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Presents abstracts of research on cheese. "Use of Reverse Osmosis Concentrated Milk for the Manufacture of Cheddar and Colby Cheese: Impact on Ca Equilibrium and Functional Properties," by M.-R. Lee, J. A. Lucey and M. E. Johnson; "A Comparison of Three Different Methods for Measuring Intact Casein in Cheese," by P. Lehtola and L. E. Metzger; "Vatless Manufacture of Mozzarella Cheese From 8X Concentrated Microfiltration Retentate," by A. V. Ardisson and S. S. H. Rizvi.

Presents abstracts of several studies on the chemistry of dairy foods. "Storage Stability of Lutein in Cheddar Cheese," by S. T. Jones, K. J. Aryana and J. N. Losso; "Probiotic, Fiber Fortified, Fat Free Plain Yogurt," by K. J. Aryana; "Effect of Emulsifying Salts on Texture of Pasteurized Process Cheddar Cheese," by N. Shirashoji, J. J. Jaeggi and J. A. Lucey.

Previous research demonstrated that the total area collectively occupied by calcium lactate crystals on Cheddar cheese surfaces increased during storage in approximately linear manners but at different rates for different cheese samples. Evidence of substantial migration of calcium and lactate ions from cheese interior to surface during surface crystal growth was also observed. The objective of the present study was to characterize the growth of individual calcium lactate crystals on the surface of Cheddar cheese during refrigerated storage. A random weight (ca. 300g) retail sample of naturally smoked Cheddar cheese exhibiting white surface crystals was obtained from a commercial source. The sample was stored at 4°C for 30 weeks and a digital photograph was taken of one of the surfaces (ca. 55x120mm) at 3 wk intervals. The total area occupied by crystals on the photographed surface was measured at 3 wk intervals using image analysis. In addition, five small (ca. 0.3 mm radius) individual crystals on the first photographed surface were chosen for observation over the 30 wk period. The crystals were evaluated for area, radius and shape factor (circularity) every 3rd week using image analysis. The area collectively occupied by crystals on the photographed surface increased in a linear manner (R2=0.95) from about 0.44% to 7.42% of the total surface area over the 30 wk period. Throughout this period, the shapes of the five individual crystals closely approximated perfect circles, and the area occupied by each of the five crystals increased in a near linear manner (R2=0.85-0.96). The radii of each of the 5 crystals increased in a non-linear manner that conformed most closely to a second order polynomial relationship (R2=0.84-0.97). The rate of increase in crystal radii decreased over time as the crystals grew larger and occupied greater area. The data are consistent with the hypothesis that crystal growth occurs in 2 stages, the first governed primarily by the level of supersaturation of calcium lactate in the serum phase and the second by the rate of migration of calcium and lactate ions through the serum phase from the cheese interior to the surface. [ABSTRACT FROM AUTHOR]

Changes in cheese physical properties during aging are related to proteolysis by coagulant and culture enzymes. Storage temperature also affects rate of aging. Cultures are important for flavor development, but less is understood about their role in textural and melting properties. Our objective was to make cheddar cheese using different cultures, to age it at 5 and 13°C, and measure physical properties over 6 months. Cheese was manufactured using Lactococcus lactis starter culture either alone or combined with one or both of lac- Lc. lactis or Lactobacillus helveticus adjunct cultures. Three replicates of cheese were made using 1500 lb milk. Cheese composition was 35.5±1.0% moisture, 52.5±2.5% FDB, 1.65±0.05% salt, and pH 5.2±0.1. All cheeses were initially stored at 5°C, then half were moved to 13°C after 21 d. Texture profile analysis (TPA) was performed using 25% and 60% compression and melting measured using a Meltmeter at 65°C. After 2 months, differences in cheese properties were observed based on cultures and storage temperature. Cultures used had more effect on hardness and cohesiveness, while storage temperature had a large impact on adhesiveness. Using 25% or 60% compression produced different TPA values, especially when the cheese fractured during compression. At 25% compression, after 2 months, the cheeses made using Lb. helveticus had the highest hardness (av. 2365 g versus 1853 g), while the cheese stored at 13°C had more adhesiveness (av.18.3 versus 11.8). At 60% compression, the control cheese stored at 5°C had the highest hardness, as it was the only cheese that did not fracture during compression. Cheeses stored at 13°C melted faster (1.39 versus 1.29 mm/s) and further (82.5% versus 75.5% height reduction) than those stored at 5°C. Adding either adjunct cultures or raising the storage temperature can accelerate the aging of cheese thus changing its textural and melting properties. Loss of a fracture point during TPA using 60% compression is a characteristic of cheese ripening. [ABSTRACT FROM AUTHOR]

The effect of protein-to-fat ratio (PFR) of cheese milk on the composition and yield of Cheddar cheese was investigated. Six cheesemaking trials, each with 4 different milk PFRs randomly selected from 24 target values in the range 0.70 to 1.15, were undertaken. The mean protein content of the cheese milks was 3.66 ± 0.1% (w/w). Cheese manufacture was standardized for starter-to-protein ratio (0.38 kg/kg protein), rennet-to-protein ratio (317 chymosin unit/kg protein), firmness of gel at cut (40 Pa), pH at set (6.55-6.6), pH at whey drainage (6.15) and pH at curd salting (5.25). The PFR values were divided into three groups (low, LPFR: 0.7 to 0.85; medium, MPFR: 0.88 to 1.0; and high, HPFR: 1.0 to 1.15) for statistical analysis using one-way analysis of variance (ANOVA). Linear regression analysis of the data was used to establish potentially significant relationships between the PFR of the cheese milk and the response variables such as cheese moisture and yield. Increasing the PFR significantly (P < 0.05) increased the levels of cheese moisture, protein, Ca and P, but significantly reduced the levels of moisture-in-non-fat substances, fat-in-dry matter and salt-in-moisture. The actual yield (YA) of the LPF cheese (11.73 kg/100 kg cheese milk) was significantly higher than the yield of the MPF (10.78 kg/100 kg) or HPF (10.33 kg/100 kg) cheeses. YA decreased linearly with PFR at a rate of of - 0.49 kg/100 kg cheese milk for every 0.1 unit increase in PFR. Cheese yield was also expressed as normalized yield, YAFPRM, which was defined as kg cheese per 100 kg milk with reference levels of fat (4.1%, w/w) and protein (3.7 %, w/w). In contrast to actual yield, YAFPRM increased significantly with PFR by 0.14 kg/100 kg milk for every 0.1 unit increase in PFR. The mean YAFPRM for the LPF cheese (10.74 kg/100 kg milk) was significantly lower than for the MPF cheese (10.91 kg/100 kg milk) which in turn was lower than for the HPF cheese (11.19 kg/100 kg milk). Consistent with the trend for YAFPRM, the mean percentage milk fat recovered in the HPF cheese (88.3) was significantly higher than for the MPF (87.7) or LPF (86.5) cheeses. [ABSTRACT FROM AUTHOR]

Mixtures of emulsifying salts (ES) are often used in the manufacture of process cheese (PC). Although ES are known to stabilize PC by interacting with cheese components, such as, casein and Ca phosphate, their underlying mechanisms of interaction are still not clearly elucidated. Objective of this study was to investigate how binary ES mixtures influence PC functionality. Three types of binary ES mixtures were prepared by combining trisodium citrate (TSC) with disodium orthophosphate (DSP), tetrasodium pyrophosphate (TSPP) or sodium hexametaphosphate (SHMP). For a total ES concentration of 3% (w/w), five different proportions (0.25:2.75, 0.875:2.125, 1.5:1.5, 2.125:0.875 and 2.75:0.25) of these mixtures were used. PC were made with constant pH (5.6±0.05) and moisture content (39.2±0.5%) using 4 month old natural Cheddar cheese as base. Functional and microstructural properties were studied using small amplitude oscillatory rheology, texture profile analysis (TPA), UW-Meltprofiler and fluorescence microscopy. The state of Ca and phosphorous (P) in cheese was determined by acid-base titration and by measuring the amount of insoluble Ca and P. The rheological parameter, loss tangent, and meltability increased while hardness (from TPA) decreased in mixtures that had high proportions of TSC or SHMP but the opposite trend was observed in mixtures that had high ratios of DSP or TSPP. The % insoluble Ca or P as % of total Ca or P increased with increasing amount of phosphate in mixtures of phosphate-based ES with TSC. Acid-base titration indicated that various types of Ca-phosphate interaction ocurred in cheese depending on the types of ES used. These results suggested that ES interacted with cheese components by several mechanisms, such as, dispersion of the original insoluble Ca phosphate, formation of new Ca salts and casein polymerization. A greater understanding of how ES mixtures influence cheese properties will help manufacturers to control the functional behavior of PC. [ABSTRACT FROM AUTHOR]

Presents abstracts of several studies on perspectives about raw milk cheeses. "Survival of Escherichia coli in Cheddar and Colby Cheese," by D. R. Henning; "Use of Heat-Treated Cheesemilk to Make High Quality Cheddar Cheese," by B. Luth; "Approaches to Ensuring the Safety of Raw Milk Cheeses," by C. Donnelly; "An Integrated Approach to the Safety of Raw Milk Cheeses," by P. S. Kindstedt.

Presents abstracts of several studies submitted for the American Dairy Science Association Dairy Foods Graduate Paper Contest. "Elucidation of the Role of Chymosin-Mediated Proteolysis in Texture Development During Cheddar Cheese Ripening," by J. A. O'Mahony, J. A. Lucey and P. L. H. McSweeney; "Compositional Factors Associated With Calcium Lactate Crystal Formation in Naturally Smoked Cheddar Cheese," by P. Rajbhandari and P. S. Kindstedt; "Influence of Calcium, Phosphorus, Residual Lactose, and Salt-to-Moisture ratio on Cheese Quality: pH Changes During Ripening," by P. Upreti, P. S. Lehtola and L. E. Metzger; "Effect of Starter Inoculation Rates and Incubation Temperatures on Physical Properties of Yogurt," by W. J. Lee and J. A. Lucey.

Previous research demonstrated that image analysis can accurately and precisely measure the area occupied by calcium lactate crystals on the surface of smoked Cheddar cheese. Naturally smoked cheese is well suited for image analysis because the dark discolored smoked surface contrasts sharply with white calcium lactate crystals. Uncolored cheese is more problematical because of insufficient contrast between crystal and background. The objective of this study was to modify the previous image analysis method to measure calcium lactate crystals on uncolored Cheddar. Combinations of image contrast and sharpening settings of the digital camera and light options were systematically evaluated to identify settings that optimized the contrast between white crystals and the straw colored cheese background. Five replicate analyses of an uncolored cheese surface containing crystals were performed using the modified settings. The area occupied by crystals was determined to be 4.85 ± 0.16% of total surface area. The coefficient of variation of 3.26% was comparable to repeatability measurements previously reported for smoked Cheddar. The thresholding error (error of underestimation) for the 5 replicate measurements was 0.05%, which was less than that previously reported with smoked Cheddar. Thus, the efficacy of the revised image analysis method was comparable to that of the original method. The revised method was used to evaluate crystal growth on a smoked surface and a non-smoked (uncolored) surface, respectively, from the same Cheddar cheese sample that was stored for 10 wk under conditions chosen to accelerate crystal growth (1°C , loose packaging). The percentage of total surface area occupied by crystals increased in a non-linear manner from 0 to ca. 4.5% for both smoked and non-smoked surfaces. The pattern of area increase for both smoked and non-smoked surfaces conformed most closely to a second order polynomial relationship (R2=0.97-0.98). Thus, crystal growth on uncolored cheese was effectively quantified using the revised image analysis method. [ABSTRACT FROM AUTHOR]

Sliced process cheese (PC) is produced using a chill roll apparatus, which enables hot cheese to quickly cool as it revolves over a cold drum. Viscosity of hot melted cheese and tensile strength of the cooled cheese sheet are key characteristics in PC processing with a chill roll apparatus. Model pasteurized PC slices were prepared from Cheddar cheeses with 2.5% of various types of emulsifying salts (ES); trisodium citrate (TSC), disodium phosphate (DSP), tetrasodium pyrophosphate (TSPP) and sodium hexametaphosphate (SHMP). Cheese mixture was heated at 86°C using a Stephan cooker. Hot melted cheeses were poured into thin plastic bags and rolled to a thickness of 2 mm. Moisture content of model PC was 46%, which is common for pasteurized sliced PC in Japan. A modified Bostwick-type consistometer was used to determine the flowability of hot melted cheeses immediately after cooking. A burst test which is a large deformation test using a ball probe was performed to create a texture map of the PC slices made with different types of ES. Peelability of PC measured by a Yamaden creep meter was also evaluated as a textural property. Melting properties were analyzed using the Schreiber test. Water soluble protein as a % of total protein of cheese was measured. PC made with TSPP exhibited the lowest flow and meltability. There was no significant difference between TSC cheese and DSP cheese for flow and meltability. The texture map demonstrated that there were no significant differences in the burst stress of TSC and DSP cheeses. However, there were significant differences (P < .0001) in burst strain. TSPP and SHMP cheese had good peelability values, while TSC cheese and DSP cheese had poor peelability. There were large amounts of water soluble protein in TSC and DSP cheese (95% and 85%, respectively), while lower levels were observed in TSPP and SHMP cheeses. Water soluble protein levels may be related to the peelability of PC slices. This study indicated that different types of ES influenced the characteristics of PC that were important for use on a chill roll apparatus. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the application of microfiltration (MF) and/or the raw milk lactoperoxidase system (LP) to improve the safety of raw milk cheeses. For this purpose, Escherichia coli K12 was selected to be added to raw milk for studying survival as a nonpathogenic surrogate organism for pathogenic E. coli and Salmonella spp. Five replications of 6 treatments of Cheddar cheese were manufactured. Each replication involved separation of skim and cream and microfiltration of a portion of the skim with 1.4 μm pore size. Cheese milks were then prepared by blending skim and cream portions and proceeding with the treatments. The 6 treatments included: cheeses made from pasteurized milk, raw milk, raw milk inoculated with E. coli K12, raw milk inoculated with E. coli K12 + LP activation, raw milk inoculated with E. coli K12 + MF, and raw milk inoculated with E. coli K12 + MF + LP activation. E. coli counts were done at 1, 14, 30, 60, 90, and 120 days of ripening time. Results indicate that there was a significant (P < 0.05) decrease in E. coli populations in all cheeses during ripening. However there was a large variation in the counts among replications during ripening. In addition, no significant (P > 0.05) effect of treatments on E. coli populations in cheeses during ripening was observed. Also results based on the percent decrease of E. coli K12 during ripening, the decrease in E. coli population was similar among treatments. These results suggest that survival of E. coli K12 present in cheeses depends on the microenvironment (pH, aw) rather than the treatments given to the milk used for manufacturing cheese. Hence it is inferred that if we can lower the E. coli counts in the cheese milk, we will lower the number of E. coli in the cheese. Application of MF, LP and MF+LP led to an average percent reduction in E. coli counts by 75, 85, and 95% respectively. Hence, utilization of MF in combination with LP activation can be an effective technique in reducing the counts of E. coli in raw milk cheeses. [ABSTRACT FROM AUTHOR]

Fat reduction in cheese is associated with many textural and functional defects. The quality attributes of process cheese are greatly influenced by the composition and nature of base cheeses. The objective of this study was to evaluate textural, viscoelastic and functional characteristics of reduced fat process cheese made from exopolysaccharide (EPS)- containing Cheddar cheese. Reduced fat process cheeses were manufactured using a 50/50 mixture of young (2 days) and aged (6 months) reduced fat Cheddar cheeses made with EPS-producing or non-producing cultures. In addition, a full fat process cheese made with no EPS was also employed in this study. Moisture and fat were standardized to 40 and 32.5% for full fat cheese and 49 and 21% for reduced fat cheese respectively. Reduced fat process cheeses made from Cheddar cheese containing no EPS were firmer, and more chewy and gummy than those made from EPS-positive Cheddar cheese. Reduced fat process cheese manufactured from EPS-positive Cheddar cheese had lower viscoelastic moduli and increased meltability. Creep/recovery test showed that EPS-positive process cheese was more deformable and did not recover its original structure as much as the EPS-negative one did. Sensory results correlated well with instrumental data. The highest sensory scores were obtained when both young and aged cheeses contained EPS. Full fat cheese was harder, chewier, gummier and less deformable than reduced fat cheeses, which might be due to the lower moisture content in the former cheese. In conclusion, EPS-containing base cheese could be used to improve texture and functionality of reduced fat process cheese. [ABSTRACT FROM AUTHOR]

Feeding unsaturated fat alters the fatty acid profile of milk. Research has shown that dietary supplementation of soybean oil will alter the fatty acid profile in milk but not in the same manner as when feeding fish oil. Data are limited on fatty acid composition in milk when a combination of soybean and fish oils are fed. There is some evidence that increasing dietary concentration of vitamin E may affect fatty acid composition of milk, especially when feeding unsaturated fat. Even though sorbitol is being used in commercial feed, limited published data are available as to its effect on milk composition. Four lactating Holstein cows were used in a Latin square design for 3 wk periods, with milk collection occurring during wk 3 for composition analyses and production of cheddar cheese. Cows were fed 4 diets: 1) control diet (CNTL; 500 IU vitamin E), 2) 2% fish oil, 0.5% soybean oil, and 500 IU of vitamin E (FSO), 3) 2% fish oil, 0.5% soybean oil, and 2000 IU of vitamin E (FSOE), and 4) 1% sorbitol (SORB, dry form; 500 IU vitamin E). Cheese yield was lower for the diets containing oil (7.8% versus 9.6%). Moisture and solids concentrations were similar among the cheeses. Crude protein concentrations (40.8, 49.2, 50.2, and 43.1%, dry basis, respectively) tended to be lower for cheeses made from cows fed the control diet. Fat concentration tended to be lower in cheese from cows fed the FSOE diet (44.1, 31.2, 29.2, and 44.0%, dry basis, respectively). Regarding texture profile analysis, cheeses made from cows fed the FSOE and FSO diets were harder than those from CNTL and SORB (13.4 and 15.7, versus 5.8 and 6.6 kgf, respectively). Oil supplemented diets resulted in lower proportions of palmitic, stearic, linoleic, and saturated fatty acids and higher proportions of unsaturated fatty acids in milk. FSOE resulted in the highest proportion of unsaturated fatty acids in milk. These results suggest that milk from cows fed fish-oil diets will likely have less fat content, and thus the characteristics of the cheese, such as yield, texture, and protein-fat ratio, will be altered. [ABSTRACT FROM AUTHOR]

Functional attributes of Cheddar cheese used in a wide variety of food products are critical to its applications and consumer acceptance. Functionality in turn is determined largely by the extent of hydrolysis. The objective of this study was to investigate the influence of coagulants and ripening temperature on the proteolysis in cheese, particularly the hydrolysis of large and hydrophobic peptides. Triplicate 400-kg batches of Cheddar cheese were made in open vats using Lactococcus lactis as starter with additional Lac- L. lactis and Lactobacillus helveticus adjunct cultures. Chymosin and Cryphonectria parasitica rennet, individually and combined (61/39%) were used as coagulants at 1X and 4X levels. Each of the above treatments were ripened for 6 months at 40 and 55°F. Proteolysis was monitored by RP-HPLC on a C8 Brownlee column with a Beckman Gold system. Trifluoroacetic acid (0.1%) and acetonitrile (80%) were used as the mobile phase, with the concentration of acetonitrile being raised from 40 to 60% over 30 min. Peptides over 3 kDa in size, and eluting at elution times ranging between 25 and 35 min were monitored. Changes in the peptide profiles over this time range occurred between 1 week and 2 months in cheeses at both 40 and 55°F. Total peak areas reduced between 2 and 4 months, indicating that these observed peptides may have gone from being relatively hydrophobic to hydrophilic, thus loosely binding with the column and eluting earlier. Cheeses having higher level of coagulant (4X) and at 55°F had ~90% of the intact caseins and large peptides hydrolyzed in 2 months. Chymosin, C. parasitica rennet and their combination did give peptide profiles that were apparently different at 2 and 4 months. These results suggest that higher levels of coagulants used in combination in cheese ripened at 55°F will hydrolyze large hydrophobic peptides that may play a role in functionality. [ABSTRACT FROM AUTHOR]

Young Cheddar cheese is characterized by excessive firmness, curdy and rubbery texture, poor meltability and lack of flavor. In a previous study, exopolysaccharide (EPS)-producing cultures improved melting, viscoelastic and textural properties of young reduced fat Cheddar cheese (Hassan et al., JDS 88: 4221-4227; Awad et al., JDS 88: 4204-4213). Since base cheese has a direct impact on the characteristics of process cheese, we hypothesized that the use of EPS-producing cultures in making base Cheddar cheese would allow the utilization of more young cheeses in making process cheese. Reduced fat process cheeses were manufactured using young (2-day) or 1-month old reduced fat Cheddar cheese made with EPS-producing or non-producing cultures. Moisture and fat of process cheese were standardized to 49 and 21%, respectively. Enzyme modified cheese (EMC) was incorporated to provide flavor of aged cheese. Exopolysaccharide-positive process cheese was softer, less chewy and gummy, and more deformable than the EPS-negative cheeses. Process cheese manufactured from EPS-containing Cheddar cheese exhibited lower viscoelastic moduli and softening temperature. The hardness, chewiness and viscoelastic moduli were lower in process cheese made from 1-month old Cheddar cheese than those in process cheese made from 2-day old cheese. Larger differences were observed between process cheeses made from 1-month old EPS-positive and negative base cheeses than those between process cheeses made from the corresponding young base cheeses. This could be because of more extensive proteolysis in the EPS-positive Cheddar cheeses than in the EPS-negative cheeses due to their higher moisture content. Sensory scores for texture of EPS-positive process cheeses were higher than those of the EPS-negative ones. [ABSTRACT FROM AUTHOR]

Cheese consumption across America has been on the rise for many years in the United States. The demand and market for cheese products are continuing to increase both a domestically and internationally. Hilmar Cheese Company, located in the Central Valley, of California is currently the largest single site producer of wholesale cheddar cheese and whey products in the United States. The company was founded in 1984 by twelve Jersey dairy farmers who wanted to capitalize on the value of their high-component milk. Today Hilmar Cheese Company processes the world's largest volume of Jersey milk, over 11 million pounds per day, with over 600 employees. The company prides itself in maintaining "mutually beneficial relationships between company owners, employees, milk producers, customers and the local community." To keep abreast the growing demand for their product, they have broken ground in Dalhart, Texas to install a second processing plant. Dalhart is located in the northwest panhandle of Texas, with a population of 7500 people; the local economy flourishes off agriculture. The Dalhart expansion of Hilmar is to be made in two phases. It is anticipated that the plant will originally have the capacity to process about 5 million pounds of milk per day with room for future expansion. The company expects to hire approximately 120 local residents, and hopes to contract their milk supply exclusively from Jersey herds. With such an expansion upon Texas's Dairy Industry one must consider the impacts the expansion could have. One may expect changes to be seen in areas such as cattle numbers, milk supply, milk prices, dairy cattle replacement availability and replacement pricing. The installation of the new plant can be expected to have local, regional and national effects on the economy in various facets. [ABSTRACT FROM AUTHOR]

Angiotensin-I-converting enzyme (ACE) increases blood pressure by converting angiotensin-I to angiotensin-II, potent vasoconstrictor and by degrading bradykinin, a vasodilatory peptide. ACE-inhibitory peptides have been isolated in various cheeses, released as a result of proteolysis during ripening. The objectives were i) to study the influence of proteolysis on the release of ACE-inhibitory peptides in probiotic Cheddar cheeses during ripening and ii) to isolate, purify and identify these peptides. Cheddar cheeses were made with starter lactococci and Lactobacillus casei 279 or L. paracasei LAFTI®L26. ACE-inhibitory activities of the water-soluble fraction of the cheeses were measured by spectrophotometric assay. Peptides were purified using reverse-phase HPLC and identified by automated Edman degradation protein sequencer and mass spectrophotometer. Presence of probiotic organism increased proteolysis in Cheddar cheeses during the nine months ripening at 4°C. The IC50 (concentrations of ACE needed to inhibit 50% of ACE activity) was highest after six months of ripening in the probiotic cheeses (0.23- 0.25 mg/mL) compared to nine months in cheeses without probiotic (0.28 mg/mL). The water-soluble extract of each cheese was subjected to several stages of chromatography fractionation. Inhibitory activity found in the crude fractions ranged from 0.1 to 0.8 mg/mL. The fraction with the highest activity was purified by a second stage chromatography. Various ACEinhibitory peptides were found, which corresponded to the αs-casein N terminal peptides, f(1-9), f(1-6), f(24-32) and β-casein N-terminal peptides, f(193-209) and f(191-209). Our results suggested that ACE inhibition in Cheddar cheeses was dependent on proteolysis. Probiotic organisms used in this study can be added successfully in Cheddar cheese in order to produce bioactive peptides. [ABSTRACT FROM AUTHOR]

Calcium lactate crystals (CLC) in hard cheeses continue to be an expense to the cheese industry. Major causes of L(+) lactate crystals appears to be 1) increasing protein concentration in cheese milk, which increases cheese yield and 2) type of packaging, which influences serum calcium migration. The research investigates the effects of protein concentration and packaging on migration of serum calcium to the surface of cheese during storage and CLC occurrence. Total and soluble calcium, phosphorus, lactic acid and citrate were measured in cheeses made with skim milk (SM1, 3.14% protein) and skim milk supplemented with ultrafiltered milk (UF) (CSM1, 6.80% protein) or NFDM (CSM2, 6.80% protein). Vacuum and gas flushed cheeses were analyzed for total and soluble calcium, lactic acid and salt at four specific distances from the center of cheeses made from whole milk (WM1) and whole milk supplemented with UF (CWM1). Cheeses made from CSM1 and CSM2, had 26% higher total calcium (1367 mg/100g and 1375 mg/100g cheese, respectively), than cheeses made from SM1 (1066 mg/100g of cheese). At pH 5.2, soluble calcium in cheeses made from CSM1 and CSM2, (550 mg/100g and 558 mg/100g cheese, respectively) was 25% higher than cheeses made from SM1 (441 mg/100g of cheese). At week 10, higher (8%) total and soluble calcium were observed on surfaces of cheeses made from WM1 that were gas flushed compared to the center of the cheese blocks. In contrast, hardly any change was observed in vacuum packaged cheeses, showing that migration of serum calcium to the surface of cheeses was more prevalent in gas flushed cheeses. These results confirm that the risk of occurrence of CLC in cheese increases with concentration of milk proteins. Additionally, loose packaging enhances serum calcium migration to cheese surfaces, increasing the concentration of calcium ions and the risk of CLC. [ABSTRACT FROM AUTHOR]

The texture of reduced fat Cheddar cheese is typically rubbery, dry and grainy. In previous studies (Awad et al., JDS 88:4204-4213; Hassan et al., JDS 88:4221-4227), an exopolysaccharide-(EPS) producing culture improved textural, melting and viscoelastic properties of reduced fat Cheddar cheese. However, this EPS-positive cheese developed bitterness after 2 to 3 months of ripening due to increased residual chymosin activity. We hypothesized that the reduced amount of chymosin needed to coagulate ultrafiltered milk might result in reduced residual chymosin activity and bitterness in cheese. The objective of this study was to improve the texture and flavor of reduced fat Cheddar cheese using a combination of EPS-producing cultures and ultrafiltration (UF). Reduced fat Cheddar cheeses were manufactured with EPS-producing and non-producing cultures using skim milk or ultrafiltered skim milk (1.2 X) adjusted to a casein/fat ratio of 1.35. The EPS-producing culture increased yield, moisture in nonfat substance, and residual chymosin activity in reduced fat Cheddar cheese. In addition, EPS-positive cheese was softer, and less gummy and rubbery than the EPS-negative cheese. The viscoelastic moduli were higher in young EPS-negative reduced fat cheese than in the EPS-positive cheese. After 3 months of ripening, whereas the viscoelastic moduli increased in the EPS-positive cheese, they decreased in the EPS-negative cheese. The creep/recovery test showed that young EPS-positive cheese was less rigid and more deformable than EPS-negative cheese. Lower (P < 0.05) residual chymosin activity was found in cheese made from UF milk compared to that in cheese made from control milk. The low UF concentration level (1.2X) did not affect the textural characteristics of cheese. Panelists reported that UF-EPS-positive cheese was less (P < 0.05) bitter than EPS-positive cheese made from control milk. Using an EPS-producing culture improved the texture and UF at 1.2 X reduced bitterness of reduced fat Cheddar cheese, which has commercial implications in the manufacture of this type of cheese. [ABSTRACT FROM AUTHOR]

In cultured dairy products, non-starter lactic acid bacteria (NSLAB) are only important in ripening and ripened cheeses. They mainly comprise facultatively homofermentative lactobacilli, e.g., Lactobacillus casei, Lb. paracasei. Lb. curvatus and Lb. plantarum, although pediococci and enterococci are found in lower numbers in some cheeses. Some obligate heterofermentative species, e.g.. Lb. brevis are occasionally found. During ripening the NSLAB grow from low numbers of c. 102to 108 cfu/g over several weeks or months depending on the cheese and its ripening temperature. NSLAB require an energy source for growth but lactose has been metabolised completely to lactate by the time exponential growth of NSLAB occurs. Citrate, arginine, sugars in lysed starter cells and in the milk fat globule membrane have been suggested as energy sources in cheese. The chromosome of at least one strain has been completely sequenced. Generally it is believed that their source is post pasteurisation contamination from equipment and air. However, many strains resist pasteurisation implying that raw milk is also a major source. The effect of NSLAB on cheese flavour has been studied for over 120 years with variable results. More recent studies have generally shown a positive effect of selected strains on cheese flavour formation. During ripening, they are responsible for converting L lactate to D lactate and cause development of white spots on aged Cheddar cheese due to calcium-D-lactate formation. Many NSLAB metabolise citrate to formate and acetoin; they also metabolise and amino acids, especially methionine to potent S containing flavour compounds like niethanethiol and its degradation compounds, as well as various S containing esters. These and other aspects of NSLAB will be discussed in the presentation. [ABSTRACT FROM AUTHOR]