【作者】 郦金龙；

【导师】 殷丽君；

【作者基本信息】 中国农业大学 ， 食品科学， 2014， 博士

【摘要】 卤水豆腐因其能够最大程度保留大豆的风味,且具有独特的甘甜口感而深受欢迎。但是以卤片(水)作为凝固剂制作卤水豆腐时,其快速而剧烈的凝胶作用使得豆腐凝胶品质较差,表现为含水率和产量低,硬度高,凝胶网络结构松散,凝胶颗粒粗糙,营养物质流失等。与此同时,快速凝胶作用也极大增加了卤水豆腐的加工难度,不利于产业化发展。本论文以传统卤水豆腐为研究对象,以解决传统卤水豆腐加工过程中快速凝胶这个技术难点为研究落脚点,通过现代乳化与缓释技术,以油包水(W/O)和水包油包水(W/O/W)乳液分散体系实现卤水的包埋与运载,达到卤水缓释的目的,从而改善卤水豆腐的多方面品质。通过研究,本文取得了以下主要结论：1.通过对W/O乳液型凝固剂多项制备参数以及乳液自身性能的考察,发现影响W/O乳液性能的主要制备因素为水相与油相质量比、水浴温度、乳化剂(818SK)浓度、均质压力等。其中较优的W/O乳液制备条件是：水相与油相质量比为4：6或5：5,818SK浓度为0.6%-1.0%,油水混合物在65℃温度下水浴15min,高速均质速率为13000r/min,剪切2min,高压均质压力为60MPa,循环均质一次。该条件下制备的乳液粒径分布均匀,黏度适宜,Mg元素包埋率高,乳液稳定性强。同时,通过优选的制备条件制得的W/O乳液能够表现出一定的缓释效果,影响缓释效果的因素主要有温度、剪切强度以及乳液自身组成等。2.通过分别考察多种制备因素对于W/O/W乳液型凝固剂自身稳定性、粒度分布、缓释效果等的影响,发现通过“两步法”可以实现W/O/W乳液的制备。W/O/W乳液中的818SK浓度以及W/O乳液与外水相质量比越高,乳液粒度越小,分布越均匀,稳定性越强。过高的818SK浓度或过高的W/O乳液与外水相质量比都容易导致W/O/W乳液黏度过大,流动性变差,以818SK浓度在1.2%～1.6%,相比6：4为宜。采用高速剪切均质制备W/O/W乳液时,过强或过弱的均质强度都不利于W/O/W乳液的稳定性,以剪切速率11000r/min,剪切持续120s为宜。外水相中的Q12S作为亲水乳化剂,其对W/O/W稳定性也有正面效果,Q12S浓度在0.8%时,W/O/W乳液已基本能达到较优状态。内水相中添加牛血清白蛋白(BSA)或者乳清分离蛋白(WPI)等天然高分子物质能够有效减小W/O/W乳液粒度,改善其稳定性。同时,通过上述条件制得的W/O/W乳液能够表现出一定的缓释效果,且缓释效果受缓释时间、温度以及乳液自身组成的多重影响。3.将研究中制得的稳定的W/O及W/O/W乳液型凝固剂应用于传统卤水豆腐的制作中,发现两种乳液型凝固剂的使用都能够有效降低豆腐凝胶的形成速率,延长凝固作用时间,明显提升卤水豆腐凝胶含水率。同时,两种乳液型凝固剂的使用也都能明显提升卤水豆腐凝胶产量,改善卤水豆腐凝胶外观与空间结构,使凝胶结构更加致密、均匀、光滑、平整。乳液型凝固剂的使用还能够大幅减小卤水豆腐凝胶硬度,使凝胶更加柔软但不易坍塌。4.将W/O及W/O/W乳液型凝固剂应用于传统卤水豆腐加工中,发现两种乳液型凝固剂的使用能够轻微减少蛋白质的损失,一定程度上提高豆腐凝胶中的蛋白质保有量,较明显地提升豆腐凝胶中大豆异黄酮的保有量。更多还原

【Abstract】 Bittern-solidified tofu is very popular for its soybean flavor and special sweet taste. However, when bittern or bittern solution is used as the tofu coagulant, the quick and intense solidification will result in several negative effects, including low water content, low yeild, high hardness, loose gel network, and loss of nutrients. The rapid solidification on the local scale also causes the coagulation process difficult to control. In this thesis, traditional bittern solidified tofu was selected as the research object and the study tried to find the solutions to the quick solidification in tofu process by the approach of adopting emulsification and controlled-release technique, in whick, water in oil (W/O) and water in oil in water (W/O/W) emuslsions as the delivery system were prepared to embed and slowly release the bittern solution, finally, to improve the quality of traditional bittern solidified tofu. Main conclusions were as follows:1. After examing the preparation parameters and characteristic of W/O emulsions, it was found that parameters including the mass ratios between water phase and oil phase, bath temperature, emulsifier (818SK) concentration, and homogeneous pressure played the key role in the emulsion preparation. The selected preparation conditions were:used mass ratio at4:6or5:5, with the818SK concentrtion from0.6%to1.0%, then kept warm in water bath at60℃for15min, finally, underwent the high pressure homogenization at60MPa for once after a2-min high speed shearing at the speed of13000r/min. Following the above processes, W/O emulsions with good particle size distribution, fine viscosity, high embedding ratio of magnesium, and good stability were prepared. These W/O emulsions also had the expected controlled-release property which was affected by the temperature, shearing strength, and the components of emulsions.2. After investigating the factors affecting the preparation of W/O/W emulsions and their stability, particle size distribution, and controlled release effect, the results showed that the higher of818SK concentration in the oil phase and the mass ratio beteween W/O emulsion and the external water phase were set, the smaller and more uniform of the emulsion particle size would be, and the better of the stability that the emulsions would have. The818SK concentration from1.2%-1.6%and the mass ratio of6:4was selected. Both of the excessive higher emulsifier concentration and the mass ratio would cause the increase of viscosity. Moreover, neither excessive strong nor excessive weak homogenization strength was benefit for the emulsion stability. Hence, sheraing speed at11000r/min for120s was chose. As the hydrophilic emulsifier, Q12S in the external water phase had the positive effect on the stability of W/O/W emulsions. When the concentration of Q12S approached to0.8%, W/O/W emulsions with good properties could be abtained. It was also found that, when bull serum albumin (BSA) or whey protein isolate (WPI) was added into the internal phase, the W/O/W emulsions with much smaller particle size and much better stability could be prepared. Under these circumstance, the W/O/W emulsions had the expected controlled-release property which was affected by the temperature, shearing strength, and the component of emulsions. 3. Both the W/O and W/O/W emulsion coagulants could postpone the solidification process, which made the tofu with greater water content, higher yield, finer macrostructure, microstructure and texture, and more acceptable color compared with the tofu solidified by the traditional coagulant.4. When W/O or W/O/W emulsion coagulants were used, results also indicated that the loss of protein and soy isoflavones during tofu preparation was decreased, and the yield of protein and soy isoflavones was increased.更多还原