【作者】 王海霞；

【导师】 李晓东；

【作者基本信息】 东北农业大学 ， 食品科学， 2018， 硕士

【摘要】 干酪是益生菌存活的良好载体,随着消费者膳食营养健康意识的提高,低脂干酪需求增加,开发益生菌低脂干酪既能降低脂肪摄入量,又能更好的保护益生菌的功能特性。胆固醇摄入过量易诱发心脑血管疾病,药物降解血清胆固醇虽快速有效,但价格昂贵且存在副作用,因此非药物途径降解血清胆固醇已成为当前研究热点。研究发现某些益生菌及其干酪制品能够调节血脂代谢、降低人体血清胆固醇,发挥其降胆固醇活性的关键在于保持菌种活性,使其在肠道内稳定增殖。益生元能选择性的刺激胃肠道内有益菌的生长从而辅助益生菌发挥其功能性,且能被益生菌发酵产生调节血脂的物质。目前低脂膳食且能降低人体血清胆固醇的益生菌干酪的研究受到学界广泛关注,但具体的降胆固醇菌株筛选模型、干酪降胆固醇活性的保持及其体内降胆固醇机理尚未明确,低脂干酪品质改善方法尚不成熟。因此,本课题主要是筛选具有高效降胆固醇活性的益生菌,与益生元组合应用于低脂契达干酪,研究益生菌及益生元组合添加对低脂干酪降胆固醇活性及品质的影响,优化出干酪最佳工艺条件,利用小鼠试验验证益生菌低脂干酪体内降胆固醇功效并初步探究其机理,为降胆固醇菌株的应用及开发具有降胆固醇的功能性乳制品提供理论基础。得出的结论如下:1.降胆固醇活性益生菌的筛选:以实验室分离鉴定的七株益生菌为研究对象,以菌株胆固醇降解率、胆盐水解酶活力及模拟胃肠道消化耐受性为评价指标,筛选出降胆固醇综合性能良好的潜力菌株。结果发现,植物乳杆菌KLDS 1.0320其胆固醇降解率达到61.22%,胆盐水解酶活力为0.71 U/mL,模拟胃肠道消化后活菌数为6.89 lg(CFU/g),各指标显著优于其他菌株(P<0.05)。其生物学特性试验结果显示,菌株生长较为旺盛,37℃为其最适生长温度,将其作为目标菌株进行下一步研究。2.低脂干酪降胆固醇活性及品质影响因素的研究:研究发酵剂添加量、益生菌添加量、最适益生元及其添加量对低脂干酪降胆固醇活性及品质的影响,结合响应面法对工艺条件进行优化。研究发现发酵剂最适添加量0.02%(w/w),植物乳杆菌KLDS 1.0320最适添加量2.00%(v/v),菊粉作为最适益生元,其最适添加量为2.00%(w/w)。在此模型下预测的成品感官评分值为87.36。根据优化出的工艺制作低脂契达干酪,成品低脂干酪的实际感官评分值为86.78,与预测值基本吻合,说明优化工艺切实可行。3.益生菌低脂契达干酪组分及成熟过程中的理化特性研究:按优化所得工艺制作低脂契达干酪(益生元组),以不含益生菌的全脂干酪(全脂空白组)、低脂干酪(低脂空白组)以及仅添加植物乳杆菌的低脂干酪(益生菌组)为对照,测定各干酪组组分及在不同成熟期的理化特性。结果表明,益生元组干酪成熟24周后,脂肪含量为14.08%,水分含量45.98%,符合低脂干酪国家标准;干酪的质构及感官特性优于低脂空白组,这是由于益生菌能够增加干酪水分含量,且菊粉作为碳水化合物基质的脂肪替代物能够使干酪感官品质更易被接受。同时,益生元及益生菌组干酪蛋白质的水解程度增强,产生了更多游离氨基酸。4.成熟期干酪菌群结构及胃肠道消化益生菌活菌数分析。益生元组干酪成熟24周,植物乳杆菌KLDS 1.0320活菌数达到8.43lg(CFU/g),较益生菌组提高了20.08%(P<0.05),同时益生菌及菊粉的添加未对发酵剂乳球菌的活性产生显著影响;模拟胃肠道消化后益生元组植物乳杆菌活菌数达到7.52 lg(CFU/g),比益生菌组提高17.31%(P<0.05),说明菊粉的添加有利于促进植物乳杆菌胃肠道消化后的存活率,从而能更好的保证干酪的降胆固醇活性。5.益生菌低脂干酪对高脂血症小鼠的影响。以高脂配方饲料喂养小鼠建立高脂模型,设饲喂普通饲料的小鼠为A组、高脂饲料的为B组、普通商业契达干酪的为C组、仅添加植物乳杆菌的干酪为D组及添加植物乳杆菌和菊粉的干酪组为E组,测定小鼠血清胆固醇相关指标。结果发现,试验35 d,与高脂B组相比,D、E组的血清总胆固醇(TC)、甘油三酯(TG)及低密度脂蛋白(LDL-C)含量均受到显著抑制(P<0.05),且动脉硬化指数(AI)值较B组分别下降了35.05%和43.81%,而C组各血脂指标与B组无显著差异(P>0.05),说明干酪中添加植物乳杆菌及益生元能够降低小鼠体内血脂水平,对高脂血症引起的动脉硬化具有更好的功效。D、E组肝脏中TC、TG显著降低(P<0.05),而粪便中TC、TG显著升高(P<0.05),说明植物乳杆菌KLDS 1.0320能使更多的胆固醇排出体外,从而降低胆固醇在肝脏的堆积。同时E组粪便中的TC和TG高于于D组(P<0.05),说明菊粉的添加能进一步加快体内胆固醇的排泄。因此,植物乳杆菌KLDS 1.0320与菊粉协同应用于干酪能更好的降低体内胆固醇水平。更多还原

【Abstract】 Cheese is a good carrier of probiotics,with the improvement of the nutritional awareness of the consumers,and increasing demand for low-fat cheese.Probiotics low-fat cheese can not only reduce fat intake,but also better protect the functional properties of probiotics.Excessive cholesterol intake is the main cause of cardiovascular and cerebrovascular diseases and the study on how to reduce the level of serum cholesterol is widely concerned.The study found that some probiotics and their dairy products have the ability to reduce human serum cholesterol and regulate blood lipid metabolism.The key to play its cholesterol-lowering activity is to maintain the bacterial activity and make it stable proliferate in the intestines.Prebiotics can selectively stimulate the gastrointestinal tract in the growth of beneficial bacteria and auxiliary probiotics play its function,and can be probiotic fermentation to produce substances that regulate blood lipids.At present,the research of low fat diet and the probiotics cheese that can reduce human serum cholesterol has been widely concerned by the academic circles.However,the specific screening of cholesterol-lowering strains,the retention of the cholesterol-lowering activity of cheese and the cholesterol-degradation mechanism in the body have not been clear.The main topic is the screening of probiotics has high cholesterol-lowering activity,combined with prebiotics used in low-fat cheese,and study on the effect of probiotics and probiotics combination on the cholesterol-lowering activity and quality of low-fat cheese,then optimal process conditions for cheese are optimized.The effect of probiotics low-fat cheese on cholesterol-lowering in vivo was explored by mouse experiment and its mechanism was explored,so as to provide theoretical basis for the application of cholesterol-lowering strain and the development of dairy products with cholesterol-lowering function.The conclusions are as follows:1.Lactobacillus plantarum KLDS 1.0320 was cultivated and determined its growth curve.Compared to seven probiotics isolated from the laboratory were studied.A strain was screened by cholesterol-lowering property,acid resistance,bile salt tolerance and bile salt hydrolytic enzyme activity.The results showed that Lactobacillus plantarum KLDS 1.0320 has better cholesterol-lowering activity than other strains,and the degradation rate of cholesterol reached63.72%,and the number of living bacteria in the simulated gastrointestinal tract was 6.89lg(CFU/g).The activity of bile salt solution was 0.71 U/m L.Its biological characteristics test results show that 37℃ is the most suitable growth temperature and the growth of the strain is more vigorous,it is studied as the target strain for the next step.2.Study on factors affecting the activity and quality of cholesterol-lowering low-fat cheese.Study on the effect of the dosage of the starter,the amount of probiotics,the optimum probiotics and the amount of its addition on the cholesterol lowering activity.The optimal fermentation conditions were: the dosage of the fermentation agent 0.02%(w/w),the amount of probiotics2.00%(v/v),the optimum probiotics is Inulin and the addition of probiotics 2.00%(w/w).With these conditions,the model predicted response sensory score of the low-fat cheese was 87.36.Making low-fat cheddar cheese with optimized process,and actual sensory scores of the half-fat cheese was up to 86.78,basically coincide with the predicted value.3.Study on the properties of low-fat cheddar cheese ripening.Making five batches cheeses with optimized process,and testing group and control group cheese composition and physical and chemical characteristics at different maturity.The fat content of the probiotic cheese was 14.08%.The degree of hydrolysis of probiotic cheese protein increased,resulting in more free amino acids.Cheese texture and sensory characteristics were better than those in low-fat blank group,close to full cheese.Indicating that the addition of inulin to promote the survival rate of Lactobacillus plantarum after gastrointestinal digestion,so as to better ensure the cholesterol-lowering activity of cheese.4.The number of viable bacteria reached 8.43 lg(CFU/g),which was 20.08% higher than that of Lactobacillus plantarum only(P<0.05).At the same time found that adding probiotics and inulin did not have significant effects on the activity of Lactococcus ferment;After simulated gastrointestinal digestion,the number of viable bacteria reached 7.52 lg(CFU/g).It was 17.31%(P<0.05)higher than that of probiotics group.5.Mice were fed with high-fat formula diet to establish a high-fat model.The cholesterol-lowering effect of probiotics cheese was studied by measuring serum cholesterol related indicators in mice.Compared with hyperlipidemia model,the contents of total cholesterol(TC),total triglyceride(TG)and low density lipoprotein cholesterol(LDL-C)in D and E groups were significantly inhibited(P<0.05),and atherogenic index(AI)values in D and E groups decreased by 35.05% and 43.81%,respectively.The TC and TG in the liver of D and E were significantly decreased(P<0.05),but TC and TG in the feces were significantly higher(P<0.05),and TC and TG in the liver of the group E were lower than those in the D group.Above mentioned,the synergistic application of Lactobacillus plantarum and inulin to cheese can better reduce the cholesterol level in the body.更多还原