不同发酵剂对Mozzarella干酪品质的影响

采用嗜热链球菌和嗜热乳杆菌作为Mozzarella干酪的发酵剂，研究单一嗜热链球菌发酵剂与嗜热链球菌和嗜热乳杆菌组成的混合发酵剂对Mozzarella干酪品质的影响。结果表明，混合菌作发酵剂制得的干酪品质优于用单一嗜热链球菌作发酵剂的干酪。     

提高嗜酸乳杆菌酸乳菌活力的研究

以嗜酸乳杆菌为主发酵剂,嗜热链球菌和保加利亚乳杆菌为辅助发酵剂制作嗜酸乳杆菌酸乳,采用正交实验,并分析发酵过程中pH、乳酸菌数以及感官品质的变化,确定混合菌种的最佳比例。结果表明,嗜酸乳杆菌1.8%、嗜热链球菌1.4%、保加利亚乳杆菌0.6%混合发酵,可以提高乳中嗜酸乳杆菌的菌活力并改善其风味。经验证,混合菌种发酵制作的酸奶在风味和保健功能等方面明显优于单一菌种发酵制作的酸乳。     

瑞士乳杆菌与干酪乳杆菌在不同原料中的发酵特性研究

研究了瑞士乳杆菌和干酪乳杆菌单独与组合,以及与嗜热链球菌和保加利亚乳杆菌组合在纯牛乳、纯豆乳和混合乳中发酵12h后pH值和酸度值变化,以此来说明它们在3种原料中的生长情况.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.     

三种乳酸菌混合培养的研究

在5L罐中对保加利亚乳杆菌、嗜酸乳杆菌和嗜热链球菌进行了单独培养及混合培养研究。实验结果表明,嗜酸乳杆菌及嗜热链球菌会抑制保加利亚乳杆菌的生长,保加亚利乳杆菌与嗜酸乳杆菌可能对嗜热链球菌的生长具有促进作用,嗜热链球菌对嗜酸乳杆菌具有促进作用,保加利亚乳杆菌对嗜酸乳杆菌的生长没有促进作用。这种实验结果为混合培养益生菌提供的实验参考。     

新型酸奶发酵剂的研究

研究了具有不同粘度,风味和保健功能的新型酸奶发酵剂,首先通过对专用酸奶菌种嗜热链球菌和保加利亚乳杆菌不同菌株的组合筛选,优选出具有不同粘度和风味的３种组合;其次,酸奶的疗效保健作用来源于嗜酸乳杆菌,通过研究缓冲盐,生长促进物质对该菌生长的影响,确定了适宜的培养基成分和发酵剂中菌种的配比。     

罗地亚9001直投型发酵剂发酵特性研究

利用罗地亚90001直投型发酵剂来发酵酸奶，探讨了利用直投型发酵剂发酵的酸奶不能作为后续发酵剂进行酸奶生产的原因。在实验中首先利用直投型发酵剂发酵牛乳，然后依次利用各代次产物作为后续发酵剂生产酸奶，直至第6代牛乳不能再正常发酵为止。同时，对每代酸奶中嗜热链球菌和保加利亚乳杆菌进行计数，并观察嗜热链球菌和保加利亚乳杆菌比例上的变化。最后将第6代不能正常发酵酸奶中的嗜热链球菌和保加利亚乳杆菌分离并进行鉴定。将二者按1：1(数量比)的比例接种牛乳，发现牛乳能够正常发酵。结果表明。利用酸奶作为后续发酵剂的第6代牛乳不能正常发酵的原因是嗜热链球菌和保加利亚乳杆菌的数量比发生变化。而导致此情况发生的原因可能是由于低温下二者的生长速率不同。     

不同乳酸菌对凝固型荔枝酸奶的发酵特性和质构的影响

以纯牛奶和荔枝汁为主要原料,以干酪乳杆菌、保加利亚乳杆菌和嗜热链球菌为发酵菌种,探讨三种乳酸菌的不同组合发酵对凝固型荔枝酸奶的发酵特性和质构的影响。结果表明:干酪乳杆菌产胞外多糖能力较强,单独发酵时胞外多糖含量达到22.50g/L,而嗜热链球菌和保加利亚乳杆菌单独发酵时胞外多糖的含量分别为5.73 g/L和0.29 g/L;各种不同乳酸菌组合发酵后酸奶的表观粘度和持水力与胞外多糖的含量呈正相关(R2=0.98);干酪乳杆菌产酸能力弱,单独发酵后p H高于其它添加有嗜热链球菌和保加利亚乳杆菌的组合,导致酸奶的硬度偏低,但干酪乳杆菌联合嗜热链球菌或保加利亚乳杆菌发酵时,发酵酸奶的硬度和乳酸菌活菌数均明显优于单独发酵组。因此,当干酪乳杆菌与嗜热链球菌及保加利亚乳杆菌联合发酵时,能充分发挥三个菌种的各自优势,菌落总数、胞外多糖含量和质构均能达到较好的品质水平。     

九种益生菌之间的相互作用及协同共生机理

为了研究9种益生菌之间的相互作用及协同共生机理,采用牛津杯扩散法,对德氏乳杆菌保加利亚亚种、植物乳杆菌、嗜热链球菌、鼠李糖乳杆菌、嗜酸乳杆菌、乳双歧杆菌、两歧双歧杆菌、干酪乳杆菌、副干酪乳杆菌9种益生菌进行拮抗试验,再将菌种之间无拮抗作用的实验组,按1%接种量以1∶1的比例两两混合发酵,测其OD600nm值。约1/3的益生菌之间都存在拮抗作用,但嗜热链球菌与德氏乳杆菌保加利亚亚种、嗜酸乳杆菌、干酪乳杆菌,以及干酪乳杆菌与嗜酸乳杆菌存在协同共生作用,由于乳杆菌有较强分解蛋白质的能力,能产生多种氨基酸可刺激嗜热链球菌生长,嗜热链球菌因产酸速率快,可以快速代谢产生乳酸、甲酸、CO2等,从而促进乳杆菌的生长。该研究分析了9种常用益生菌之间的相互作用,为益生菌混合发酵、微生物制剂的开发提供理论依据。     

保加利亚乳杆菌和嗜热链球菌相互作用的研究

探讨了嗜热链球菌和保加利亚乳杆菌之间的相互作用(拮抗和共生效果)，指出这两个菌种的许多菌株在代谢过程中会产生过氧化氢、细菌素等抑菌性物质，导致嗜热链球菌与保加利亚乳杆菌间表现出非协同生长的现象。在此基础上，建立了评价发酵剂之间相互作用的新的指标体系，旨在方便优良酸奶发酵剂菌种的筛选工作。     

酸奶与乳酸饮料中乳酸菌的分离鉴定及发酵性能试验

本文对4个不同地区引进酸奶发酵剂及昆明市场现有的5种乳酸饮料中的乳酸菌进行了分离鉴定。分离菌株基本与行业生产标准要求选用菌株相一致,从每份酸奶样品中均分离到保加利亚乳杆菌和嗜热链球菌,从2份乳酸饮料样品中分别分离到干酪乳杆菌和嗜酸乳杆菌。     

Changes in chemical composition and sensory qualities of peanut milk fermented with lactic acid bacteria

The effects of fermentation of aqueous extracts of peanuts (peanut milk) with Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus salivarius ssp. thermophilus, separately and in combination, on selected chemical and sensory qualities were investigated. Changes in pH, titratable acidity and viable cell populations indicated that there was a synergistic interaction between L. delbrueckii ssp. bulgaricus and S. salivarius ssp. thermophilus during fermentation. Analysis of headspace volatiles revealed that hexanal, which is one of the compounds responsible for undesirable green/beany flavor in peanut milk, completely disappeared as a result of fermentation. S. salivarius ssp. thermophilus was more effective than L. delbrueckii ssp. bulgaricus in reducing the hexanal content. The acetaldehyde content of peanut milk increased during fermentation. Changes in concentrations of these volatile compounds were correlated with sensory evaluation scores which showed that a significant (P less than or equal to 0.05) decrease in green/beany flavor and a significant increase in creamy flavor occurred as a result of fermentation.     

基于快速成熟模型的藏灵菇发酵切达干酪挥发性风味物质分析

通过建立快速成熟干酪模型,采用固相微萃取法提取传统藏灵菇发酵的切达干酪模型与商品发酵剂制作的切达干酪模型中挥发性成分,并结合气相色谱-质谱联用技术和气相色谱-嗅闻技术对萃取成分进行鉴定,结果表明醇类和酯类是藏灵菇发酵切达干酪成熟过程中的主要风味物质。藏灵菇发酵切达干酪模型中风味物质的种类和含量都明显高于商业发酵剂制作的切达干酪模型,其中酯类物质的变化最为显著。感官评价和风味分析结果表明,藏灵菇发酵切达干酪模型中酯类和醇类物质种类和含量更为丰富,风味更强,水果香味更浓郁,还具有酒香味。     

Thermally-dried immobilized kefir on casein as starter culture in dried whey cheese production

The aim of the present study was to evaluate the use of thermally-dried immobilized kefir on casein as a starter culture for protein-enriched dried whey cheese. For comparison reasons, dried whey cheese with thermally-dried free kefir culture and with no starter culture were also produced. The effect of the nature of the culture, the ripening temperature and the ripening process on quality characteristics of the whey cheese was studied. The association of microbial groups during cheese maturation suggested repression of spoilage and protection from pathogens due to the thermally-dried kefir, as counts of coliforms, enterobacteria and staphylococci were significantly reduced in cheeses produced using thermally-dried kefir starter cultures. The effect of the starter culture on production of volatile compounds responsible for cheese flavor was also studied using the SPME GC/MS technique. Thermally-dried immobilized kefir starter culture resulted in an improved profile of aroma-related compounds. The preliminary sensory evaluation ascertained the soft, fine taste and the overall improved quality of cheese produced with the thermally-dried immobilized kefir. The potential of protein-based thermally-dried starter cultures in dairy products is finally highlighted and assessed.     

Influence of starter culture ratios and warm room treatment on free fatty acid and amino acid in Swiss cheese

Quantification of water-soluble volatile free fatty acids (FFA) and free amino acids (FAA) was performed as a ripening index and an indirect measure of flavor development in Swiss-type cheeses. The objective of this research was to assess the effect of warm room treatment (WRT) and usage ratio of starter cultures, Streptococcus thermophilus and Lactobacillus helveticus vs. propionibacteria, on the concentration of FFA and FAA in pilot plant-scale Swiss cheese. A capillary gas chromatograph equipped with a flame ionization detector was used for the analysis of FFA in Swiss cheese. Free amino acids were analyzed by the Cd-ninhydrin method. Starter culture ratios did not affect development of FAA during the cheese ripening. However, duration of WRT had an effect on the concentration of FAA in the Swiss cheese. Free amino acids increased considerably during WRT. A continuous increase in FAA was shown during 70-d ripening time after WRT. The concentrations of C2:0 and C3:0 fatty acids were affected by starter culture ratios after 2-wk WRT, but these differences had mostly disappeared after 3-wk WRT. Similar concentrations of FFA and FAA reported in previous studies were developed in Swiss cheese with a 3-wk WRT and a 0.33:1 ratio of Streptococcus thermophilus and Lactobacillus helveticus to propionibacteria.     

乳酸菌发酵酸豆乳香气成分检测分析及评价

采用顶空固相微萃取(SPME)与气相色谱- 质谱(GC-MS)联用检测分析技术,并结合感官评分法对保加利亚乳杆菌、瑞士乳杆菌和嗜热链球菌3 种乳酸菌混合发酵的豆乳进行香气分析和评价,探讨不同乳酸杆菌及其与嗜热链球菌按比例混合发酵对酸豆乳香气的影响。感官评定结果表明,乳酸菌种及其混合比例对发酵酸豆乳的香气有明显影响。香气检测分析发现,对比发酵前样品,发酵后酸豆乳中酮类、酸类含量显著增加,而醛类和醇类含量明显减少,3 种酸豆乳中相同关键香气成分含量有差异。感官评定与香气检测分析结果一致,1:1 的保加利亚乳杆菌和嗜热链球菌组成的菌种产香浓郁,产酸力高,是豆乳发酵的优选菌种。     

解淀粉芽孢杆菌GSBa-1凝乳酶在马苏里拉干酪中的应用

对分离自酒曲的1 株解淀粉芽孢杆菌GSBa-1发酵所产凝乳酶进行研究,该酶凝乳活力高而蛋白水解活力低,纯酶凝乳活力可达1.46×106 SU/g;使用该凝乳酶和商品凝乳酶制作马苏里拉干酪,并对干酪理化成分、成熟过程中pH值和微生物指标及干酪成熟前后质构特性、游离脂肪酸、可溶性蛋白、风味和干酪性能等指标进行对比分析。结果显示,理化成分上菌株凝乳酶与商品凝乳酶制作的干酪相接近（P＜0.05）。干酪在成熟过程中,发酵剂存活数先增加后减少,但其差异不大;菌株凝乳酶制作的干酪pH 4.6可溶性蛋白含量较多,干酪的游离氨基酸总量（76 mg/100 g）也高于商品凝乳酶制作的干酪游离氨基酸总量（55.3 mg/100 g）;菌株凝乳酶制作的干酪质构特性优于商品凝乳酶制作的干酪;电镜结果显示,菌株凝乳酶制作的干酪内部网状结构更充实;菌株凝乳酶具有稍强的蛋白水解活力,导致其制作的干酪风味物质种类多于商品凝乳酶制作的干酪,风味物质更加丰富。干酪样品的保形性和拉丝性实验测定结果显示,2 种凝乳酶制作的干酪性能差异不大（P＞0.05）;对2 种凝乳酶制作的干酪进行感官评定,其总评分相接近。以上结果表明,解淀粉芽孢杆菌GSBa-1凝乳酶在一定程度上可代替小牛凝乳酶应用于马苏里拉干酪的生产。     

热激处理菌种对奶酪品质的影响

为研究热激处理（63 ℃、20 min）发酵剂菌种（唾液链球菌嗜热亚种和保加利亚乳杆菌德氏亚种混合菌种）对奶酪成熟过程中品质特性的影响,对两种不同菌种所制作奶酪基本组成及成熟过程中的质构、感官、蛋白降解、风味物质等指标进行了测定。结果表明,热激处理菌种对奶酪基本组成影响不大,但热激处理菌种有利于奶酪成熟过程中蛋白质的降解,进而使奶酪的硬度和咀嚼性显著降低,也促使奶酪在成熟120 d时形成了更多的醛类、酮类、酯类等主要挥发性风味物质,同时奶酪的风味和组织状态的感官评价也较好。     

保加利亚乳杆菌与嗜热链球菌发酵夸克的工艺条件优化

以脱脂乳为原料,保加利亚乳杆菌和嗜热链球菌混合发酵剂制备夸克。以乳清OD500nm值、夸克校正产率及感官品质为评定指标,对凝乳酶添加量、CaCl2添加量、发酵剂嗜热链球菌与保加利亚乳杆菌配比、切割pH值4个因素进行考察。在此基础上对夸克感官评分进行四因素两水平的正交试验。结果表明：在凝乳酶添加量0.015%、嗜热链球菌与保加利亚乳杆菌配比3:2、CaCl2添加量0.02%、切割pH值为4.5时,所得夸克的感官评分最高,具有浓郁的奶香味,酸味清爽无颗粒感。     

驼乳干酪的工艺优化及成熟期间的理化特性

研究了驼乳干酪最佳加工工艺及成熟期间理化和微生物指标的变化。确定了驼乳干酪的最佳工艺参数:发酵剂的添加量为0.006%,CaC12的添加量为0.03 g/L,pH值为6.1,凝乳酶的添加量为0.06 g/L,凝乳温度为35℃。驼乳干酪的干物质质量分数约为45%,随成熟时间的延长,驼乳干酪的蛋白质、脂肪、乳糖、水分,质量分数下降;硬度、咀嚼性升高,但黏着性和弹性降低;pH4.6-SN的质量分数、12%TCA-SN和5%PTA-SN的质量分数都有不同程度的上升;发酵剂乳酸菌数在逐渐降低,非发酵剂活菌数却在逐渐增高。     

Effect of mesophilic lactobacilli and enterococci adjunct cultures on the final characteristics of a microfiltered milk Swiss-type cheese

The effect of four associations of adjunct cultures composed of mesophilic lactobacilli and enterococci, either solely or combined, on the microbiological, biochemical and sensory characteristics of Swiss-type cheese made using microfiltered cows’ milk and supplemented with propionibacteria was studied. The global pattern of growth was similar to that generally observed in raw milk cheese and interactions between microflora were highlighted during ripening. Enterococci, which negatively affected the survival of streptococci starters, seemed to play a limited role in the formation of volatile compounds, probably due to their low levels throughout ripening. On the contrary, mesophilic lactobacilli, which affected the evolution of propionibacteria, enterococci and L. delbrueckii subsp. lactis starter counts, modified free amino acid content, production of volatile compounds and organoleptic properties of mature cheese. This population appeared to be of major importance in the formation of cheese flavor as it was positively related to numerous potential flavor compounds such as alcohols and their corresponding esters, acetaldehyde and 4-methyl-4-heptanone. The original mesophilic lactobacilli present in milk could play an important role in the sensorial diversity of raw milk Swiss-type cheeses such as Comte.