【作者】 李锋；

【导师】 华欲飞；

【作者基本信息】 江南大学 ， 粮食、油脂与植物蛋白工程， 2004， 硕士

【摘要】 本论文主要应用不同的大豆蛋白制品——豆浆、脱脂豆粉和大豆浓缩蛋白为原料制备大豆酸奶。旨在扩大这些大豆蛋白产品的应用领域,同时又能使乳品企业制备大豆酸奶增加选择范围。针对目前大豆酸奶所存在的问题,本论文深入分析了影响大豆酸奶风味、质构的因素。通过对扫描电子显微镜得到的图像进行数字化处理以及应用MATLAB软件,在酸奶类产品的微观结构的研究中引入分形这个概念,为食品的研究和加工领域解决和解释这一类问题提供新的思路和方法。本论文首先使用乳酸菌保加利亚乳杆菌和嗜热链球菌,通过四种不同的菌种驯化方式,以提高大豆酸奶的可滴定酸度为主要目标,达到改善其产品质量的目的。结果表明,逐渐增加其中的豆乳含量进行驯化培养,豆乳与牛乳比为8:2发酵效果较好。使用经驯化的菌种对豆乳进行发酵实验,针对影响大豆酸奶的主要因素固形物含量、发酵温度、发酵时间、原料杀菌温度、接种量进行单因素实验,根据单因素实验结果,以固形物含量、接种量、发酵时间对豆浆、脱脂豆粉和大豆浓缩蛋白每一种原料进行三因素三水平的正交实验,最终确定三种原料的最佳工艺条件,并进行相应的各项理化性质的检验和感官评定。针对大豆酸奶的风味,采用抑制离子排斥色谱法和GC-MS的固相微萃取法分析不同类型大豆酸奶的发酵过程中有机酸的变化以及最终产品的主要风味成分。通过离子色谱,分析了三种不同的大豆原料制备的大豆酸奶在从发酵起始至发酵终止丙酮酸、柠檬酸、乳酸的变化;利用GC-MS的固相微萃取技术分析比较了豆浆酸奶和酸牛奶的主要风味物质,从中发现了影响大豆酸奶产品风味的主要物质以及和酸牛奶产品之间的差异。利用扫描电子显微镜的图像和MATLAB的编程,通过显微照片及数值图像的灰度值分布并计算图像的灰度水平变化方差,发现了两种酸奶的均匀或一致性程度存在着差异。应用计盒维数法的基本原理考察了大豆酸奶和酸牛奶是否具有以自相似性为特征的分形结构,并最终确定豆浆酸奶和酸牛奶的分形维数分别为1.9105、1.9268。更多还原

【Abstract】 Different types of soy proteins, i.e. soy milk, defatted soy flour and soy protein concentrate were used in this study to prepare soy based yoghurt with the aim to increase the applications of the soy proteins in the dairy products and expand the source material flexibility of the yoghurt making. Soybean yoghurt flavor and finally quality of product construct were analyzed in depth in order to solve the problems presented in the domestic yoghurt of soybean. Image analysis was carried out for the digitalized scanning electron microscope(SEM) using MATLAB software to study the microstructure of yoghurt and the concept of fractal was introduced to provide a new and effective method to resolve and explain problems in the filed of yoghurt studies.Starting with common lactic acid bacterial (Lactobacillus bulgaricus, Streptocoeus theromophilus), four bacterial domestication methods was used in the first part of this study in order to increase the titration acidity and improve the product quality of soybean yoghurt. Results showed that lactic acid bacterial were domesticated by increasing soymilk content of the yogurt base. A soy/cow milk ratio of 8:2(W/W) was finally obtained at which bacteria could grow well. Fermentation experiments using the domesticated bacterial were conducted and the effects of solid content, fermentation time and sterilization temperature for each kind of material on the total acid degree and yogurt texture were studied. Optimized fermentation conditions for three kinds of soy proteins were obtained and the physicochemical property analysis and sensory properties were compared. Organic acids and volatile off-flavor compounds in the soy based yoghurt were isolated and analyzed by ion exclusion chromatography and GC-MS of solid phase micro-extraction (SPME) samples respectively. Changes in acetone acid, citric acid and lactic acid contents in the fermented course for different of soy proteins were analyzed. Major volatile off-flavor compounds for dairy and soy based yoghurt were compared and their influences on the flavor profiles of soy based yoghurt were suggested.Grey level distribution and variance analysis of the digitalized image of SEM micrographs based on the MATLAB programming were carried out, which showed that the consistency for soy based and dairy yoghurt was different. Box counting method was applied to investigate the fractal structure and the fractal dimension for soy based and dairy yoghurt was determined to be 1.9105 and 1.9268 respectively.更多还原