Influence of lamb rennet paste containing probiotic on proteolysis and rheological properties of pecorino cheese

Pecorino cheeses made from heat-treated ewes’ milk using traditional lamb rennet paste (RP), lamb rennet paste containing Lactobacillus acidophilus (LA-5; RPL), and lamb rennet paste containing a mix of Bifidobacterium lactis (BB-12) and Bifidobacterium longum (BB-46; RPB) were characterized for proteolytic and rheological features during ripening. Consumer acceptance of cheeses at 60 d of ripening was evaluated. Lactobacillus acidophilus and Bifidobacterium mix displayed counts of 8 log₁₀ cfu/g and 9 log₁₀ cfu/g, respectively, in cheese during ripening. The RPB cheese displayed a greater degradation of casein (CN) matrix carried out by the enzymes associated to both Bifidobacterium mix and endogenous lactic acid microflora, resulting in the highest values of non-CN N and water-soluble N and the highest amount of α_s-CN degradation products in cheese at 60 d of ripening. The RPL cheese displayed intermediate levels of lactic acid bacteria and of N fractions. The percentage of γ-CN in RP and RPL cheeses at 60 d was 2-fold higher than in the cheese curd of the same groups, whereas the mentioned parameter was 3-fold higher in RPB cheese than in the corresponding fresh curd according to its highest plasmin content. The lower hardness in RPB at the end of ripening could be ascribed to the greater proteolysis observed in cheese harboring the Bifidobacterium mix. Although differences in proteolytic patterns were found among treatments, there were no differences in smell and taste scores.     

Encapsulation of probiotic bacteria in lamb rennet paste: effects on the quality of Pecorino cheese

Lamb rennet pastes containing encapsulated Lactobacillus acidophilus and a mix of Bifidobacterium longum and Bifidobacterium lactis were produced for Pecorino cheese manufacture from Gentile di Puglia ewe milk. Cheeses were denoted as RP cheese when made with traditional rennet paste, RP-L cheese when made with rennet paste containing L. acidophilus culture, and RP-B cheese when made with rennet paste containing a mix of B. lactis and B. longum. Biochemical features of Pecorino cheese were studied at 1, 15, 30, 60, and 120 d of cheese ripening. The effect of encapsulation and bead addition to rennet acted on a different way on the viability of probiotic. Lactobacillus acidophilus retained its viability for 4 to 5 d and then showed a fast reduction; on the other hand, B. longum and B. lactis experienced kinetics characterized by an initial death slope, followed by a tail effect due to acquired resistance. At 1 d of ripening, the levels of L. acidophilus and bifidobacteria in cheese were the lowest, and then increased, reaching the highest levels after 30 d; such cell loads were maintained throughout the ripening for L. acidophilus, whereas bifidobacteria experienced a decrease of about 1 log cfu/g at the end of ripening. Enzymatic activities and biochemical features of cheeses were influenced by the type of rennet used for cheesemaking. Greater enzymatic activity was recorded in RP-L and RP-B cheese due to the presence of probiotic bacteria released from alginate beads. A positive correlation was found between enzymatic activities and water-soluble nitrogen and proteose-peptone in RP-B and RP-L cheeses; water-soluble nitrogen and proteose-peptone were the highest in RP-B. Principal component analysis distinguished RP-L from the other cheeses on the basis of the conjugated linoleic acid content, which was higher in the RP-L due to the ability of L. acidophilus to produce conjugated linoleic acid in the cheese matrix.     

Influence of an artisanal lamb rennet paste on proteolysis and textural properties of Murcia al Vino cheese

The aim of this study was to evaluate the influence of lamb rennet paste on the proteolysis and textural properties of Murcia al Vino cheese, compared with calf rennet. The enzyme concentration was adjusted according to its milk-clotting activity. The use of rennet paste led to higher values of all nitrogen fractions studied. Significant increases were observed in the water-soluble nitrogen fraction as a result of the lower pH of rennet paste cheeses; although the rennet paste is not characterised, three proteases are reported in the references consulted which can justify the greater proteolysis compared with calf rennet. The use of natural rennet paste produces a cheese with a more hydrolysed protein matrix, which is associated with significant changes in texture. The greater firmness determined in the rennet paste cheese was associated with higher fracture stress, lower fracture strain and lower moisture content.     

Probiotic in lamb rennet paste enhances rennet lipolytic activity, and conjugated linoleic acid and linoleic acid content in Pecorino cheese

Cheeses manufactured using traditional lamb rennet paste, lamb rennet paste containing Lactobacillus acidophilus, and lamb rennet paste containing a mix of Bifidobacterium lactis and Bifidobacterium longum were characterized for the lipolytic pattern during ripening. Lipase activity of lamb rennet paste, lamb rennet containing Lb. acidophilus, and lamb rennet containing a mix of bifidobacteria was measured in sheep milk cream substrate. Rennet paste containing probiotics showed a lipase activity 2-fold greater than that displayed by traditional rennet. Total free fatty acid (FFA) in sheep milk cream was lower in lamb rennet paste (981 μg/g of milk cream) than in lamb rennet containing Lb. acidophilus (1,382.4 μg/g of milk cream) and in lamb rennet containing a mix of bifidobacteria (1,227.5 μg/g of milk cream) according to lipase activity of lamb rennet paste. The major increase of FFA in all cheeses occurred during the first 30 d of ripening with the greatest values being observed for C16:0, C18:0 C18:1. At 60 d of ripening all cheeses showed a reduction in the amount of free fatty acids; in particular, total free fatty acids underwent a decrease of more than 30% from 30 to 60 d in cheeses manufactured using traditional lamb rennet paste, whereas the same parameter decreased 10% in cheeses manufactured using lamb rennet paste containing Lb. acidophilus and cheeses manufactured using lamb rennet paste containing a mix of B. lactis and B. longum. Cheese containing Lb. acidophilus was characterized by the greatest levels of total conjugated linoleic acids (CLA) 9-cis, 11-trans CLA and 9-trans, 11-trans CLA, whereas cheese containing bifidobacteria displayed the greatest levels of free linoleic acid. Rennet pastes containing viable cells of Lb. acidophilus and a mix of B. lactis and B. longum were able to influence the amount of FFA and CLA in Pecorino cheese during ripening.     

Influence of lamb rennet paste on the lipolytic and sensory profile of Murcia al Vino cheese

The influence of lamb rennet paste (71.1% chymosin, 177 international milk-clotting units/mL, 4.57U/g of lipase activity) during the ripening of Murcia al Vino goat cheese was studied. The aim of this study was to improve the knowledge of the effect of lamb rennet paste on the lipolytic patterns in this type of cheese by reference to the evolution of total and free fatty acids. A sensory analysis was carried out to compare cheeses made with commercial and paste rennet. The rennet paste showed higher lipolytic activity, enhancing the production of short-chain free fatty acids. In addition, the cheese produced with lamb rennet paste had a slightly more bitter and piquant taste, making it an attractive commercial alternative that can be used to develop new varieties of goat cheese.     

Production of biogenic amines during the ripening of Pecorino Abruzzese cheese

The production of biogenic amines (BA) during the manufacturing and ripening of sheep milk Pecorino Abruzzese cheeses prepared from raw milk without starter culture (A) and from pasteurized milk with added starter (B) were compared. At the end of ripening (60 days), the total BA contents of cheeses of batches A and B were 697 and 1086 mg kg⁻¹, respectively; the dominant BA were different. Single isolates of enterococci, pseudomonads and Enterobacteriaceae were screened for their potential to produce BA. Qualitative tests indicated a large spread of BA-forming cultures among the members of the Enterobacteriaceae and lactic acid bacteria (LAB). Differences among the levels of BA produced in UHT milk by representative isolates of coliforms, Pseudomonas and LAB were observed in relation to the microbial group or the isolate. The results emphasize the need to improve the general hygienic conditions of Pecorino Abruzzese cheese manufacture and control the indigenous bacterial population.     

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.     

Influence of residual rennet and proteolysis on the exudation of whey from Feta cheese during storage

A change in the quantity of rennet added to the cheesemilk resulted in a corresponding change in the level of residual rennet in Feta cheese. Casein proteolysis and exudation of whey from Feta cheese during storage were proportional to the quantity of residual rennet in the cheese. It is likely that with proteolysis, the three-dimensional casein network becomes weaker and gradually disintegrates. The water-holding ability of the casein gels is thereby greatly reduced and moisture is released from the interstices of the casein gel. This free moisture and soluble material, including peptides and amino acids formed during proteolysis, are released as exudate during the storage of Feta cheese.     

不同包装方式对半硬质干酪成熟期间蛋白质降解的影响

对真空包装和涂蜡包装的半硬质干酪成熟过程中蛋白降解进行了研究。结果表明:2种包装的干酪在成熟过程中pH 4.6SN含量和12%TCA-SN含量都随着时间的延长逐渐增大,且2组数据之间差异显著(P<0.05);2种包装的干酪中游离氨基酸总量随成熟时间的延长而逐渐增加,各种氨基酸含量变化的显著性不同;SDS-PAGE电泳图谱显示2种干酪在成熟期内蛋白质都发生了明显的降解,且涂蜡包装的干酪蛋白降解程度较真空包装的深,在成熟45 d后较为明显。     

Chemometric analysis of proteolysis during ripening of Ragusano cheese

Chemometric modeling of peptide and free amino acid data was used to study proteolysis in Protected Denomination of Origin Ragusano cheese. Twelve cheeses ripened 3 to 7 mo were selected from local farmers and were analyzed in 4 layers: rind, external, middle, and internal. Proteolysis was significantly affected by cheese layer and age. Significant increases in nitrogen soluble in pH 4.6 acetate buffer and 12% trichloroacetic acid were found from rind to core and throughout ripening. Patterns of proteolysis by urea-PAGE showed that rind-to-core and age-related gradients of moisture and salt contents influenced coagulant and plasmin activities, as reflected in varying rates of hydrolysis of the caseins. Analysis of significant intercorrelations among chemical parameters revealed that moisture, more than salt content, had the largest single influence on rates of proteolysis. Lower levels of 70% ethanol-insoluble peptides coupled to higher levels of 70% ethanol-soluble peptides were found by reversed phase-HPLC in the innermost cheese layers and as the cheeses aged. Non-significant increases of individual free amino acids were found with cheese age and layer. Total free amino acids ranged from 14.3 mg/g (6.2% of total protein) at 3 mo to 22.0 mg/g (8.4% of total protein) after 7 mo. Glutamic acid had the largest concentration in all samples at each time and, jointly with lysine and leucine, accounted for 48% of total free amino acids. Principal components analysis and hierarchical cluster analysis of the data from reversed phase-HPLC chromatograms and free amino acids analysis showed that the peptide profiles were more useful in differentiating Ragusano cheese by age and farm origin than the amino acid data. Combining free amino acid and peptide data resulted in the best partial least squares regression model (R(2) = 0.976; Q(2) = 0.952) predicting cheese age, even though the peptide data alone led to a similarly precise prediction (R(2) = 0.961; Q(2) = 0.923). The most important predictors of age were soluble and insoluble peptides with medium hydrophobicity. The combined peptide data set also resulted in a 100% correct classification by partial least squares discriminant analysis of cheeses according to age and farm origin. Hydrophobic peptides were again discriminatory for distinguishing among sample classes in both cases.     

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     

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     

Secondary proteolysis in Serra cheese during ripening and throughout the cheese-making season

 Experimental Serra cheeses were manufactured from raw ewe’s milk and thistle flowers following a two-way factorial design. The content of nitrogen soluble in water (WSN), in 2% trichloroacetic acid (2% TCA-N), in 12% TCA (TCA-N) and in 5% phosphotungstic acid (5% PTA-N), and the pH and salt-in-moisture concentration were measured throughout the ripening period (sampling at 0, 7, 21 and 35 days) and the cheese-making season (sampling in November, February and May). Proteolysis in 35-day-old Serra cheese was quantitatively high [average values of 34.6% and 11.9% for WSN/TN (total nitrogen) and 2% TCA-N/TN, respectively], but qualitatively low (average values of 5.8% and 1.2% for 12% TCA-N/TN and 5% PTA-N/TN, respectively). The ratios WSN/TN and 2% TCA-N/TN were lowest for cheeses ripened in February, whereas the ratio 12% TCA-N/TN was highest for cheeses ripened in November. By 35 days of ripening, the average pH and salt-in-moisture concentration values were 5.2 and 4.8%, respectively. No correlation was found to occur between the measured pH or salt-in-moisture concentration and the values of soluble nitrogen fractions throughout the cheese-making season. Received: 14 February 1996/Revised version: 4 June 1996     

The role of immobilized rennet on carbon cloth in flavor development during ripening of Gouda cheese

Rennet-free Gouda (RFG) cheese was prepared to investigate the influence of rennet on the non-volatile and volatile profiles of cheese and was characterized by HPLC and GC/MS analyses. Chymosin, a major protease in rennet, was immobilized onto oxidized and chemically modified carbon cloth. The chymosin immobilization efficiency was 60.4%, and the milk-clotting activity used as an index of the stability of the immobilized chymosin decreased by around 20% in 2 weeks. However, the activity was maintained at 70–80% from 2 weeks to 32 weeks and was more stable than that of chymosin solution alone. Non-volatile (organic acids) and volatile profiles of the RFG cheese and rennet-containing normal Gouda cheese were not significantly different during ripening with a few exceptions. Therefore, it can be concluded that cheese flavor is developed by lactic acid fermentation, irrespective of the presence of rennet.     

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on Cheddar cheese quality: proteolysis during ripening

Proteolysis in cheese is influenced by the state of proteins (protein-calcium-phosphate interactions), level of indigenous milk enzymes (plasmin), externally added milk-clotting enzymes (chymosin), and endogenous and exogenous enzymes from starter and non-starter lactic acid bacteria (NSLAB). The objective of this study was to determine how different levels of calcium (Ca) and phosphorus (P), residual lactose, and salt-to-moisture ratio (S/M) in cheese influence proteolysis during ripening. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), 2 levels of lactose at pressing (2.4 vs. 0.78%), and 2 levels of S/M (6.4 vs. 4.8%) were manufactured. The cheeses were analyzed for changes in pH 4.6-soluble N, and starter and NSLAB counts during 48 wk of ripening. Cheeses at d 1 were also analyzed for residual chymosin, plasmin, and plasminogen activity. A significant increase in soluble N was observed during ripening for all the treatments. Cheeses with low Ca and P, low lactose, and low S/M treatments exhibited higher levels of proteolysis as compared to their corresponding high treatments. Differences in the rate of proteolysis for cheeses with different levels of Ca and P might be due to changes in protein conformation and differences in residual chymosin in the cheeses. Cheeses with low Ca and P were manufactured by lowering the pH at set and drain, which led to higher chymosin retention in cheeses with low Ca and P compared with high Ca and P. Differences in proteolysis between treatments with different levels of lactose were also partly attributed to residual chymosin activity. In all treatments, a major fraction of plasmin existed as plasminogen, indicating minimal contribution of plasmin to proteolysis in Cheddar cheeses. The number of starter bacteria, in all treatments, decreased significantly during ripening. However, the decrease was larger in the case of high S/M treatments compared with low S/M treatments. In contrast, the number of NSLAB increased during ripening, and low S/M cheeses had higher counts compared with high S/M cheeses. The differences in proteolysis due to S/M were partially attributed to changes in protein conformation or bacterial proteolytic activity.     

Changes during manufacture and ripening of cheddar cheese prepared with fungal rennet substitute of Rhizopus oligosporus

Studies were made on the manufacture and ripening of cheddar cheese prepared with a milk-clotting enzyme of R. oligosporus and compared with rennet cheese. The curd working properties, yields and quality of green cheese from R. oligosporus enzyme were fairly comparable with calf-rennet. During the ripening period the changes in moisture, acidity, pH and fat content of both the cheese were similar. The soluble nitrogen was comparatively low while maturity index was higher during ripening in R. oligosporus cheese than calf-rennet cheese. Organoleptically, R. oligosporus cheese was rated lower than calf-rennet cheese, developing transient bitterness during ripening like other fungal rennet substitutes.     

Effect of a hygienized rennet paste and a defined strain starter on proteolysis,texture and sensory properties of semi-hard goat cheese

A hygienized rennet paste (HRP) and a defined strain starter culture, including Lactobacillus casei subsp. casei IFPL as adjunct, were considered for manufacturing Majorero cheese, a Spanish traditional variety made from goat milk. Influence of both factors on physicochemical characteristics, proteolysis, rheological and sensory properties, was evaluated throughout the ripening. Cheeses produced either industrially (IL) or in artisanal manner (AL) were compared with the experimental lot (EL), which included HRP and IFPL starter in its manufacture. Results showed a low level of primary proteolysis, expressed by a low content of non-casein nitrogen (NCN), in experimental cheeses. Despite the slightly poor texture (hard and crumbly) related to the high TS and salt contents, a good general acceptability was attained for EL, with the best scores for aroma and flavour intensities achieved at 30 ripening days. In fact, the sensory panel detected the “piquant” flavour (typical of the artisanal cheese variety) in EL after 15 days of ripening.