【作者】 李银聪；

【导师】 阚建全； 杜木英；

【作者基本信息】 西南大学 ， 食品科学， 2011， 硕士

【摘要】 作为一种极具地方特色的传统发酵乳制品,酸牦牛奶深受人们喜爱,它主要由牦牛主产区牧民采用传统发酵方法制作而成,风味独特,营养丰富,并具有一定保健功能,这种保健功能很可能与其中的微生物菌群有极大关系。由于受各地区地理地貌和气候环境,发酵温度、时间和制作方法,牧民生活习惯、挤奶用具以及发酵容器具等等因素的影响,各地区自然发酵酸牦牛奶中的优势微生物存在一定差异,但以乳酸菌为主。乳酸菌不仅可以改善食品的风味,提高食品营养价值、保藏性能和附加值,大量研究表明,它还具有多种生理功能,如促进食物营养成分的分解、吸收,调节机体的胃肠道正常菌群,维持和改善机体的正常机能,降低血清胆固醇,增强机体免疫力,抗氧化活性等。对于乳酸菌的研究起步我国比较晚,拥有自主知识产权的乳酸菌及其制剂较少,得到大量推广应用的更是微乎其微。本研究正是在这种背景下开始的。本论文主要以西藏和川西青藏高原牧民自制的自然发酵酸牦牛奶为研究对象,分析鉴定其中的优势微生物,并从中分离筛选出一些优良菌种,研究乳酸菌的抗氧化活性,为我国传统酸奶工业化生产提供实验数据,并对建立青藏高原乃至我国酸奶微生物资源库奠定一定的基础。研究结果如下：(1)自然发酵酸牦牛奶样品中的微生物数量研究表明,在取自西藏和川西青藏高原的10份自然发酵酸牦牛奶样品中微生物含量均很高,其中主要是乳酸菌,活菌数达到了107cfu/g以上：其次为酵母菌,来自西藏地区的样品中酵母菌活菌数普遍高于来自川西地区的样品,前者均为106cfu/mL数量级,后者在105～106cfu/mL数量级之间。(2)自然发酵酸牦牛奶样品中乳酸菌鉴定结果表明,从这10份样品中分离鉴定得到15株乳酸菌。其中,球菌8株,分别是肠膜明串珠菌肠膜亚种(L. mesenteroides subsp. mensenteroides)、野生链球菌(S. ferus)、嗜热链球菌(S.thermophilus)、棉籽糖乳球菌(L.raffinolactis),唾液链球菌(S. salivarius)、乳酸乳球菌乳酸亚种(L. lactis subsp. lactis)、乳明串珠菌(L. lactis)和肠膜明串珠菌葡聚糖亚种(L. mesenteroides subsp. dextranicum);杆菌7株,分别为口乳杆菌(L. oris)、发酵乳杆菌(L. fermentum)、干酪乳杆菌(L. casei)、植物乳杆菌(L.plantarum)、德氏乳杆菌乳亚种(L.delbrueckii subsp.lactis)、短乳杆菌(L. brevis)和瑞士乳杆菌(L. helveticus)。(3)自然发酵酸牦牛奶样品中酵母菌鉴定结果表明,从这10份样品中分离鉴定得到酵母菌8株,即：乙醇假丝酵母(C. ethanolica)、马克斯克鲁维酵母(H. marxianus)、酿酒酵母(S.cerevisiae)、克劳森酒香酵母(B.claussenii)、清酒假丝酵母(C. sake)、发酵毕赤氏酵母(P. fermentans)、异常汉逊酵母(H. anomala)和郎比可酒香酵母(B. lambicus)。(4)以该15株乳酸菌作为被试菌株测定其抗氧化活性,研究结果表明,在对H2O2的耐受能力、清除超氧自由基(O-2.)的能力、螯合Fe2的能力、抗脂质过氧化的能力和清除DPPH自由基的能力等五个指标中,15株乳酸菌都具有抗氧化活性,只是抗氧化活性水平相差较大,其中DX-1、DX-3和DLDQ1-1菌株对各个测定指标都显示了较高的抗氧化水平,显示有进一步研究开发的价值。更多还原

【Abstract】 As a sort of traditional fermented dairy products with local characteristics, yak yogurt is very popular. It is mainly made by yak herders of the main producing area in traditional fermentation methods,with unique flavor, nutrient-rich and some health functions.Such health care function may have great relationships with its microbial flora.Because of different geography and climate of regions, fermentation temperature, time and producing methods, yak herders’living habits, milking equipment and the fermentation vessel,ect., there are some differences of the advantages of micro-organisms among regional natural fermentation yak yogurt, but mainly lactic acid bacteria (LBA)LBA can not only improve the flavor of food, improve food nutritional value, storage performance and value, it also has a variety of physiological functions shown by a large number of studies, such as promoting the decomposition and absorption of food nutrients,regulating the body’s normal flora of the gastrointestinal tract to maintain and improve the body’s normal function, lowering serum cholesterol, enhancing immunity, antioxidant activity and so on. Late starting of the study on LBA in China,we have few independent intellectual property rights of LBA and its preparations. Its application is minimal. This study began in this context.Using yak yogurt made in Tibet and western Sichuan of Tibetan Plateau by Tibetan nomads as study Object.this paper mainly analyzed and identified the preponderant micro-organisms, and isolated some good bacteria to provide theoretical basis for industrial production of traditional yogurt,and to lay a foundation for the establishment of yogurt Microbial Resources of the Tibetan Plateau and even the whole Coutry. Test results are as follows:(1) Study on naturally fermented yak milk samples have shown that microorganism numbers of the 10 samples from Tibet and western Sichuan Plateau were high.Most were LBA with 107cfu/g or more viable cells numbers; followed by yeast, while yeast cell counts of samples from Tibet regions wer generally higher than that from western Sichuan, the former wer 106cfu/mL and the latter between 105 to 106cfu/mL.(2) 15 strains of LBA were isolated and identified from 10samples, of which 8 strains of Lactococcus, namely:L.mesenteroides subsp.mensenteroides, S.ferus, S.thermophilus, L.raffinolactis, S.salivarius, L.lactis subsp.lactis, L. lactis and L.mesenteroides subsp.dextranicum; bacilli 7, namely:L.oris, L.fermentum, L.casei, L.plantarum.L.delbrueckii subsp.lactis, L.brevis and L.helveticus.(3) 8 strains of yeast were isolated and identified from 10samples. namely:C.ethanolica, H. marxianus, S.cerevisiae, B.claussenii, C.sake, P.fermentans, H.anomala and B. lambicus.(4) Using the 15 strains of LBA asolated as objects, determined their antioxidant activity. The results showed that 15 strains had different levels of antioxidant activity with 5 indicators: in the tolerance of H2O2, the ability of clearing superoxide radical (O-2-),chelating ability of Fe2-,the ability of preventing lipid to peroxide and clearing ability of DPPH radical. Strain DX-1, DX-3 and DLDQ1-1 shown high antioxidant activity in all measured indicators and had value of further research and development.更多还原