Casein breakdown during ripening of Idiazabal cheese: influence of starter and rennet type

The objective of this work was to determine the effect of starter and rennet type on casein breakdown during Idiazabal cheese ripening. Four batches of cheeses were manufactured with two rennets, commercial calf rennet and artisanal lamb rennet, and the use of natural flora or a commercial starter. Electrophoretic analysis of cheese samples showed six bands identified as α_s1‐, α_s2 + β‐, α_s1‐I‐, γ₁‐, β‐I‐ and para‐κ‐casein. As expected, the casein breakdown during cheese ripening was considerably affected by rennet type and the use of a commercial starter. The artisanal lamb rennet produced a higher hydrolysis of casein fractions than the commercial calf rennet, probably owing to its high percentage of chymosin (around 78%). The effect of addition of starter on proteolysis was dependent on the casein fractions generated by artisanal lamb rennet or commercial calf rennet. © 2000 Society of Chemical Industry     

Changes in the rheological properties of Iranian UF-Feta cheese during ripening

The frequency sweep test was used to evaluate storage modulus (G′), loss modulus (G′′) and loss tangent [tan (δ)] of Iranian UF-Feta cheese during ripening period (3, 20, 40 and 60 days). With development of ripening, storage and loss moduli increased at varying rates. The rate of increase in G′ was greater than that in G′′ resulting in a reduction in tan (δ). That is, storage modulus was dominant to loss modulus and as a result the elasticity nature was greater than the viscous nature of cheese samples. Due to the disruption of fat globules and proteolysis, protein matrix rearranged and formed a more compact texture containing aggregates of casein. Ripening did not influence the pH level and also the concentrations of dry matter, fat, salt, and total nitrogen in dry matter. However, water soluble nitrogen increased significantly (P < 0.05).     

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.     

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.     

契达干酪应力松弛特性与成熟度相关性研究

测定了契达干酪不同成熟期样品的应力松弛时间、弹性模量和成熟度指数,分析了其与干酪成熟度之间的相关性。结果表明,弹性模量随成熟期呈降低趋势。应力松弛时间随成熟期先增大后降低,并在7出现最大值。7~90d样品应力松弛时间呈单调递减。各成熟期样品的应力随测试时间的衰减规律符合对数规律。随成熟期的增加,可溶性氮质量分数pH4.6-SN和12%TCA-SN均呈增大趋势,增大幅度分别为18.07%和8.2%。弹性模量和应力松弛时间与成熟度指数分别呈极显著和显著线性相关。     

Insoluble calcium content and rheological properties of Colby cheese during ripening

Colby cheese was made using different manufacturing conditions (i.e., varying the lactose content of milk and pH values at critical steps in the cheesemaking process) to alter the extent of acid development and the insoluble and total Ca contents of cheese. Milk was concentrated by reverse osmosis (RO) to increase the lactose content. Extent of acid development was modified by using high (HPM) and low (LPM) pH values at coagulant addition, whey drainage, and curd milling. Total Ca content was determined by atomic absorption spectroscopy, and the insoluble (INSOL) Ca content of cheese was measured by the cheese juice method. The rheological and melting properties of cheese were measured by small amplitude oscillatory rheometry and UW-Melt Profiler, respectively. There was very little change in pH during ripening even in cheese made from milk with high lactose content. The initial (d 1) cheese pH was in the range of 4.9 to 5.1. The INSOL Ca content of cheese decreased during the first 4 wk of ripening. Cheeses made with the LPM had lower INSOL Ca content during ripening compared with cheese made with HPM. There was an increase in melt and maximum loss tangent values during ripening except for LPM cheeses made with RO-concentrated milk, as this cheese had pH <4.9 and exhibited limited melt. Curd washing reduced the levels of lactic acid produced during ripening and resulted in significantly higher INSOL Ca content. The use of curd washing for cheeses made from high lactose milk prevented a large pH decrease during ripening; high rennet and draining pH values also retained more buffering constituents (i.e., INSOL Ca phosphate), which helped prevent a large pH decrease.     

Proteolysis in ultra-filtered and conventional Iranian white cheese during ripening

Conventional and ultra-filtered (UF) Iranian white cheeses were made with almost identical gross chemical composition and the extent and characteristics of proteolysis were studied during ripening. UF cheeses exhibited a lower rate of development of pH 4.6-soluble nitrogen than conventional cheeses. The rates of degradation of α_s1-casein and particularly β-casein were lower in UF cheeses than in conventional cheeses. Plasmin activity was lower in UF cheeses than that in conventional cheese, whereas coagulant activity was higher in the former. Noticeable qualitative and quantitative differences were observed in reverse-phase high performance liquid chromatography (RP-HPLC) peptide profiles between UF and conventional white cheeses and chemometric analysis of peak height data distributed the cheeses into two separate groups. The levels of free amino acids in UF cheeses were lower than in conventional cheeses. Lower peptide degradation and production of amino acids suggested slower ripening, which may have been associated with the weak aroma development characteristic of UF cheeses.     

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。     

Proteolytic and lipolytic changes during the ripening of a Spanish craft goat cheese (Armada variety)

The proteolytic and lipolytic changes during the ripening process were investigated in four batches of Armada goat's milk cheese (an artisanal variety produced in the North of Spain), by determining the classical nitrogen fractions, caseins and their degradation products, free amino acids, as well as the acidity of the fat, thiobarbituric acid (TBA) number and free fatty acids. Values obtained for the nitrogen fractions and for caseins and their degradation products show that this cheese undergoes very little protein degradation. A low free amino acids content was observed throughout the ripening process with a predominance of Pro followed by Leu+Ile, Glu acid, Phe, His+Lys and Val. The lipid degrada-tion was very intense from the second month of ripening, only comparable to that reported for cheeses ripened by moulds. The average free fatty acids content increased 20-fold during ripening, reaching final values of 44·5 g kg⁻¹. All the free fatty acids increased considerably during ripening, resulting in a predominance of saturated and unsaturated long-chain acids, followed by medium-chain acids, C₁₀ principally. Short-chain fatty acid content by the end of ripening was higher than that presented in other cheese varieties with a similar high degree of lipolysis. © 1997 SCI.     

A model describing Debaryomyces hansenii growth and substrate consumption during a smear soft cheese deacidification and ripening

A mechanistic model for Debaryomyces hansenii growth and substrate consumption, lactose conversion into lactate by lactic acid bacteria, as well as lactose and lactate transfer from the core toward the rind was established. The model described the first step (14 d) of the ripening of a smear soft cheese and included the effects of temperature and relative humidity of the ripening chamber on the kinetic parameters. Experimental data were collected from experiments carried out in an aseptic pilot scale ripening chamber under 9 different combinations of temperature (8, 12, and 16°C) and relative humidity (85, 93, and 99%) according to a complete experimental design. The model considered the cheese as a system with 2 compartments (rind and core) and included 5 state evolution equations and 16 parameters. The model succeeded in predicting D. hansenii growth and lactose and lactate concentrations during the first step of ripening (curd deacidification) in core and rind. The nonlinear data-fitting method allowed the determination of tight confidence intervals for the model parameters. The residual standard error (RSE) between model predictions and experimental data was close to the experimental standard deviation between repeated experiments.     

Texture Changes During the Ripening of Port Salut Argentino Cheese in 2 Sampling Zones

ABSTRACT: Texture changes during ripening of Port Salut Argentino cheese for different sampling zones were studied. Compression relaxation tests were performed and results were analyzed using both Maxwellian and Peleg's models. Elastic equilibrium modulus obtained from the Maxwellian model decreased from 1.22 to 0.11 10⁴Pa during ripening. The constants derived from Peleg's model, k₁ and k₂, diminished with ripening time from 1.18 to 0.71 min and from 1.27 to 1.12, respectively. Asymptotic equilibrium modulus from Peleg's model decreased from 0.95 to 0.07 10⁴Pa during ripening. Rate parameters derived from a 1st order kinetics applied to both equilibrium moduli showed that the decrease was faster in the external zone (0.0846 d⁻¹) than in the central zone (0.0368 d⁻¹). The correlation between equilibrium moduli, salt concentration, moisture content, and maturation indexes was obtained with a determination coefficient of 0.76.     

含大豆分离蛋白的干酪在成熟过程中化学组成和感官特性的变化

分析了不同大豆分离蛋白含量的干酪在成熟期化学组成（水分、蛋白质、脂肪、灰分）的变化，评价了其感官特性。结果表明，质量分数为5%大豆分离蛋白的干酪与纯牛乳干酪相比，其感官特性最佳。     

Effect of the inclusion of artichoke silage in the ration of lactating ewes on the properties of milk and cheese characteristics during ripening

The effect of including artichoke silage in the rations of dairy ewes on milk characteristics and biochemical changes of ripened cheeses was evaluated. Four groups of lactating ewes were fed rations containing 0, 10, 20, or 30% artichoke silage on a dry matter basis. Bulk milk samples were collected 3 times during the feeding period, and semi-hard cheeses were manufactured and sampled during ripening. Milk composition and cheese yield were not affected by diet. Inclusion of 20 and 30% artichoke silage reduced the firmness of the curds at a level only detected by the Gelograph (Gelograph-NT, Gel-Instrumente, Thalwil, Switzerland) probe. Inclusion of artichoke silage in ewes’ diet decreased fat and total free fatty acids content of these cheeses and increased total free amino acids content. Despite the effect of diet on cheese ripening characteristics, the overall sensory scores for cheeses corresponding to artichoke silage diets were statistically higher than those for the control cheeses.     

Effect of the inclusion of whole citrus in the ration of lactating ewes on the properties of milk and cheese characteristics during ripening

The effect of including citrus fruits (CF) in the rations of dairy ewes on the milk characteristics and biochemical changes of cheeses during ripening was evaluated. For this purpose, 48 lactating ewes (Guirra breed) were divided into 4 homogeneous groups and fed with isoenergetic and isoprotein rations containing CF at 0, 10, 20, and 30% on a dry matter basis in substitution of dry barley and pelleted beet pulp. During the experimental period, 3 batches of bulk milk were collected from each group and semi-hard cheeses were manufactured. Cheeses were sampled at 15, 30, and 60 d of ripening. Milk coagulation parameters and cheese yield were not negatively affected by the inclusion of CF in the ration. Physicochemical composition of cheeses at 60 d showed statistical differences for lower total solids and fat content of 30% CF cheeses. Proteolysis of cheeses measured by water-soluble nitrogen and total free amino acids content was not influenced by the ration. Differences between rations with respect to free fatty acids were significant for medium- and long-chain free fatty acids, and therefore for total content, but differences did not show a trend related to the increase of CF in the diet. The inclusion of CF in the ration of lactating ewes up to levels of 30% did not negatively affect the properties of milk and the biochemical and sensory characteristics of cheeses.     

Effect of different curd-washing methods on the insoluble Ca content and rheological properties of Colby cheese during ripening

A curd-washing step is used in the manufacture of Colby cheese to decrease the residual lactose content and, thereby, decrease the potential formation of excessive levels of lactic acid. The objective of this study was to investigate the effect of different washing methods on the Ca equilibrium and rheological properties of Colby cheese. Four different methods of curd-washing were performed. One method was batch washing (BW), where cold water (10°C) was added to the vat, with and without stirring, where curds were in contact with cold water for 5 min. The other method used was continuous washing (CW), with or without stirring, where curds were rinsed with continuously running cold water for approximately 7 min and water was allowed to drain immediately. Both methods used a similar volume of water. The manufacturing pH values were similar in all 4 treatments. The insoluble (INSOL) Ca content of cheese was measured by juice and acid-base titration methods and the rheological properties were measured by small amplitude oscillatory rheology. The levels of lactose in cheese at 1 d were significantly higher in CW cheese (0.06-0.11%) than in BW cheeses (∼0.02%). The levels of lactic acid at 2 and 12 wk were significantly higher in CW cheese than in BW cheeses. No differences in the total Ca content of cheeses were found. Cheese pH increased during ripening from approximately 5.1 to approximately 5.4. A decrease in INSOL Ca content of all cheeses during ripening occurred, although a steady increase in pH took place. The initial INSOL Ca content as a percent of total Ca in cheese ranged from 75 to 78% in all cheeses. The INSOL Ca content of cheese was significantly affected by washing method. Stirring during manufacturing did not have a significant effect on the INSOL Ca content of cheese during ripening. Batch-washed cheeses had significantly higher INSOL Ca contents than did CW cheeses during the first 4 wk of ripening. The maximum loss tangent values (meltability index) of CW cheese at 1 d and 1 wk were significantly higher compared with those of BW cheeses. In conclusion, different curd washing methods have a significant effect on the levels of lactose, lactic acid, meltability, and INSOL Ca content of Colby cheese during ripening.     

Hot topic: Changes in angiotensin-converting enzyme inhibition and concentrations of the tripeptides Val-Pro-Pro and Ile-Pro-Pro during ripening of different Swiss cheese varieties

The angiotensin-converting enzyme (ACE) inhibitory activity and the concentration of the 2 ACE-inhibiting tripeptides Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP) were studied during cheese ripening in 7 Swiss cheese varieties. The semi-hard cheeses Tilsiter, Appenzeller 1/4 fat, Tête de Moine, and Vacherin fribourgeois and the extra-hard and hard cheeses Berner Hobelkäse, Le Gruyère, and Emmentaler were investigated. Three loaves of each variety manufactured in different cheese factories were purchased at the beginning of commercial ripeness and investigated at constant intervals until the end of the usual sale period. Good agreement was found between ACE-inhibitory activity and the total concentration of VPP and IPP at advanced ripening stages. In most of the investigated varieties ACE-inhibitory activity and the concentration of the 2 tripeptides initially increased during the study period. A decline in the concentration of VPP and IPP was obtained toward the end of the investigated period for Tilsiter and Gruyère. The ratio of VPP/IPP decreased during ripening in all varieties with the exception of Emmentaler. However, large variations were observed among the cheese varieties as well as the individual loaves of the same variety. Chemical characterization of the investigated cheeses revealed that qualitative differences in the proteolysis pattern, not quantitative differences in the degree of proteolysis, are responsible for the observed variations in the concentrations of VPP and IPP. The presence of Lactobacillus helveticus in the starter culture was associated with elevated concentrations of VPP and IPP. The results of the present study show that concentrations of VPP and IPP above 100 mg/kg are attainable in semi-hard cheese varieties after ripening periods of about 4 to 7 mo and that stable concentrations of the 2 antihypertensive tripeptides can be expected over several weeks of cheese ripening.     

Free amino acid profile during ripening of ewe's milk cheese from the Croatian island Krk

The aim of this study was to determine the content of free amino acids (FAA) and their ratio in ewe's milk cheese from the island Krk during its ripening. FAA content was determined by reversed phase HPLC (RP‐HPLC) of cheese aqueous/ethanol extracts after FAA were transformed into their 6‐aminoquinolyl‐N‐hydroxysuccinimidyl carbamate derivatives. Their concentration increased during ripening, reaching the value of 5% in cheese dry matter. The dominant FAA were glutamic acid>leucine>valine>aspartic acid>phenylalanine>serine>proline, and higher content of nonessential vs essential FAA was revealed. Krk cheese has, in relation to other cheeses, higher values for glutamic acid/leucine, glutamic acid/phenylalanine, glutamic acid/proline and smaller values for leucine/aspartic acid, valine/aspartic acid, phenylalanine/aspartic acid ratios, while other ratios are comparable to those of other hard ovine cheeses.     

Microbiological and physicochemical characteristics and aminopeptidase activities during ripening of Serrano cheese

The physicochemical and microbiological characteristics and the aminopeptidase activity variation of Serrano cheese during winter and summer were investigated. Samples from different producers varied significantly, showing nonstandardized procedures for the manufacturing and ripening of this product. There were no significant changes in aminopeptidase activity during maturation and most of the enzyme activity found in the water extracts of cheese would have their origin in lactobacillus and enterococci, suggesting autolysis of these micro-organisms. Results show an increase in free amino acids during maturation, with higher amounts in the summer product.