【作者】 闵建；

【导师】 李理；

【作者基本信息】 华南理工大学 ， 粮食、油脂与植物蛋白工程， 2010， 硕士

【摘要】 本课题组前期研究表明瑞士乳杆菌(LH-B02)和干酪乳杆菌(L.casei-01)作为益生菌能够在纯豆乳中生长产酸凝乳用于生产大豆奶酪,因此在此基础上研究此二乳酸杆菌与普通酸奶生产菌组合发酵生产大豆酸奶进行研究。研究了不同的菌种组合在豆乳中的发酵情况。干酪乳杆菌和瑞士乳杆菌分别与保加利亚乳杆菌、嗜热链球菌组合发酵豆乳的pH值、酸度值、质构和口感,结果表明在豆乳中添加一部分纯牛奶有利于乳酸菌的发酵以及良好风味的形成,应用瑞士乳杆菌、保加利亚乳杆菌、嗜热链球菌这一组合发酵剂制备的产品在各项指标上均优于应用干酪乳杆菌、保加利亚乳杆菌、嗜热链球菌的组合发酵剂制备的产品。研究了豆水比、牛奶的添加比例对酸豆乳质构的影响。采用pH值、酸度值、质构和扫描电镜等方法分析表明以1:10豆水比磨浆得到的纯豆乳发酵制得的酸豆乳质构更好,以豆乳和牛乳比例为7:3混合发酵的混合酸乳质构最优。研究了瑞士乳杆菌、干酪乳杆菌以及不同的组合菌种在豆乳中的发酵过程。结果表明,瑞士乳杆菌在纯牛乳和混合乳中产酸能力很强,在纯豆乳中产酸能力不够强,生长不够好;干酪乳杆菌在纯豆乳中生长产酸能力比瑞士乳杆菌强;研究还得出瑞士乳杆菌和干酪乳杆菌组合,以及他们分别与嗜热链球菌和保加利亚乳杆菌组合在纯豆乳生长产酸能力相当;SDS-PAGE结果分析表明在12小时内对蛋白质的降解程度比较小。另外,还对采用HPLC法测定了三个菌种组合发酵混合乳生产大豆混合酸乳的L-乳酸和D-乳酸含量,结果表明干酪乳杆菌与瑞士乳杆菌组合发酵混合酸乳得到的L-乳酸含量比例较高。研究了酸豆乳制备过程中胰蛋白酶抑制子的活力变化情况。以大豆胰蛋白酶抑制因子为对象研究了工艺过程对大豆胰蛋白酶抑制因子的影响,结果表明采用碳酸氢钠溶液浸泡12小时后抑制因子活力没有上升;温度对胰蛋白酶抑制因子的活力影响较为明显,温度越高时间越长抑制因子失活越快,其中在100℃灭菌15min可以有效降低抑制因子活力到合适的要求;乳酸菌发酵对抑制因子活力有一定的影响,但是不同的乳酸菌组合发酵对抑制因子活力影响差异不明显。更多还原

【Abstract】 Lactobacillus helveticus LH-B02 and Lactobacillus casei L.casei-01 were proved growing well in soy milk to produce soy cheese, so we studied them combination of Lactobacillus bulgaricus and Streptococcus thermophilus in soy milk.The growth of different combinations of Lactic acid bacteria in soymilk under fermentation were sdudied. The pH value, acidity, sensory characteristics and texture properties of soy-based yogurt fermented by the starter combination of Lactobacillus casei L.casei-01, Streptococcus thermophilus IFFI 6038, Lactobacillus bulgaricus AS1.1482 and the starter combination of Lactobacillus helveticus LH-B02 Streptococcus thermophilus IFFI 6038, Lactobacillus bulgaricus AS1.1482 were studied. The results indicated that the optimal soy-based yogurt was able to be obtained when a mixture of soymilk and reconstituted skim milk (7:3) was made and fermented by the starter combination of Lactobacillus helveticus LH-B02 Streptococcus thermophilus IFFI 6038, Lactobacillus bulgaricus AS1.1482 in this study.The effect of addition of reconstituted milk and ratio of soy with water on texture was studied. The four kinds of soy milk were made by water at ratios of 1:6, 1:8, 1:10, and 1:12. These four kinds of soy milk were fermented by Lactobacillus helveticus LH-B02 Streptococcus thermophilus IFFI 6038, Lactobacillus bulgaricus AS1.1482, and the pH value, titratable acidity and texture properties were studied. The soy milk made by water at ratio of 1:10 added 10%, 20%, and 30% milk were also studied; and the four kinds of soy-based yogurt were stored 1day at 4℃prior to microstructure analysis. Finally, we choose the ratio with water and soy 1:10 and the addition of reconstituted milk 30%.Fermentation process of Lactobacillus helveticus, Lactobacillus casei and the combinations of other different LAB were also studied. The pH values and titratable acidity of fermented reconstituted skim milk (RSM), pure soymilk (PSM) and mixed milk (MM) by single Lactobacillus helveticus LH-B02, Lactobacillus casei L.casei-01, and the combination of Streptococcus thermophilus IFFI 6038 and Lactobacillus bulgaricusAS1.1482 were determined. The single Lactobacillus helveticus LH-B02 grew well in RSM, the production of acidity was higher than Lactobacillus casei L.casei-01, but Lactobacillus helveticus LH-B02 grew not so well in PSM. Comparing to Lactobacillus helveticus LH-B02, Lactobacillus casei L.casei-01 grew well in PSM. The combination of Lactobacillus helveticus LH-B02 and Lactobacillus casei L.casei-01, the respective combination of Streptococcus thermophilus IFFI 6038 and Lactobacillus bulgaricusAS1.1482 can grow well in PSM. The SDS-PAGE analysis proved that the protein depredated by lactic acid bacteria was almost unchanged but for lipase. Furthermore, the L-lactic acid and D-lactic acid of soy-based yogurt fermented by 6038+1482+L.casei-01、6038+1482+LH-B02 and L.casei-01+LH-B02 were determined by HPLC. The result showed that the highest ratio of L-lactic acid was soy-based yogurt fermented by L.casei-01+LH-B02.The trypsin inhibitor (TI) activities of soy products were studied in the producing of soy-based yogurt. The results showed that soy soaking by 0.5% sodium bicarbonate solution for 12 hours can’t increase the activity of soy TI. It showed that the effect of temperature and time were obvious. The soy TI can decrease to the aim of our need under 100℃for 15min. The effects of fermentation by lactic acid bacteria (LAB) and addition of milk were also studied. We can conclude that the activities of TI can be decreased by LAB, but there was no more different among different combination of LAB, and the addition of milk can also reduce the activity of TI.更多还原