新疆塔城地区哈萨克族传统奶酪中酵母菌的分离鉴定

为保护新疆哈萨克族传统奶酪中的优良酵母菌株,从新疆塔城牧区不同牧场采集的10份哈萨克族传统奶酪样品中,分离得到44株酵母菌。采用形态学、生理生化特性鉴定、5.8S rDNA序列同源性分析相结合的方法,对分离菌株进行鉴定。共鉴定出5个种,其中34株库德毕赤酵母（Pichia kudriavzevii）,为优势菌株,6株戴尔有孢圆酵母（Torulaspora delbrueckii）,2株乳酸克鲁维酵母（Kluyve- romyces lactis ）,1株马克思克鲁维酵母（Kluyveromyces marxianus ）,1株发酵毕赤酵母（Pichia fermentans ）。结果表明,哈萨克族传统奶酪制品中所含酵母菌与其他地区的存在差异性,有其独特的酵母菌资源。     

酒曲中酵母菌的分离鉴定及果酒发酵的初步研究

酵母菌是决定果酒品质的关键因素。采用稀释涂布平板法分离纯化酒曲中的菌株,以传统形态学及分子系统发育分析对酵母菌进行初步鉴定,从6种市售酒曲样品中分离出10株酵母菌,经 26S rDNA 序列分析,有3株为库德里亚夫毕赤酵母(Pichia kudriavzevii),1株为异常毕赤酵母(Pichia anomala),2株克鲁维酵母(Kluyveromyces marxianus),3株酿酒酵母(Saccharomyces cerevisiae),1株葡萄牙棒孢酵母(Clavispora lusitaniae)。通过初筛将筛选出的酵母菌CK-03用于猕猴桃汁发酵,发酵液经顶空固相微萃取-气质联用技术(solid phase microextractiongas chromatography/mass spectrometry,SPME-GC/MS)测定分析,结果显示共检测出25种挥发性成分,主要为酯类和醇类物质。     

新疆伊犁牧区发酵乳制品中酵母菌的分离和多样性分析

为保护新疆民族传统工艺制作的奶酪中经几千年驯化的优良酵母菌株,从新疆伊犁牧区少数民族家中采集样品20份,分离得到33株酵母菌,并对其进行生理生化鉴定、利用26S rDNA D1/D2区域序列分析对这些菌株进行了分类鉴定和多样性分析。共鉴定出4属5种,其中唐布拉牧区和那拉提牧区的优势菌株为发酵毕赤氏酵母(Pichia fermentans),托里县和布尔津县采集的样品中的优势菌种为酿酒酵母(Saccharomyces cerevisiae);马克斯克鲁维酵母(Kluyveromyces marxianus)和酿酒酵母(Saccharomyces cerevisiae)是奶酪样品中的共同菌株。     

椰纤果发酵液中降解细菌纤维素酵母菌株的分离及鉴定

从被微生物污染的椰纤果发酵液中分离筛选出13株能够降解细菌纤维素的酵母菌株,并对这些菌株产生的纤维素酶粗酶液进行了酶活测定。选择羧甲基纤维素酶活(CMCA)和滤纸酶活(FPA)较高的酵母菌株3-1进行了鉴定,鉴定酵母菌株3-1为东方伊萨酵母(Issatchenkiaorientalis),菌株培养液CMCA为71.48IU,FPA为81.07IU。     

新疆传统发酵牛乳中酵母菌的分离鉴定

以新疆塔城地区自然发酵牛乳为原料,对发酵酸奶中酵母菌进行分离。通过形态学和生理生化特性对其进行鉴定。研究结果表明：从酸牛奶中分离得到3株酵母菌,通过显微镜观察及生理生化特性鉴定,确定2株属于克鲁维酵母属Kluyveromyces,为马克斯克鲁维酵母Kluyveromyces marxianus;1株属于酵母属Saccharomyces,为酿酒酵母Saccharomyces cerevisiae。     

微波杀菌处理杏汁中残留微生物鉴定

杏汁经微波杀菌(控制微波温度67℃,杀菌3次),从杀菌后杏汁中分离鉴定出3株细菌和1株酵母菌。经形态学、生理生化试验初步鉴定,并分别采用16S r DNA和ITS序列鉴定分离的细菌和酵母菌株,结果表明:残存的细菌分别为短小芽孢杆菌(Bacillus pumilus)、蜡样芽孢杆菌(Bacillus cereus)和解淀粉芽孢杆菌(Bacillus amyloliquefaciens),残存的酵母菌为毕氏酵母(Pichia),且残留微生物均有耐热、耐微波特性。研究确定了微波处理的残留微生物,为完善杏汁微波杀菌工艺提供理论指导。     

水塔老陈醋大曲酵母的分离鉴定及产乙醇和乙酸乙酯特性

采用传统分离培养方法,从水塔老陈醋大曲中分离纯化出21株酵母菌,利用26S r DNA D1/D2序列分析方法结合形态学特征,对分离纯化的酵母菌进行鉴定,并用其发酵糯米糖化液,用静态顶空-气质联用的方法测定发酵后乙醇和乙酸乙酯的含量。结果发现:21株酵母菌鉴定结果为2株弗比恩酵母(Cyberlindnera fabianii),8株扣囊复膜酵母(Saccharomycopsis fibuligera)、6株异常威克汉姆酵母(Wickerhamomyces anomalus)、3株葡萄牙棒孢酵母(Clavispora lusitaniae)、2株东方伊萨酵母(Issatchenkia orientalis)。21株菌株发酵后产物乙醇和乙酸乙酯的含量存在较大差别,其中产生乙酸乙酯和乙醇最多的菌株分别为异常威克汉姆酵母m12(含量为4.4415 g/L)和扣囊复膜酵母q25(含量为48.577 g/L);产生最少的则分别为扣囊复膜酵母q6(含量为0.0037 g/L)和东方伊萨酵母q12(含量为11.4555 g/L)。提示老陈醋大曲中不同种类的酵母菌在发酵中对乙醇和乙酸乙酯具有不同的贡献。     

一株鸭梨酒酵母菌的鉴定

从市售鸭梨果皮中分离出1株酵母菌，经形态与培养特征、酵母假菌丝的观察、酵母菌子囊孢子的观察和生理生化试验，初步鉴定将酵母菌株GY定为酵母属的酿酒酵母(Saccharomyces cerevisive)。(孙悟)     

Biolog微生物自动鉴定系统在糟醅酵母菌鉴定中的应用初探

本研究从白酒糟醅样品中分离纯化出2株酵母菌,经菌落特征观察和镜检后,利用Biolog微生物自动鉴定系统进行鉴定,确定其分别为指甲毕奇酵母菌(Pichia onychis)布鲁塞尔德克酵母酋A(Dekkera bruxellenensis A),研究表Biolog微生物自动鉴定系统可用于白酒醅中酵母菌的鉴定.其鉴定速度快,操作简便.     

酿酒葡萄中内生酵母菌的分离与初步鉴定

采用组织块培养法,从优质酿酒葡萄品种"赤霞珠"中分离出12株内生酵母菌,其中春季4株,夏季3株,秋季5株;从酿酒葡萄的不同组织部位均分离到了内生酵母菌,其中根部6株、茎部2株、叶部1株、果实3株。经形态、培养特征、子囊孢子和假菌丝的观察及生理生化实验,初步鉴定出这些菌株分别为瓶形酵母和克勒克酵母,其中瓶形酵母6株,克勒克酵母6株。     

Cheese yeasts

Numerous traditionally aged cheeses are surface ripened and develop a biofilm, known as the cheese rind, on their surfaces. The rind of such cheeses comprises a complex community of bacterial and fungal species that are jointly responsible for the typical characteristics of the various cheese varieties. Surface ripening starts directly after brining with the rapid colonization of the cheese surface by yeasts. The initially dominant yeasts are acid and salt-tolerant and are capable of metabolizing the lactate produced by the starter lactic acid bacteria and of producing NH₃ from amino acids. Both processes cause the pH of the cheese surface to rise dramatically. This so-called deacidification process enables the establishment of a salt-tolerant, Gram-positive bacterial community that is less acid-tolerant. Over the past decade, knowledge of yeast diversity in cheeses has increased considerably. The yeast species with the highest prevalence on surface-ripened cheeses are Debaryomyces hansenii and Geotrichum candidum, but up to 30 species can be found. In the cheese core, only lactose-fermenting yeasts, such as Kluyveromyces marxianus, are expected to grow. Yeasts are recognized as having an indispensable impact on the development of cheese flavour and texture because of their deacidifying, proteolytic, and/or lipolytic activity. Yeasts are used not only in the production of surface-ripened cheeses but also as adjunct cultures in the vat milk in order to modify ripening behaviour and flavour of the cheese. However, yeasts may also be responsible for spoilage of cheese, causing early blowing, off-flavour, brown discolouration, and other visible alterations of cheese.     

Flavour compound production by Yarrowia lipolytica, Saccharomyces cerevisiae and Debaryomyces hansenii in a cheese-surface model

A simple cheese model mimicking a cheese surface was developed for the detection of cheese flavour formation of yeasts. A total of 56 flavour compounds were detected by dynamic headspace sampling followed by gas chromatography–mass spectrometry analysis. Yarrowia lipolytica CBS 2075 primarily produced sulphides, furans and short-chain ketones; Saccharomyces cerevisiae D7 primarily produced esters and Debaryomyces hansenii D18335 primarily produced branched-chain aldehydes and alcohols. For several of the detected flavour compounds, an increase in production was observed upon exposure to dairy-relevant environmental stress conditions including high NaCl concentration and low temperature. The predominant yeasts on the cheese surface may be important for development of flavour, and thus the use of yeasts as ripening cultures has the potential to affect the flavour of cheese.     

Yeasts as adjunct starters in matured Cheddar cheese

Debaryomyces hansenii and Yarrowia lipolytica are typical foodborne yeast species frequently associated with dairy products and capable of predominating the yeast composition in such systems. The two species fulfil a number of criteria to be regarded as co-starters for cheesemaking. They are known for their proteolytic and lipolytic activity as well as their compatibility and stimulating action with the lactic acid starter cultures when co-inoculated. Recent studies indicated that yeasts could be included as part of starter cultures for the manufacturing of cheese, enhancing flavour development during the maturation. The potential of D. hansenii and Y. lipolytica as agents for accelerated ripening of matured Cheddar cheese has been evaluated during four cheese treatments. The interaction between the two yeast species and the lactic acid bacteria was surveyed incorporating (i) D. hansenii, (ii) Y. lipolytica, (iii) both species as adjuncts to the starter culture and (iv) a control cheese without any additions for the production of matured Cheddar cheese. The physical and chemical properties of the cheeses were monitored in order to evaluate the contribution of the yeasts to cheese maturation. The yeasts grew in association with the lactic acid bacteria without any inhibition. The yeasts species when individually added contributed to the development of bitter flavours despite accelerated development of strong Cheddar flavours. When both species were incorporated as part of the starter culture, the cheese, however, had a good strong flavour after a reduced ripening period. The cheese retained this good flavour and aroma after 9 months of production. The simultaneous application of D. hansenii and Y. lipolytica as part of the starter culture for the production of matured Cheddar cheese is proposed.     

Aroma compound production in cheese curd by coculturing with selected yeast and bacteria.

The microorganisms involved in cheese ripening produce various volatile compounds and induce typical flavors that contribute to cheese variety. To investigate aroma compound generation of cheese microflora, we used a dynamic headspace-gas chromatography-mass spectrometry analysis. To obtain good sensitivity and repeatability of quantification, dynamic headspace conditions and sample preparation were first optimized and led to an extraction set up in which samples were heated at 60 degrees C and diluted with water without pH adjustment. Then three different yeasts and three Geotrichum candidum commonly used in mold surface ripened cheeses were studied in pure culture in a cheese model medium. Thirty-nine cocultures of these three yeasts, the three G. candidum, and five bacteria were studied in the same medium to assess the interaction between microorganisms on aroma compound production. Twenty-four volatile compounds belonging to different chemical classes (alcohols, aldehydes, esters, sulfides, terpenes) were identified and quantified. Yeasts and especially Kluyveromyces lactis produced large amounts of alcohols, aldehydes, esters, and terpenes when cultured alone or in association. Geotrichum candidum and especially G. candidum strain G3 generated the largest amount of sulfides when cultured alone or in association. Finally, bacteria also produced aroma compounds but, except for Brevibacterium linens strain B5, which produced dimethyl trisulfide and ketones, no specific trend in the production of particular aroma compounds could be evidenced.     

一种硬质蒙古干酪的感官评价研究

对蒙古干酪的颜色、质构、微观结构和感官品评进行了研究。蒙古干酪外部亮度稍暗,偏微红色,内部干酪颜色趋向于纯色。在质构上,其硬度、弹性、黏着性和回复性分别为23.18 N、47.25、7.40和5.60,在硬度上和Cheddar干酪类似,但是其他3个方面要差一些。蒙古干酪具有致密的酪蛋白胶束组成微观结构,脂肪脱去形成的孔洞很少。蒙古干酪的综合感官分为69.23分,由于质地和口感的原因使得得分较低,但仍在可接受范围内。     

The Influence of Sodium Chloride on the Activity of Yeast in the Production of Single Cell Protein in Whey Permeate

Whey can contain substantial amounts (6 to 10%) of sodium chloride, such as whey from the pressing of hard cheese or when from making Domiati cheese where salt is added to milk prior to renneting. Nine different lactose-fermenting yeasts were cultured in shake flasks using Cheddar cheese whey permeate as the fermentation medium. The pH and temperature of growth media were kept at 5 and 32°C, respectively. We studied the effect of 3, 6, or 9% concentrations of sodium chloride on the ability of yeasts to convert whey into biomass.Kluyveromyces marxianus var. marxianus ATCC 28244 and Candida tropicalis ATCC 20401 were more efficient in producing cell mass from 0 to 9% salt permeate than the other strains.     

Nisin延长低脂再制干酪保质期的应用

Nisin已广泛应用于食品保质期的研究中,本试验研究在贮存过程中,Nisin对低脂再制干酪细菌、肠杆菌、霉菌和酵母菌的抑菌效果及pH的变化。在低脂再制干酪样品中,空白样品贮藏到5个月时,样品变质不可食用,添加0.2%、0.3%Nisin的样品到6个月时,细菌总数、肠杆菌、酪霉菌和酵母菌合格,而添加0.2%Nisin、0.3%Nisin抑菌效果差异不显著,因此添加0.2%Nisin为宜。随着贮藏期时间的增加,pH显著增加。     

Molecular Identification of Yeasts Associated with Traditional Egyptian Dairy Products

ABSTRACT:  This study aimed to examine the diversity and ecology of yeasts associated with traditional Egyptian dairy products employing molecular techniques in yeast identification. A total of 120 samples of fresh and stored Domiati cheese, kariesh cheese, and "Matared" cream were collected from local markets and examined. Forty yeast isolates were cultured from these samples and identified using the restriction-fragment length polymorphism (RFLPs) of 5.8S-ITS rDNA region and sequencing of the domains D1 and D2 of the 26S rRNA gene. Yeasts were identified as  Issatchenkia orientalis  (13 isolates),  Candida albicans  (4 isolates),  Clavispora lusitaniae  ( Candida lusitaniae ) (9 isolates),  Kodamaea ohmeri  ( Pichia ohmeri ) (1 isolate),  Kluyveromyces marxianus  (6 isolates), and  Candida catenulata  (7 isolates). With the exception of  C. lusitaniae , the D1/D2 26S rRNA gene sequences were 100% identical for the yeast isolates within the same species. Phylogenetic reconstruction of  C. lusitaniae  isolates grouped them into 3 distinguished clusters. Kariesh cheese was found to be the most diverse in its yeast floras and contained the highest total yeast count compared with other examined dairy products. This was linked to the acidic pH and lower salt content of this cheese, which favor the growth and survival of yeasts in foodstuffs. Stored Domiati cheese also contained diverse yeast species involving isolates of the pathogenic yeast  C. albicans . This raises the possibility of dairy products being vehicles of transmission of pathogenic yeasts.     

High-pressure processing of Turkish white cheese for microbial inactivation

High-pressure processing (HPP) of Turkish white cheese and reduction of Listeria monocytogenes, total Enterobacteriaceae, total aerobic mesophilic bacteria, total molds and yeasts, total Lactococcus spp., and total Lactobacillus spp. were investigated. Cheese samples were produced from raw milk and pasteurized milk and were inoculated with L. monocytogenes after brining. Both inoculated (ca. 10(7) to 10(8) CFU/g) and noninoculated samples were subjected to HPP in a high-pressure food processor at 50 to 600 MPa for 5 and 10 min at 25 degrees C. Reductions in L. monocytogenes, total aerobic mesophilic bacteria, Lactococcus spp., and Lactobacillus spp. in both pasteurized- and raw-milk cheese samples and reductions in total molds and yeasts and total Enterobacteriaceae counts in raw-milk cheese samples increased with increased pressure (P < or = 0.05). The maximum reduction of the L. monocytogenes count, ca. 4.9 log CFU/g, was obtained at 600 MPa. Because of the highly inhibitory effect of pasteurization, the total molds and yeasts and total Enterobacteriaceae counts for the cheese samples produced from pasteurized milk were below the detection limit both before and after HPP. There was no significant difference in inactivation of L. monocytogenes, total aerobic mesophilic bacteria, Lactococcus spp., and Lactobacillus spp. under the same treatment conditions for the raw milk and pasteurized milk cheeses and for 5- and 10-min treatment times (P > 0.05). No significant change was detected in pH or water activity of the samples before and after HPP. Our findings suggest that HPP can be used effectively to reduce the microbial load in Turkish white cheese.     

Methods to extend the shelf‐life of cottage cheese – a review

Under typical refrigeration conditions (4–7 °C), unopened fresh cottage cheese only lasts for approximately 3 weeks unless preservatives are added. The spoilage of cottage cheese during storage is primarily due to the growth of Gram‐negative psychrotrophic bacteria, yeasts and moulds. To extend its shelf‐life, along with a strict sanitation practice throughout the manufacturing process, an appropriate preservation approach is generally applied. Many methods to preserve cottage cheese have been reported. These can be classified into three categories, namely food‐grade chemicals, heat treatment and modified atmosphere packaging. In this review, factors responsible for the spoilage of cottage cheese during storage and the methods to extend its shelf‐life are discussed.