Ripening Of Cheddar Cheese Research Articles

The effect of exposure to pressure of 50 MPa on Cheddar cheese ripening

The possibility of acceleration of commercial Cheddar cheese ripening by exposure to a high pressure (HP) treatment of 50 MPa for 3 days at 25°C at different stages of ripening was investigated. Proteolysis was examined in the treated and untreated cheeses by measurement of pH 4.6 water soluble nitrogen, expressed as g/100 g total N (pH 4.6 SN/TN), urea-PAGE, reverse phase (RP) HPLC, analysis of molecular mass distribution by gel permeation and measurement of free amino acids (FAA) in the pH 4.6 SN. There was an immediate increase in pH 4.6 SN/TN and FAA in cheese HP-treated at 2 days of age, although this effect decreased with cheese age. Urea-PAGE analysis of cheese samples indicated that HP treatment accelerated degradation of α s1-casein and accumulation of α s1-I-casein (f 24-199). RP-HPLC profiles indicated quantitative but not qualitative differences between treated and non-treated samples. Confocal laser scanning microscopy did not indicate any gross structural changes in the cheese matrix as a result of exposure to 50 MPa for 3 days at 25°C. It was concluded that the enhancement of proteolysis observed may be attributed to a combination of the temperature and pressure used in the treatment.

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 104, 105, 106 and 107 cfu NSLAB g−1, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.

PURIFICATION AND CHARACTERIZATION OF AMINOPEPTIDASE FRACTIONS FROM SQUID (ILLEX ILLECEBROSUS) HEPATOPANCREAS

Atlantic short finned squid hepatopancreas (HP) aminopeptidases (APs) were partially separated from endoproteinases to determine their usefulness in accelerating Cheddar cheese ripening. Squid HP endoproteinases were predominantly cysteine proteases. The main peptidases identified in squid HP were APs. Several of the APs identified were metalloproteases and were activated by Ca 2+ , Mn 2+ , Zn 2+ or Mg 2+ salts. Squid HP homogenate was held at pH 7 at 0C for 20 h, incubated with 5 mM ZnSO 4 , fractionated by ammonium sulfate (20-80%) and dialyzed against 25 mM ZnSO 4 . The procedure resulted in a 3-186 fold increase in the ratio of exopeptidase to endoproteinase activity with different AP substrates. Recovery of specific APs ranged between 14-47%. The partially purified squid HP peptidases had a higher ratio ofexopeptidase to endoproteinase activity than two commercial products with AP activity, Flavozyme and Neutrase.

The isolation and identification of yeasts obtained during the manufacture and ripening of Cheddar cheese

Sources of yeast, which may contaminate the curd during the manufacture of Cheddar cheese, were examined in a single cheese factory. A total of 77 yeast species present in the factory environment, manufacturing and ripening of Cheddar cheese were identified according to cellular long-chain fatty acid analysis and verified with conventional identification techniques. Product line samples were taken at critical control points in the manufacturing process and analysed after incubation at 25°C for 96 h. The progression of yeast species during cheese-making and ripening was monitored after renneting and at subsequent 48-h intervals. Dominant species wereDebaryomyces hanseniiandCryptococcus albidus, whileYarrowia lipolytica, Rhodotorula minuta, Torulaspora delbrueckii, Rhodotorula glutinisandKluyveromyces marxianuswere present at low numbers. The results obtained showed that yeasts were present in all cheese samples examined, at quantities ranging from 9×102to 1·4×107cfu g−1.

Purification and characterization of L-methionine gamma-lyase from brevibacterium linens BL2

L-Methionine gamma-lyase (EC 4.4.1.11) was purified to homogeneity from Brevibacterium linens BL2, a coryneform bacterium which has been used successfully as an adjunct bacterium to improve the flavor of Cheddar cheese. The enzyme catalyzes the alpha,gamma elimination of methionine to produce methanethiol, alpha-ketobutyrate, and ammonia. It is a pyridoxal phosphate-dependent enzyme, with a native molecular mass of approximately 170 kDa, consisting of four identical subunits of 43 kDa each. The purified enzyme had optimum activity at pH 7.5 and was stable at pHs ranging from 6.0 to 8.0 for 24 h. The pure enzyme had its highest activity at 25 degreesC but was active between 5 and 50 degreesC. Activity was inhibited by carbonyl reagents, completely inactivated by DL-propargylglycine, and unaffected by metal-chelating agents. The pure enzyme had catalytic properties similar to those of L-methionine gamma-lyase from Pseudomonas putida. Its Km for the catalysis of methionine was 6.12 mM, and its maximum rate of catalysis was 7.0 &mgr;mol min-1 mg-1. The enzyme was active under salt and pH conditions found in ripening Cheddar cheese but susceptible to degradation by intracellular proteases.

Monitoring Proteolysis During Cheddar Cheese Ripening Using Two‐Dimensional Gel Electrophoresis

ABSTRACTA 2‐D gel electrophoretic method, consisting of isoelectric focusing and alkaline urea‐PAGE was used to monitor proteolysis during ripening (180d, 5°C and 8°C) of full‐ and reduced‐fat Cheddar cheese. The method enabled quantifying changes in levels of peptides in cheese with good spot‐resolution. Results can complement those from other analyses, especially those for determining low MW peptides. Notable effects were found for cheese composition and ripening temperature on gel pattern and on relative levels of selected proteolysis products. In both cheese varieties, most peptides reached a maximum during the first 3 ripening months and gradually disappeared as ripening advanced.

Aminopeptidase Activities of Starter and Non-Starter Lactic Acid Bacteria under Simulated Cheddar Cheese Ripening Conditions

Abstract The effects of pH, NaCl and CaCl2 concentration on aminopeptidase activities of lactic acid bacteria were investigated in order to assess the potential role of these enzymes on proteolysis during cheese ripening. A NaCl concentration of around 4% and a CaCl2 concentration of around 125 mM were selected for study to approximate concentrations present in the moisture phase of ripening Cheddar cheese. At pH 5.2, the pH of mature Cheddar cheese, aminopeptidase activities were partially inhibited in comparison to activities at physiological pH (7.5). However, most of the hydrolysis activities at the lower pH could be either partially or fully restored by the addition of NaCl and/or CaCl2 at concentrations found in the moisture phase of ripening Cheddar cheese. There was a major difference between the Lys p-NA hydrolysis activity of lactococci and lactobacilli in that the activity of lactococci was stimulated in the presence of salts while the activity of the lactobacilli was inhibited. These results indicate that variations in salt concentration are important parameters in cheese ripening and flavour development due to their effect on peptidase activities. A decrease in the concentration of NaCl, for instance, while perhaps increasing the risk of growth of contaminating microflora, may reduce bitter flavour development through increased PepN activity of selected non-starter lactobacilli if used as adjuncts.

Increasing Starter Cell Lysis in Cheddar Cheese Using a Bacteriocin-Producing Adjunct

A novel method for increasing the rate of starter lysis during Cheddar cheese ripening has been developed, using a bacteriocin-producing strain as a starter adjunct. Citrate-utilizing Lactococcus lactis ssp.lactis DPC3286 encodes production of lactococcins A, B, and M and exhibits a lytic effect against lactococcal starter cultures. Cheddar cheese was manufactured using DPC3286 as an adjunct with the cheese-making strain Lactococcus lactis ssp. cremoris HP. The effects on starter cell lysis, proteolysis, and flavor development were assessed over a 60-mo period. Cheese manufactured with the bacteriocin-producing adjunct exhibited increased cell lysis, elevated concentrations of free amino acids, and higher sensory evaluation scores than cheese manufactured with HP alone or with an adjunct culture negative for bacteriocin production.

Role of starter enzymes during ripening of Cheddar cheese made from pasteurized milk under controlled microbiological conditions

Abstract Proteolysis and flavour development in Cheddar cheeses made without starter or with a proteinase-positive (prt+) or a proteinase-negative (prt−) strain of Lactococcus lactis ssp. cremoris were monitored during ripening. The results showed that the coagulant and plasmin were mainly responsible for the degradation of caseins while small peptides and free amino acids (FAA) were produced mainly by starter enzymes. Although starter peptidases were capable of producing some small peptides and FAA in the cheese made with the proteinase-negative starter, proteinase activity resulted in increased levels of small peptides and amino acids in the cheese made with the proteinase-positive starter. The flavour intensity and flavour acceptability of the chemically-acidified cheeses were poor. The cheeses made with the prt+ starter received the highest scores for flavour intensity and flavour acceptability.

Monitoring proteolysis and cheese juice composition during ripening of Cheddar cheese made from microfiltered milk

Des fabrications de fromages cheddar ont ete realisees a partir de trois types de laits de fabrication : lait pasteurise HTST (LP), lait thermise (LT) et melanges de lait ecreme microfiltre selon le procede Bactocatch® et de creme pasteurisee (MF). L'evolution de la flore bacterienne des fromages MF et LT etait similaire, avec un fort developpement des especes appartenant au groupe Lb casei et une croissance de la population denombree en Lc (au contraire des fromages LP, ou cette derniere flore decroissait de pres de 3 log). Comme attendu, la teneur en spores mesophiles des fromages MF etait tres inferieure a celle des autres fromages. La proteolyse des trois categories de fromages a ete suivie a la fois par analyse des fragments peptidiques contenus dans l'extrait aqueux et dans le jus interne obtenu par pressage et par le suivi electrophoretique des caseines non degradees. Les teneurs en fractions azotees solubles dans le TCA 12% etaient tres similaires, avec toutefois une difference significative, a 6 mois d'affinage, entre fromages LP et fromages MF. Cette difference n'etait pas retrouvee lors de l'analyse des composants azotes des jus. Sur un autre plan, la comparaison des extraits aqueux et des jus montrait que ces derniers contenaient systematiquement plus de materiel azote que les extraits aqueux. La proteolyse de la caseine β etait significativement plus elevee dans les fromages MF que dans les deux autres categories de fromage, peut-etre en raison d'une activation accrue du systeme plasmine-plasminogene resultant de l'operation de microfiltration. Tous les fromages etaient classes en categorie I mais de legeres differences de qualites organoleptiques en faveur des fromages MF etaient trouvees (flaveur consideree comme typique du fromage cheddar).

Aromatic amino acid catabolism by lactococci

Summary - While catabolism of amino acids is believed to play an important role in cheese f1avor development, the pathways present in cheese microflora are poorly understood. To determine the pathways of aromatic amino acid catabolism in lactococci and effects of Cheddar cheese ripening conditions on catabolic enzymes and products, eight starter lactococcal strains were screened. Cell-free extracts prepared from these strains were found to contain an œ-ketoglutarate-dependent aminotransferase activity with tryptophan, tyrosine and phenylalanine. Tryptophan, tyrosine and phenylalanine aminotransferase specifie activities (Ilmol product formed/mg proteinlmin) ranged from 0.30 to 2.8 10-3, 0.93 to 7.3 10-3 and 1.5 to 7.2 10-3, respectively. Metabolites produced from tryptophan by a cellfree extract of Lactococcus lactis S3 were indolepyruvic acid, indoleacetic acid and indole-3-aldehyde. Indoleacetic acid and indole-3-aldehyde can form spontaneously from indolepyruvic acid under the conditions employed. A defined medium was used to determine whether the aminotransferase(s) was expressed and which metabolite(s) accumulate under conditions that simulated those of ripening Cheddar cheese in terms of pH, salt, temperature and carbohydrate starvation. The results indicated that the aminotransferase(s) was expressed and stable under these conditions. The tryptophan metabolites that accumulated were determined to be strain-specific. lactococcus / aminotransferase / aromatic amino acid / catabolism / cheese flavor

Accelerated ripening of Cheddar cheese at elevated temperatures

Abstract Blocks (20 kg) of Cheddar cheese from a single vat were obtained from a local factory. Half the cheeses were cooled rapidly (15 h) to ripening temperature (8, 12 or 16 °C) and half were cooled slowly over 8 days to the same ripening temperatures. Cheeses were ripened for 9 months at 7 different time/temperature combinations. Ripening temperature had little influence on the number of non-starter lactic acid bacteria in the cheeses after 9 months, although rapid cooling to and ripening at 8 °C drastically reduced the growth rate of these adventitious bacteria. Proteolysis (as determined by urea-polyacrylamide gel electrophoresis; increases in water-soluble N; increases in phosphotungstic acid-soluble N; Cd ninhydrin-reactive amino groups; and reverse-phase HPLC) and lipolysis were accelerated by increasing the ripening temperature and by slow cooling of the cheeses. The rate of ripening was increased or decreased by changing the temperature. Cheeses ripened at 16 °C generally received the highest flavour scores, particularly early during ripening. However, the texture of these cheeses deteriorated after prolonged ripening at 16 °C. Maturation at 12 °C was considered to be optimal for the commercial acceleration of Cheddar cheese ripening.

Accelerated Ripening of Reduced-Fat Cheddar Cheese Using Four Attenuated Lactobacillus helveticus CNRZ-32 Adjuncts

Cheddar cheese that contained 33% less fat than normal was made with Lactobacillus helveticus CNRZ-32 adjuncts attenuated by spray-drying, freeze-drying, or freezing. Cheeses were analyzed during 6 mo of ripening for lactobacilli, pH, lactose, galactose, total lactic acid, D(–)-lactic acid, 5% phosphotungstic acid-soluble N, and 12% TCA-soluble N. Chemical analytical results for cheeses made with adjuncts could largely be explained using the cellular properties of the adjuncts. The extent of cell attenuation was a better tool for predicting changes in lactose, galactose, total lactic acid, and proteolysis than was cell viability. Cell viability was a better tool for predicting cheese pH, initial concentrations of lactobacilli, and D(–)-lactic acid than was cell attenuation. Cheese flavor intensity was enhanced in all cheeses made with adjuncts, but cheeses made with adjuncts spray-dried at a high outlet air temperature of 120°C had the least off-flavor intensity. Other sensory measures were not statistically different among the cheeses, even though the cellular properties of the adjuncts and chemical measures of cheese ripening were statistically different.

Properties of Lactobacillus helveticus CNRZ-32 Attenuated by Spray-Drying, Freeze-Drying, or Freezing

Lactobacillus helveticus CNRZ-32 was attenuated for use in accelerated ripening of Cheddar cheese. The goal was to delay acid production without reducing enzyme activity. Changes in the cellular properties of viability, enzyme activity, lactic acid production, and permeability were measured for each attenuation treatment. The viabilities were highest for frozen and freeze-dried cells. Viabilities were lower for cells spray-dried at an outlet air temperature of 82°C and lowest for 120°C. Aminopeptidase and β-galactosidase activities decreased with each treatment. Low temperature spray-dried cells had the highest residual aminopeptidase and β-galactosidase activities by a substantial margin. Acid production was similar for the frozen, freeze-dried, and low temperature spray-dried cells, and no lag time occurred; however, high temperature spray-dried cells had a 5-h lag time before producing acid. The increase in permeability was greatest for high temperature spray-dried cells. Viability did not necessarily indicate the extent of cell attenuation. Low temperature spray-dried cells had low viability, but the greatest lactic acid production and enzyme activity. High temperature spray-dried cells had the best balance between delaying acid production and maintaining enzyme activity.

Lactic Acid Bacteria in Cheddar Cheese Made with Sodium Chloride, Potassium Chloride or Mixtures of the Two Salts

Three different split lots of Cheddar cheese curd were prepared with added sodium chloride (NaCl) potassium chloride (KCl) or mixtures of NaCl/KCl (2:1 1:1 1:2 and 3:4 all on wt/wt basis) to achieve a final salt concentration of 1.5 or 1.75%. At intervals during ripening at 3±1°C samples were plated with All-Purpose Tween (APT) and Lactobacillus Selection (LBS) agar. Isolates were obtained of bacteria that predominated on the agar media. In the first trial (Lactococcus lactis subsp. lactis plus L. lactis subsp. cremoris served as starter cultures) L. lactis subsp.lactis Lactobacillus casei and other lactobacilli were the predominant bacteria regardless of the salting treatment Received by the cheese. In the second trial (L. lactis subsp. lactis served as the starter culture) unclassified lactococci L. lactis subsp. lactis unclassified lactobacilli and L. casei predominated regardless of the salting treatment given the cheese. In the third trial (L. lactis subsp. cremoris served as the starter culture) unclassified lactococci unclassified lactobacilli L. casei and Pediococcus cerevisiae predominated regardless of the salting treatment applied to the cheese Thus use of KCl to replace some of the NaCl for salting cheese had no detectable effect on the kinds of lactic acid bacteria that developed in ripening Cheddar cheese.

Developments in microencapsulation science applicable to cheese research and development. A review

Abstract The applications of microcapsules for cheese technology are reviewed. Proteolytic enzymes for use in cheese ripening may be encapsulated in microcapsules to avoid premature proteolysis in cheese milk. Alginate, milk fat, and phospholipid have been used as encapsulating materials. Alginate is not a natural constituent in milk products, and, in addition, the alginate capsules are rather leaky. Milk fat capsules show good encapsulation properties. However, strong detergents, which do not have GRAS status, are needed to keep them stable. Phospholipids form membrane structures, liposomes, in contact with water. These liposomes are stable without added detergents, and the phospholipids are natural constituents of the milk fat membrane. Controlled release of enzymes in the cheese can be achieved by technologically altering the stability of the liposomes with respect to time, temperature and pH. Liposomes may be constructed with different sizes and number of lamellae, according to the preparation method. The various types of liposome (MLV, SUV, REV and DRV) are defined and described. Several enzymes have been encapsulated in liposomes. DRV liposomes have shown the highest efficiency for the encapsulation of enzymes. Various liposome-encapsulated enzymes have been used to accelerate the ripening of Cheddar, Saint Paulin, Domiati and Gouda cheese. Liposome-encapsulated enzymes have a potential for use in accelerated cheese ripening, but the price of the phospholipid must be reduced, and a good and cheap scaled-up preparation method must be developed.

Monitoring Cheddar cheese ripening by chemical indices of proteolysis

Two Cheddar cheeses from two different production plants were ripened over 24 weeks at 10 degrees C and then analysed for peptides soluble in citrate buffer at pH 4.6 by reversed-phase (RP)-HPLC. Thirteen peptides with a chain length of between 35 and 65 amino acid residues and molecular masses between 3800 and 7400 were isolated and assigned to the corresponding amino acid sequences of the casein fractions via Edman degradation and amino acid composition. All peptides were fragments of the region K29-S96 of beta-casein A1 and A2, and eleven of them had M93 as the C-terminal. The amounts and proportions of these peptides varied differently during ripening of the two cheeses, so they may be suitable markers for characterizing the stage of ripening.

Starters as finishers: Starter properties relevant to cheese ripening

Abstract Although the properties of starters relevant to cheese manufacture have been extensively studied and reviewed, there is little detailed information available on the contribution of starters to cheese ripening. Using extensive reference to in-vitro and in-situ studies on ripening which are currently being carried out in the authors' laboratories, this review concentrates on the roles of mesophilic starters in Cheddar cheese ripening and gives examples of data pertinent to the concepts under consideration. Particular attention is paid to the hydrolytic production of peptides, amino acids, free fatty acids and glycerol through primary ripening processes and to the production of ammonia through secondary ripening reactions. The general lack of information on the significance of starters to secondary ripening reactions important for the production of flavour compounds is highlighted. Enzymological, chemical and physiological factors involved in ripening are discussed, including concepts of starter strain variation in the activities, specificities, stabilities, concentrations and compartmentalisation of enzymes involved in ripening. The effects of the cheese environment on enzyme function and microbial physiology, including variations in the resistance of starter cells to lysis, are also discussed. The validity of using the parameter of colony forming units/g cheese (i.e. viable cell densities recovered) as a reference for comparison of levels of ripening enzyme levels is examined, as is the relationship between cell density, cell mass and enzyme concentrations.

Poster D5 Accelerated ripening of cheddar cheese from buffalo milk

Poster D5 Accelerated ripening of cheddar cheese from buffalo milk

Salmonellae, Salmonellosis, and Dairy Foods: A Review

Salmonellae continue to be a major concern for the dairy industry because these bacteria have caused recent outbreaks of illness and have been isolated from various dairy products in the market place. Salmonellae are generally not heat resistant and normally grow at 35 to 37°C, but they can grow at much lower temperatures, provided that the incubation time is suitably extended. To minimize problems, foods should be held at or below 2 to 5°C at all times. Both conventional and rapid methods are available to isolate salmonellae from dairy foods and to identify the bacteria. Salmonellae behave differently in different kinds of cheese: they survived in ripening Cheddar cheese for up to 7 mo at 13°C and for 10 mo at 7°C; in cold-pack cheese food for several weeks, depending on the pH and preservative used; and in Domiati cheese 13 to 36 d, depending on the manufacturing process used. When Mozzarella cheese was made, temperatures of stretching and molding (60°C) killed all salmonellae present, but, in cottage cheese, survival of the pathogen depended on the cooking temperature of curd. Spray drying of skim milk killed substantial numbers of salmonellae, but some survivors remained. Butter readily supported growth of salmonellae at room temperature, and neither freezing nor refrigeration for brief periods eliminated salmonellae from butter. Use of appropriate hygienic procedures, e.g., Hazard Analysis Critical Control Point system, during processing should reduce the likelihood of salmonellosis outbreaks associated with dairy foods.