干酪促熟附属发酵剂的研究进展

干酪成熟时间较长且费用较高,干酪促熟成为降低生产成本的有效途径之一。干酪促熟常用的方法有酶法、修饰发酵剂细胞、提高成熟温度、高压处理等,但均存在一定的不足,限制了其在干酪工业中的应用。非发酵剂乳酸菌可促进干酪风味的形成并加速成熟．已成为干酪促熟方法的研究热点之一。介绍了干酪生产及成熟过程中微生物的作用,特别介绍了干酪附属发酵剂发展的原由并综述了其在干酪成熟过程中研究进展。     

干酪促熟方法的研究进展

干酪成熟时间较长，费用较高，导致生产成本增加。因此干酪的促熟受到人们普遍关注。干酪促熟常用的方法有酶法、修饰发酵剂细胞、悬浮液系统、提高成熟温度、高压处理等。其中提高成熟温度和高压处理法不需要额外的干酪添加剂，是应用于生产中成本较低且易实现的方法。本文主要就以上两种方法促熟干酪作以详述。     

酶法促熟干酪的研究进展

干酪促熟常用的方法有酶法；修饰发酵剂细胞；提高成熟温度；悬浮液系统法等．其中的酶法促熟干酪研究较为系统。论述了酶法促熟干酪中常用的酶类及其作用，并对其应用前景作以展望。     

切达干酪加速成熟方法及其研究现状

概述了对切达干酪的加速成熟的现状与研究方法,通过提高温度、添加促熟酶、修饰发酵剂细胞、高压处理等方法缩短切达干酪的成熟时间,提高经济效益。     

快速成熟切达干酪复合发酵剂的筛选

以促进切达干酪成熟为目的,筛选发酵菌种,菌种添加量、菌种比例,确定发酵剂对切达干酪促熟的影响。利用响应面中心旋转组合设计,优化出具有促熟效果的复合发酵剂的最佳配比,即:保加利亚乳杆菌(Lb)添加量为0.92 kg/100 kg原料乳,嗜热链球菌(St)添加量为0.77 kg/100 kg原料乳,瑞士乳杆菌(Lh)添加量为1.08 kg/100 kg原料乳,复合发酵剂的总添加量2.77%。使用优化的复合发酵剂,通过验证试验加工的切达干酪与R704商业发酵剂对照样比对,结果复合发酵剂具有显著的促熟效果(P0.01)。     

生物技术在干酪加工中的应用

综述了生物技术在原料乳品质改进、凝乳酶、干酪发酵剂、干酪促熟、干酪包装及乳清处理等不同干酪加工环节中的应用.     

发酵剂对牦牛乳硬质干酪成熟过程中生物胺的影响

乳酸菌产生物胺的能力具有菌株特异性,因此,为了探究不同种类发酵剂对牦牛乳硬质干酪中生物胺形成的影响,该试验利用高效液相色谱对3种不同发酵剂制作的硬质干酪成熟过程中生物胺进行了测定和分析。结果表明,嗜热和嗜温发酵剂牦牛乳硬质干酪中检测出2-苯乙胺、腐胺、尸胺、组胺和酪胺,混合发酵剂干酪中检测出腐胺、2-苯乙胺、尸胺和酪胺。各生物胺之间呈现正相关性。3种不同发酵剂干酪在1～6个月成熟过程中,其各生物胺整体呈现增加趋势,嗜热、嗜温和混合发酵剂干酪中总生物胺最高含量分别为(448.3±9.6)、(456.8±58.4)、(293±24.5)mg/kg。组胺和酪胺是2种毒性相对高的生物胺,嗜热发酵剂干酪中组胺和嗜温发酵剂干酪中酪胺最高,其最高含量分别为(20.8±7.9)、(92.9±6.7)mg/kg,混合发酵干酪中未检测出组胺,酪胺含量次之,3种不同发酵剂干酪中组胺、酪胺含量均低于推荐安全剂量50 mg/kg和100 mg/kg。这为合理选择发酵剂和控制干酪中生物胺形成提供了依据。     

不同方法促熟干酪成熟期间微生物及氨基酸研究

以0、15、30、45、60、75、90 d促熟干酪中主要微生物（乳杆菌、乳球菌、肠球菌、微球菌）和游离氨
基酸含量为指标,研究添加复合处理发酵剂和中性蛋白酶促熟干酪成熟过程对游离氨基酸和微生物菌落数的影响。
结果表明,添加处理发酵剂和中性蛋白酶可增加干酪中游离氨基酸含量,添加处理发酵剂可不同程度降低干酪中微
生物菌落数,添加中性蛋白酶对干酪成熟过程中微生物影响不明显（P＞0.05）。     

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。     

原料乳中干酪非发酵剂乳酸菌的研究

非发酵剂乳酸菌（NSLAB）是天然存在于原料乳中的一类独特的微生物,一般在干酪成熟过程中发挥作用;着重阐述了非发酵剂乳酸菌（NSLAB）的定义、分类状况,分析其对干酪风味形成、质构变化等的影响,提出了研究非发酵剂乳酸菌应注意的问题,为研究干酪的风味多样性提供科学思路。     

Use of high pressure treatment to attenuate starter bacteria for use as adjuncts for Cheddar cheese manufacture

Attenuated starter bacteria cannot produce acid during cheese manufacture, but contain enzymes that contribute to cheese ripening. The aim of this study was to investigate attenuation of starter bacteria using high pressure treatment, for use in combination with a primary starter for Cheddar cheese manufacture, and to determine the effect of such adjunct cultures on secondary proteolysis during ripening. Lactococcus lactis ssp. cremoris HP and L. lactis ssp. cremoris 303 were attenuated by pressure treatment at 200 MPa for 20 min at 20 °C. Cheddar cheese was manufactured using untreated cultures of both these starter strains, either alone or in combination with their high pressure-treated equivalents. High pressure-treated starters did not produce acid during cheese manufacture and starter counts in cheeses manufactured using high pressure-treated starter did not differ from those of the controls. Higher levels of cell lysis were apparent in cheese manufactured using high pressure-treated strains than in the controls after 26 d of ripening. Small differences were observed in the peptide profiles of cheeses, analysed by reversed-phase HPLC; cheeses manufactured using high pressure-treated starters also had slightly higher levels of amino acids than the relevant controls. Overall, addition of high pressure-treated starter bacteria as a secondary starter culture accelerated secondary proteolysis in Cheddar cheese.

Industrial relevance

Attenuated starters provide extra pool of enzymes, which can influence cheese ripening, without affecting the cheese making schedule. This paper presents an alternative method for attenuation of starter bacteria using high pressure treatment and their subsequent use to accelerate secondary proteolysis in Cheddar cheese during ripening.     

Conventional and omics approaches shed light on Halitzia cheese,a long-forgotten white-brined cheese from Cyprus

Production and ripening of Halitzia cheese was examined by conventional physicochemical and microbiological analyses along with state-of-the art metagenomics. Cheese was made from (A) raw goat milk without the addition of starters; (B) pasteurised goat milk without the addition of starters; (C) pasteurised milk with the addition of starters. The type and counts of microorganisms were mainly influenced by ripening time; microbial counts for lactic acid bacteria were predominant and remained stable with little or no variation throughout ripening. Coliforms and coagulase positive staphylococci declined during ripening and at the end of ripening the staphylococci were not detected. Yeasts were detected at low counts but in great diversity throughout ripening. Metagenomics analysis confirmed the results obtained by the classical microbiological analysis. The physicochemical parameters during ripening were also determined; at 60 days the pH value and moisture, fat, protein, ash, and salt contents did not significantly differ amongst cheese types.     

The role of autolysis of lactic acid bacteria in the ripening of cheese

The importance of autolysis of lactic acid bacteria in cheese ripening is evident from the literature. However, the mechanisms and the consequences still require investigation. The consequences of autolysis of mesophilic starters in Cheddar cheese are discussed and highlights from current physiological and genetic studies on starter autolysis are presented. The relative merits of measuring starter autolysis in cheese by viable starter cell densities, electron microscopic observations and assay of cell-free cytoplasmic enzymes are discussed for cheese studies using different starter strains and added phage to achieve different levels of autolysis. The balance of both the intact and autolysed starter cells in young curd appear to be important in cheese ripening. The intact cells are necessary for physiological reactions such as lactose fermentation and oxygen removal and possibly for a number of flavour reactions. In contrast, the main consequence of autolysed cells in cheese is to accelerate the peptidolytic reactions. The possible influences of autolysis of adventitious lactic acid bacteria during cheese ripening are discussed.     

Survey of bacterial proteins released in cheese: a proteomic approach

During the ripening of Emmental cheese, the bacterial ecosystem confers its organoleptic characteristics to the evolving curd both by the action of the living cells, and through the release of numerous proteins, including various types of enzymes into the cheese when the cells lyse. In Emmental cheese these proteins can be released from thermophilic lactic acid bacteria used as starters like Lactobacillus helveticus, Lb delbruecki subsp. lactis and Streptococcus salivarius subsp. thermophilus and ripening bacteria such as Propionibacterium freudenreichii. The aim of this study was to obtain a proteomic view of the different groups of proteins within the cheese using proteomic tools to create a reference map. A methodology was therefore developed to reduce the complexity of cheese matrix prior to 2D-PAGE analysis. The aqueous phase of cheese was prefractionated by size exclusion chromatography, bacterial and milk proteins were separated and subsequently characterised by mass spectrometry, prior to peptide mass fingerprint and sequence homology database search. Five functional groups of proteins were identified involved in: (i) proteolysis, (ii) glycolysis, (iii) stress response, (iv) DNA and RNA repair and (v) oxidoreduction. The results revealed stress responses triggered by thermophilic lactic acid bacteria and Propionibacterium strains at the end of ripening. Information was also obtained regarding the origin and nature of the peptidases released into the cheese, thus providing a greater understanding of casein degradation mechanisms during ripening. Different peptidases arose from St thermophilus and Lb helveticus, suggesting that streptococci are involved in peptide degradation in addition to the proteolytic activity of lactobacilli.     

Starter strain related effects on the biochemical and sensory properties of Cheddar cheese

A detailed investigation was undertaken to determine the effects of four single starter strains, Lactococcus lactis subsp. lactis 303, Lc. lactis subsp. cremoris HP, Lc. lactis subsp. cremoris AM2, and Lactobacillus helveticus DPC4571 on the proteolytic, lipolytic and sensory characteristics of Cheddar cheese. Cheeses produced using the highly autolytic starters 4571 and AM2 positively impacted on flavour development, whereas cheeses produced from the poorly autolytic starters 303 and HP developed off-flavours. Starter selection impacted significantly on the proteolytic and sensory characteristics of the resulting Cheddar cheeses. It appeared that the autolytic and/or lipolytic properties of starter strains also influenced lipolysis, however lipolysis appeared to be limited due to a possible lack of availability or access to suitable milk fat substrates over ripening. The impact of lipolysis on the sensory characteristics of Cheddar cheese was unclear, possibly due to minimal differences in the extent of lipolysis between the cheeses at the end of ripening. As anticipated seasonal milk supply influenced both proteolysis and lipolysis in Cheddar cheese. The contribution of non-starter lactic acid bacteria towards proteolysis and lipolysis over the first 8 months of Cheddar cheese ripening was negligible.     

Effect of different manufacturing parameters on the characteristics of Graviera Kritis cheese

The objective of the present study was to improve the characteristics of Graviera Kritis cheese. The influence of lactic acid and propionic acid starters was studied and then the effect of washing and salting the curd combined with the use of starters was investigated. Although the traditional technology without starters resulted in the highest organoleptic characteristics, it was shown that the use of starters could improve texture characteristics of the cheeses if it is combined with a curd wash to control acidity development. Lower pH values and higher contents of low molecular weight nitrogenous substances were consistent with texture defects. Moreover, the ripening at higher temperatures increased proteolysis levels and decreased cheese quality.     

Microbiological study of Manura, a hard cheese made from raw ovine milk in the Greek island Sifnos

Changes in the microbial flora of Manura, a raw ovine milk cheese, were studied during ripening. In general, the various microbial groups developed better on the cheese surface than in the interior, but red wine treatment had an inhibitory effect on their growth and microbial counts decreased ( P  < 0.05) more rapidly on the cheese surface than in the interior. NaCl and moisture of the cheese affected microbial levels significantly. Thus, Enterobacteriaceae and coliforms were reduced sharply ( P  < 0.05) during ripening on a straw bed (∼3 months) and they were not detected in mature cheese. Lactic acid bacteria predominated over the other microbial groups throughout ripening. Leuconostoc mesenteroides ssp. cremoris , Pediococcus pentosaceus and Lactobacillus paracasei ssp. paracasei , frequently found in maturing cheese, could be used as starters to make this cheese. Moreover, the lactic acid bacteria predominating in mature cheese, such as Weissella paramesenteroides , Lactobacillus bifermentans and Lactobacillus brevis , may contribute to cheese ripening through their biochemical activities.     

Changes of composition and free fatty acid contents of Urfa cheeses (a white-brined Turkish cheese) during ripening: Effects of heat treatments and starter cultures

The influences of heat treatments (at 65 °C for 20 min or 72 °C for 5 min) applied to the milk and addition of mesophilic or thermophilic starter cultures, prior to cheese-making, on the composition and free fatty acid contents of Urfa cheeses were evaluated throughout the ripening period. Sensory evaluation of cheese samples was also performed on 90th day. The basic composition of ripened cheese samples was not significantly affected by the heat treatments and starter cultures. Heat treatments adversely affected the lipolysis and sensory properties of Urfa cheeses, particularly at 72 °C. The FFA contents of cheeses made from mesophilic and thermophilic cultures were similar. Cheese made from raw milk had a higher level of lipolysis than the cheeses made from milk inoculated with mesophilic or thermophilic lactic starters (p < 0.05).     

Characterization of aromatic properties of old-style cheese starters

Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30°C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of γ-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. γ-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects.     

海藻酸钠固定化乳酸菌促熟干酪效果的研究

对海藻酸钠固定化乳酸菌促熟干酪的效果进行了研究。结果表明，在干酪粒中添加10^6CFU／g固定化乳酸菌，水溶性氮（WSN）、三氯乙酸氮（TCASN）和磷钨酸氮（PTASN）含量较对照组明显增大；ADV值在添加固定化乳酸菌干酪中成熟初期变化不大，45d后明显增大；感官评定结果表明，干酪粒中添加10^5CFU／g固定化乳酸菌干酪成熟60d时风味和质地较好，可比对照组干酪成熟期缩短30d左右。