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。     

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。     

Microencapsulation of enzymes for potential application in acceleration of cheese ripening

An encapsulation efficiency of 70% was achieved when flavourzyme was encapsulated in selected polymers and gelled in 0.1 m CaCl₂ containing 0.1% (w/v) chitosan. Enzyme retention in capsules did not increase with alginate concentration or with coating of capsules with 0.15% (w/v) alginate or 0.05% (w/v) poly l-lysine. Gelling duration of 10 min was found to be optimum, while 2.0% trisodium citrate was necessary for efficient release of encapsulated flavourzyme. During 10-week storage after freeze-drying and freezing, about 80% retention of enzyme activity was noted in flavourzyme capsules with or without poly l-lysine coating, while air-dried capsules retained about 53% activity and 32% on coating with poly l-lysine over 10 weeks. Flavourzyme leakage from capsules increased with an increase in the duration of the simulated cheese press from 4 to 16 h. Capsule addition before rennetting resulted in an even distribution compared with capsule addition before salting.     

Mechanisms of incorporation and release of enzymes into cheese during ripening

The enzymes involved in cheese ripening and the factors affecting their activity in cheese is reviewed. The review begins by outlining the various enzymes that contribute to cheese ripening including those originating from milk, coagulant, starter and non-starter Lactic Acid Bacteria, and those added as exogenous preparations to accelerate flavour development. Factors influencing the retention, release and residual activity of these enzymes in cheese are discussed along with an outline of innovative methods to enhance the retention and release of exogenous enzymes.     

Quantitative proteomic analysis of bacterial enzymes released in cheese during ripening

Due to increasingly available bacterial genomes in databases, proteomic tools have recently been used to screen proteins expressed by micro-organisms in food in order to better understand their metabolism in situ. While the main objective is the systematic identification of proteins, the next step will be to bridge the gap between identification and quantification of these proteins. For that purpose, a new mass spectrometry-based approach was applied, using isobaric tagging reagent for quantitative proteomic analysis (iTRAQ), which are amine specific and yield labelled peptides identical in mass. Experimental Swiss-type cheeses were manufactured from microfiltered milk using Streptococcus thermophilus ITG ST20 and Lactobacillus helveticus ITG LH1 as lactic acid starters. At three ripening times (7, 20 and 69 days), cheese aqueous phases were extracted and enriched in bacterial proteins by fractionation. Each sample, standardised in protein amount prior to proteomic analyses, was: i) analysed by 2D-electrophoresis for qualitative analysis and ii) submitted to trypsinolysis, and labelled with specific iTRAQ tag, one per ripening time. The three labelled samples were mixed together and analysed by nano-LC coupled on-line with ESI-QTOF mass spectrometer. Thirty proteins, both from bacterial or bovine origin, were identified and efficiently quantified. The free bacterial proteins detected were enzymes from the central carbon metabolism as well as stress proteins. Depending on the protein considered, the quantity of these proteins in the cheese aqueous extract increased from 2.5 to 20 fold in concentration from day 7 to day 69 of ripening.     

Biochemistry of cheese ripening

Rennet-coagulated cheeses are ripened for periods ranging from about two weeks to two or more years depending on variety. During ripening, microbiological and biochemical changes occur that result in the development of the flavour and texture characteristic of the variety. Biochemical changes in cheese during ripening may be grouped into primary (lipolysis, proteolysis and metabolism of residual lactose and of lactate and citrate) or secondary (metabolism of fatty acids and of amino acids) events. Residual lactose is metabolized rapidly to lactate during the early stages of ripening. Lactate is an important precursor for a series of reactions including racemization, oxidation or microbial metabolism. Citrate metabolism is of great importance in certain varieties. Lipolysis in cheese is catalysed by lipases from various source, particularly the milk and cheese microflora, and, in varieties where this coagulant is used, by enzymes from rennet paste. Proteolysis is the most complex biochemical event that occurs during ripening and is catalysed by enzymes from residual coagulant, the milk (particularly plasmin) and proteinases and peptidases from lactic acid bacteria and, in certain varieties, other microorganisms that are encouraged to grow in or on the cheese. Secondary reactions lead to the production of volatile flavour compounds and pathways for the production of flavour compounds from fatty acids and amino acids are also reviewed.     

温度对大豆奶酪成熟特性的研究

分别研究了大豆奶酪在不同的温度条件下的成熟特性.氨基酸态氮分析、质构分析以及风味品尝的结果均表明采用变温培养,即先在30℃成熟2d后再15℃成熟54d的大豆奶酪成熟度最好,其氨基酸态氮含量最高、硬度最低,品尝口感最好.     

Proteolysis indices related to cheese ripening and typicalness in PDO Grana Padano cheese

Different chemical indices related to proteolysis and ripening time have been investigated in Grana Padano (n = 155) and Parmigiano-Reggiano (n = 27) cheese samples using ion-exchange chromatography and capillary electrophoresis. Levels of intact caseins, γ-casein and free amino acids in cheese were not strictly related to the maturation period, varying among samples of the same age. A peptide, identified by HPLC/electrospray ionization-mass spectrometry as pyroglutamyl-γ₃-casein, resulted from cyclisation of N-terminal glutamic acid into a pyroglutamic acid residue. Based on the peak area ratio of pyroglutamyl-γ₃-casein and γ₃-casein, an equation, suitable for determination of the cheese age, is proposed. The commercial classes of Grana Padano ripened over 16 and 20 months can be identified by adopting a minimum threshold value for this peak area ratio.     

提高成熟温度加快Mozzarella干酪成熟的研究

制作2批Mozzarella干酪A和B，分别在4℃(A)和7℃(B)下成熟，观察其在成熟期间的变化及测定可溶性N的含量等指标，可知在7℃下成熟的干酪在制作后30d的蛋白水解性、功能特性等和4℃下成熟50d的干酪无显著差异，而和7℃下成熟50d的干酪有显著差异。说明成熟温度显著影响干酪的蛋白水解性。在7℃下贮藏的Mozzarella干酪成熟30d可达到4℃下贮存50d的成熟度，即将成熟温度从4℃提高到7℃，可将成熟期缩短20d左右。     

加速腌鱼风味成熟新技术的研究

通过GC-MS技术及感官评定,探索新型技术来加速腌鱼风味成熟。结果表明采用间歇微波可以加快风味成熟,添加风味蛋白酶对改善腌鱼的风味品质具有明显的效果。在腌制液中添加0.4%的风味蛋白酶作用2h后再用间歇微波处理1min,使得腌鱼制品产生了多达60多种的挥发性风味化合物,大大改善了鱼制品的风味,提高了腌鱼产品的风味品质。     

凝乳酶对牦牛乳硬质干酪成熟期间蛋白降解的影响

以新鲜牦牛乳为原料,采用小牛皱胃酶、木瓜蛋白酶和微生物凝乳酶制作硬质干酪,探讨凝乳酶种类对牦牛乳硬质干酪成熟期间蛋白质降解的影响。结果表明:三种凝乳酶牦牛乳硬质干酪成熟过程中,不同凝乳酶牦牛乳硬质干酪在成熟期间蛋白质降解能力存在较大差异,总氮（TN）、p H4.6水溶性氮（p H4.6-SN/TN）、12%的三氯乙酸氮（12%TCA-N/TN）、5%磷钨酸氮（5%PTA-N/TN）含量、游离氨基酸均随成熟时间延长不同程度的增加,蛋白氮和酪蛋白氮逐渐降低,多肽氮呈先升高后下降趋势,且微生物凝乳酶降解牦牛乳硬质干酪蛋白能力显著（p<0.05）高于木瓜蛋白酶和小牛皱胃酶。      

干酪快速成熟的研究进展

综述了国内外干酪快速成熟的研究状况,探讨了脂质体微胶囊中性蛋白酶用于加快干酪成熟的可行性。     

Accelerated ripening of cheese using liposome-encapsulated enzyme

Improved efficiency of liposome encapsulation of a cheese-ripening enzyme and increased retention of encapsulated enzyme by cheese curd are reported. The economy of enzyme usage for accelerating the rate of ripening of Cheddar cheese has been improved about 100-fold over previously reported methods. This has made feasible the use of microencapsulated enzymes for large-scale cheese production. Objective measurement of cheese ripening by proteolytic indices, and subjective evaluation of flavour quality and intensity by trained taste panels, indicate that cheeses are ripened by the microencapsulated enzyme in half the normal time. Investigations aimed at further improving the efficiency and commercial feasibility of the process are reported, and the possibility of using this technology for other aspects of food processing are discussed.     

Application of linear discriminant analysis to different proteolysis parameters for assessing the ripening of Manchego cheese

Different proteolysis parameters, the nitrogenous fractions and the breakdown of caseins, were determined for Manchego cheeses at different stages of ripening. Linear discriminant analysis was applied to these parameters to ascertain the degree of ripening. Two discriminant functions enabling 100% correct classification of the cheeses into fresh, medium ripe and aged were found.     

Use of ozone to reduce molds in a cheese ripening room

Cheese ripening rooms have an unusual environment, an environment that encourages mold growth. Ozone has been applied in various ways in the food industry. One useful advantage of ozone is that it inactivates molds. In this study, a cheese ripening room was ozonated, and the effectiveness of this treatment was evaluated both in air and on surfaces through sampling on a weekly basis over a 3-month period. The results obtained indicate that ozone treatment reduced the viable airborne mold load but did not affect viable mold on surfaces. Only by wiping the surfaces with a commercial sanitizer was it possible to decrease the viable mold load on surfaces. To improve overall hygiene in the ripening room, a combination of cleaning regimes is recommended. The mold genera occurring most frequently in the air of the cheese ripening room were Penicillium, Cladosporium, and Aspergillus, which accounted for 89.9% of the mold isolates. Penicillium and Aspergillus were identified to the species level, and data showed that P. brevicompactum and P. aurantiogriseum, as well as A. versicolor, were the species most frequently isolated.     

Chemometrical analysis of proteolytic profiles during cheese ripening

This research note gives a presentation of chemometrical analysis of proteolytic profiles obtained by electrophoresis and chromatography. An explanation of how the proteolytic profiles can be transformed to a multivariate data set and some basic information about multivariate statistical techniques as principal component analysis and discriminant analysis are provided. Some of the recent and most relevant research is presented to illustrate how this technique can be used in research on proteolysis during cheese ripening.