【作者】 杨明；

【导师】 冯凤琴；

【作者基本信息】 浙江大学 ， 食品工程（专业学位）， 2014， 硕士

【摘要】 豆腐是我国的传统食品,营养丰富,具有极高的食用价值,但是豆腐类制品的保质期很短,尤其是在炎热的夏季,极易腐败,除了制约豆制品产业的发展,还会引起食品安全问题。因此,研发有效的豆腐保鲜技术势在必行,而安全高效的豆腐专用保鲜剂则是解决豆腐保鲜难题的经济、有效和可行途径之一。本课题首先对腐败问题较突出的散装老豆腐及盒装内酯豆腐中腐败细菌进行了分离鉴定,并通过致腐细菌回接实验进一步探究了致腐细菌与豆腐腐败现象之间的关系；之后,选取了几种有抑菌功能的食品添加剂包括单月桂酸甘油酯(GML)、单月桂酸蔗糖酯、6-葡萄糖酸内酯、柠檬酸及Nisin,采用微量稀释比浊法测定比较了它们对豆腐腐败菌的抑制效果(以最低抑制浓度表示),同时考察以GML为主体的复配保鲜剂的协同增效作用,最后,将上述保鲜剂应用于散装老豆腐进行了保鲜效果验证,同时测定了添加保鲜剂对老豆腐水分含量、色泽、质构等理化指标的影响。结果表明,导致散装老豆腐腐败变质的主要腐败菌为梨形肠杆菌(Enterobacter-pyrinus)、发酵乳杆菌(Lactobacillus-fermentum)和肠膜明串珠菌(Leuconostoc-mesenteroides)；而导致盒装内酯豆腐腐败变质的主要腐败菌为类短短芽孢杆菌(Brevibacillus-parabrevis)。发酵乳杆菌、梨形肠杆菌及肠膜明串珠菌分别是导致豆腐发粘、涨袋及质构变软的主要微生物；GML和Nisin对上述4种致腐细菌的抑制效果最佳；GML与Nisin复配增效效果最明显,对3种革兰氏阳性菌均有协同增效作用。老豆腐保鲜实验结果表明,在老豆腐中添加0.04%GML+0.02%δ-葡萄糖酸内酯、0.04%GML+0.02%柠檬酸均可显著延长老豆腐的货架期,在4℃、20℃及30℃贮藏温度下,延长时间分别为2天、1天及6小时。此外,添加上述保鲜剂会使老豆腐的弹性增加、内聚性减少、回弹性降低,并降低老豆腐的白度、使其颜色偏黄。更多还原

【Abstract】 Tofu is a traditional Chinese food with high edible value and rich nutrition, but the short shelf life of tofu not only restricts its industrialized development, but also causes food safety issues, especially in summer. Thus, it is necessary to develop an effective preservation technology, and adding the safe, efficient and dedicated preservative may offer an economical, resultful and feasible way to keep tofu fresh.In this study, spoilage bacteria were separated and characterized from firm tofu in bulk and boxed lactone tofu which were perishable, and the relationships between putrid phenomena and spoilage bacteria were preliminarily studied through pathogens inoculation experiments. Meanwhile, five food additives with bacteriostatic function including glycerol monolaurate (GML), sucrose monolaurate, glucono-δ-lactone, citric acid and nisin were chosen to inhibit the spoilage microorganisms. The minimum inhibitory concentrations (MIC) of each antibacterial agent and synergistic effects between GML and other antimicrobial agents were measured and compared. Then, preservatives mentioned above were applied in firm tofu to investigate the effect of preservation and the influence on moisture content, color and texture of firm tofu.Results showed that the main spoilage bacteria of firm tofu in bulk were Enter obacter-pyrinus, Lactobacillus-fermentum and Leuconostoc-mesenteroides. While Brevibacillus-parabrevis was the spoilage bacteria of boxed lactone tofu. The Enter obacter-pyrinus, Lactobacillus-fermentum and Leuconostoc-mesenteroides could cause sack expanding, clamminess and softening of tofu, respectively. Antibacterial activities of GML or nisin against each strain were better than the other preservatives. The synergistic effect of GML and nisin was the best, especially for gram-positive bacteria. The preservation results showed that adding0.04%GML+0.02%glucono-δ-lactone (w/w) or0.04%GML+0.02%citric acid (w/w) into firm tofu could significantly extend the shelf life of tofu at4℃,20℃,30℃for2d,1d and6h, respectively. Moreover, preservatives may impact the texture of firm tofu, like springiness increasing, cohesiveness and resilience reducing, and make the firm tofu less white and more yellow.更多还原