Quality Of Cheddar Cheese Research Articles

The impact of seasonal calving systems with varying pasture allowance on Cheddar cheese composition, nutritional quality and ripening characteristics

The objective of this study was to examine the impact of stage of lactation (early, mid and late) and proportion of pasture in the cows diet (high: GRS, medium: PMR and no: TMR) on the composition and quality of Cheddar cheese. Triplicate trials were carried out in each stage of lactation, and milk protein and fat contents were standardized for Cheddar cheese manufacture at pilot scale. As cheese milks were standardized for milk fat and protein contents, gross composition did not differ as a result of diet. Fatty acid profiles of GRS cheese were significantly different from TMR, while PMR profiles were less distinct and more similar to both GRS and TMR profiles, as illustrated by partial least squares discriminatory analysis. Fatty acids including CLA C18:2 cis-9, trans-11, C22:1 n-9 and C18:3 n-3 were most influential in this separation of profiles. Fatty acid profiling revealed that GRS derived cheese contained higher proportions of nutrients considered beneficial for human health including higher proportions of unsaturated fatty acids and omega-3 fatty acids. A biomarker model utilizing the proportions of 5 fatty acids was constructed and was effective at distinguishing between cheese of GRS, TMR and PMR feeding systems. Proportions of ρ-κ-casein, αs2-casein and αs1-casein in cheese also differed between diets while proportions of ρ-κ-casein, αs1-casein and β-casein were lowest in late lactation cheese. The impact of diet was less influential compared with that of stage of lactation on the ripening characteristics of cheese. An index of primary proteolysis was highest in late lactation cheese. The peptides derived from the proteolysis of κ-casein and β-casein and levels of secondary proteolysis, in particular, the proportions of 12 free amino acids were most influenced by stage of lactation. Overall this study demonstrated the effects of increasing pasture allowance and stage of lactation on the nutritional quality and ripening properties of Cheddar cheese.

Silkworm pupae protein-based film incorporated with Catharanthus roseus leaf extract-based nanoparticles enhanced the lipid stability and microbial quality of cheddar cheese

The study aimed to develop a silkworm pupae protein-based film for enhancing the lipid oxidative and microbial stability of cheddar cheese. The bioactive properties were imparted to the silkworm pupae protein-based film using an optimum level (2.0%) of Catharanthus roseus leaf extract-based nanoparticles (Cat-Ros-NPs) synthesised following a green method. The cheese samples were packaged within the treated film (T2, containing 2.0% Cat-Ros-NPs) and compared with control samples [control (cheese samples without any film), T0 (cheese samples within the films without any bioactive agent) and T1 {cheese samples within the films containing 2.0% C. roseus leaf extract (Cat-Ros-Ext)}] during 90 days trial (4±1 °C). The addition of bioactive agents (Cat-Ros-Ext or Cat-Ros-NPs) increased the thickness (µm) as well as density (g/ml) of the film, thereby decreasing the transmittance (%), solubility (%), moisture content (%), and water-vapour transmission rate (mg/mt2). Both the bioactive agents increased the redness (a*) and yellowness (b*) whereas decreased the brightness (L*) of the film. The films enhanced the antioxidant and antimicrobial properties of the enclosed cheese samples during storage and the highest values were recorded for the samples packed within T2 films. The cheese samples packaged within T2 and T1 films showed significantly lower values for lipid oxidation and microbial counts. This positive effect of the films (T2 and T1) was also recorded on protein oxidation (total-carbonyl content) after day 30 and sensory quality after day 60. Our results indicate the successful use of silkworm pupae protein for the development of bioactive packaging for cheddar cheese.

EFFECT OF PSYCHROTROPHIC BACTERIAL CONTAMINATION OF RAW MILK ON ORGANIC ACID CONTENT ‎AND FLAVOROF AGED CHEDDAR CHEESE

Cheddar cheese was made from milk which had been inoculated with psychrotrophs 48hr.. prior to pasteurization. This was compared to ‘control cheese. The cheese was stored at 7 °C and evaluated at 0, 5, 30, 60 and 180 days. ‘All cheese made with psychrotroph-treated milk had significant lower flavor score than control cheese. The predominant flavors of the 180 day-treated cheese were bitter and unclean. High performance. liquid chromatography (HPLC) analysis indicated significant increases of citric, pyruvic, lactic, formic, acetic and propionic acids with ‘aging of Cheddar cheese. Only orotic acid decreased with aging. The control cheese had lower values than the treated cheese for pyruvic, lactic and formic acids. The control cheese had higher propionic acid value than did the treated cheese.The aroma and flavor quality of Cheddar cheese was attributed to a delicate balance of organic acids produced as metabolites by culture bacteria during fermentation.

Effect of edible coating based on zedo gum containing Thymus essential oil and Cinnamomum extract on quality of cheddar cheese

Effect of edible coating based on zedo gum containing Thymus essential oil and Cinnamomum extract on quality of cheddar cheese

Locust protein hydrolysates have the potential to enhance the storage stability of cheese

The study evaluated the efficacy of locust protein hydrolysates (LoPHs) to enhance the quality of Cheddar cheese (ChCh) during storage. The locust protein (LoP) was pre-treated [microwave (Mic) or ultrasonication (Ult) or no treatment (Not)] before hydrolysis using alcalase enzyme (3% w/w). The ChCh samples containing LoPHs at the maximum level of 1.5% were evaluated for quality for 3 months (4 ± 1 °C) and subjected to gastrointestinal simulation. Both pre-treatments (Mic and Ult) significantly (P < 0.05) enhanced the antimicrobial and antioxidant activities of the LoPHs (Ult > Mic > Not). The ChCh samples with LoPHs exhibited significantly (P < 0.05) lower means for lipid oxidation (TBARS and free fatty acids), protein oxidation (total-carbonyl content) and microbial counts (psychrophilic, total plate and yeast/moulds) during the storage. A positive effect was found on the sensory quality of ChCh samples after one month of storage. The gastrointestinal simulation improved the antioxidant capacity of the stored ChCh samples. LoPHs can be used as a novel bio-preservative for cheese.

Effect of midday pasteurizer washing on thermoduric organisms and their progression through Cheddar cheese manufacturing and ripening

Thermoduric bacteria are known to affect the quality of Cheddar cheese, with manifested defects including slits, weak body, and blowing. Thermoduric bacteria are likely to increase in numbers during cheese-making, as in-process conditions are conducive to proliferation. The present study was conducted to track thermoduric bacterial progression during an 18- to 20-h Cheddar cheese production run and during ripening when the pasteurizer was washed at midway through the production day. This study also correlated a broad range of chemical changes to the growth of thermoduric bacteria during ripening. Three independent cheese trials were performed at 3.5- ± 0.5-mo intervals. Samples were drawn in duplicates at 4 different times of the day: at the start of the run (vat 1), prior to a midday wash of the pasteurizer (vat 20), after the midday wash of the pasteurizer (vat 21), and at the end of the run (vat 42) for raw milk, pasteurized milk, and cheese. Cheeses were also tested during ripening for 6 mo. Results showed that raw milk total bacterial counts comprised 0.24% thermoduric mesophiles (TM) and 0.12% thermoduric thermophiles (TT). The thermoduric thermophilic bacterial counts increased by log10 1.23 during the pasteurizer run of 9 to 10 h, indicating a buildup of thermoduric thermophilic bacteria during the pasteurization process itself. Midday washing reduced thermophilic counts by log10 1.36, as evident by pre- and post-midday wash counts. However, a thermophilic buildup during post-midday wash was again noticed near the end of the 20-h run. We found that TT bacteria decreased in the first 60 d of ripening, whereas TM bacteria increased during the same period. However, TT bacteria increased later during 60 to 180 d of ripening. Bacillus licheniformis was the most frequently isolated bacteria in this study and was recovered at all production stages sampled during the cheese-making and ripening. We observed a significant increase in the level of orotic and uric acids in the vat made at the end of the day. No significant difference in the overall chemical composition, proteolysis, sugar, or other organic acids was observed in cheese made at the start versus the end of the production run.

Selection of potential molecular markers for cheese ripening and quality prediction by NMR spectroscopy

Predicting cheese quality as early as possible after ripening is important for quality control in the cheese industry. The main aim of this study was to investigate potential metabolites for predictive models of Cheddar cheese quality. Metabolites in aqueous extracts of Cheddar cheese were identified by Nuclear Magnetic Resonance. The metabolites were used to measure the kinetics of up to 450 days ripening in Cheddar cheese. The proton ratios of citrulline and arginine relative to the overall proton content of the aqueous extract are the most important indices for assessing the ripening of Cheddar cheese. The ratios of citrulline and arginine decrease by 59% and 69%, respectively, after 450 days ripening. In comparison to the premium batch B cheese, batch C which was predicted to attain a lower quality level, had higher serine and β-galactose as well as lower lactic acid levels and also had a less mature sensorial profile. Tyrosine, tyramine and lysine are highly correlated with mature Cheddar cheese sensory attributes. β-Galactose and glycerol are correlated with young Cheddar cheese sensory attributes. These metabolites can be used to predict cheese quality.

Evaluation of the Perceptual Interactions among Aldehydes in a Cheddar Cheese Matrix According to Odor Threshold and Aroma Intensity.

To evaluate the contributions of 3-methylbutanal, 2-methylbutanal, 2-methylpropanal, and benzaldehyde in cheddar cheese models, the threshold values, optimal concentration ranges, and perceptual actions of these compounds were determined at various concentrations. The thresholds for 3-methylbutanal, 2-methylbutanal, 2-methylpropanal, and benzaldehyde in the cheese matrix were 150.31, 175.39, 150.66, and 500.21 μg/kg, respectively, which were significantly higher than the corresponding values in water. The optimal concentration ranges of these aldehydes were determined as 150–300, 175–325, 150–350, and 500–1500 μg/kg, respectively. Based on the results of the threshold method and Feller’s model, five binary mixtures were found to have synergistic effects, and only the pair of 2-methylpropanal and benzaldehyde was determined to have a masking effect. In addition, the synergistic olfactory effects between the four ternary mixtures and the quaternary mixture of these aldehydes were also assesSsed using Feller’s model. In a σ-τ plot analysis, synergism was usually observed when these odor pairs were at their threshold levels. In summary, the results suggested that perceptual interactions among these aldehydes exist in a cheese model variably with different concentrations and threshold ratios. This study will be helpful to a further understanding of the nutty aroma and improving the aroma quality of cheddar cheese.

Effect of Pseudomonas fluorescens proteases on the quality of Cheddar cheese

The objective of this study was to investigate the effect of adding different levels of a thermoresistant protease produced by a Pseudomonas fluorescens strain to milk on the manufacture and quality of Cheddar cheese. Fresh raw milk was collected, standardized, and pasteurized at 72°C for 15 s, and the enzyme was added to give a protease activity of 0.15 or 0.60 U/L (treatments P1 and P4, respectively), while one sample had no enzyme added (control). Milk was stored at 4°C for 48 h and Cheddar cheese was manufactured after 0 and 48 h of storage. Results indicated that the protease was active in milk during 48 h of storage; however, its effect on milk composition was minimal. The protein that was preferentially hydrolyzed by the protease over storage was β-casein, followed by κ-casein. The mean cheese yield and recovery of fat and protein obtained for all cheeses were not affected by protease activity. The protease showed low activity during cheese manufacture, possibly because of unfavorable conditions, including low pH. One of the factors that might have influenced protease activity was the pH of the curd (approximately 6.55 after acidification and 5.35 at milling), which was lower than that at which the enzyme would have optimum activity (pH 7 to 9). Consequently, the composition, pH, patterns of proteolysis, and hardness of all cheeses produced were similar and in accordance with values expected for that type of cheese, independently of the protease activity level. However, slight increases in proteolysis were observed in P4 cheeses and produced using milk stored for 48 h. Both the P1 and P4 cheeses had higher concentrations of free amino acids (FAA) compared with the control, whereas urea-PAGE electrophoretograms indicated a greater breakdown of caseins in the P4 cheese samples, which may be related to possible increases in numbers of proteolytic bacteria in milk during storage. Therefore, the thermoresistant psychrotrophic bacterial protease(s) tested in this study may affect the manufacture or quality of Cheddar cheese during ripening to a relatively limited extent. However, controlling initial levels of proteolytic bacteria in raw milk remains essential, because proteolysis affects the development of flavor and texture in cheese.

Incorporating mixed rations and formulated grain mixes into the diet of grazing cows: Effects on milk composition and coagulation properties, and the yield and quality of Cheddar cheese

Effects of different strategies for feeding supplements to grazing dairy cows on the composition and coagulation properties of milk and the subsequent yield and quality of Cheddar cheese were measured. The experiment used milk from 72 Holstein-Friesian cows, averaging 45d in milk, fed according to 1 of 3 feeding strategies: (1) cows grazed a restricted allowance of perennial ryegrass pasture [approximately 14kg of dry matter (DM)/cow per day, to ground level] supplemented with milled wheat grain fed in the milking parlor and alfalfa hay offered in the paddock (control); (2) same pasture and allowance as control, supplemented with a formulated grain mix containing wheat grain, corn grain, and canola meal fed in the parlor and alfalfa hay fed in the paddock (FGM); or (3) same pasture and allowance as control, supplemented with a partial mixed ration comprising the same formulated grain mix but mixed with alfalfa hay and presented on a feed pad after each milking (PMR). For all strategies, supplements provided the same metabolizable energy and grain:forage ratio (78:22, DM basis). Within each feeding strategy, milk was sampled from cows receiving either 8 or 16kg (DM) of supplement/cow per day. There were 2 replicated groups of 6 cows per supplement amount per dietary strategy; approximately 250L of milk was sampled from each for analyses of composition and coagulation properties and the manufacture of Cheddar cheese. The experiment had a 14-d adaptation period and a 14-d measurement period. For cows fed according to the control strategy, those fed 16kg/cow per day produced milk with lower concentrations of milk fat than cows fed 8kg/cow per day. This effect was not observed for cows fed according to the FGM and PMR strategies. Milk from cows fed 16kg of DM/cow per day according to the control strategy yielded less Cheddar cheese than milk from cows fed according to the PMR strategy, with cheese yields from FGM cows being intermediate. Amount of supplement offered had minor effects on percentages of some fatty acids. We observed few other effects of feeding strategy on milk composition, types of milk protein, milk coagulation properties, or the composition and quality of the resultant Cheddar cheese. These data show that, compared with the traditional control strategy, feeding PMR or FGM may increase milk fat concentration and the subsequent yield of Cheddar cheese without compromising cheese composition or quality.

The mathematical modelling of cheese ripening

A mathematical model is developed for the ripening of cheese. Such models may assist predicting final cheese quality using measured initial composition. The main constituent chemical reactions are described with ordinary differential equations. Numerical solutions to the model equations are found using Matlab. Unknown parameter values have been fitted using experimental data available in the literature. The results from the numerical fitting are in good agreement with the data. Statistical analysis is performed on near infrared data provided to the MISG. However, due to the inhomogeneity and limited nature of the data, not many conclusions can be drawn from the analysis. A simple model of the potential changes in acidity of cheese is also considered. The results from this model are consistent with cheese manufacturing knowledge, in that the pH of cheddar cheese does not significantly change during ripening. References D. Dawson and J. Feagan, Bacteriology of cheddar cheese: A study of starter organisms in manufacture and maturing. J. Dairy Res. 24 , 210–224, 1957. M.A. Drake, R.E. Miracle and D.J. McMahon, Impact of fat reduction on flavor and flavor chemistry of Cheddar cheeses. Journal of Dairy Science 93 , 5069–5081, 2010. M. Fenelon and T. Guinee, Primary proteolysis and textural changes during ripening in cheddar cheeses manufactured to different fat contents. Int. Dairy J. 10 , 151–158, 2000. R. Hutkins and N. Nannen, pH homeostasis in lactic acid bacteria. J. Dairy Sci. 76 , 2354–2365, 1992. M. Johnson, Cheese pH–-what's behind the rise and fall? Technical Report 14, Wisconsin Center for Dairy Research, December 2002. J.K. Kim, K. Starzak, G.W. Preckshot, R. Marshall and R.K. Bajpai, Critical reactions in ripening of cheeses–-a kinetic analysis. Appl. Biochem. Biotech. 45 , 51–68, 1994. B.A. Law and A.S. Wigmore, Microbial proteinases as agents for accelerated cheese ripening. Int. J. Dairy Tech. 35 , 75–76, 2007. R. Lawrence, L. Creamer, and J. Gilles, Texture development during cheese ripening. J. Dairy Sci. 70 , 1748–1760, 1987. R. Marsili, Monitoring chemical changes in cheddar cheese during aging by high performance liquid chromatography and gas chromatography techniques. Journal of Dairy Science 68 , 3155–3161, 1985. K. Presser, D. Ratkowsky, and T. Ross, Modelling the growth rate of Escherichia coli as a function of pH and lactic acid concentration. Appl. Environ. Microbiol. 63 , 2355–2360, 1997. S. Rehman, D. Waldron, and P. Fox, Effect of modifying lactose concentration in cheese curd on proteolysis and in quality of Cheddar cheese. Int. Dairy J. 14 , 591–597, 2004. T. Singh, M. Drake, and K. Cadwallader, Flavour of cheddar cheese: A chemical and sensory perspective. Compr. Rev. Food Sci. F. 2 , 166–189, 2003. S. Toelstede and T. Hofmann, Kokumi-active glutamyl peptides in cheeses and their biogeneration by Penicillium roquefortii. Agric. Food Chem. 13 , 3738–3748, 2009.

Texture, flavor, and sensory quality of buffalo milk Cheddar cheese as influenced by reducing sodium salt content

The adverse health effects of dietary sodium demand the production of cheese with reduced salt content. The study was aimed to assess the effect of reducing the level of sodium chloride on the texture, flavor, and sensory qualities of Cheddar cheese. Cheddar cheese was manufactured from buffalo milk standardized at 4% fat level by adding sodium chloride at 2.5, 2.0, 1.5, 1.0, and 0.5% (wt/wt of the curd obtained). Cheese samples were ripened at 6 to 8°C for 180 d and analyzed for chemical composition after 1 wk; for texture and proteolysis after 1, 60, 120, and 180 d; and for volatile flavor compounds and sensory quality after 180 d of ripening. Decreasing the salt level significantly reduced the salt-in-moisture and pH and increased the moisture-in-nonfat-substances and water activity. Cheese hardness, toughness, and crumbliness decreased but proteolysis increased considerably on reducing the sodium content and during cheese ripening. Lowering the salt levels appreciably enhanced the concentration of volatile compounds associated with flavor but negatively affected the sensory perception. We concluded that salt level in cheese can be successfully reduced to a great extent if proteolysis and development of off-flavors resulted by the growth of starter and nonstarter bacteria can be controlled.

Preparation and characterization of milk protein films and their application for packaging of Cheddar cheese.

Casein and whey protein concentrate (WPC) films, plasticized with glycerol and sorbitol independently, were prepared by casting. The film thickness, water vapour and oxygen permeation and tensile and moisture sorption properties of the films were determined. The tensile strength (TS), tensile strain (TE) and elastic modulus (EM) of the films ranged from 0.71 to 4.58MPa, 19.22 to 66.63% and 2.05 to 6.93MPa, respectively. The film properties were influenced by the type of biopolymer (casein and whey protein concentrate), plasticizer and its concentration. Increasing the plasticizer concentration, increased the film thickness, TE and water vapour permeability (WVP), but decreased the TS and EM. As the concentration of plasticizer increased to the highest level, the film thickness increased from 0.168 to 0.305mm for glycerol-plasticized films and from 0.251 to 0.326mm for sorbitol-plasticized films. The film thickness increased because the amount of plasticizer in the film network increased and the amount of biopolymer remained same. Casein films showed superior tensile properties as compared to WPC films. The WVP of both casein and WPC films lied between 3.87 and 13.97g.mm./(m(2).h.kPa). The moisture sorption isotherms of both films were typical of high-protein material, and were adequately described by the GAB model. The oxygen permeability of casein films was relatively lower than that of WPC films, regardless of the plasticizer used. The sensory data revealed that the organoleptic quality of Cheddar cheese was unaffected by milk-protein film packaging.

The impact of reduced sodium chloride content on Cheddar cheese quality

The effect of varying salt (sodium chloride) addition levels of 0.50%, 1.25%, 1.80%, 2.25%, 2.50% and 3.00% (w/w) on the quality of Cheddar cheese was assessed. Reducing the salt adversely impacted Cheddar flavour and texture. The key compositional parameters of moisture-in-non-fat-substances and salt-in-moisture were most affected. Decreasing salt resulted in a concomitant reduction of pH, a slight reduction in buffering capacity and an increase in water activity and growth of starter and non-starter lactic acid bacteria that resulted in enhanced proteolysis. Lipolysis was not impacted by salt reduction. To produce quality reduced salt Cheddar cheese cognisance must be taken on how to reduce proteolysis, limit growth of NSLAB, reduce water activity, achieve pH 5.0–5.4 by modifications to the cheese making procedure to create a more appropriate environment for selected starter and/or adjunct cultures to generate acceptable Cheddar flavour and texture.

Effect of zinc fortification on Cheddar cheese quality

Zinc-fortified Cheddar cheese containing 228mg of zinc/kg of cheese was manufactured from milk that had 16mg/kg food-grade zinc sulfate added. Cheeses were aged for 2 mo. Culture activity during cheese making and ripening, and compositional, chemical, texture, and sensory characteristics were compared with control cheese with no zinc sulfate added to the cheese milk. Compositional analysis included fat, protein, ash, moisture, zinc, and calcium determinations. The thiobarbituric acid (TBA) assay was conducted to determine lipid oxidation during aging. Texture was analyzed by a texture analyzer. An untrained consumer panel of 60 subjects evaluated the cheeses for hardness, off-flavors, appearance, and overall preference using a 9-point hedonic scale. Almost 100% of the zinc added to cheese milk was recovered in the zinc-fortified cheese. Zinc-fortified Cheddar cheese had 5 times more zinc compared with control cheese. Zinc-fortified cheese had higher protein and slightly higher fat and ash contents, whereas moisture was similar for both cheeses. Zinc fortification did not affect culture activity during cheese making or during the 2-mo aging period. The TBA value of control cheese was higher than that of zinc-fortified cheese at the end of ripening. Although zinc-fortified cheese was harder as determined by the texture analyzer, the untrained consumer panel did not detect differences in the sensory attributes and overall quality of the cheeses. Fortification of 16mg/kg zinc sulfate in cheese milk is a suitable approach to fortifying Cheddar cheese without changing the quality of Cheddar cheese.

Rapid Prediction of Composition and Flavor Quality of Cheddar Cheese Using ATR–FTIR Spectroscopy

Multiple methods are required for analysis of cheese flavor quality and composition. Chromatography and sensory analyses are accurate but laborious, expensive, and time consuming. A rapid and simple instrumental method based on Fourier transform infrared (FTIR) spectroscopy was developed for simultaneous analysis of Cheddar cheese composition and flavor quality. Twelve different Cheddar cheese samples ripened for 67 d were obtained from a commercial cheese manufacturer along with their moisture, pH, salt, fat content, and sensory flavor quality data. Water-soluble components were extracted from the cheese, dried on zinc selenide FTIR crystal and scanned (4000 to 700 cm(-1)). Infrared spectra of the samples were correlated with their composition and flavor quality data to develop multivariate statistical regression and classification models. The models were validated using an independent set of ten 67-d-old test samples. The infrared spectra of the samples were well defined, highly consistent within each sample and distinct from other samples. The regression models showed excellent fit (r > 0.92) and could accurately determine moisture, pH, salt, and fat contents as well as the flavor quality rating in less than 20 min. Furthermore, cheeses could also be classified based on their flavor quality (slight acid, whey taint, good cheddar, and so on). The discrimination of the samples was due to organic acids, amino acids, and short chain fatty acids (1800 to 900 cm(-1)), which are known to contribute significantly to cheese flavor. The results show that this technique can be a rapid, inexpensive, and simple tool for predicting composition and flavor quality of cheese.

Cheddar Cheese Fluoridation and Dental Health

The main objective of this study was to determine what effect the additionof sodium fluoride would have on the Cheddar cheese quality. Raw milk waspasteurized and separated for three treatments as follows: control, supplementedwith 4 ppm and 40 ppm fluoride. Cheddar cheese was processed for eachtreatment and ripened for 120 days at 7oC and sampled at 60 and 120 days.Analyses performed included both sensory evaluation and gas chromatographywith headspace sampling (GCHS). Under conditions of this study significantP&lt; 0.05 higher mean flavor and body/texture scores were observed in both thecontrol cheese samples and those with 4 ppm added fluoride than those with 40ppm added fluorides.The predominant flavor criticisms in Cheddar cheese treated with 40 ppm addedfluoride after 120 days were flat, lacks flavor and bitter. The predominantbody/texture criticisms noted in Cheddar cheese treated with 40 ppm addedfluoride after 120 days were open, mealy, corky, crumbly, pasty and curdy.GCHS results showed that Acetone, 2- butanone, ethanol, 2-pentanone andpropanol increased significantly (P&lt; 0.05) with aging of the Cheddar cheese.However after 60 days of ripening, the control cheese had significantly (P&lt;0.05) lower Acetone, 2-pentanone and higher ethanol values than the fluoridatedcheese. By 120 days, the control cheese had significantly (P&lt; 0.05) higher 2-butanone values than both treated cheese and higher ethanol than the cheesefluoridated at 40 ppm.

Influence of Calcium and Phosphorus, Lactose, and Salt-to-Moisture Ratio on Cheddar Cheese Quality: pH Changes During Ripening

The pH of cheese is an important attribute that influences its quality. Substantial changes in cheese pH are often observed during ripening. A combined effect of calcium, phosphorus, residual lactose, and salt-to-moisture ratio (S/M) of the cheese on the changes in cheese pH during ripening was investigated. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%), and S/M (6.4 vs. 4.8%) were manufactured. All the cheeses were salted at a pH of 5.4, pressed for 5h, and then ripened at 6 to 8°C. The pH of the salted curds before pressing and the cheeses during 48 wk of ripening was measured. Also, cheeses were analyzed for water-soluble Ca and P, organic P, and bound inorganic P during ripening. Changes in organic acids’ concentration and shifts in the distribution of Ca and P between different forms were studied in relation to changes in pH. Cheeses with low S/M exhibited a larger increase in acid production during ripening compared with high S/M cheeses. Cheeses with the highest concentration of bound inorganic P exhibited the highest pH, whereas cheeses with the lowest concentration of bound inorganic P exhibited the lowest pH among the 8 treatments. Although conversion of lactose to short-chain, water-soluble organic acids decreased cheese pH, bound inorganic phosphate buffered the changes in cheese pH. Production of acid in excess of the buffering capacity (which was the case in low Ca and P and low S/M treatments) led to a low pH, whereas solubilization of bound inorganic P in excess to acid production (which was the case in high Ca and P and high S/M treatments) led to an increase in pH. However, for cheeses with high Ca and P and low S/M, changes in cheese pH were influenced by the level of residual lactose. Hence, pH changes in Cheddar cheese can be modulated by a concomitant control on the amount and state of Ca and P, level of residual lactose, and S/M of the cheese.

Influence of Calcium and Phosphorus, Lactose, and Salt-to-Moisture Ratio on Cheddar Cheese Quality: pH Buffering Properties of Cheese

The pH buffering capacity of cheese is an important determinant of cheese pH. However, the effects of different constituents of cheese on its pH buffering capacity have not been fully clarified. The objective of this study was to characterize the chemical species and chemical equilibria that are responsible for the pH buffering properties of cheese. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), residual lactose (2.4 vs. 0.78%), and salt-to-moisture ratio (6.4 vs. 4.8%) were manufactured. The pH-titration curves for these cheeses were obtained by titrating cheese:water (1:39 wt/wt) dispersions with 1 N HCl, and backtitrating with 1 N NaOH. To understand the role of different chemical equilibria and the respective chemical species in controlling the pH of cheese, pH buffering was modeled mathematically. The 36 chemical species that were found to be relevant for modeling can be classified as cations (Na+, Ca2+, Mg2+), anions (phosphate, citrate, lactate), protein-bound amino acids with a side-chain pKa in the range of 3 to 9 (glutamate, histidine, serine phosphate, aspartate), metal ion complexes (phosphate, citrate, and lactate complexes of Na+, Ca2+, and Mg2+), and calcium phosphate precipitates. A set of 36 corresponding equations was solved to give the concentrations of all chemical species as a function of pH, allowing the prediction of buffering curves. Changes in the calculated species concentrations allowed the identification of the chemical species and chemical equilibria that dominate the pH buffering properties of cheese in different pH ranges. The model indicates that pH buffering in the pH range from 4.5 to 5.5 is predominantly due to a precipitate of Ca and phosphate, and the protonation equilibrium involving the side chains of protein-bound glutamate. In the literature, the precipitate is often referred to as amorphous colloidal calcium phosphate. A comparison of experimental data and model predictions shows that the buffering properties of the precipitate can be explained, assuming that it consists of hydroxyapatite [Ca5(OH)(PO4)3] or Ca3(PO4)2. The pH buffering in the region from pH 3.5 to 4.5 is due to protonation of side-chain carboxylates of protein-bound glutamate, aspartate, and lactate, in order of decreasing significance. In addition, pH buffering between pH 5 to 8 in the backtitration results from the reprecipitation of calcium and phosphate either as CaHPO4 or Ca4H(PO4)3.

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.