研究者提出小麦面筋强度的形成取决于储藏蛋白分子间的二硫键,但未达成统一认识。本文以新型添加剂单宁酸为小麦粉添加剂,研究分析抗氧化剂单宁酸对面筋强度的影响与作用机理,进而阐明单宁酸作为新型小麦粉强筋添加剂的可行性,并为进一步探索小麦面筋强度的形成机理提供理论基础。本文包含以下两方面内容：一部分是单宁酸对小麦粉烘焙品质以及流变特性的影响及其改良作用。同时对单宁酸在面包老化过程中的影响进行了研究。另一部分是从多个角度对单宁酸对小麦蛋白的改良机制进行了深入的探讨和研究。首先单宁酸对面粉理化特性以及烘焙品质均起到了良好的改良效果。当单宁酸添加量为0.3%时,面包体积明显增大,面粉的粉质特性和拉伸特性均有所提高。在对面包的评分中虽然含量为0.3%的面包所得分数最高,但是由于风味和颜色的影响,评分优势并不明显。其次由于单宁酸是一种抗氧化剂,而常用面粉强筋剂均为氧化剂,氧化剂通常会为面包带来更易老化的问题。本文用单宁酸作为添加剂,研究了单宁酸对面包老化的影响,得到当面包添加量为0.3%时候,面包的老化明显减缓,硬度明显降低,芯质更为柔软,从而得到结论,单宁酸时一种很好的抗老化剂。在实验证明单宁酸确实能改良面筋强度后,本文研究了单宁酸对小麦粉蛋白的改性作用,发现虽然单宁酸破坏了面筋蛋白中的二硫键,却仍然对面粉品质起到了较好的改良效果。而这一结论与之前科学家所得到的结论并不一致,于是本文又测定了单宁对面筋蛋白自由氨基的影响,随着单宁酸的添加,面筋强度变大,自由氨基数目减少,于是推测得出,随着单宁酸的加入,新的交联产生,而这种新的交联同样达到了二硫键强筋的效果。而以上的变化结果均表明单宁酸对小麦粉中蛋白质的改性作用与其他强筋剂完全不同。本文运用动态流变仪检测了面筋蛋白的改变状况,然后用SEM观察面筋蛋白的结构变化,进一步证明了单宁酸对面筋蛋白的改性。二硫键长久以来被认为是改变面筋强度,改变面筋蛋白结构中最有效的改良靶点,而本文所提出的单宁酸,作为一种抗氧化剂,一种新型添加剂,为面粉研究者们开辟了一条新的思路,为以后新型面粉添加剂的研究带来新的可能,也为面筋蛋白的结构明朗化提供了理论基础。更多还原

【Abstract】 In China, common wheat (Triticum aestivum L.) is one of the most important staple food crops and the cheapest source of calories and protein for local inhabitants. And China is the one of the most important wheat growing and consuming countries in the world. However, before the 1980s, flour milled from Chinese wheat had lower dough strength and poorer end-use quality even at a similar protein level to wheat from some other countries. China imports large amounts of wheat grain from western countries in order to meet the requirement for various foods such as bread, dumpling, noodles, steambread and cake.So the new, safty and efficient additives are needed to investigated.The effects of tannic acid, which is present in many plants, on the structure of gluten protein and the properties of dough and bread were studied.This thesis has two parts of research. First is about the impact of tannic acid on the rheological properties and breadmaking quality. And tannic acid gave a really good influence on the rheological properties. Second is about the effects of tannic acid on the gluten protein structure. Tannic acid is really different from other redox agents of gluten protein. The reduction agents can also act positive influence on gluten proteinTannic acid was added at 0.1%,0.2% and 0.3% respectively during dough making process. The tannic acid acted negatively on disulphide bond formation and can interact with gluten proteins by other covalent bonds as detected by UV-spectroscopy and dynamic rheometry. The rheological properties and texture of the bread were measured by a Farinograph, Extensograph and texture profile analyzer, respectively. Texture analysis indicated little change in adhesiveness and resilience of bread at three levels of tannic acid compared with the control, but the changes of hardness and chewiness of bread made with addition of tannic acid, indicated that tannic acid could delay the bread staling process. The effect of tannic acid on flour and dough is different from other flour redox agents. It broken down the disulphide bonds but also acted positive effects on dough property and bread quality. Disulphide bonds are always commonly considered as the most important factor to change the quality of bread. But this paper presents a new concept of some other covalent bonds can also improve the quality of flour and bread, and use this property to investigate the new, safety and efficient additives of flour.更多还原