EFFECT OF CALCIUM AND PHOSPHORUS, RESIDUAL LACTOSE AND SALT-TO-MOISTURE RATIO ON TEXTURAL PROPERTIES OF CHEDDAR CHEESE DURING RIPENING

The texture profile analysis (TPA) parameters and meltability of Cheddar cheeses with varying levels of calcium (Ca) and phosphorus (P) content, residual lactose content and salt‐to‐moisture (S/M) ratio were studied at 0, 1, 2, 4, 6 and 8 months of ripening. The TPA hardness had an inverse relationship with the meltability of Cheddar cheese and at any given ripening time, lower TPA hardness corresponded to higher meltability of Cheddar cheese. Higher Ca and P content (0.67% Ca and 0.53% P) in Cheddar cheese resulted in up to 22.8, 5.7, 14.6, 13.5 and 35.2% increase in hardness, springiness, cohesiveness, resilience and chewiness values, respectively, and up to 23.5 and 27.7% decrease in meltability and adhesiveness values during ripening compared to the Cheddar cheese prepared with lower Ca and P content (0.53% Ca and 0.39% P). Higher residual lactose content (1.4%) in Cheddar cheese resulted in up to 24.6, 8.8 and 20.0% increase in hardness, cohesiveness and chewiness values, respectively, and up to 12.7% decrease in meltability value in the Cheddar cheese during ripening compared to the lower lactose content (0.78%). High S/M ratio (6.4) resulted in up to 29.4, 30.3 and 29.4% increase in hardness, adhesiveness and chewiness values, respectively, and up to 7.3% decrease in meltability value in Cheddar cheese compared to low S/M ratio (4.8) during ripening.     

Dynamic Rheological Properties of Process Cheese: Effect of Ca and P Content,Residual Lactose,Salt-to-Moisture Ratio and Cheese Temperature

Four treatments of Cheddar cheese with two levels (high and low) of calcium (Ca) and phosphorus (P), and two levels (high and low) of residual lactose were manufactured. Each treatment was subsequently split prior to the salting step of cheese manufacturing process and salted at two levels (high and low) for a total of eight treatments. After two months of ripening, each treatment of Cheddar cheese was used to manufacture process cheese using a twin-screw Blentech process cheese cooker. NFDM, butter oil, trisodium citrate (emulsifying salt), and water were added along with Cheddar cheese for process cheese formulation. All process cheese food formulations were balanced for moisture (43.5%), fat (25%), and salt (2%), respectively. Dynamic rheological characteristics (G′ and G″) of process cheese were determined at 1.5Hz frequency and 750 Pa stress level by using a Viscoanalyzer during heating and cooling, temperature ranges from 30°C to 70°C then back to 30°C. High Ca and P content, and high S/M (HHH and HLH) cheeses had the significantly higher elastic (G′) and viscous (G″) modulus than other cheeses during heating from 30°C to 70°C, and cooling from 70°C to 30°C. No significant difference was observed among the other process cheeses during heating and cooling. Viscoelastic properties of process cheeses were also determined in terms of transition temperature (where G′?=?G″), and tan δ during heating (30°C to 70°C). Cheeses with high Ca and P, high lactose, and high S/M content had higher transition temperature than low Ca and P, low lactose, and low S/M content process cheeses. Low Ca and P and low S/M content cheeses (LLL, LHH, LHL, HLL) exhibited more viscous characteristics than high Ca and P and high S/M content process cheeses (HHL, HLH, LLH, HHH) during heating from 30°C to 70°C. Low Ca and P, low lactose, low S/M content (LLL) process cheese was observed for highest tan δ values (0.39 to 1.43), whereas high Ca and P, high lactose, high S/M content process (HHH) had the least (0.33 to 1.06) during heating. This study demonstrates that different characteristics of natural cheese used in process cheese manufacturing have significant impact on process cheese rheological and viscoelastic properties.     

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 5 h, 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.     

Understanding the role of natural cheese calcium and phosphorous content,residual lactose and salt‐in‐moisture content on block‐type processed cheese functional properties: Cheese hardness and flowability/meltability

Four treatments of natural Cheddar cheese with two levels (high and low) of calcium (Ca) and phosphorus (P), and two levels (high and low) of residual lactose were manufactured. Each treatment was subsequently split prior to the salting step of cheese manufacturing processed and salted at two levels (high and low) for a total of eight treatments. The eight treatments included: high Ca and P, high lactose, high salt‐in‐moisture (S/M) content (HHH); high Ca and P, high lactose, low S/M (HHL); high Ca and P, low lactose, high S/M (HLH); high Ca and P, low lactose, low S/M (HLL); low Ca and P, high lactose, high S/M (LHH); low Ca and P, high lactose, low S/M (LHL); low Ca and P, low lactose, high S/M (LLH); and low Ca and P, low lactose, low S/M (LLL). After 2 months of ripening, each treatment of natural Cheddar cheese was used to manufacture processed cheese using a twin‐screw Blentech processed cheese cooker. All of the processed cheese food formulations were balanced for moisture, fat and salt. Texture and melt‐flow characteristics of the processed cheese were evaluated with different techniques, including texture profile analysis (TPA) for hardness and melt profile analysis. There was a considerable increase in cheese hardness for the processed cheeses prepared from high Ca and P content, and high S/M natural cheeses compared with low Ca and P content and low S/M natural cheeses. Moreover, definite decrease in flow rate and extent of flow was observed for processed cheeses manufactured from high Ca and P content, and high S/M natural cheeses than that of low Ca and P content and low S/M natural cheeses. No considerable trend was observed in hardness and melt‐flow characteristics for the processed cheeses manufactured from high and low residual lactose content natural Cheddar cheeses. This study strongly demonstrates that the characteristics of natural cheese (calcium and phosphorus content, lactose content and salt‐in‐moisture content) used in processed cheese manufacture have a significant impact on processed cheese functionality.     

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on Cheddar cheese quality: changes in residual sugars and water-soluble organic acids during ripening

Cheddar cheese ripening involves the conversion of lactose to glucose and galactose or galactose-6-phosphate by starter and nonstarter lactic acid bacteria. Under ideal conditions (i.e., where bacteria grow under no stress of pH, water activity, and salt), these sugars are mainly converted to lactic acid. However, during ripening of cheese, survival and growth of bacteria occurs under the stressed condition of low pH, low water activity, and high salt content. This forces bacteria to use alternate biochemical pathways resulting in production of other organic acids. The objective of this study was to determine if the level and type of organic acids produced during ripening was influenced by calcium (Ca) and phosphorus (P), residual lactose, and salt-to-moisture ratio (S/M) of cheese. 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. The cheeses were analyzed for organic acids (citric, orotic, pyruvic, lactic, formic, uric, acetic, propanoic, and butyric acids) and residual sugars (lactose, galactose) during 48 wk of ripening using an HPLC-based method. Different factors influenced changes in concentration of residual sugars and organic acids during ripening and are discussed in detail. Our results indicated that the largest decrease in lactose and the largest increase in lactic acid occurred between salting and d 1 of ripening. It was interesting to observe that although the lactose content in cheese was influenced by several factors (Ca and P, residual lactose, and S/M), the concentration of lactic acid was influenced only by S/M. More lactic acid was produced in low S/M treatments compared with high S/M treatments. Although surprising for Cheddar cheese, a substantial amount (0.2 to 0.4%) of galactose was observed throughout ripening in all treatments. Minor changes in the levels of citric, uric, butyric, and propanoic acids were observed during early ripening, whereas during later ripening, a substantial increase was observed. A gradual decrease in orotic acid and a gradual increase in pyruvic acid content of the cheeses were observed during 12 mo of ripening. In contrast, acetic acid did not show a particular trend, indicating its role as an intermediate in a biochemical pathway, rather than a final product.     

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.     

Effect of natural cheese characteristics on process cheese properties

Natural cheese is the major ingredient utilized to manufacture process cheese. The objective of the present study was to evaluate the effect of natural cheese characteristics on the chemical and functional properties of process cheese. Three replicates of 8 natural (Cheddar) cheeses with 2 levels of calcium and phosphorus, residual lactose, and salt-to-moisture ratio (S/M) were manufactured. After 2 mo of ripening, each of the 8 natural cheeses was converted to 8 process cheese foods that were balanced for their composition, including moisture, fat, salt, and total protein. In addition to the standard compositional analysis (moisture, fat, salt, and total protein), the chemical properties (pH, total Ca, total P, and intact casein) and the functional properties [texture profile analysis (TPA), modified Schreiber melt test, dynamic stress rheometry, and rapid visco analysis] of the process cheese foods were determined. Natural cheese Ca and P, as well as S/M, significantly increased total Ca and P, pH, and intact casein in the process cheese food. Natural cheese Ca and P and S/M also significantly affected the final functional properties of the process cheese food. With the increase in natural cheese Ca and P and S/M, there was a significant increase in the TPA-hardness and the viscous properties of process cheese food, whereas the meltability of the process cheese food significantly decreased. Consequently, natural cheese characteristics such as Ca and P and S/M have a significant influence on the chemical and the final functional properties of process cheese.     

Effect of calcium and phosphorus, residual lactose, and salt-to-moisture ratio on the melting characteristics and hardness of cheddar cheese during ripening

ABSTRACT:  Meltability, melt profile parameters, and hardness of cheddar cheese prepared with varying levels of calcium (Ca) and phosphorus (P) content, residual lactose content, and salt-to-moisture ratio were studied at 0,1, 2, 4, 6, and 8 mo of ripening. Meltability, melt profile parameters, and hardness of cheddar cheeses measured at 0, 1, 2, 4, 6, and 8 mo of ripening showed significant interaction between the levels of Ca and P, residual lactose, salt-to-moisture ratio, and ripening time for most of the properties studied. cheddar cheese prepared with high Ca and P (0.67% Ca and 0.53% P) resulted in up to 6.2%, 4.5%, 9.6%, 5.0%, and 22.8% increase in softening time, softening temperature, melting time, melting temperature, and hardness, respectively, and 23.5%, 9.6%, and 3.2% decrease in meltability, flow rate, and extent of flow, respectively, compared to the cheddar cheese prepared with low Ca and P (0.53% Ca and 0.39% P). cheddar cheese prepared with high lactose (1.4%) content resulted in up to 7.7%, 7.0%, 4.9%, 4.2%, and 24.6% increase in softening time, softening temperature, melting time, melting temperature, and hardness, respectively, and 14.7%, 12.7%, and 2.8% decrease in meltability, flow rate, and extent of flow respectively compared to the cheddar cheese prepared with low lactose (0.78%) content. cheddar cheese prepared with high salt-to-moisture ratio (6.4%) resulted in up to 21.8%, 11.3%, 12.9%, 4.1%, and 29.4% increase in softening time, softening temperature, melting time, melting temperature, and hardness, respectively, and 13.2%, 28.6%, and 2.6% decrease in meltability, flow rate, and extent of flow, respectively, compared to the cheddar cheese prepared with low salt-to-moisture ratio (4.8%) during ripening.     

Effect of lactose standardization of milk using low-concentration factor ultrafiltration: Effect of reducing the lactose-to-casein ratio on the properties of milled-curd Cheddar cheese

The pH of cheese is determined by the amount of lactose fermented and the buffering capacity of the cheese. The buffering capacity of cheese is largely determined by the protein contents of milk and cheese and the amount of insoluble calcium phosphate in the curd, which is related to the rate of acidification. The objective of this study was to standardize both the lactose and casein contents of milk to better control final pH and prevent the development of excessive acidity in Cheddar cheese. This approach involved the use of low-concentration factor ultrafiltration of milk to increase the casein content (～5%), followed by the addition of water, ultrafiltration permeate, or both to the retentate to adjust the lactose content. We evaluated milks with 4 different lactose-to-casein ratios (L:CN): 1.8 (control milk), 1.4, 1.1, and 0.9. All cheesemilks had similar total casein (2.3%) and fat (3.4%) contents. These milks were used to make milled-curd Cheddar cheese, and we evaluated cheese composition, texture, functionality, and sensory properties over 9 mo of ripening. Cheeses made from milks with varying levels of L:CN had similar moisture, protein, fat, and salt contents, due to slight modifications during manufacture (i.e., cutting the gel at a smaller size than control) as well as control of acid development at critical steps (i.e., cutting the gel, whey drainage, salting). As expected, decreasing the L:CN led to cheeses with lower lactic acid, residual lactose, and insoluble Ca contents, as well as a substantial pH increase during cheese ripening in cheeses. The L:CN ratio had no significant effect on the levels of primary and secondary proteolysis. Texture profile analysis showed no significant differences in hardness values during ripening. Maximum loss tangent, an index of cheese meltability, was lower until 45 d for the L:CN 1.4 and 0.9 treatments, but after 45 d, all reduced L:CN cheeses had higher maximum loss tangent values than the control cheese (L:CN 1.8). Sensory analyses showed that cheeses made from milks with reduced L:CN contents had lower acidity, sourness, sulfury notes, and chewdown cohesiveness. Standardization of milk to a specific L:CN ratio, while maintaining a constant casein level in the milk, would allow Cheddar cheese manufacturers to have tighter control of pH and acidity.     

Influence of ripening temperature on the volatiles profile and flavour of Cheddar cheese made from raw or pasteurised milk

Cheddar cheeses were made from raw (R1, R8) or pasteurised (P1, P8) milk and ripened at 1°C (P1, R1) or 8°C (P8, R8). Volatile compounds were extracted from 6 month-old cheeses and analysed, identified and quantified by gas chromatography-mass-spectrometry. A detailed sensory analysis of the cheeses was performed after 4 and 6 months of ripening. The R8 cheeses had the highest and P1 the lowest concentrations of most of the volatile compounds quantified (fatty acids, ketones, aldehydes, esters, alcohols, lactones and methional). The R8 and P8 cheeses contained higher levels of most of the volatiles than R1 and P1 cheeses. Ripening temperature and type of milk influenced most of the flavour and aroma attributes. Principal component analysis (PCA) of aroma and flavour attributes showed that P1 and R1 had similar aroma and flavour profiles, while R8 had the highest aroma and flavour intensities, highest acid aroma and sour flavour. The age of cheeses influenced the perception of creamy/milky and pungent aromas. PCA of the texture attributes separated cheeses on the basis of ripening temperature. The R8 and P8 cheeses received significantly higher scores for perceived maturity than P1 and R1 cheeses. The P1 and R1 cheeses had similar values for perceived maturity. In a related study, it was found that concentrations of amino acids and fatty acids were similar in R1 and P1 during most of the ripening period, and R1 and P1 cheeses had low numbers of non-starter lactic acid bacteria (NSLAB). The panel found that ripening temperature, type of milk and age of cheeses did not influence the acceptability of cheese. It is concluded that NSLAB contribute to the formation of volatile compounds and affect the aroma and flavour profiles and the perceived maturity of Cheddar cheese.     

Impact of modifications in acid development on the insoluble calcium content and rheological properties of Cheddar cheese

Cheddar cheese was made from milk concentrated by reverse osmosis (RO) to increase the lactose content or from whole milk. Manufacturing parameters (pH at coagulant addition, whey drainage, and milling) were altered to produce cheeses with different total Ca contents and low pH values (i.e., <5.0) during ripening. The concentration of insoluble (INSOL) Ca in cheese was measured by cheese juice method, buffering by acid-base titration, rheological properties by small amplitude oscillatory rheometry, and melting properties by UW-Melt Profiler. The INSOL Ca content as a percentage of total Ca in all cheeses rapidly decreased during the first week of aging but surprisingly did not decrease below approximately 41% even in cheeses with a very low pH (e.g., ∼4.7). Insoluble Ca content in cheese was positively correlated (r = 0.79) with cheese pH in both RO and nonRO treatments, reflecting the key role of pH and acid development in altering the extent of solubilization of INSOL Ca. The INSOL Ca content in cheese was positively correlated with the maximum loss tangent value from the rheology test and the degree of flow from the UW-Melt Profiler. When cheeses with pH <5.0 where heated in the rheometer the loss tangent values remained low (<0.5), which coincided with limited meltability of Cheddar cheeses. We believe that this lack of meltability was due to the dominant effects of reduced electrostatic repulsion between casein particles at low pH values (<5.0).     

Rheological Properties of Cheddar Cheese as Influenced by Fat Reduction and Ripening Time

Fat reduction in Cheddar cheese resulted in an increase in viscoelasticity as evidenced by increases in G’and G”. Proteolysis during ripening led to softening of all cheeses and thus decreases in G’and G” for cheeses containing 34, 27, and 20% fat. Cheese with 13% fat showed a decrease in G’upon ripening, but no change in G”. This lack of change in viscous behavior may be important to the texture of reduced-fat Cheddar cheese and overall acceptability. Dynamic rheological testing was helpful in understanding rheological behavior associated with fat reduction in cheese.     

Impact of Using Exopolysaccharides (EPS)-Producing Strain on Qualities of Half-Fat Cheddar Cheese

Yield, textural, proteolysis, melting, and sensory properties of exopolysaccharide-producing Lactobacillus paracasei on properties of half-fat (about 16 g fat/100 g cheese) Cheddar cheese during ripening at 8℃ for up to six months were investigated. The results revealed that B-3 cheese, made with 2.0% (v/v) high yield exopolysaccharide-producing L. paracasei in combination with 0.011% (w/w) commercial Cheddar culture (B-3 cheese), had a 10.15, 7.71, and 10.04% separately increase in moisture content and had a 7.70, 5.05, and 6.76% separately increase in yield compared with B-2, B-4, and B-5 cheese, texture and melting characteristics were significantly improved (P < 0.05), sensory score surpassed B-4 and B-5 cheese and was similar to the full-fat one. Any differences of B-3 cheese detected among half-fat Cheddar cheeses were attributed to the presence of high yield exopolysaccharide-producing L. paracasei.     

Effect of proteolysis and calcium equilibrium on functional properties of natural cheddar cheese during ripening and the resultant processed cheese

The changes in proteolysis, calcium (Ca) equilibrium, and functional properties of natural Cheddar cheeses during ripening and the resultant processed cheeses were investigated. For natural Cheddar cheeses, the majority of the changes in pH 4.6 soluble nitrogen as a percentage of total nitrogen (pH 4.6 SN/TN) and the soluble Ca content occurred in the first 90 d of ripening, and subsequently, the changes were slight. During ripening, functional properties of natural Cheddar cheeses changed, that is, hardness decreased, meltability was improved, storage modulus at 70 °C (G'T=70) decreased, and the maximum tan delta (TDmax) increased. Both pH 4.6 SN/TN and the soluble Ca were correlated with changes in functional properties of natural Cheddar cheeses during ripening. Kendall's partial correlation analysis indicated that pH 4.6 SN/TN was more significantly correlated with changes in hardness and TDmax. For processed cheeses manufactured from natural Cheddar cheeses with different ripening times, the soluble Ca content did not show significant difference, and the trends of changes in hardness, meltability, G'T=70, and TDmax were similar to those of natural Cheddar cheeses. Kendall's partial correlation analysis suggested that only pH 4.6 SN/TN was significantly correlated with the changes in functional properties of processed cheeses.     

Effect of Ca and P Content,Residual Lactose,and Salt-to-Moisture Ratio on the Model Parameters of Process Cheese Linear Viscoelastic Properties

The main aim of this study was to investigate the influence of two different levels (high and low) of Ca and P (calcium and phosphorous) content, residual lactose, and salt-to-moisture (S/M) ratio on viscoelastic properties of eight different process cheeses. Frequency sweep was performed at 750 Pa on all experimental process cheese samples to determine the power-law model parameters. Process cheeses with high Ca and P content and high S/M ratio were significantly harder (P < 0.05) (higher storage and loss modulus, and lower creep and recovery compliance) compared to low Ca and P content and low S/M ratio process cheeses. However, no significant difference was observed (P > 0.05) for power-law parameters between high/low residual lactose content process cheese samples. Six-element Kelvin-Voigt model was used to predict the creep compliances for eight different process cheeses. This model described the affect of above treatment's retardation spectra (compliances, viscosities, and retardation times) obtained from creep tests. Both of these measurements indicated the similar trend on linear viscoelastic properties for eight different process cheeses.     

Effect of different curd-washing methods on the insoluble Ca content and rheological properties of Colby cheese during ripening

A curd-washing step is used in the manufacture of Colby cheese to decrease the residual lactose content and, thereby, decrease the potential formation of excessive levels of lactic acid. The objective of this study was to investigate the effect of different washing methods on the Ca equilibrium and rheological properties of Colby cheese. Four different methods of curd-washing were performed. One method was batch washing (BW), where cold water (10°C) was added to the vat, with and without stirring, where curds were in contact with cold water for 5 min. The other method used was continuous washing (CW), with or without stirring, where curds were rinsed with continuously running cold water for approximately 7 min and water was allowed to drain immediately. Both methods used a similar volume of water. The manufacturing pH values were similar in all 4 treatments. The insoluble (INSOL) Ca content of cheese was measured by juice and acid-base titration methods and the rheological properties were measured by small amplitude oscillatory rheology. The levels of lactose in cheese at 1 d were significantly higher in CW cheese (0.06-0.11%) than in BW cheeses (∼0.02%). The levels of lactic acid at 2 and 12 wk were significantly higher in CW cheese than in BW cheeses. No differences in the total Ca content of cheeses were found. Cheese pH increased during ripening from approximately 5.1 to approximately 5.4. A decrease in INSOL Ca content of all cheeses during ripening occurred, although a steady increase in pH took place. The initial INSOL Ca content as a percent of total Ca in cheese ranged from 75 to 78% in all cheeses. The INSOL Ca content of cheese was significantly affected by washing method. Stirring during manufacturing did not have a significant effect on the INSOL Ca content of cheese during ripening. Batch-washed cheeses had significantly higher INSOL Ca contents than did CW cheeses during the first 4 wk of ripening. The maximum loss tangent values (meltability index) of CW cheese at 1 d and 1 wk were significantly higher compared with those of BW cheeses. In conclusion, different curd washing methods have a significant effect on the levels of lactose, lactic acid, meltability, and INSOL Ca content of Colby cheese during ripening.     

Nonstarter lactic acid bacteria biofilms and calcium lactate crystals in Cheddar cheese

A sanitized cheese plant was swabbed for the presence of nonstarter lactic acid bacteria (NSLAB) biofilms. Swabs were analyzed to determine the sources and microorganisms responsible for contamination. In pilot plant experiments, cheese vats filled with standard cheese milk (lactose:protein = 1.47) and ultrafiltered cheese milk (lactose:protein = 1.23) were inoculated with Lactococcus lactis ssp. cremoris starter culture (8 log cfu/mL) with or without Lactobacillus curvatus or Pediococci acidilactici as adjunct cultures (2 log cfu/mL). Cheddar cheeses were aged at 7.2 or 10°C for 168 d. The raw milk silo, ultrafiltration unit, cheddaring belt, and cheese tower had NSLAB biofilms ranging from 2 to 4 log cfu/100 cm². The population of Lb. curvatus reached 8 log cfu/g, whereas P. acidilactici reached 7 log cfu/g of experimental Cheddar cheese in 14 d. Higher NSLAB counts were observed in the first 14 d of aging in cheese stored at 10°C compared with that stored at 7.2°C. However, microbial counts decreased more quickly in Cheddar cheeses aged at 10°C compared with 7.2°C after 28 d. In cheeses without specific adjunct cultures (Lb. curvatus or P. acidilactici), calcium lactate crystals were not observed within 168 d. However, crystals were observed after only 56 d in cheeses containing Lb. curvatus, which also had increased concentration of d(−)-lactic acid compared with control cheeses. Our research shows that low levels of contamination with certain NSLAB can result in calcium lactate crystals, regardless of lactose:protein ratio.