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.     

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。     

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.     

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。     

The effect of ovine and bovine milk on the textural properties of Lighvan cheese during ripening

The effect of milk origin on the physicochemical characteristics, microstructure and texture of Lighvan cheese was investigated over a 90‐day ripening period. Besides fat, other physicochemical properties of Lighvan cheese were affected by milk type. The moisture content of Lighvan cheese decreased when half or all the ovine milk was substituted with bovine milk. The Lighvan cheese's microstructural properties and porosity were affected by type of milk and ripening time. Compaction of cheeses manufactured from ovine and mixed ovine and bovine milk is similar, and more than that of bovine Lighvan cheese. Ovine Lighvan cheese is harder and less brittle than bovine and mixed bovine and ovine.     

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.     

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。     

干酪成熟过程中发酵剂的作用

介绍干酪成熟过程中乳酸菌发酵剂及二级发酵剂的作用,包括在干酪风味、质地、加速干酪成熟、产生抗菌素及营养和颜色等多方面作用,同时分析成熟期间发酵剂控制不当会引起的负面作用,提出应用具有选择性的发酵剂或经遗传修饰的发酵剂生产干酪具有较强的应用前景。     

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.     

Mesophilic lactobacilli in Fiore Sardo cheese: PCR-identification and evolution during cheese ripening

The mesophilic lactobacilli colonizing Fiore Sardo ewe's milk cheese were characterized. They seemed to be the dominant non-starter lactic acid bacteria composing its natural microflora, with a viable cell number varying from 10⁵ CFU g⁻¹ (1-day-old cheese) to 10⁸ CFU g⁻¹ (30-day-old cheese) and then slowly decreasing up to 10⁴ CFU g⁻¹ after 7 months’ ripening. Considering the relevance of mesophilic lactobacilli in affecting the cheese ripening, a PCR-based taxonomic identification of the Lactobacillus species isolated was performed. Cheese samples were collected from 3 farms and 457 isolates from cheeses at different ripening times were analysed with species-specific primers for L. plantarum, L. casei group, L. paracasei, L. casei, L. rhamnosus, L. pentosus, L. paraplantarum, L. curvatus, L. graminis and L. sake. L. plantarum and L. paracasei were the most frequently detected species. Moreover, the development and the evolution during ripening of the facultatively heterofermentative Lactobacillus species (FHL) were different in the three batches of cheese.     

Effect of sequential ventilation on cheese ripening and energy consumption in pilot ripening rooms

The aim of this work was to enable improvements in cheese maturation through control of airflow and climatic conditions in ripening rooms, and the minimisation of energy consumption using sequential ventilation. Sensors and advanced software were installed to monitor and control pilot scale ripening chambers of 12.3 and 4.2 m³. Techniques in computational fluid dynamics were used to improve the ventilation uniformity and level around the cheeses. The initial chamber (12.3 m³) was modified by reducing the room length from 3.2 to 1.1 m by changing the location of the wall in front of the cheese stack, altering the location of the two fans and varying their flow rate from 160 to 250 m³ h^?1. Sequential ventilation (1/3 of ripening time) did not significantly affect the respiratory activities, microbiological, physico-chemical or sensory characteristics of ripened, pressed, non-cooked cheeses, but it did lead to a reduction in energy consumption of approximately 18%.     

Chemical changes during the ripening of Domiati cheese made from dried milk

The ripening of Domiati cheese made from fresh and dried milk was investigated. Nitrogen fractions were determined, the proteinaceous fraction of cheese was analysed on Sephadex G-100 and the free fatty acids were determined by gas-liquid chromatography. The nitrogen fractions from fresh milk cheese had higher nitrogen concentrations than those from cheese made from dried milk. The elution pattern of the proteinaceous fractions and the pattern of free fatty acids of fresh and dried milk cheese were similar. However, the small molecular weight N fractions and the concentration of free fatty acids were higher in the former cheese than the latter.     

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。     

Accelerated ripening of Cheddar cheese at elevated temperatures

Blocks (20 kg) of Cheddar cheese from a single vat were obtained from a local factory. Half the cheeses were cooled rapidly (15 h) to ripening temperature (8, 12 or 16 °C) and half were cooled slowly over 8 days to the same ripening temperatures. Cheeses were ripened for 9 months at 7 different time/temperature combinations. Ripening temperature had little influence on the number of non-starter lactic acid bacteria in the cheeses after 9 months, although rapid cooling to and ripening at 8 °C drastically reduced the growth rate of these adventitious bacteria. Proteolysis (as determined by urea-polyacrylamide gel electrophoresis; increases in water-soluble N; increases in phosphotungstic acid-soluble N; Cd ninhydrin-reactive amino groups; and reverse-phase HPLC) and lipolysis were accelerated by increasing the ripening temperature and by slow cooling of the cheeses. The rate of ripening was increased or decreased by changing the temperature. Cheeses ripened at 16 °C generally received the highest flavour scores, particularly early during ripening. However, the texture of these cheeses deteriorated after prolonged ripening at 16 °C. Maturation at 12 °C was considered to be optimal for the commercial acceleration of Cheddar cheese ripening.     

Phase transition of triglycerides during semi-hard cheese ripening

Sixteen semi-hard cheeses varying by their protein (20.2–24.1%), fat (23.7–31.1%) and dry matter (50.2–57.9%) contents were manufactured and ripened in controlled conditions. Fluorescence (vitamin A) and mid-infrared (2780–3000 cm⁻¹ region) spectra were collected on the 16 different cheeses at 1, 21, 51 and 81 days of ripening. The data tables containing the mid-infrared and fluorescence spectra of the different cheeses were analyzed by principal component analysis and canonical correlation analysis methods. The obtained similarity maps showed that it was possible to discriminate the cheeses at the four different ripening times from the infrared and fluorescence spectra. In addition, the interest to combine the two spectroscopies was demonstrated since a better discrimination of the four stages was obtained using canonical correlation analysis. The examination of the spectral patterns associated with the principal components and the canonical variates showed that the structure of triglycerides acyl chains in fat globules was modified during cheeses ripening. The shift of the methylene bands in the infrared region and the changes of the shape of vitamin A fluorescence spectra agree with partial crystallization of triglycerides from 21 to 81 days of storage.     

Effect of β-casein concentration in cheese milk on rennet coagulation properties,cheese composition and cheese ripening

Effects of the use of a β-casein powder to enrich cheese milk on rennet coagulation properties of milk, cheese composition and cheese ripening were investigated. Casein content of control milk was 2.5%, whereas that for the three enriched milks was adjusted with β-casein powder at 2.7%, 2.9% and 3.1%. The β-casein to α-casein ratio of these cheese milks was, respectively, 0.70, 0.79, 0.89 and 0.99. Rennet coagulation properties were related not only to casein concentration but also to the proportion of β-casein and α_s-casein presents in milks. Milk with higher concentration of β-casein had poorer coagulation properties. Cheeses could be produced by using a miniature cheese making process. Moisture, ash and calcium contents decreased, while protein content and β-casein increased in cheese as casein and β-casein concentration increased in milk. As a result, hardness was higher in enriched cheeses than in control cheese. During cheese ripening, α-casein was hydrolyzed, but the rate of degradation of α-casein decreased as protein and β-casein concentration increased in cheese. β-Casein seemed to be not hydrolyzed. The rate of decrease of hardness was also slower for enriched cheeses.     

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.