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PubMed2006

Improvement of texture and structure of reduced-fat Cheddar cheese by exopolysaccharide-producing lactococci.

The objective of this study was to evaluate the effect of capsular and ropy exopolysaccharide (EPS)-producing strains of Lactococcus lactis ssp. cremoris on textural and microstructural attributes during ripening of 50%-reduced-fat Cheddar cheese. Cheeses were manufactured with added capsule- or ropy-forming strains individually or in combination. For comparison, reduced-fat cheese with or without lecithin added at 0.2% (wt/vol) to cheese milk and full-fat cheeses were made using EPS-nonproducing starter, and all cheeses were ripened at 7 degrees C for 6 mo. Exopolysaccharide-producing strains increased cheese moisture retention by 3.6 to 4.8% and cheese yield by 0.28 to 1.19 kg/100 kg compared with control cheese, whereas lecithin-containing cheese retained 1.4% higher moisture and had 0.37 kg/100 kg higher yield over the control cheese. Texture profile analyses for 0-d-old cheeses revealed that cheeses with EPS-producing strains had less firm, springy, and cohesive texture but were more brittle than control cheeses. However, these effects became less pronounced after 6 mo of ripening. Using transmission electron microscopy, fresh and aged cheeses with added EPS-producing strains showed a less compact protein matrix through which larger whey pockets were dispersed compared with control cheese. The numerical analysis of transmission electron microscopy images showed that the area in the cheese matrix occupied by protein was smaller in cheeses with added EPS-producing strains than in control cheese. On the other hand, lecithin had little impact on both cheese texture and microstructure; after 6 mo, cheese containing lecithin showed a texture profile very close to that of control reduced-fat cheese. The protein-occupied area in the cheese matrix did not appear to be significantly affected by lecithin addition. Exopolysaccharide-producing strains could contribute to the modification of cheese texture and microstructure and thus modify the functional properties of reduced-fat Cheddar cheese.

Animals↗
PubMed2003

Effect of pH on the chemical composition and structure-function relationships of cheddar cheese.

The objectives of this study were to determine the effect of pH on chemical, structural, and functional properties of Cheddar cheese, and to relate changes in structure to changes in cheese functionality. Cheddar cheese was obtained from a cheese-production facility and stored at 4 degrees C. Ten days after manufacture, the cheese was cut into blocks that were vacuum-packaged and stored for 4 d at 4 degrees C. Cheese blocks were then high-pressure injected one, three, or five times with a 20% (wt/wt) glucono-delta-lactone solution. Successive injections were performed 24 h apart. Cheese blocks were then analyzed after 40 d of storage at 4 degrees C. Acidulant injection decreased cheese pH from 5.3 in the uninjected cheese to 4.7 after five injections. Decreased pH increased the content of soluble calcium and slightly decreased the total calcium content of cheese. At the highest level, injection of acidulant promoted syneresis. Thus, after five injections, the moisture content of cheese decreased from 34 to 31%, which resulted in decreased cheese weight. Lowered cheese pH, 4.7 compared with 5.3, also resulted in contraction of the protein matrix. Acidulant injection decreased cheese hardness and cohesiveness, and the cheese became more crumbly. The initial rate of cheese flow increased when pH decreased from 5.3 to 5.0, but it decreased when cheese pH was further lowered to 4.7. The final extent of cheese flow also decreased at pH 4.7. In conclusion, lowering the pH of Cheddar cheese alters protein interactions, which then affects cheese functionality. At pH greater than 5.0, calcium solubilization decreases protein-to-protein interactions. In contrast, at pH lower than 5.0, the acid precipitation of proteins overcomes the opposing effect caused by increased calcium solubilization and decreased calcium content of cheese, and protein-to-protein interactions increase.

Calcium↗
PubMed2001

Microbiological and biochemical characteristics of Canestrato Pugliese cheese made from raw milk, pasteurized milk or by heating the curd in hot whey.

Canestrato Pugliese cheeses were produced from raw ewes' milk (R and R(II) cheeses), pasteurized ewes' milk (P cheese) and by heating the curd in hot whey according to a traditional protocol (T cheese). R(II) differed from R cheese mainly by having been produced from raw milk with a higher number of somatic cells, 950.000 vs. 750.000 ml(-1), respectively. Compared to P and T cheeses, R and R(II) cheeses had a higher concentration (one or two orders of magnitude) of cheese-related bacteria such as adventitious mesophilic lactobacilli, enterococci and staphylococci. At the end of ripening, all cheeses contained less than 1.0 log cfu g(-1) of total and fecal coliforms, and Escherichia coli and Staphylococcus aureus were not detected. As shown by phenotypic identification and RAPD-PCR, R cheese contained the largest number of mesophilic lactobacilli species and the greatest diversity of strains within the Lactobacillus plantarum species. Primary proteolysis did not differ appreciably among the cheeses. On the contrary, both urea-PAGE and the RP-HPLC analyses of the water-soluble N fractions showed the more complex profiles in cheeses produced by raw milks. R and R(II) cheeses had the highest values of water-soluble N/total N (ca. 30%) and the highest concentration of total free amino acids (ca. 40 mg g(-1) which approached or exceeded those reported for Italian cheeses with very high level of proteolysis during ripening. The main differences between R-R(II) and P-T cheeses were the concentrations of aspartic acid, proline, alanine, isoleucine, histidine and lysine. The water-soluble extracts of R and R(II) cheeses contained levels of amino-, imino- and di-peptidase activities, which were about twice those found in P and T cheeses. Cheeses differed slightly in the concentration of total free fatty acids that ranged between 1673 and 1651 mg kg(-1) in R and R(II) cheeses, and 1397 and 1334 mg kg(-1) in P and T cheeses. Butyric, caproic, capric, palmitic, oleic and linoleic acids were found at the highest concentrations.

Animals↗
PubMed2003

A preliminary study on the effect of adding yeast extract to cheese curd on proteolysis and flavour development of reduced-fat Cheddar.

Yeast extract was used as a nutrient for growing lactobacilli in reduced-fat Cheddar cheese as early growth of non-starter lactic acid bacteria (NSLAB) in Cheddar cheese is suppressed by pasteurization of milk and the hostile environment of the cheese. Reduced-fat Cheddar cheese was manufactured from 100 kg standardized milk on two occasions. After milling, the curd was divided into two portions, C and E. To control portion, C, salt was added at normal levels. A mixture of salt and yeast extract was added to the experimental, E. The cheeses were ripened for 7 months at 8 degrees C and assessed for proteolysis and NSLAB growth during ripening. Mean % moisture, fat, protein, salt and pH were 40.6, 20.5, 31.1, 1.72 and 5.22 respectively, in E cheeses, and 39.5, 20.5, 30.9, 1.68 and 5.22, respectively, in C cheese. NSLAB counts in E cheeses were 10(1), 10(3), 10(5) cfu/g compared with 0, 10(1), 10(4) cfu/g in C respectively, after 1, 7 and 30 d of ripening. After 60 d, cell densities of NSLAB were similar (approximately 10(6) cfu/g) in C and E cheese. Addition of yeast extract to curd affected neither the electrophoretic patterns of cheese nor its water-soluble N content during ripening. However, the total free amino acids were significantly higher in E cheese than C cheese throughout ripening, suggesting faster secondary proteolysis in the former cheeses. A 6-member trained descriptive panel evaluated the cheese at 7 months and found that the E cheeses had higher intensities of whey, fruity, sulphur, nutty, sweet and sour flavours, but had lower intensities of brothy flavours as compared to C cheeses. Also, the E cheeses were perceived to be more mature than corresponding C cheese. Results show that addition of yeast extract to cheese curd is a promising method of enhancing flavour development in ripened cheeses.

Cheese↗
PubMed2002

Effect of pH and calcium concentration on some textural and functional properties of mozzarella cheese.

The effects of Ca concentration and pH on the composition, microstructural, and functional properties of Mozzarella cheese were studied. Cheeses were made using a starter culture (control) or by direct acidification of the milk with lactic acid or lactic acid and glucono-delta-lactone. In each of three trials, four cheeses were produced: a control, CL, and three directly-acidified cheeses, DA1, DA2, and DA3. The cheeses were stored at 4 degrees C for 70 d. The Ca content and pH were varied by altering the pH at setting, pitching, and plasticization. The mean pH at 1 d and the Ca content (mg/g of protein) of the various cheeses were: CL, 5.42 and 27.7; DA1, 5.96 and 21.8; DA2, 5.93 and 29.6; DA3, 5.58 and 28.7. For cheeses with a high pH (i.e., approximately 5.9), reducing the Ca content from 29.6 to 21.8 mg/g of protein resulted in a significant decrease in the protein level and increases in the moisture content and mean level of nonexpressible serum (g/g of protein). Reducing the Ca concentration also resulted in a more swollen, hydrated para-casein matrix at 1 d. The decrease in Ca content in the high-pH cheeses coincided with increases in the mean stretchability and flowability of the melted cheese over the 70-d storage period. The fluidity of the melted cheese also increased when the Ca content was reduced, as reflected by a lower elastic shear modulus and a higher value for the phase angle, delta, of the melted cheese, especially after storage for <12 d. The melt time, flowability, and stretchability of the low-Ca, high-pH DA1 cheese at 1 d were similar to those for the CL cheese after storage for > or = 12 d. In contrast, the mean values for flowability and stretchability of the high-pH, high-Ca DA2 cheese over the 70-d period were significantly lower than those of the CL cheese. Reducing the pH of high-Ca cheese (27.7 to 29.6 mg/g of protein) from -5.95 to 5.58 resulted in higher flowability, stretchability, and fluidity of the melted cheese. For cheeses with similar pH and Ca concentration, the method of acidification had little effect on composition, microstructure, flowability, stretchability, and fluidity of the melted cheese.

Animals↗
PubMed2003

Effect of calcium and water injection on structure-function relationships of cheese.

Our objectives were to determine the effect of calcium and water injection on cheese structure and to relate changes in structure to changes in functional properties of cheese. Cheese with fat and moisture content similar to that of low-moisture part-skim Mozzarella was made according to a direct-acid, stirred/pressed-curd procedure. The cheese was then cut into blocks that were high-pressure-injected from one to five times, with either water or a 40% calcium chloride solution. Successive injections were performed 24 h apart. After 42 d of refrigerated storage, cheese microstructure and functionality were analyzed. When injected three or more times, water tended to increase cheese weight. The control, uninjected cheese, had the typical structure of a stirred/pressed-curd cheese: protein matrix interspersed with areas that originally contained fat and/or serum. Injecting water increased the area of cheese matrix occupied by protein, but it did not affect textural properties or melting of cheese. In contrast, when calcium was injected, a decrease in cheese weight was observed that was manifested through syneresis. The moisture content and pH of the cheese decreased as well. Calcium injection also decreased the area of cheese matrix occupied by protein. Cheese hardness increased, and cohesiveness and melting of cheese decreased upon calcium injection. We concluded that adding calcium to cheese alters how the proteins interact, which is manifested as changes in cheese microstructure. Such changes in cheese structure provide an understanding of changes in functional attributes of the cheese.

Calcium↗
PubMed2006

Proteolysis and microstructure of Piacentinu Ennese cheese made using different farm technologies.

The aim of this study was to provide the biochemical and structural characterization of Piacentinu Ennese cheese and to evaluate the impact of different farm technologies on cheese proteolysis and microstructure. Fifteen cheeses were manufactured according to traditional technology, i.e., from raw milk and farmhouse rennet in the absence of starter culture. Pasteurized milk, commercial rennet, and starter were used for production of 20 nontraditional cheeses. Proteolysis in Piacentinu Ennese cheese was monitored during a 2- to 10-mo ripening time. Low rates of overall proteolysis were observed in cheese, as percentages of total N soluble at pH 4.6 and in 12% trichloroacetic acid were about 11.40 and 8.10%, respectively, after 10 mo of age. Patterns of primary proteolysis by urea-PAGE showed that alpha(s)-caseins were degraded to a larger extent than were beta-caseins, although a considerable amount of both caseins was still intact after 10 mo. Reversed phase-HPLC analysis of the cheese peptide fractions showed a slow decrease in the levels of hydrophobic peptides coupled to increasing levels of hydrophilic compounds as the cheese aged. The structural characteristics of Piacentinu Ennese cheese were evaluated by scanning electron microscopy after 2, 4, and 6 mo of age. The micrographs showed a sponge-like structural network with a well-distributed system of empty spaces, originally occupied by whey and fat. The microstructure changed during cheese ripening to become more compact with cavities of smaller size. Farm technology significantly affected cheese proteolysis and microstructure. Nontraditional cheeses had higher levels of pH 4.6-soluble N and showed a larger hydrolysis of alpha(s)-casein fractions by urea-PAGE analysis than did traditional cheeses. Large differences between cheese-types also concerned the patterns of secondary proteolysis. Nontraditional cheeses had higher levels of 12% trichloroacetic acid-soluble N and showed larger proportions of free amino acids and hydrophilic peptides in the HPLC profiles of the corresponding 70% ethanol-soluble N fraction than traditional cheeses. Nontraditional cheeses also had a more open structure with a coarser and less continuous appearance than did traditional cheeses. A large amount of variability in cheese proteolysis and structure within nontraditional treatment reflected farm-dependent changes in manufacturing conditions related to the use of various types of rennet and starter.

Agriculture↗
PubMed2004

Factors affecting calcium lactate and liquid expulsion defects in Cheddar cheese.

This paper summarizes the results of 2 studies designed to investigate the influence of several manufacturing and curing treatments on the appearance of Cheddar cheese defects. Specifically, 2 defects, calcium lactate crystal formation and the expulsion of free liquid (weeping) were monitored in Cheddar cheese. Both studies were conducted at a commercial cheese manufacturing facility that produces Cheddar in 18.14-kg (40-lb) blocks. In the first study we monitored cheese calcium, both total and soluble during manufacture and early curing. In the second study we measured cheese pH from 3 d through 8 mo, as well as some factors that are influenced by cheese pH. Early cheese pH (3 d to 7 d) patterns were used to select vats of cheese for retail packaging. Mild Cheddar packaged at 30 d postmanufacture and sharp Cheddar packaged at 8 mo postmanufacture from the same vats were monitored for the incidence and severity of the defects. Our results indicated that factors measured in early stages of manufacture and curing (less than 7 d) such as cheese pH at mill, lactic acid concentration, nonprotein nitrogen, and calcium (total and soluble) in cheese did not correlate with the appearance of either calcium lactate or expulsion of free liquid in packaged cheeses. Factors including pH, lactic acid concentrations, and soluble calcium measured during curing (greater than 7 d) of cheese were found to be statistically significant in the development of defects and appeared to be associated with use of specific starter culture groups. In the study, 5 different starter culture groups, each consisting of a 4-strain blend of Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis, were used to manufacture the cheeses. Cheese manufactured with one particular culture group showed no incidence of calcium lactate crystal formation or weeping during curing and shelf-life of cheeses in this study. This starter group also generated the least amount of pH change in cheese during the first month of curing. From these results we conclude that starter culture group, more than any other factor measured, played an important role in the development of calcium lactate and liquid expulsion defects in Cheddar cheese. Starter culture group appeared to strongly influence cheese pH, lactic acid, and soluble calcium concentrations during curing and storage.

Calcium↗