Evolution of lipolysis during the ripening of traditional Feta cheese

Lipolysis was studied during ripening of traditional Feta cheese produced in two small dairies, A and B. The cheeses were made from a thermized mixture of ewes’/goats’ milk by using yoghurt as starter and artisanal rennet from lambs’ and kids’ abomasa (cheese A) or mixed artisanal rennet with calf rennet (cheese B).The acid degree value and the free fatty acids (FFA) contents in both cheeses increased sharply up to 18 d (pre-ripening period at 15 °C) and continued to increase throughout ripening. In both mature cheeses, acetic acid was found at high levels (13–18% of the total FFAs). However, except for this, all FFA contents differed significantly (P < 0.05) between the two cheeses throughout ripening. The levels of individual and total C2:0–C8:0, C10:0–C14:0 and C16:0–C18:2 fatty acids were significantly higher (P < 0.05) in cheese A than in cheese B. Presumably the difference, especially in the C2:0–C8:0 content, was due mainly to the type of the rennet used. Butyric acid was the dominant FFA in cheese A (20% of the total FFAs at 120 d), while the most abundant FFAs in cheese B were capric (18%) and lauric acid (18%). In general, the lipolysis degree of the two cheeses was higher than those reported for the industrially-made Feta cheese.In organoleptic evaluation, cheese A had a piquant taste that was attributed to its high content of butyric acid and showed a significantly (P < 0.05) higher total score than cheese B.     

Acceleration of cheese ripening at elevated temperature. An estimation of the optimal ripening time of a traditional Argentinean hard cheese

The effect of elevated ripening temperature on physicochemical, biochemical and sensory characteristics in Reggianito Argentino cheese was evaluated to determine the optimal time for cheese ripening at 18 °C that ensures typical cheese characteristics. Cheeses ripened at 12 or 18 °C and 85% relative humidity were analysed at 2, 4 and 6 months. Seventy-eight variables (as determined by urea-PAGE, RP-HPLC of the water-soluble at pH 4.6 fraction, free amino acids, free fatty acids and sensory analysis) were considered for the principal component analysis. The statistical analysis allowed determination of the optimal time for ripening Reggianito Argentino cheese at 18 °C, which was ranged between 2 and 3 months. In conclusion, the results obtained were not only useful in characterising the ripening of an Argentinean hard cheese, but also in evaluating the effect of an increase of ripening temperature on the main physicochemical, biochemical and sensory changes of Reggianito Argentino cheese.     

Influence of traditional smoking on the triglyceride composition during the ripening of Idiazabal cheese

 The influence of traditional smoking on the triglyceride (TG) composition of Idiazabal cheese during ripening was studied using HPLC. The partition numbers (PNs) of the TGs ranged between 22 and 53, the groupings of TG peaks with PN values of 36, 34, and 38 being the main contributors. Statistically significant differences between the smoked and the unsmoked cheeses were recorded during the ripening period. Smoking had a significant effect on certain groups of TGs at different ripening times and no effect on others. The differences in the TG profiles of the cheeses were the result of differing levels of lipolytic activity, which was heightened by smoking. Received: 29 December 1997 / Revised version: 9 March 1998     

Influence of traditional smoking on the triglyceride composition during the ripening of Idiazabal cheese

 The influence of traditional smoking on the triglyceride (TG) composition of Idiazabal cheese during ripening was studied using HPLC. The partition numbers (PNs) of the TGs ranged between 22 and 53, the groupings of TG peaks with PN values of 36, 34, and 38 being the main contributors. Statistically significant differences between the smoked and the unsmoked cheeses were recorded during the ripening period. Smoking had a significant effect on certain groups of TGs at different ripening times and no effect on others. The differences in the TG profiles of the cheeses were the result of differing levels of lipolytic activity, which was heightened by smoking. Received: 29 December 1997 / Revised version: 9 March 1998     

Evolution of microbial populations during traditional Feta cheese manufacture and ripening

In three different dairies (A, B and C) located in Peloponess region (Southern Greece), traditional Feta cheese trials took place February to March using mixtures of sheep's and goat's milk. Only small variations in the evolution of microbial groups were observed during the whole ripening period. The main groups, such as thermophilic cocci, mesophilic lactococci, thermophilic lactobacilli, nonstarter lactic acid bacteria (NSLAB), presumptive Leuconostoc, enterococci and micrococci, reached their highest levels during the first 16 days, and then declined approximately 1-2 log units until the end of ripening. The remaining groups investigated, comprising yeasts, coliforms and Escherichia coli, were highest at day 4. The yeasts remained constant, while coliforms and E. coli decreased sharply and were not detectable after 120 days of ripening. A number of 146 isolates (dairy A) taken from all stages of the manufacturing and ripening process were purified and studied. Lactobacillus plantarum (58/146) and isolates of related species Lactobacillus pentosus and Lactobacillus paraplantarum (16/146) were the most common microorganisms found during cheese ripening. Streptococcus thermophilus (23/146) and Lactobacillus delbrueckii subsp. bulgaricus (20/146) were detected in high levels up to 20 days, and then gradually reduced. Enterococcus faecium (29/146) was found in all manufacturing and ripening stages.     

Influences of rennet and container types on proteolysis of traditional Kurdish cheese during the ripening

The effect of rennet and container types was evaluated on proteolysis of traditional Kurdish cheese during 60 days ripening. The enzymes involved were commercial chymosin and traditional rennet from lamb abomasum. Goat skin (traditional container) and plastic containers were used as storage containers. The trend of proteolysis was determined by measuring the content of nitrogen (N) in compounds soluble in water, 12% trichloroacetic acid and 5% phosphotungstic acid along with the urea–polyacrylamide gel electrophoresis method. The results showed that the nitrogen in compounds soluble in water, 12% trichloroacetic acid and 5% phosphotungstic acid was higher in ripened cheeses into plastic containers; however, the containers had no significant effect on the breakdown of α‐ and β‐caseins (P < 0.05). Using commercial rennet caused the breakdown of α‐ and β‐caseins and the level of nitrogen in compounds soluble in water to increase. Finally, however, the amount of α‐ and β‐caseins breakdown was trivial, and α‐casein was decreased more than β‐casein in all samples.     

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.     

The effects of beeswax coating on quality of Kashar cheese during ripening

The aim of this study was to evaluate the effects of the application of beeswax coating on the microbiological, physicochemical and sensory properties of Kashar cheese during ripening (120 day). Kashar cheeses were coated with two different thickness of beeswax (single‐layer coating, BW1, and double‐layer coating, BW2). For comparison, vacuum packaged (VP) and without packaging material (control) were also studied. Generally, no differences were found in total aerobic mesophilic bacteria, LAB on M‐17 agar, coliform bacteria and S. aureus counts among cheeses. Microbiological analyses also showed the beeswax‐coated cheeses presented a decrease of 2.5 logarithmic units on mould counts compared to control at 120th day. The control cheese had significantly (P < 0.05) higher dry matter, fat and protein contents, followed by BW1. However, the coating reduced formation of a thick crust layer by delaying moisture loss. At the end of 120‐day storage period, no significant differences in pH and acidity values were observed among the cheeses studied. Compared to other cheeses, control and BW1 cheeses had higher levels of WSN and ripening index in the end of storage. In the result of sensory analysis, while cheese BW1 and control were more preferred by the panellists, cheese VP received the lowest scores.     

The influence of seasons and ripening time on yeast communities of a traditional Brazilian cheese

The occurrence and effects of the dry and rainy seasons on yeast populations in traditional Serro Minas cheese, one of the most popular cheeses produced from raw milk in Brazil, were studied over the course of 60 days of ripening. Enzymatic activity exhibited by these yeast isolates was also studied. A total of 19 yeast species were identified via sequence analysis of the D1/D2 domains of the large subunit of the rRNA gene. Fourteen yeast species were obtained from cheese produced during the dry season, and fifteen species were obtained from cheese produced during the rainy season. High diversity indices for the yeast species were determined for cheese manufactured during both seasons (average H′_D = 1.7 and H′_R = 1.5, respectively). The predominant species in Serro Minas cheese included Debaryomyces hansenii, Kodamaea ohmeri and Kluyveromyces marxianus. D. hansenii 28.12 showed low lipolytic and high proteolytic activity. K. marxianus 83F and 60P demonstrated lipolytic and β-galactosidase activity, respectively. K. ohmeri 88A displayed low lipolytic and β-galactosidase activity. Maximal lipase, β-galactosidase and protease activity was observed at 20 °C and pH 6.0, 30 °C and pH 7.0 and 50 °C and pH 6.0, respectively. Considering that D. hansenii 28.12, K. ohmeri 88A and K. marxianus 60P together showed protease, lipase and β-galactosidase activity in this study, further research on the possibility of including these yeasts as part of a starter culture and research on their effects on the sensory properties of Serro Minas cheese merit more study.     

Changes in physicochemical and organoleptic properties of traditional Iranian cheese Lighvan during ripening

Lighvan cheese was studied to determine the physicochemical and biochemical changes over 90 days of ripening in brine. Acidity, pH, dry matter, fat values, lipolysis level, water‐soluble nitrogen (WSN), total nitrogen (TN), ripening index (RI), trichloroacetic acid‐soluble nitrogen (TCA‐SN) and organoleptic assessments were analysed. Dry matter and fat values decreased during ripening. Lipolysis level, RI, TCA‐SN values and salt content increased continuously until the end of the ripening period, but total nitrogen decreased throughout a 90‐day storage period. The ripening stage was the main factor affecting the cheese’s sensory properties.     

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。     

Changes in the physicochemical,microstructural and rheological properties of traditional Kope cheese during ripening

The effect of ripening time on the microstructural, physicochemical and rheological characteristics of traditional Kope cheese ripened in clay pots was investigated. The moisture content, pH and total nitrogen (TN)/dry matter (DM) of the cheese decreased, and DM, fat in DM and water‐soluble nitrogen/TN increased during this period. Storage and loss moduli increased, while loss tangent decreased; as a result, the elasticity characteristics were greater than the viscous characteristics of the samples. Microstructure images showed that the size of pores and casein network density increased significantly during ripening and, after 90 days, the structure of many pores became very similar to each other.     

Biochemical changes throughout the ripening of a traditional Spanish goat cheese variety (Babia-Laciana)

The physico-chemical characteristics, proteolysis (classical nitrogen fractions, caseins and their degradation products and free amino acids), and lipolysis (fat acidity and free fatty acids) were studied throughout the ripening of three batches of Babia-Laciana cheese, a Spanish traditional variety made from raw goats’ milk. The main compositional characteristics of this cheese at the end of the ripening are its high content of total solids (TS) (78.0±2.4 g 100 g⁻¹ of cheese) and fat (61.1±1.2 g 100 g⁻¹ of TS), the presence of residual lactose (1.6±0.8 g 100 g⁻¹ of TS) and its low content of sodium chloride (1.1±0.7 g 100 g⁻¹ of TS) and ash (2.8±0.5 g 100 g⁻¹ of TS). Its pH values (4.44±0.72) are extraordinarily low. The evolution and final values of the different nitrogen fractions show that this cheese undergoes a very slight proteolysis, a fact which was corroborated when the caseins and their degradation products were quantified: β-casein did not undergo any modification throughout ripening, while only 21% of the α_s-caseins were degraded. Free amino acids content increased by a factor of about 7 throughout ripening, resulting in a high content of γ-amino butyric acid and a low content of glutamic acid at the end of the process. Fat acidity increased very slightly, approximately 4.5 times, during ripening, reaching final values of 3.5±2.2 mg KOH g⁻¹ of fat. The total free fatty acids content showed a similar evolution to fat acidity. At the end of the ripening process, the main free fatty acid was C_18:1, followed by C₁₆ and C₁₀.     

The diversity and evolution of microbiota in traditional Turkish Divle Cave cheese during ripening

The microbial diversity of traditional Turkish Divle Cave cheese was evaluated in three independent batches. Using molecular techniques, twenty three bacterial species were identified in the interior and outer part of the cheese on days 60 and 120. Bacilli and Gammaproteobacteria classes were predominant during early stages of ripening and Actinobacteria at later stages. Nineteen species of filamentous fungi and five yeast species were identified and the most frequently isolated species were Penicillium polonicum, Penicillium biforme, Penicillium roqueforti, Penicillium chrysogenum and Debaryomyces hansenii. The microbiota displayed similar communities among batches, but high diversity in different parts of the cheese during ripening. Novel cheese starter cultures could be developed after the technological characterisation of the isolated strains.     

Studies on the ripening of stilton cheese: Proteolysis

The pH of fresh Stilton curd, which 2 h after coagulation was ∼6·7, decreased to ∼4·8 in 4 day-old cheeses but increased gradually thereafter to ∼6 at the end of ripening (70 days). At the end of the normal ripening period, ∼60% of the total N (TN) was water soluble (WSN) and ∼58% of the WSN was soluble in 70% ethanol, while 40% was diffusible on dialysis against water; free amino acid N (phosphotungstic acid-soluble, PTA-N) reached ∼4·8% of TN. The levels of TNBS-reactive amino groups were highly correlated with the values of WSN and 12% TCA-N but showed a greater change in the PTA extract than the value of PTA-N. Dialysable WSN was resolved into five peptide fractions by chromatography on Sephadex G-10; these fractions were very heterogeneous and contained up to eight ninhydrin-positive peptides when examined by TLC. Chromatography on DEAE cellulose revealed a high level of heterogeneity in the 70% ethanol-soluble and -insoluble fractions and this was confirmed by the wide range of N-terminal groups. The free amino acids (FAA, as measured by ion exchange chromatography) represented 6·8% and 9·9% of TN in the 70 day-old experimental cheeses and in commercial samples, respectively. Valine, leucine, lysine and glutamic acid accounted for ∼50% of total FAA throughout the ripening period.     

Studies on the ripening of stilton cheese: Lipolysis

The levels of free fatty acids (FFA) in Stilton cheese showed very slight increases during the first 28 days, but they then increased rapidly up to the end of ripening. Some individual FFA, as mole percentages of total FFA, changed irregularly during ripening. Long-chain FFA were present at higher concentrations than were lower fatty acids. A relatively high level of carbonyl compounds, methyl ketones in particular, were present in Stilton during ripening. A good recovery of methyl ketones was obtained using a method based on reverse-phase high-performance liquid chromatography. The concentration of each methyl ketone did not depend on the level of available fatty acids. While the proportions of C₁₃ and C₁₅ ketones were relatively low compared with their precursor C₁₄ and C₁₆ fatty acids, the concentrations of C₇ and C₉ ketones were relatively high compared with their precursor C₈ and C₁₀ fatty acids. With the exception of C₇ and C₉ ketones, which showed consistent and considerable increases up to the end of ripening (C₇ + C₉ accounted for 60% of total methyl ketones), the relative concentrations of methyl ketones fluctuated during ripening; this is probably the result of interconversions of the methyl ketones and/or their reduction to secondary alcohols.     

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。     

The effects of lipase‐encapsulating carriers on the accelerated ripening of Kashar cheese

In this study, lipase enzymes were encapsulated in κ‐carragenan, gellan and sodium alginate using emulsion and extrusion techniques and were then added to cheese milk together with rennet. The effects of the encapsulating material and ripening period on the chemical, textural and sensory characteristics of Kashar cheese were investigated. The study demonstrated that sodium alginate, gellan and κ‐carrageenan could successfully be used as lipase carrier systems to accelerate the fat breakdown process during the ripening of Kashar cheese. Those samples treated with κ‐carrageenan capsules showed the highest rate of lipolysis and proteolysis compared to those treated with the other capsules.