干酪脂类的代谢及其对风味的作用

干酪成熟期间脂类的代谢对干酪风味有着重要的作用。文中对干酪中的脂类、脂肪酸、干酪的脂解作用和参与其中的酶,以及干酪成熟过程中脂解作用对干酪风味的作用进行了探讨,并对存在的问题和今后的研究方向进行了分析。     

Effect of artisanal kid rennet paste on lipolysis in semi-hard goat cheese

This study examined the use of hygienised kid rennet pastes in model cheese systems and also in goat milk semi-hard cheeses to promote lipolysis. The results obtained indicated that the use of rennet paste caused greater lipolysis and increased, mostly, the short-chain free fatty acid (FFA) content. The model systems made with whole goat’s milk using rennet paste and commercial rennet mixture exhibited a higher FFA content than did the rennet paste-free controls (31,600 vs. 25,600 μmol/kg cheese). For the pilot cheeses made with bovine rennet and rennet paste mixture, the increase in FFA level after 45 days of ripening compared with the cheeses prepared only with commercial rennet was as much as 6600 (μmol/kg cheese) and the increase in the butyric acid content was also 1650 (μmol/kg cheese). Moreover, after 15 days of ripening, industrially prepared cheeses made with rennet paste exhibited greater levels of FFA than did the cheeses made with commercial rennet (11,500 μmol/kg at 45 days of ripening). Their flavour was stronger and the organoleptic characteristics were better accepted, which implies less ripening time for commercial cheese manufacture.     

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.     

Biochemical and microbiological characterization of artisan kid rennet extracts used for Cabrales cheese manufacture

Four samples of artisanal kid rennet extracts from four different Cabrales cheese producers were biochemically and microbiologically characterized. Most samples had a very acidic pH (around pH 4.0), which may condition their biochemical and microbial variables. The milk-clotting activity of the extracts was assessed using a Formagraph apparatus. The properties of these artisanal rennets were found to be comparable to a 1/10 dilution of 1:10,000 commercial calf rennet; their enzymatic potentials, measured with a semi-quantitative commercial system (API ZYM), showed only very slight differences. A large population of lactobacilli was found in all artisanal kid rennet samples, whereas coliforms, enterococci, staphylococci and leuconostocs were only occasionally encountered. Sixty-four representative colonies were classified by PCR amplification and the sequencing of a stretch of their 16S rDNA genes. Strains of Lactobacillus plantarum completely dominated one of the extracts. In all others samples, strains of this homofermentative species and of the heterofermentative Lactobacillus brevis were present in similar amounts.     

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.     

Influence of lamb rennet paste on composition and proteolysis during ripening of Pecorino foggiano cheese

Rennet pastes produced by lambs subjected to three different feeding systems (mother suckling [MS], artificial rearing [AR], and artificial rearing with Lactobacillus acidophilus supplementation [ARLB]) and slaughtered at two different ages (20 and 40 d) were used for the manufacture of Pecorino foggiano cheese. Composition and proteolysis during ripening of Pecorino foggiano cheese (four replicates batches) were analyzed. Proteolysis was greater in cheeses made with rennet pastes from lambs slaughtered at 20 d, as shown by analysis of nitrogen fractions (water-soluble N and proteose peptones). Supplementation of milk substitute with L. acidophilus may have influenced the growth dynamics of lactic acid bacteria in the rennet pastes, with positive effects on levels of lactobacilli in cheese at the beginning of the ripening time. Lower pH values in ARLB cheese during ripening, together with higher cell loads, suggest that supplementation of milk replacer with L. acidophilus resulted in higher proteolytic activity, as also confirmed by the composition of the pH 4.6—insoluble nitrogen fraction. No differences were found in total concentration of free amino acids among the experimental cheeses; phenylalanine, isoleucine, leucine, lysine were found at the highest levels. The addition of probiotic bacteria to milk substitute in lamb rearing appears to give good-quality lamb rennet paste.     

Influence of rennet milk-clotting activity on the proteolytic and sensory characteristics of an ovine cheese

Roncal cheese (regulated by an Apellation of Origin) is a traditional hard cheese manufactured from raw ewe's milk in the region of Navarre in Spain. Roncal cheeses, manufactured using two lamb rennets with different milk-clotting activity levels, were evaluated to compare their chemical, proteolytic, and sensory characteristics. A preliminary study of samples of lamb rennets indicated that a large proportion of such rennets did not fulfil current microbiological requirements and likewise revealed considerable variation in the milk-clotting activity of the samples examined. Trends in the overall physicochemical parameter values (pH, dry matter, fat, and protein) were similar in both cheese batches. Proteolysis of the nitrogen fractions was observed to take place at a faster rate in the cheeses made using the rennet with the higher milk-clotting activity (soluble nitrogen, non-protein nitrogen, and amino acid nitrogen values around 13–20% higher than in the cheeses made using the rennet with the lower milk-clotting activity after 180 days of ripening). Urea-PAGE electrophoretic analysis of the caseins from the cheeses manufactured using both types of rennet showed that the β-caseins were less susceptible to proteolysis than the α_s-caseins. The effect of the different milk-clotting activity levels was most pronounced on the α_s-caseins, in which the rennet with the higher milk-clotting activity gave higher breakdown. Nevertheless, the differences in the proteolysis rates did not yield any appreciable sensory differences.     

Proteolysis in rennet casein-based cheese analogues

Rennet caseins manufactured from mid- or late-lactation milk were used to prepare pilot- and commercial-scale Mozzarella-type cheese analogues. Mid-lactation rennet casein and analogues made from it contained low levels of plasmin; late-lactation rennet caseins and analogues made from them had higher levels of plasmin while pilot-scale analogues had higher levels of plasmin than commercial-scale analogues. The cheese analogues were stored at 8°C for 32 weeks during which time total bacterial counts increased from ∼10⁴ to 10⁷–10⁸ cfu g⁻¹, with non-starter lactic acid bacteria dominating the microflora. Proteolysis, as reflected by pH 4.6-soluble nitrogen and free amino acids, increased on storage of all the analogues. The increase was greater in the analogues manufactured from late-lactation rennet caseins than in those manufactured from mid-lactation rennet casein and in pilot-scale analogues than in commercial-scale analogues, reflecting the differences in plasmin levels as well as slight differences in composition. Polyacrylamide gel electrophoretograms of the cheese analogues showed that β-casein was hydrolysed more extensively than α_s1-casein and that the concentration of γ-caseins increased on storage. The degree of hydrolysis of β-casein was greater in the cheese analogues manufactured from late-lactation rennet caseins than in those manufactured from mid-lactation rennet casein and in the pilot-scale analogues than in the commercial-scale analogues reflecting the corresponding plasmin levels. Seventeen peptides in the pH 4.6-soluble extract of the cheeses were isolated and partially sequenced; all originated from the N-terminal region of β-casein; 9 peptides had Lys₂₉ of β-casein as the N-terminal, 6 peptides had Arg₁ of β-caesin as the N-terminal and the remaining two peptides had Ile₃₀ and Phe₃₃ of β-casein as the N-terminal, respectively. The pattern of casein hydrolysis in the cheese analogues suggests that plasmin was the primary proteolytic agent contributing to initial hydrolysis of the caseins while microbial proteinases and peptidases may have contributed to the high levels of free amino acids.     

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.     

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.     

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.     

干酪的成熟及其风味物质

对干酪的成熟机理和风味物质的形成进行了综述，并介绍了一些干酪的主要风味物质和测定方法以及存在的问题和发展趋势。     

Changes in lipolysis and volatile fraction of a goat cheese manufactured employing a hygienized rennet paste and a defined strain starter

The effect of a hygienized rennet paste (HRP) and a defined strain starter IFPL on the volatile fraction of goat cheese (Majorero) was examined. Three batches were made and those cheeses produced either industrially (IL) or in artisanal manner (AL) were compared with the experimental lot (EL), which included both HRP and IFPL starter in its manufacture. Analysis of the volatile fraction was by static headspace connected to GC–MS and this disclosed a total of 28 components belonging to the following chemical families: fatty acids, esters, ketones, aldehydes and alcohols. Most of the volatile components identified appeared in all lots but at different concentrations. IL cheeses were distinguished from the other lots, including HRP in their manufacture, essentially by a lower presence of esters and FFA (both branched-chain and aliphatic acids). The use of HRP and a defined strain starter culture (including Lb. casei IFPL 731 as adjunct) directly affected lipolysis degree. This was reflected in an increase in the mono-and diglyceride concentrations and in a greater content of short-chain FFA, particularly butanoic acid, an important flavour component, which imparts a desirable sharp, “piquant” taste to Majorero cheese. The IFPL starter culture also had a significant effect on concentrations of compounds such as 2-methyl-1-propanol, 3 methyl-1-butanol, isoamyl butyrate and acetoin.     

Simultaneous use of transglutaminase and rennet in white-brined cheese production

The effects of renneting temperature (30 °C or 34 °C) on textural properties, proteolysis and yield of white-brined cheese made by simultaneous use of microbial transglutaminase (mTG) and rennet were investigated. Incorporation of mTG resulted in higher yield values for experimental cheeses than for the control cheeses at both renneting temperatures. The total solids contents of the cheeses treated with mTG were remarkably lower than the control cheeses; but the former cheeses had higher protein-in-dry matter levels. The TPA profiles of the cheeses showed that the incorporation of mTG led to modification in the textural properties. The development of proteolysis in the cheeses treated with mTG was slightly slower than the control cheeses at both coagulation temperatures. To conclude, the specific action of mTG on milk proteins could be successfully exploited to modify the textural properties and to increase the yield of white-brined cheese.     

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.