一种青稞格瓦斯的制备及挥发性风味成分分析

采用单因素及正交试验对以青稞原料的格瓦斯发酵工艺进行优化,并利用顶空固相微萃取-气相色谱-质谱联用技术(SPME-GC-MS)分析青稞格瓦斯挥发性风味成分。结果表明:原料经灭酶处理所得青稞汁中β-葡聚糖含量比未灭酶处理提高了36.08%;最佳发酵条件为青稞汁含量(以白利度计)14%,菌种添加量1.4 g/L,面包酵母菌与乳酸菌的添加比例为1∶1,温度30℃,时间10 h;经10 h熟化后,获得的青稞格瓦斯总酸度为1.76g/L、酒精度为2.13%vol、β-葡聚糖含量为15.75 mg/L、氨基氮含量为12.26 mg/100 m L;其主要挥发性风味成分为乙醇(53.46%)、异戊醇(13.08%)、苯乙醇(6.09%)、乙酸异戊酯(3.17%)等;色泽金黄透亮、酸甜苦味均衡、有成熟水果香与酒香。     

固、液态发酵生产微生物脂肪酶

目前脂肪酶生产主要有固、液态两种发酵方法。该文对两种发酵方法进行详细对比,概述固、液态发酵生产脂肪酶菌种及发酵底物,并对分批、补料分批、连续发酵等技术进行对比;介绍数学模型在脂肪酶生产中应用,并展望利用酶工程技术和数学模型改良脂肪酶生产。     

家庭自制格瓦斯饮料

介绍格瓦斯饮料的特点,以及以一些常见食品为原料制作家庭格瓦斯饮料的方法,重点介绍面包格瓦斯、玉米面格瓦斯和豆奶格瓦斯的制作方法。     

微生物发酵竹香鸡加工技术

研究了利用微生物发酵技术,添加益生菌生长促进剂加工竹香鸡的加工工艺和技术要点。     

量热法监控生物发酵过程的研究

量热法是生物热化学的重要方法之一,适合于生物体系各个层次的研究。在生物反应器的发酵过程中,量热法作为一种新的技术,简单适用,有着很大的市场前景。本文主要通过对生物发酵过程中罐体热流变化的研究,得出热量控制对生物发酵的影响,从而为大规模生产发酵过程的在线控制提供一定指导意义。     

微生物发酵法生产食品风味物质

微生物发酵法已经成为生产食品风味物质的一种重要手段.主要对食品中的常见的芳香风味物质(主要包括醛类、酮类、酯类、萜类等)和味感风味物质的微生物发酵进行了概述,并介绍了几种用于生产风味物质的发酵方式.     

茁霉多糖的微生物发酵及在食品工业中的应用

茁霉多糖具有很好的成膜性 ,形成的薄膜透明、防油、不透气 ,可作包衣和包装材料及纸的上光剂 ,代替淀粉制成低热量食品等 ,具有广阔的工业化应用前景。本文就茁霉多糖的生物学性质、影响微生物发酵的重要因素进行了综述 ,并简要叙述了茁霉多糖在食品工业中的应用     

馒头面团发酵过程中的微生物变化

探讨馒头面团长时间发酵过程中的酵母菌、醋酸茵、乳酸菌、大肠杆菌等微生物的变化。结果表明,发酵初期酵母菌数量增长较快,随着发酵的进行又逐步下降,最终酵母活力降至零;乳酸菌可以与酵母共生,并相互有利,它的变化与酵母密切相关;醋酸菌主要利用酵母的发酵产物,它的变化趋势基本上和酵母的趋势保持一致。大肠杆菌36h不超标。     

中国传统食醋微生物污染及控制措施研究进展

食醋微生物污染是导致食醋腐败变质的最主要原因,有效地检测和控制污染微生物是保证食醋安全以及进一步发展的基础。该文对食醋污染微生物的原因、危害以及种类进行了综述,开放式发酵环境及容器管道的不洁是食醋污染微生物的主要原因,致使胀气、产膜、发黏及浑浊等现象发生,最终造成企业经济损失并对消费者健康造成隐患。总结了目前的检测方法和控制措施,现有的传统微生物培养检测方法弊端很多,非培养技术更能满足快速准确的检测要求。除加热和添加防腐剂等常用控制措施外,紫外线消毒、膜过滤等技术也逐渐应用。针对现有研究的不足,展望了食醋污染微生物未来的研究方向,以期为食醋污染微生物的深入研究及有效控制提供参考和理论依据。     

Microbial and chemical changes in 'Sobrasada' during ripening

‘Sobrasada’ is a raw-cured product typical of Mallorca (Balearic Islands). Throughout its ripening process the product, like other raw-cured sausages, undergoes a series of chemical and microbial changes which lead to the formation of its desirable final characteristics.In the ‘sobrasada’ studied, the breeds, feeding and casings used in the Balearic Islands were employed. The evolution of different groups of microorganisms was followed: mesophylic aerobic microorganisms, lactic acid bacteria, Enterobacteriaceae, yeasts and moulds, group D Streptococcus, proteolytic microorganisms and lipolytic microorganisms. It was found that the predominant flora, from the beginning to the end, was made up of lactic acid bacteria. Conversely, Enterobacteriaceae disappeared as ripening went on, and the rest of the microbial groups studied underwent little variation along the process.An important characteristics of the product is the fast fall of pH, from values near 6·0 to values around 5·3, in the first week.     

Microbial community dynamics during the Scamorza Altamurana cheese natural fermentation

The growth dynamics of the natural microbial community responsible for the fermentation of Scamorza Altamurana, a typical Southern Italian cheese made using backslopping, was investigated applying a polyphasic approach combining 1) microbial enumeration with culture media, 2) randomly amplified polymorphic DNA (RAPD) fingerprinting of microbial communities, 3) sequencing of partial 16S ribosomal DNA (rDNA) genes, and 4) physiological tests. Viable cell counts on different culture media showed that the cocci community prevailed during the 18 h of curd fermentation and the 6 d of cheese ripening. RAPD fingerprinting made it possible to isolate 25 different strains identified by 16S rDNA sequencing as belonging to five species of Lactobacillus, three species of Streptococcus, one species of Weissella, and one species of Enterococcus. The physiological analyses of all lactic acid bacteria strains revealed that the isolates belonging to Streptococcus genus were the most acidifying, whereas lactobacilli were most proteolytic. Streptococcus thermophilus C48W and Lactobacillus delbrueckii subsp. bulgaricus B15Z dominated all through the fermentation process. Furthermore, they seemed to be stable in a subsequent whey sample analyzed after 7 mo. The recovery of strains endowed with interesting technological features, such as acidifying and proteolytic activities, and surviving in natural whey could allow the upscaling of cheese processing safeguarding the organoleptic characteristics of Scamorza Altamurana and could possibly improve other fermented dairy products.     

Use of lipase from Rhizomucor miehei in dry fermented sausages elaboration: Microbial, chemical and sensory analysis

Three different amounts of lipase (0.075, 0.100 and 0.150 LU/g) from Rhizomucor miehei (Palatase M 200L Novo Nordisk) were used to determine the correct amount to use in dry fermented sausages. Determination of acidity values through fourteen days of ripening showed that 0.100 LU/g was the most appropriate. Two types of fermented sausages were manufactured, addition of the enzyme being the only difference between them. Addition of Palatase did not affect product stability (pH and A(w)), and the growth of micro-organisms. In spite of the increase in acidity value, no rancidity developed as determined by both chemical and sensory analysis. Increases in the liberation of palmitic, palmitoleic, stearic, oleic and linoleic acids were found when lipase was used. Juiciness and taste were slightly better in the sausages with Palatase than in those without, but these differences were not reflected in the overall acceptability.     

Microbial modification of the texture of grated cassava during fermentation into akyeke

The traditional akyeke inoculum and fermenting akyeke, an indigenous cassava product, were investigated to identify microbial species responsible for the modification of cassava texture during fermentation. Both field and laboratory samples were examined and only some cultures isolated on Plate Count Agar and Malt Extract Agar were found to be capable of causing a softening of cassava tissue when plated directly on sterile cassava slices. The cassava tissue softening isolates on PCA were tentatively identified as Bacillus subtilis and isolates on MEA as Candida tropicalis and Zygosacchromyces florentinus. The population of B. subtilis in the laboratory sample of inoculum was found to be 2.4 x 10(9) cfu g(-1) and increased during dough fermentation from 1.1 x 10(7) to 3.5 x 10(9) cfu g(-1) after 96 h. C. tropicalis was present in the inoclum at 3.0 x 10(9) cfu g(-1) and increased during dough fermentation from 3.2 x 10(6) to 6.9 x 10(7) cfu g(-1) whilst Z. florentinus was present in the inoclum at 9.1 x 10(8) cfu g(-1) and increased from 8.1 x 10(5) to 7.5 x 10(6) cfu g(-1) during dough fermentation.     

宣恩火腿发酵过程中表面微生物群落演替规律

为揭示宣恩火腿发酵过程中微生物群落演替规律,运用高通量测序技术分析不同发酵时间火腿表面细菌和真菌群落组成,并对物种相关性和微生物群落功能进行分析.结果表明:宣恩火腿表面细菌群落多样性在发酵过程中持续增加,共检出11个门和96个属;发酵前、中期,木糖葡萄球菌(Staphylococcus xylosus)占绝对优势(>9...     

Microbial succession and metabolite changes during fermentation of saeu-jeot: Traditional Korean salted seafood

Saeu-jeot is made by the fermentation of highly salted [approximately 25% (w/v)] shrimp in Korea. Saeu-jeot samples were prepared in triplicate and their cell number, bacterial community, and metabolites were monitored periodically for 183 days. Quantitative PCR showed that bacterial populations were much more abundant than archaeal populations during the entire saeu-jeot fermentation period, which suggested that bacterial populations, not archaeal populations, might be primarily responsible for saeu-jeot fermentation. Pyrosequencing analysis revealed that Proteobacteria were dramatically replaced with halophilic Firmicutes as the fermentation progressed and members of Pseudoalteromonas, Staphylococcus, Salimicrobium, and Alkalibacillus were sequentially dominant and, eventually, Halanaerobium predominated after 66 days of fermentation. Halophilic archaeal genera, Halorubrum, Halolamina, Halobacterium, Haloarcula, and Haloplanus belonging to Euryarchaeota, were dominant, but their communities were relatively constant over the entire fermentation period. Metabolite analysis using a ¹H NMR spectroscopy showed that the amount of metabolites including amino acids, glycerol, and nitrogen compounds rapidly increased during the early fermentation stage, but their levels were relatively constant or they decreased after approximately 49 days of fermentation. A statistical analysis based on bacterial communities and metabolites demonstrated that members of Halanaerobium might be responsible for the production of acetate, butyrate, and methylamines after 66 days of fermentation, which could be considered as a potential indicator to decide the appropriate seafood fermentation time. This study will provide insights into the microbial succession and metabolites of fermented seafood and allow for a greater understanding of the relationships between the microbial community and metabolites in seafood fermentation.     

Microbial diversity in Tunisian olive fermentation brine as evaluated by small subunit rRNA - Single strand conformation polymorphism analysis

The microbial diversity of a Tunisian olive fermentation brine was analysed using a culture-independent approach based on the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). SSCP patterns show a remarkably simple microbial community but higher for bacterial community than for the eukaryotic community. This study did not show the presence of archaeal populations. After PCR amplification, two small subunit (SSU) rRNA clone libraries of Bacteria and Eucarya populations were established. Three bacteria and only one eukaryotic phylotype were identified. Two dominant bacteria showed 100% phylogenetic similarity to the 16S rRNA sequences of Lactobacillus plantarum and Lactobacillus collinoides and represent 85% of bacterial community. The third bacteria phylotype was phylogenetically close related to the 16S rRNA sequence of a moderately halophilic bacterium belonging to the class gamma Proteobacteria. The dominant eukaryotic phylotype was identified as a Pichia membranaefaciens.     

Physical,chemical and microbiological changes during green plant juice fermentation

Protein was precipitated from alfalfa juice by fermentation at 30°C, 35°C and 40°C.During fermentation there was a decrease in the pH, the total non-structural carbohydrate and the solid content while there was an increase in the lactic acid concentration and the population of the lactic acid bacteria in the juice. The lactic acid bacteria, which were initially only about 0·1% to 1·0% of the total bacteria count in the juice, predominated after a period of fermentation, producing mostly lactic acid and considerable amounts of acetic acid but only trace amounts of other volatile fatty acids.The addition of some lactic acid bacteria cultures—Lactobacillus plantarum and Pediococcus cereviseae—to the juice at the beginning of fermentation substantially reduced the lag phase and the final pH of the juice.     

Kefir grains as a starter for whey fermentation at different temperatures: chemical and microbiological characterisation

We report here a comparative analysis of the growth, acidification capacity, and chemical and microbiologic composition between kefir grains after 20 subcultures in whey at 20, 30, and 37°C and the original kefir grains coming from milk along with a determination of the microbiological composition of the fermented whey as compared with that of traditional fermented milk. When fermentation was carried out repeatedly at 30 or 37°C, kefir grains changed their kefir-like appearance, exhibited reduced growth rates, had a lower diversity of yeasts and water content, and a higher protein-to-polysaccharide ratio compared with the original kefir grains. In contrast, at 20°C kefir grains could remain in whey for prolonged periods without altering their acidification capacity, growth rate, macroscopic appearance or chemical and microbiologic composition-with the only difference being a reduction in certain yeast populations after 20 subcultures in whey. At this incubation temperature, the presence of Lactobacillus kefiranofaciens, Lb. kefir, Lb. parakefir, Lactococcus lactis, Kluyveromyces marxianus, Saccharomyces unisporus, and Sac. cerevisiae was detected in kefir grains and in fermented whey by denaturing-gradient-gel electrophoresis (DGGE). In whey fermented at 20°C the number of lactic-acid bacteria (LAB) was significantly lower (P<0·05) and the number of yeast significantly higher (P<0·05) than in fermented milk. Since the DGGE profiles were similar for both products, at this temperature the microbiologic composition of fermented whey is similar to that of fermented milk. We therefore suggest a temperature of 20°C to preserve kefir grains as whey-fermentation starters.     

人工接种泡菜与自然发酵泡菜风味物质的对比分析

利用高效液相色谱法、氨基酸自动分析仪及气相色谱方法,对人工接种和自然发酵泡菜中的有机酸、氨基酸和挥发性风味物质进行了对比分析。