新型大豆酸奶的研究

本研究以大豆为主要原料,经过膨化处理,将保加利亚乳杆菌(L.bulgaricus)和嗜热乳酸链球菌(Str.thermophilus)混合作为发酵剂进行乳酸发酵。用L9(34)正交实验得出最佳工艺条件,研制出了具有浓郁风味的乳酸菌发酵酸奶。     

基于16S rRNA测序分析罗伊氏乳杆菌酸乳对健康小鼠肠道菌群的影响

目的:通过16S rRNA测序,探讨新型罗伊氏乳杆菌(Lactobacillus reuteri)发酵酸乳对健康小鼠肠道菌群的影响。方法:将24只KM小鼠分为4组,空白组(Ctr组,灌胃无菌水),对照组(BS组,灌胃传统酸乳,即保加利亚乳杆菌(Lactobacillus bulgaricus)和嗜热链球菌(Streptococcus thermophilus)发酵酸乳),混合发酵酸乳组(LBS组,灌胃L. reuteri、L. bulgaricus和S. thermophilus 3菌混合发酵酸乳),以及L. reuteri单独发酵酸乳组(L组,灌胃L. reuteri发酵酸乳)。连续灌胃10 d后收集各组小鼠粪便,通过16S rRNA测序分析各组小鼠肠道中菌群丰度、多样性及菌落组成结构。结果:与BS组相比,LBS组和L组小鼠体重增加百分比显著降低(P<0.0001);PCA与门水平菌群聚类分析表明,L组与Ctr组PCA空间距离以及2组菌群比例最为接近;属水平菌群分析表明,LBS和L组中另枝菌属(Alistipes)和副拟杆菌属(Parabacteroides)两类潜在益生菌的丰...     

豆腐脑酸奶制作工艺

以大豆和牛奶为原料制备新型发酵制品-豆腐脑酸奶.利用保加利亚乳杆菌(L.bulgaricus)和嗜热乳酸链球菌(S.thermophilus)混合作为发酵剂进行乳酸发酵,通过单因素试验和通过单因素试验和L9(34)正交实验得出最佳工艺条件,同时对成品进行了理化指标、微生物指标的检验和感官评定,研制出具有浓郁风味,营养丰富的乳酸菌发酵的豆腐脑酸奶.     

运用SPE-GC/MS技术分析马克思克鲁维酵母对发酵乳中游离脂肪酸的影响

利用固相萃取及气相色谱质谱联用仪(solid-phase extraction-gas chromatography mass spectrometry,SPEGC/MS)技术,分析以马克思克鲁维酵母菌(Kluyveromyces marxianus)和乳酸菌(Streptococcus thermophilus,ST;Lactobacillus bulgaricus,LB)为混合发酵剂的发酵乳中游离脂肪酸含量变化,并对整个发酵过程进行跟踪监测。结果发现:使用SPE-GC/MS共检测出12种游离脂肪酸,其中短链及中链脂肪酸(C4-C12)有5种,长链饱和脂肪酸(C14-C18)7种,不饱和脂肪酸2种。2种发酵乳中主要的游离脂肪酸为棕榈酸、硬脂酸、肉豆蔻酸、油酸,且随着发酵时间的延长,混菌发酵乳中的含量显著高于双菌发酵乳(P0.001)。在发酵1~6 h范围内,马克思克鲁维酵母菌的添加显著增加了双菌发酵乳中游离脂肪酸的含量(P0.001)。     

SPME-GC-MS结合ROAV分析单菌及复配发酵牛乳中关键性风味物质

采用固相微萃取-气相色谱-质谱联用技术检测分析Streptococcus thermophilus与Lactobacillus delbrueckii subsp.bulgaricus单菌及复配发酵牛乳中的挥发性风味物质,结合相对气味活度值(relative odor activity value,ROAV)探讨发酵牛乳中关键性风味物质。结果表明:本实验共鉴定出100种挥发性风味物质,包括酸类、酮类、醛类、醇类、酯类、烷烃类和芳香族类化合物等。主成分分析表明,表征S.thermophilus单菌发酵乳的关键性风味物质是双乙酰、正壬醛和甲苯;表征L.bulgaricus单菌发酵乳的关键性风味物质是正庚醛、丁酸-2-甲基丙酯和1-庚醇;表征S.thermophilus与L.bulgaricus复配发酵乳的关键性风味物质是乙醛、3-甲基正丁醛、乙偶姻、2-壬酮、2-庚酮、醋酸乙烯酯、碳酸庚基苯基酯、甲酸乙烯酯和2-壬醇。相较于单菌发酵,复配发酵的风味物质组成、各组分相对含量及关键性风味物质均发生改变。     

乳酸发酵番茄汁中间生产试验

将筛选出的保加利亚乳杆菌(L. bulgaricus)和嗜热链球菌(Str. thermophilus)应用于乳酸发酵番茄汁的中试生产中。先在20升发酵罐内进行了两批试验,确立了初步的生产工艺流程,然后在500升发酵罐进行了进一步试验,获得了成功,生产出的乳酸发酵番茄汁pH为4.0～4.3,乳酸含量0.7％左右,加蔗糖3％,不添加防腐剂、香精、色素等化学物质。保存半年后经检测,其理化及微生物学指标均符合国家规定标准。申试结果为工业规模生产奠定了基础。     

乳酸菌对羊乳酸奶体外降血糖和抗氧化功能的影响

目的：以羊奶为发酵原料,探究不同乳酸菌对发酵羊奶体外降血糖和抗氧化功能活性影响。方法：以3株实验室保存的具有降血糖、抗氧化功能的乳酸菌和酸奶商业发酵剂Lactobacillus bulgaricus(LB)和Streptococcus thermophiles(ST)为发酵菌株,采用功能菌株单菌发酵和联合商业发酵剂混合发酵两种方式发酵羊奶,分析不同乳酸菌发酵羊酸奶体外抗氧化和降血糖功能。结果：单菌发酵和混合发酵羊奶,其体外降血糖活性和抗氧化活性均有不同程度提高;其中乳酸片球菌（Pediococcus acidilactici）GC215单菌发酵羊酸奶的DPPH自由基清除率和还原活性最高,分别为87.35%和359.17μmol/L L-半胱氨酸还原当量;PTIO自由基清除率为11.25%;马里甘草乳杆菌（Liquorilactobacillus mali）L31发酵羊酸奶对α-葡萄糖苷酶抑制率比未发酵羊奶提高了44.08%,短乳杆菌（Lactobacillus brevis）PC-2与保加利亚乳杆菌和嗜热链球菌混合发酵羊酸奶对α-淀粉酶活性抑制最高,为82.30%。结论：功能性乳酸菌发...     

新型大豆酸奶的研究

本研究以大豆为主要原料，经过膨化处理，将保加利亚乳杆菌(L．bulgaricus)和嗜热乳酸链球菌(Str．themophilus)混合作为发酵剂进行乳酸发酵。用L9(3^4)正交实验得出最佳工艺条件，研制出了具有浓郁风味的乳酸菌发酵酸奶。     

基于SPME-GC-MS法分析发酵乳中挥发性风味物质

利用固相微萃取-气质联用技术(SPME-GC-MS)检测嗜热链球菌(Streptococcus thermophilus)IMAU20537和德氏乳杆菌保加利亚亚种(Lactobacillus delbrueckii subsp.bulgaricus)IMAU20240的单菌发酵乳和二者复配发酵乳贮藏期间的挥发性风味物质。结果表明:三种发酵乳的风味物质包括酸类、醇类、醛类、酮类、酯类、含氮化合物和芳香族及其衍生物。其中,酮类化合物在S.thermophilus IMAU20537发酵乳风味物质中种类最多,占种类总量的27.27%;醛类化合物在L.delbrueckii subsp.bulgaricus IMAU20240发酵乳中种类最多,为20.83%;复配发酵乳中酮类和醛类化合物的种类相同,均占22.73%;而且三种发酵乳在贮藏不同时间内相对峰面积最高的物质均是酮类化合物。分析发现,复配发酵乳在贮藏期间的风味物质种类较两株单菌的发酵乳增多,其中,一些主要的风味化合物如乙醛、乙酸、双乙酰、乙偶姻等对于构成其特征风味具有重要作用。     

新疆伊犁地区乳制品中乳酸菌发酵和益生特性及其复合发酵方案优化

对7株实验室保存的优良乳酸菌在酸乳发酵过程中的酸化能力、产香能力以及酸乳质构进行测定,并通过抑菌、胃肠液耐受性以及抗生素敏感性等实验探究菌株的益生特性,筛选其中性能较优良的菌株进行组合复配,以获得最优的复合发酵菌株组合方案。单菌株发酵实验结果表明乳明串珠菌Leuconostoc lactis XKN1-5、乳杆菌属Lactobacillus delbrueckii subsp. bulgaricus BSTS6-4凝乳时间短(7 h左右),酸乳酸度可达96°T,酸化能力较其他菌株好;L. delbrueckii subsp. bulgaricus BSTS6-3、Streptococcus thermophilus XSXN1-2发酵制得的酸奶质构特性较好;L. delbrueckii subsp. bulgaricus BSTS6-1、S. thermophilus XSXN1-1产香性能最优,其中菌株XSXN1-1双乙酰质量浓度达到2.02 mg/L,乙醛质量浓度可达16 mg/L,能够明显改善酸奶的风味。益生实验结果表明,乳杆菌菌株Lactobacillus fermentum BST2-3、L. delbrueckii subsp. bulgaricus(BSTS6-1、BSTS6-3、BSTS6-4)能够抑制肠道致病菌的生长;L. fermentum BST2-3、L. delbrueckii subsp. bulgaricus(BSTS6-1、BSTS6-4)的黏附性较好;L. fermentum BST2-3在模拟胃肠液处理9 h后活菌数仍可达10~6 CFU/mL;且7株乳酸菌对大部分所试抗生素表现出敏感,安全性较高。最后按照产酸、产香、质构以及益生特性将菌株分类并进行酸乳复合发酵,获得复合发酵的最优菌株组合为菌株L. delbrueckii subsp. bulgaricus(BSTS6-4、BSTS6-3)、S. thermophilus XSXN1-1、L. fermentum BST2-3。     

发酵羊乳中乳酸菌低产粘菌株的筛选

对从商业乳酸菌发酵剂分离纯化的11株保加利亚乳杆菌和11株嗜热链球菌在发酵羊乳中的粘度进行了研究。结果表明,保加利亚乳杆菌L.b-124菌株和L.b-346菌株、嗜热链球菌S.t-222菌株和S.t-346菌株具有较低的产粘能力,凝乳时间也较短;将L.b-346菌株与S.t-346菌株按杆菌和球菌1:1比例混合后在43℃下发酵羊乳时,可获得较低的发酵粘度。     

发酵羊奶中乳酸菌耐热菌株的筛选

对从商业乳酸菌发酵剂分离纯化的11株保加利亚乳杆菌和11株嗜热链球菌在发酵羊奶中的耐热性进行了研究。结果表明,保加利亚乳杆菌L.b-346和L.b-124菌株、嗜热链球菌S.t-883菌株和S.t-124菌株的耐热性较好;当L.b-346菌株、L.b-124菌株与S.t-883菌株、S.t-124菌株按杆菌和球菌以不同比例配合时,L.b-346菌株与S.t-124菌株以1∶2比例配合,可获得较高的耐热性。     

AMINO ACID COMPOSITION AND NUTRITIONAL IMPLICATIONS OF MILK FERMENTED BY VARIOUS LACTIC CULTURES

A total of nine milk products were analyzed for total and free amino acids and total and nonprotein nitrogen. The products were: (1) whole milk (WM), (2) skim milk (SM), (3) WM fermented by Streptococcus thermophilus, (4) SM fermented by S. thermophilus, (5) WM fermented by Lactobacillus bulgaricus, (6) SM fermented by L. bulgaricus, (7) WM fermented by L. acidophilus, (8) SM fermented by L. acidophilus and (9) commercially prepared buttermilk. Essential amino acid content of the fermented milk was lower than that of the whole or skim milk. Fermentation of milk by lactic cultures decreased the total lysine (except butter milk) and methionine contents of all the samples. Since these two amino acids are limiting amino acids in protein malnourished areas, lactic fermentation of milk may be undesirable based on the chemical scores of the protein. However, the free amino acid content, including that of lysine and methionine, increases significantly upon lactic fermentation of milk. This predigestion of protein might result in an increased availability of the amino acids to offset the reduction in amino acids during fermentation and may even result in a better quality protein. Biological evaluation of the fermented milk proteins is necessary to evaluate their nutritional quality. L. bulgaricus was the most proteolytic of all the organisms used.     

凝结芽孢杆菌发酵乳的工艺优化

该研究对凝结芽孢杆菌发酵乳生产工艺进行了优化。以凝结芽孢杆菌13002、保加利亚乳杆菌CGMCC 1.290、嗜热链球菌CGMCC 1.2741共发酵的新型发酵乳为研究对象,以不同菌种复配比、菌种接种量、发酵基低聚果糖添加量进行单因素实验,再以感官评分为响应值,通过Box-Behnken中心组合建立数学模型研究发酵乳的最佳生产工艺。结果表明,菌种复配比（凝结芽孢杆菌：（嗜热链球菌:保加利亚乳杆菌=1:1））3:1、低聚果糖添加量1.50%、接种量1.50%为最佳工艺条件。在该优化条件下,测定发酵乳的平均滴定酸度值为90.59,与模型预测酸度值（93.25）拟和率达97.15%,说明此凝结芽孢杆菌发酵乳具有一定的竞争优势,为新型发酵乳研发提供理论基础和拓展思路。     

富含γ-氨基丁酸酸奶的制备及质构特性研究

本试验对单菌发酵、混菌发酵和添加不同底物浓度的L-谷氨酸钠对酸奶感官特性和质构特性的影响作用进行了研究,为开发富含γ-氨基丁酸的新型功能发酵乳制品提供依据。试验结果表明,当底物L-谷氨酸钠的添加浓度为75mmol/L,辅酶浓度为20μmol/L,植物乳杆菌NDC75017、德氏乳杆菌保加利亚亚种、嗜热链球菌3株菌混合（L.P∶L.b∶S.t=0.5∶0.5∶1.5）按2%的比例添加量,在43℃条件下发酵酸奶时,酸奶的感官特性和质构特性最好。此时酸奶的粘度为1 466.5±1.0p·s、保水力为71.7±3.2%、硬度为77.3±1.7g、凝聚性为48.1±1.2g、粘性指数为146.8±0.9p·s;用高效液相色谱法检测酸奶中GABA的含量高达46mg/100g。综合酸奶口感、质构特性及GABA含量等指标,最终选择添加底物L-谷氨酸钠的浓度为75mmol/L,植物乳杆菌NDC75017、德氏乳杆菌保加利亚亚种、嗜热链球菌3株菌作为酸奶发酵的混合发酵剂。     

Influence of temperature on associative growth of Streptococcus thermophilus and Lactobacillus bulgaricus

Compatibility of Streptococcus thermophilus and Lactobacillus bulgaricus during associative growth as dependent on optimum growth temperature was determined. Optimum growth temperatures for 9 strains of S. thermophilus and 10 strains of L. bulgaricus ranged from 35 to 42 degrees C for S. thermophilus and 43 to 46 degrees C for L. bulgaricus. Streptococcus thermophilus and L. bulgaricus strains exhibiting similar to divergent optimum growth temperatures were combined (1:1 vol/vol) and incubated in milk at 37, 42, and 45 degrees C until pH 4.2 was reached. Initial and postincubation cell numbers were determined by plate count method. Streptococcus thermophilus strains reached greater cell numbers than L. bulgaricus at 37, 42, and 45 degrees C in 93.3% of the mixed culture trials. Average rod-coccus ratios obtained at 37, 42, and 45 degrees C were 1:2.2, 1:8, and 1:2.4, respectively. Optimum growth temperatures had no influence on growth of L. bulgaricus and S. thermophilus in mixed culture. Rather, temperature appeared to influence compatibility by determining the concentration or type of stimulatory factor(s) produced by L. bulgaricus. All strains of S. thermophilus exhibited an uncoupling of growth from acid production. Optimum temperature for acid production ranged from 2 to 8 degrees C above optimum growth temperature. These findings warrant consideration in the manufacture of yogurt and other fermented milk products.     

黑甜玉米片发酵乳的研制

对具有营养保健功能的黑甜玉米片发酵乳的加工工艺进行了初步探讨。结果表明:以黑甜玉米粒为原料,经过系列加工及强化后制得营养丰富的黑甜玉米片;按照黑甜玉米片浆:牛乳=1:3的配比,将保加利亚乳杆菌和嗜热链球菌以1:1混合作为发酵剂进行发酵,采用接种量3%,加蔗糖量8%,发酵温度43℃,发酵时间6h等工艺条件,可得到品质优良、风味独特的黑甜玉米片发酵乳。     

酮香型羊酸奶的研制及与牛酸奶风味物质的比较

以羊奶粉为主要原料,选用丁二酮乳链球菌、嗜热链球菌和保加利亚乳杆菌相配合的发酵剂研制山羊酸奶,酮香型羊酸奶各因素的最佳配比为丁二酮乳链球菌、嗜热链球菌及保加利亚乳杆菌配比为1∶1∶2,菌种添加量为4%,加糖量为8%,发酵温度为40℃。采用SPME-GC-MS技术,对羊酸奶中风味物质进行分析,检测出19种主要风味物质,以酮类、醇类、呋喃类和羧酸类为主,主要特征风味物质是丁二酮、乙酸、甲酸甲酯、辛酸、丁醛、棕榈酸、苹果酸、DL-丙氨酸、呋喃甲醇、庚醇、邻苯二甲酸二乙酯。     

Effect of Inoculation Level of Lactobacillus rhamnosus and Yogurt Cultures on Conjugated Linoleic Acid Content and Quality Attributes of Fermented Milk Products

ABSTRACT:  The effect of inoculation concentration of Lactobacillus rhamnosus and yogurt cultures and storage time on conjugated linoleic acid (CLA) content and quality attributes of fermented milk products was determined. Yogurt culture ( Lactobacillus bulgaricus and Streptococcus thermophilus, 1:1 ratio, YC ) , L. rhamnosus (LB), and LB co-cultured with yogurt culture, were inoculated at 10⁶, 10⁷, 10⁸ CFU/mL into a milk with hydrolyzed soy oil as the lipid source. CLA content, microbial counts, acidity, texture, and volatile flavor profile of the fermented milk products were stable during storage at 4 °C for 14 d. Total CLA contents ranged from 0.51 to 1.00 mg CLA/g lipid following 14 d of storage. Inoculation level of L. rhamnosus and yogurt cultures had no significant effect on CLA content and texture, but affected acidity and the volatile flavor profile of the fermented milk products. The fermented milk products produced by L. rhamnosus co-cultured with yogurt culture with 10⁷ CFU/mL total inoculation level resulted in a high CLA content and desirable quality characteristics. This research demonstrated that the optimal inoculation concentration and the combination of L. rhamnosus and yogurt cultures were important factors to produce fermented milk products with CLA content and acceptable quality attributes.     

Contribution of Streptococcus thermophilus to growth-stimulating effect of yogurt on rats

The origin of the growth-stimulating factor in yogurt was studied in rats fed liquid or freeze-dried diets of milk, yogurt, milks fermented individually by Streptococcus thermophilus and Lactobacillus bulgaricus, milks to which cells of Streptococcus thermophilus and Lactobacillus bulgaricus were added. Diets containing sonicated cells, cell supernatant, and cell fractions also were fed. Milk fermented by Streptococcus thermophilus and milk plus Streptococcus thermophilus cells stimulated growth as effectively as did yogurt. That finding and the absence of stimulation in rats fed Lactobacillus bulgaricus showed that Streptococcus thermophilus is responsible for stimulation of growth by yogurt. Growth was stimulated by an intracellular factor and not by fermentative changes in the milk.