Functionality of process cheese made from Cheddar cheese with various rennet levels and high-pressure processing treatments.

Due to its versatility and shelf stability, process cheese is gaining interest in many developing countries. The main structural component (base) of most processed cheese formulations is young Cheddar cheese that has high levels of intact casein. Exporting natural Cheddar cheese base from the United States to distant overseas markets would require the aging process to be slowed or reduced. As Cheddar cheese ripens, the original structure is broken down by proteolysis and solubilization of insoluble calcium phosphate. We explored the effect of varying rennet levels (we also used a less proteolytic rennet) and application of high-pressure processing (HPP) to Cheddar cheese, as we hoped these treatments might limit proteolysis and concomitant loss of intact casein. To try to retain high levels of insoluble Ca, all experimental cheeses were made with a high-draining pH and from concentrated milk. To compare our intact casein results with current practices, we manufactured a Cheddar cheese that was prepared according to typical industry methods (i.e., use of unconcentrated milk, calf chymosin [higher levels], and low draining pH value [∼6.2]). All experimental cheeses were made from ultrafiltered milk with protein and casein contents of ∼5.15% and 4.30%, respectively. Three (low) rennet levels were used: control (38 international milk clotting units/mL of rennet per 250 kg of milk), and 25% and 50% reduced from this level. All experimental cheeses had similar moisture contents (∼37%) and total Ca levels. Four days after cheese was made, half of the experimental samples from each vat underwent HPP at 600 MPa for 3 min. Cheddar cheese functionality was monitored during aging for 240 d at 4°C. Cheddar cheese base was used to prepare process cheese after aging for 14, 60, 120, 180, and 240 d. Loss tangent (LT) values of cheese during heating were measured by small strain oscillatory rheology. Intact casein levels were measured using the Kjeldahl method. Acid or base titrations were used to determine the buffering capacity and insoluble Ca levels as a percentage of total Ca. The LTmax values (an index of meltability) in process cheese increased with aging for all the cheese bases; the HPP treatment significantly decreased LTmax values of both base (natural) and process cheeses. All experimental cheeses had much higher levels of intact casein compared with typical industry-make samples. Process cheese made from the experimental treatments had visually higher stretching properties than process cheese made from Cheddar with the typical industry-make procedure. Residual rennet activity was not affected by rennet level, but the rate of proteolysis was slightly slower with lower rennet levels. The HPP treatment of Cheddar cheese reduced residual rennet activity and decreased the reduction of intact casein levels. The HPP treatment of Cheddar cheese resulted in process cheeses that had slightly higher hardness values, lower LTmax values, and retained higher storage modulus values at 70°C. We also observed that the other make procedures we used in all experimental treatments (i.e., using a less proteolytic chymosin, using a concentrated cheese milk, and maintaining a high draining pH value) had a major effect on retaining high levels of intact casein.

Slower proteolysis in Cheddar cheese made from high-protein cheese milk is due to an elevated whey protein content.

A growing number of companies within the cheese-making industry are now using high-protein (e.g., 4-5%) milks to increase cheese yield. Previous studies have suggested that cheeses made from high-protein (both casein and whey protein; WP) milks may ripen more slowly; one suggested explanation is inhibition of residual rennet activity due to elevated WP levels. We explored the use of microfiltration (MF) to concentrate milk for cheese-making, as that would allow us to concentrate the casein while varying the WP content. Our objective was to determine if reducing the level of WP in concentrated cheese milk had any impact on cheese characteristics, including ripening, texture, and nutritional profile. Three types of 5% casein standardized and pasteurized cheese milks were prepared that had various casein:true protein (CN:TP) ratios: (a) control with CN:TP 83:100, (b) 35% WP reduced, 89:100 CN:TP, and (c) 70% WP reduced, 95:100 CN:TP. Standardized milks were preacidified to pH 6.2 with dilute lactic acid during cheese-making. Composition, proteolysis, textural, rheological, and sensory properties of cheeses were monitored over a 9-mo ripening period. The lactose, total solids, total protein, and WP contents in the 5% casein concentrated milks were reduced with increasing levels of WP removal. All milks had similar casein and total calcium levels. Cheeses had similar compositions, but, as expected, lower WP levels were observed in the cheeses where WP depletion by MF was performed on the cheese milks. Cheese yield and nitrogen recoveries were highest in cheese made with the 95:100 CN:TP milk. These enhanced recoveries were due to the higher fraction of nitrogen being casein-based solids. Microfiltration depletion of WP did not affect pH, sensory attributes, or insoluble calcium content of cheese. Proteolysis (the amount of pH 4.6 soluble nitrogen) was lower in control cheeses compared with WP-reduced cheeses. During ripening, the hardness values and the temperature of the crossover point, an indicator of the melting point of the cheese, were higher in the control cheese. It was thus likely that the higher residual WP content in the control cheese inhibited proteolysis during ripening, and the lower breakdown rate resulted in its higher hardness and melting point. There were no major differences in the concentrations of key nutrients with this WP depletion method. Cheese milk concentration by MF provides the benefit of more typical ripening rates.

Effect of substituting whey cream for sweet cream on the textural and rheological properties of cream cheese.

In the manufacture of cream cheese, sweet cream and milk are blended to prepare the cream cheese mix, although other ingredients such as condensed skim milk and skim milk powder may also be included. Whey cream (WC) is an underutilized fat source, which has smaller fat droplets and slightly different chemical composition than sweet cream. This study investigated the rheological and textural properties of cream cheeses manufactured by substituting sweet cream with various levels of WC. Three different cream cheese mixes were prepared: control mix (CC; 0% WC), cream cheese mixes containing 25% WC (25WC; i.e., 75% sweet cream), and cream cheese mixes with 75% WC (75WC; i.e., 25% sweet cream). The CC, 25WC, and 75WC mixes were then used to manufacture cream cheeses. We also studied the effect of WC on the initial step in cream cheese manufacture (i.e., the acid gelation process monitored using dynamic small amplitude rheology). Acid gels were also prepared with added denatured whey proteins or membrane proteins/phospholipids (PL) to evaluate how these components affected gel properties. The rheological, textural, and sensory properties of cream cheeses were also measured. The WC samples had significantly higher levels of PL and insoluble protein compared with sweet cream. An increase in the level of WC reduced the rate of acid gel development, similar to the effect of whey phospholipid concentrate added to mixes. In cream cheese, an increase in the level of added WC resulted in significantly lower storage modulus values at temperatures <20°C. Texture results, obtained from instrumental and sensory analyses, showed that high level of WC resulted in significantly lower firmness or hardness values and higher stickiness compared with cream cheeses made with 25WC or CC cream cheeses. The softer, less elastic gels or cheeses resulting from the use of high levels of WC are likely due to the presence of components such as PL and proteins from the native milk fat globule membrane. The use of low levels of WC in cream cheese did not alter the texture, whereas high levels of WC could be used if manufacturers want to produce more spreadable products.

Effects of the depletion of whey proteins from unconcentrated milk using microfiltration on the yield, functionality, and nutritional profile of Cheddar cheese.

Some European dairies use low concentration factor microfiltration (MF) in their cheese plants. Removal of whey protein (WP) from milk before cheesemaking using microfiltration without concentration provides the opportunity to produce a value-added by-product, milk-derived whey. However, few studies have focused on the effects on cheese properties caused by the depletion of WP from cheese milk. Most studies have concentrated cheese milk using MF in addition to depletion of WP. In our approach, cheese milk was not concentrated during WP depletion using MF. We wanted to quantify residual WP levels in cheese made from MF milk and to explore whether WP depletion from milk would influence functionality, nutritional profile, and cheese quality during ripening. Casein (CN) contents for all milks were kept at ∼2.5%, to eliminate the confounding factor of concentration of CN, which was observed in some previous MF studies. Cheese milks had similar ratios of CN to fat. Three standardized milks were produced with various CN:true protein (TP) ratios: (a) control with a CN:TP ratio of 83:100, (b) 35% WP depletion, 89:100 CN:TP, and (c) 70% WP depletion, 95:100 CN:TP. Cheddar cheeses were made from MF milk with various WP depletion levels and aged for 9 mo, and their functionality was evaluated during ripening. We found no major differences in cheese composition or pH values between samples. Cheese yield, solids recovery, and nitrogen recovery were slightly higher in the 95:100 CN:TP cheeses compared with the control. These enhanced recoveries reflect that MF-treated milk started with a higher fraction of CN-based protein solids, rather than WP solids. The standardized milk from the 95:100 CN:TP treatment also had a slightly higher fat content compared with the control, likely helping to increase cheese yield. Rheological properties of cheeses during heating were similar between treatments. Hardness initially decreased with age for all cheeses due to proteolysis or solubilization, or both, of calcium phosphate. Maximum loss tangent (LT), an index of cheese meltability, was slightly lower for the control cheese until 30 d of ripening, but after 30 d, all treatments exhibited similar maximum LT values. The temperature where LT = 1 (crossover temperature), an index of softening point during heating, was slightly lower for MF cheese compared with the control cheeses during ripening. Microfiltration treatment had no significant influence on proteolysis. Sensory properties were similar between the cheeses, except for bitterness. Bitterness intensity was slightly lower in the MF cheeses than in the control cheeses and increased in all cheeses during ripening. We detected no major differences in the concentrations of key nutrients or vitamins between the various cheeses. Depletion of WP in cheese milk by MF did not negatively affect cheese quality, or its nutritional profile, and resulted in similar cheesemaking yields.

Behavior of stabilizers in acidified solutions and their effect on the textural, rheological, and sensory properties of cream cheese.

Stabilizers are routinely added during cream cheese manufacture to help prevent syneresis during storage. We investigated how different types of stabilizers affected the texture, rheology, and sensory properties of cream cheese. Cream cheeses were manufactured with 0.33% xanthan gum (XG), locust bean gum (LBG), guar gum (GG), or a combination (CBN) of these 3 stabilizers (0.11% of each). Rheological properties of solutions of the individual stabilizers and their combination (equal amounts) were also determined under conditions similar to the aqueous phase of cream cheese (0.6% gum, 1.8% NaCl, and pH 5). Dynamic small amplitude rheological properties of the cream cheeses were measured during heating from 5 to 80°C at the rate of 1°C/min and cooling at the same rate (because most cream cheese is hot packed/filled before cooling). Measured rheological parameters included storage modulus (G') and loss tangent. Hardness of cream cheeses was determined by texture profile analysis. Quantitative spectrum descriptive sensory analysis was also performed. Distinct differences were observed between the rheological properties of solutions of the individual stabilizers and the CBN containing all the stabilizers. Results showed that CBN solution formed a strong, thermally reversible gel due to synergistic interaction between stabilizers, whereas XG solution formed a weak gel that was not greatly affected by temperature. Solutions of LBG and GG behaved rheologically as entangled polymer solutions. In the high-temperature (>35°C) region, cream cheeses made with XG and CBN showed higher G' values compared with other cream cheeses. The G' values were higher for XG- and CBN-stabilized cream cheeses than LBG- and GG-stabilized cream cheeses at several temperature regions during the cooling cycle. The CBN-stabilized cream cheeses had higher hardness values than the cream cheeses manufactured with the individual stabilizers. Differences were observed between the sensory attributes of cream cheeses stabilized with CBN and those made with individual stabilizers. At low temperatures, the higher hardness and G' values of CBN-stabilized cream cheeses could be due to synergistic interaction between XG and galactomannans. The higher elasticity of XG-stabilized cream cheeses at high temperatures could be due to its higher thermal stability. This study showed that the stabilizers added during manufacture of cream cheese affected its texture, rheological, and sensory properties.

Low- and reduced-fat milled curd, direct-salted Gouda cheese: Comparison of lactose standardization of cheesemilk and whey dilution techniques.

Control of acidity is critical for cheese quality, as high acidity can be associated with poor flavor and textural attributes. We investigated an alternative method to control cheese acidity, specifically in low-fat (LF) and reduced-fat (RF) milled curd, direct-salted Gouda cheese, which involved altering the initial lactose content of cheesemilk. In traditional Gouda cheese manufacture, a critical technique to control acidity is whey dilution (WD); that is, partial removal of whey and its replacement with water. Direct standardization of the lactose content of milk during the ultrafiltration process could be a simpler and more effective technique to control cheese acidity. This study compared the effect of traditional WD at 2 different levels, 15 and 30% (WD15 and WD30), with the alternative approach of adjustment of the lactose content of milk using low-concentration-factor ultrafiltration (LCF-UF). The composition, texture, functionality, and sensory properties of these LF and RF Gouda cheeses were evaluated. A milled curd, direct-salted cheese manufacturing protocol was used. Milks used for cheesemaking had a lactose-to-casein (L:CN) ratio of approximately 1.8, which is the typical ratio found in milk, whereas milks prepared with lactose standardization (LS) were made from UF concentrated milks with water added during filtration to achieve a L:CN ratio of approximately 1.1. Cheeses made with LS exhibited lower lactose and lactic acid contents than WD30 and WD15, leading to significantly higher pH values in the cheese. Dynamic small-amplitude oscillatory rheology indicated that use of LS led to cheeses with a lower crossover temperature (melting point) than the cheeses made with WD. Cheeses made with LS had lower insoluble Ca contents, likely caused by the addition of water required to achieve the lower L:CN ratio in these milks. Sensory analysis also indicated that LS cheeses had lower acidity and softer texture. These results suggest that standardization of the L:CN ratio of milk could be a useful alternative to WD (or a curd rinse step) to reduce acidity in cheeses. In addition, LS could be used to help soften texture and increase meltability, if desired in lower-fat cheese types.

Effects of processing conditions on the texture and rheological properties of model acid gels and cream cheese.

Manufacture of cream cheese involves the formation of an initial acid-induced gel made from high-fat milk, followed by a series of processing steps including shearing, heating, and dewatering that complete the conversion of the acid gel into a complex cheese product. We investigated 2 critical parameters for their effect on the initial gel: homogenization pressure (HP) of the high-fat cheese milk, and fermentation temperature (FT). The impact of a low (10 MPa) and high (25 MPa) HP, and low (20°C) and high (26°C) FT were investigated for their effects on rheological and textural properties of acid-induced gels. Intact acid gels were sheared and heated to 80°C, and then their rheological properties were analyzed to help understand the effect of shearing/heating processes on the gel characteristics. The effect of HP on fat globule size distribution and the amount of protein not involved in emulsion droplets (i.e., in the bulk phase) were also studied. For cream cheese trials, a central composite experimental design was used to explore the effect of these 2 parameters (HP and FT) on the texture, rheology, and sensory properties of experimentally manufactured cream cheese. Storage modulus (G') and hardness values of cream cheeses were obtained from small amplitude oscillatory rheology tests and texture profile analysis, respectively. Quantitative spectrum descriptive sensory analysis was also performed. Consistency of acid gels (measured using a penetration test) increased with an increase in FT and with an increase in HP. Although stiffer acid-induced gels were formed at high FT, after the heating and shearing processes the apparent viscosity of the samples formed at high FT was lower than those formed at low FT. For the cream cheeses, significant prediction models were obtained for several rheological and textural attributes. The G' values at 8°C, instrumental hardness, and sensory firmness attributes were significantly correlated (r > 0.84); all these attributes significantly decreased with an increase in FT, and HP was not a significant parameter in the prediction models developed for these attributes. Significant interactions were observed between the HP and FT terms for these prediction models. Higher HP increased the amount of protein adsorbed at interface of fat globules but decreased bulk phase protein content (which may be important for crosslinking this gelled emulsion system). At higher FT temperature, coarser gel networks were likely formed. The combined effect of a coarser acid gel network at high FT, and less bulk phase casein available for crosslinking the acidified emulsion gel with an increase in HP, could have contributed to the lower stiffness/firmness observed in cream cheese made under conditions of both high FT and high HP. Stickiness of cream cheese greatly increased under conditions of high FT and high HP, whereas the sensory attributes cohesiveness of mass and difficulty to dissolve decreased. This study helped to better understand the complex relationships between the initial acid-induced gel phase and properties of the (final) cream cheese.

Investigating the properties of high-pressure-treated, reduced-sodium, low-moisture, part-skim Mozzarella cheese during refrigerated storage.

We proposed that the performance and sensory properties of reduced-Na, low-moisture, part-skim (LMPS) Mozzarella cheese could be extended by the application of high hydrostatic pressure (HHP) to cheese postmanufacture and thereby decrease microbial and enzymatic activity. Fermentation-produced camel chymosin was also used as a coagulant to help reduce proteolysis during storage. Average composition of the LMPS Mozzarella cheeses was 48.6 ± 0.6% moisture, 22.5 ± 0.4% fat, 24.5 ± 0.6% protein, and 1.0 ± 0.1% NaCl. Blocks of cheeses were divided into 3 groups randomly after manufacture and stored at approximately 4°C for 20 wk. The control group was not HHP treated. Two weeks after manufacture, 2 groups of cheese samples were treated with HHP at 500 or 600 MPa for 3 min and then returned to storage at approximately 4°C. Analysis was performed during 20 wk of storage after cheese manufacture. Texture profile analysis (TPA) and dynamic low-amplitude oscillatory rheology were used to monitor cheese functionality. Quantitative descriptive analysis was conducted with 9 trained panelists using a 15-point scale to evaluate texture and flavor attributes of unmelted cheese as well as cheeses melted on pizzas. Pressure treatments at 500 and 600 MPa resulted in approximately 1 and 2 log reduction in the numbers of starter culture, respectively, compared with the control when measured 1 d after HHP treatment. Starter numbers continued to decrease in all cheeses over the 20 wk of storage, but the decrease was larger in the HHP-treated cheeses. Even though the initial numbers of nonstarter lactic acid bacteria were the same in all cheeses, the numbers of these bacteria increased faster in the control cheeses. High-pressure treatment of LMPS Mozzarella cheese resulted in an initial (1 d after HHP treatment) increase in pH, but by 2 wk after HHP treatment there was no statistical difference in pH values between control and HHP-treated samples. Immediately after treatment, HHP-treated cheeses exhibited significantly lower TPA and sensory (unmelted) hardness. However, by 14 wk after pressure treatment, the 600-MPa HHP-treated cheese had significantly higher TPA compared with control or 500-MPa HHP-treated cheeses. Sensory panels also indicated that by 14 wk after HHP treatment, the 600-MPa treated samples were significantly firmer than the control or 500-MPa treated cheeses. Compared with control cheese, cheeses treated at 600 or 500 MPa exhibited lower water-soluble nitrogen values at 6 and 10 wk after pressure treatment, respectively. By 10 wk after pressure treatment, the levels of intact αS1-casein were significantly higher in all HHP-treated cheeses compared with the control. Pizza sensory panels indicated that 600-MPa treated cheese was significantly chewier and exhibited lower blister quantity and higher strand thickness compared with control cheeses. High hydrostatic pressure treatment of low-Na, LMPS Mozzarella cheese could result in the extension of its desired baking characteristics when the cheese is stored at refrigerated temperature.

Effect of standardizing the lactose content of cheesemilk on the properties of low-moisture, part-skim Mozzarella cheese.

The texture, functionality, and quality of Mozzarella cheese are affected by critical parameters such as pH and the rate of acidification. Acidification is typically controlled by the selection of starter culture and temperature used during cheesemaking, as well as techniques such as curd washing or whey dilution, to reduce the residual curd lactose content and decrease the potential for developed acidity. In this study, we explored an alternative approach: adjusting the initial lactose concentration in the milk before cheesemaking. We adjusted the concentration of substrate available to form lactic acid. We added water to decrease the lactose content of the milk, but this also decreased the protein content, so we used ultrafiltration to help maintain a constant protein concentration. We used 3 milks with different lactose-to-casein ratios: one at a high level, 1.8 (HLC, the normal level in milk); one at a medium level, 1.3 (MLC); and one at a low level, 1.0 (LLC). All milks had similar total casein (2.5%) and fat (2.5%) content. We investigated the composition, texture, and functional and sensory properties of low-moisture, part-skim Mozzarella manufactured from these milks when the cheeses were ripened at 4°C for 84d. All cheeses had similar pH values at draining and salting, resulting in cheeses with similar total calcium contents. Cheeses made with LLC milk had higher pH values than the other cheeses throughout ripening. Cheeses had similar moisture contents. The LLC and MLC cheeses had lower levels of lactose, galactose, lactic acid, and insoluble calcium compared with HLC cheese. The lactose-to-casein ratio had no effect on the levels of proteolysis. The LLC and MLC cheeses were harder than the HLC cheese during ripening. Maximum loss tangent (LT), an index of cheese meltability, was lower for the LLC cheese until 28d of ripening, but after 28d, all treatments exhibited similar maximum LT values. The temperature where LT=1 (crossover temperature), an index of softening point during heating, was higher for MLC and LLC cheese at 56 and 84d of ripening. The LLC cheese also had lower blister color and less stretch than MLC and HLC cheese. Adjusting the lactose content of milk while maintaining a constant casein level was a useful technique for controlling cheese pH, which affected the texture, functionality, and sensory properties of low-moisture, part-skim Mozzarella cheese.

Angiotensin-I-converting enzyme-inhibitory peptides in commercial Wisconsin Cheddar cheeses of different ages.

Bioactive peptides, including angiotensin-I-converting enzyme-inhibitory (ACEI) peptides, were investigated in commercially produced Wisconsin Cheddar cheeses that ranged in age from ≤ 6d to more than 2 yr. The ACEI activity of cheese was determined in water-soluble extracts (WSE) that were fractionated for components with molecular weight (MW) ≤ 3,000 Da, and peptides identified using HPLC and tandem mass spectrometry. The number of types of bioactive peptides increased with an increase in ripening time. Six of the identified ACEI peptides, Ile-Pro-Pro (IPP), Val-Pro-Pro (VPP), Glu-Lys-Asp-Glu-Arg-Phe (EKDERF), Val-Arg-Tyr-Leu (VRYL), Tyr-Pro-Phe-Pro-Gly-Pro-Ile-Pro-Asn (YPFPGPIPN), and Phe-Phe-Val-Ala-Pro (FFVAP), with known high ACEI activity (low IC50 values, the concentration needed to inhibit ACE to 50% of its original activity) were synthesized and used to quantify the amounts of these peptides in various cheese extracts. The concentrations of these 6 ACEI peptides increased up to a certain stage of ripening. The maximum contents of IPP, VPP, and EKDERF were 2.8, 7.4, and 5.3mg/100 g of cheese, respectively, and these levels were found in a 1-yr-old Cheddar cheese sample. The maximum content of VRYL (7.5mg/100 g of cheese) was found in a 2-yr-old Cheddar cheese sample, whereas the maximum content of YPFPGPIPN (6.8 mg/100 g of cheese) was found in a 6-mo-old Cheddar cheese sample. Trace amounts of FFVAP were found in these cheeses. Aged Cheddar cheese was found to be a rich source of ACEI peptides even though large differences exist between cheeses from different manufacturers.

Low-sodium Cheddar cheese: Effect of fortification of cheese milk with ultrafiltration retentate and high-hydrostatic pressure treatment of cheese.

Low-sodium cheeses often exhibit an acidic flavor due to excessive acid production during the manufacturing and the initial stage of ripening, which is caused by ongoing starter culture activity facilitated by the low salt-in-moisture levels. We proposed that this excessive starter-induced acidity could be prevented by the fortification of cheese milk with ultrafiltration (UF) retentates (to increase curd buffering), and by decreasing microbial activity using the application of high-hydrostatic pressure (HHP) treatment (that is, to reduce residual starter numbers). Camel chymosin was also used as a coagulant to help reduce bitterness development (a common defect in low-sodium cheeses). Three types of low-Na (0.8% NaCl) Cheddar cheeses were manufactured: non-UF fortified, no HHP applied (L-Na); UF-fortified (cheese milk total solids = 17.2 ± 0.6%), no HHP applied (L-Na-UF); and UF-fortified, HHP-treated (L-Na-UF-HHP; 500 MPa for 3 min applied at 1 d post-cheese manufacture). Regular salt (2% NaCl) non-UF fortified, non-HHP treated (R-Na) cheese was also manufactured for comparison purposes. Analysis was performed at 4 d, 2 wk, and 1, 3, and 6 mo after cheese manufacture. Cheese functionality during ripening was assessed using texture profile analysis and dynamic low-amplitude oscillatory rheology. Sensory Spectrum and quantitative descriptive analysis was conducted with 9 trained panelists to evaluate texture and flavor attributes using a 15-point scale. At 4 d and 2 wk of ripening, L-Na-UF-HHP cheese had ~2 and ~4.5 log lower starter culture numbers, respectively, than all other cheeses. Retentate fortification of cheese milk and HHP treatment resulted in low-Na cheeses having similar insoluble calcium concentrations and pH values compared with R-Na cheese during ripening. The L-Na-UF cheese exhibited significantly higher hardness values (measured by texture profile analysis) compared with L-Na cheese until 1 mo of ripening; however, after 1 mo, all low-Na cheeses exhibited similar hardness values, which were significantly lower than R-Na cheese. Pressure treatment significantly increased maximum loss tangent (meltability) from rheology testing and decreased melt temperature. Sensory results indicated only very slight bitterness (<2.5 out of 15-point scale) was detected in all cheeses during the 6 mo of ripening. The L-Na-UF-HHP cheese did not significantly differ in bitterness and acidity from R-Na cheese during ripening. Pressures treatment of cheese at 500 MPa and cheese milk retentate fortification could be used to improve the quality of low-Na cheese.

Evaluation of X-ray fluorescence spectroscopy as a method for the rapid and direct determination of sodium in cheese.

Cheese manufacturers indirectly determine Na in cheese by analysis of Cl using the Volhard method, assuming that all Cl came from NaCl. This method overestimates the actual Na content in cheeses when Na replacers (e.g., KCl) are used. A direct and rapid method for Na detection is needed. X-ray fluorescence spectroscopy (XRF), a mineral analysis technique used in the mining industry, was investigated as an alternative method of Na detection in cheese. An XRF method for the detection of Na in cheese was developed and compared with inductively coupled plasma optical emission spectroscopy (ICP-OES; the reference method for Na in cheese) and Cl analyzer. Sodium quantification was performed by multi-point calibration with cheese standards spiked with NaCl ranging from 0 to 4% Na (wt/wt). The Na concentration of each of the cheese standards (discs: 30mm×7mm) was quantified by the 3 methods. A single laboratory method validation was performed; linearity, precision, limit of detection, and limit of quantification were determined. An additional calibration graph was created using cheese standards made from natural or process cheeses manufactured with different ratios of Na:K. Both Na and K calibration curves were linear for the cheese standards. Sodium was quantified in a variety of commercial cheese samples. The Na data obtained by XRF were in agreement with those from ICP-OES and Cl analyzer for most commercial natural cheeses. The XRF method did not accurately determine Na concentration for several process cheese samples, compared with ICP-OES, likely due to the use of unknown types of Na-based emulsifying salts (ES). When a calibration curve was created for process cheese with the specific types of ES used for this cheese, Na content was successfully predicted in the samples. For natural cheeses, the limit of detection and limit of quantification for Na that can be determined with an acceptable level of repeatability, precision, and trueness was 82 and 246mg/100g of cheese, respectively. Calibration graphs should be created with standards that reflect the concentration range, ratio, and salt type present in the cheeses. This XRF method can be successfully used for the rapid and direct measurement of Na content in a wide variety of natural cheeses. Commercial process cheese manufacturers use proprietary blends of ES. We did find that the XRF technique worked for process cheese when the calibration graphs were created with the specific types of ES actually used.

Effect of camel chymosin on the texture, functionality, and sensory properties of low-moisture, part-skim Mozzarella cheese.

The objective of this study was to compare the effect of coagulant (bovine calf chymosin, BCC, or camel chymosin, CC), on the functional and sensory properties and performance shelf-life of low-moisture, part-skim (LMPS) Mozzarella. Both chymosins were used at 2 levels [0.05 and 0.037 international milk clotting units (IMCU)/mL], and clotting temperature was varied to achieve similar gelation times for each treatment (as this also affects cheese properties). Functionality was assessed at various cheese ages using dynamic low-amplitude oscillatory rheology and performance of baked cheese on pizza. Cheese composition was not significantly different between treatments. The level of total calcium or insoluble (INSOL) calcium did not differ significantly among the cheeses initially or during ripening. Proteolysis in cheese made with BCC was higher than in cheeses made with CC. At 84 d of ripening, maximum loss tangent values were not significantly different in the cheeses, suggesting that these cheeses had similar melt characteristics. After 14 d of cheese ripening, the crossover temperature (loss tangent = 1 or melting temperature) was higher when CC was used as coagulant. This was due to lower proteolysis in the CC cheeses compared with those made with BCC because the pH and INSOL calcium levels were similar in all cheeses. Cheeses made with CC maintained higher hardness values over 84 d of ripening compared with BCC and maintained higher sensory firmness values and adhesiveness of mass scores during ripening. When melted on pizzas, cheese made with CC had lower blister quantity and the cheeses were firmer and chewier. Because the 2 types of cheeses had similar moisture contents, pH values, and INSOL Ca levels, differences in proteolysis were responsible for the firmer and chewier texture of CC cheeses. When cheese performance on baked pizza was analyzed, properties such as blister quantity, strand thickness, hardness, and chewiness were maintained for a longer ripening time than cheeses made with BCC, indicating that use of CC could help to extend the performance shelf-life of LMPS Mozzarella.

Effect of various high-pressure treatments on the properties of reduced-fat Cheddar cheese.

A major problem with reduced-fat cheese is the difficulty in attaining the characteristic flavor and texture of typical full-fat versions. Some previous studies have suggested that high hydrostatic pressure (HHP) can accelerate the ripening of full-fat cheeses. Our objective was to investigate the effect of HHP on reduced-fat (~7.3% fat) Cheddar cheese, with the goal of improving its flavor and texture. We used a central composite rotatable design with response surface methodology to study the effect of pressure and holding time on the rheological, physical, chemical, and microbial characteristics of reduced-fat Cheddar cheese. A 2-level factorial experimental design was chosen to study the effects of the independent variables (pressure and holding time). Pressures were varied from around 50 to 400 MPa and holding times ranged from 2.5 to 19.5 min. High pressure was applied 1 wk after cheese manufacture, and analyses were performed at 2 wk, and 1, 3, and 6 mo. The insoluble calcium content as a percentage of total Ca in cheeses were not affected by pressure treatment. Pressure applications ≥ 225 MPa resulted in softer cheese texture during ripening. Pressures ≥ 225 MPa increased melt, and resulted in higher maximum loss tangent values at 2 wk. Pressure treatment had a greater effect on cheese microbial and textural properties than holding time. High-pressure-treated cheeses also had higher pH values than the control. We did not observe any significant difference in rates of proteolysis between treatments. In conclusion, holding times of around 5 min and pressures of ≥ 225 MPa could potentially be used to improve the excessively firm texture of reduced-fat cheese.

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.

Standardization of milk using cold ultrafiltration retentates for the manufacture of Swiss cheese: effect of altering coagulation conditions on yield and cheese quality.

Fortification of cheesemilk with membrane retentates is often practiced by cheesemakers to increase yield. However, the higher casein (CN) content can alter coagulation characteristics, which may affect cheese yield and quality. The objective of this study was to evaluate the effect of using ultrafiltration (UF) retentates that were processed at low temperatures on the properties of Swiss cheese. Because of the faster clotting observed with fortified milks, we also investigated the effects of altering the coagulation conditions by reducing the renneting temperature (from 32.2 to 28.3°C) and allowing a longer renneting time before cutting (i.e., giving an extra 5min). Milks with elevated total solids (TS; ∼13.4%) were made by blending whole milk retentates (26.5% TS, 7.7% CN, 11.5% fat) obtained by cold (<7°C) UF with part skim milk (11.4% TS, 2.5% CN, 2.6% fat) to obtain milk with CN:fat ratio of approximately 0.87. Control cheeses were made from part-skim milk (11.5% TS, 2.5% CN, 2.8% fat). Three types of UF fortified cheeses were manufactured by altering the renneting temperature and renneting time: high renneting temperature=32.2°C (UFHT), low renneting temperature=28.3°C (UFLT), and a low renneting temperature (28.3°C) plus longer cutting time (+5min compared to UFLT; UFLTL). Cutting times, as selected by a Wisconsin licensed cheesemaker, were approximately 21, 31, 35, and 32min for UFHT, UFLT, UFLTL, and control milks, respectively. Storage moduli of gels at cutting were lower for the UFHT and UFLT samples compared with UFLTL or control. Yield stress values of gels from the UF-fortified milks were higher than those of control milks, and decreasing the renneting temperature reduced the yield stress values. Increasing the cutting time for the gels made from the UF-fortified milks resulted in an increase in yield stress values. Yield strain values were significantly lower in gels made from control or UFLTL milks compared with gels made from UFHT or UFLT milks. Cheese composition did not differ except for fat content, which was lower in the control compared with the UF-fortified cheeses. No residual lactose or galactose remained in the cheeses after 2 mo of ripening. Fat recoveries were similar in control, UFHT, and UFLTL but lower in UFLT cheeses. Significantly higher N recoveries were obtained in the UF-fortified cheeses compared with control cheese. Because of higher fat and CN contents, cheese yield was significantly higher in UF-fortified cheeses (∼11.0 to 11.2%) compared with control cheese (∼8.5%). A significant reduction was observed in volume of whey produced from cheese made from UF-fortified milk and in these wheys, the protein was a higher proportion of the solids. During ripening, the pH values and 12% trichloroacetic acid-soluble N levels were similar for all cheeses. No differences were observed in the sensory properties of the cheeses. The use of UF retentates improved cheese yield with no significant effect on ripening or sensory quality. The faster coagulation and gel firming can be decreased by altering the renneting conditions.

Insoluble calcium content and rheological properties of Colby cheese during ripening.

Colby cheese was made using different manufacturing conditions (i.e., varying the lactose content of milk and pH values at critical steps in the cheesemaking process) to alter the extent of acid development and the insoluble and total Ca contents of cheese. Milk was concentrated by reverse osmosis (RO) to increase the lactose content. Extent of acid development was modified by using high (HPM) and low (LPM) pH values at coagulant addition, whey drainage, and curd milling. Total Ca content was determined by atomic absorption spectroscopy, and the insoluble (INSOL) Ca content of cheese was measured by the cheese juice method. The rheological and melting properties of cheese were measured by small amplitude oscillatory rheometry and UW-Melt Profiler, respectively. There was very little change in pH during ripening even in cheese made from milk with high lactose content. The initial (d 1) cheese pH was in the range of 4.9 to 5.1. The INSOL Ca content of cheese decreased during the first 4 wk of ripening. Cheeses made with the LPM had lower INSOL Ca content during ripening compared with cheese made with HPM. There was an increase in melt and maximum loss tangent values during ripening except for LPM cheeses made with RO-concentrated milk, as this cheese had pH <4.9 and exhibited limited melt. Curd washing reduced the levels of lactic acid produced during ripening and resulted in significantly higher INSOL Ca content. The use of curd washing for cheeses made from high lactose milk prevented a large pH decrease during ripening; high rennet and draining pH values also retained more buffering constituents (i.e., INSOL Ca phosphate), which helped prevent a large pH decrease.

Characterization of the rheological, textural, and sensory properties of samples of commercial US cream cheese with different fat contents.

In this study, 18 commercial samples of cream cheeses from the United States, including full-fat, Neufchatel or one-third less fat, and fat-free cheeses were analyzed for their rheological, textural, and sensory properties. Dynamic rheological properties were measured by small-amplitude oscillatory rheology during heating from 5 to 80 degrees C and cooling from 80 to 5 degrees C. The parameters measured were storage modulus (G') and loss tangent (LT). Hardness of cream cheeses was determined by penetration and spreadability tests with a texture analyzer. Quantitative descriptive sensory analysis was performed by a trained panel to determine textural properties including firmness, stickiness, cohesiveness of mass, gumminess, difficulty to dissolve, particle size, and difficulty to spread. Principal component analysis of sensory and instrumental parameters was performed to identify relationships between these different parameters and to group samples with similar characteristics. A standard recipe for preparation of cheesecakes was used to test the influence of type of cream cheese on cake properties. Hardness of cheesecakes was also determined by penetration. Most full-fat cream cheeses showed significantly greater G' values than the Neufchatel or fat-free cheeses at temperatures below 25 degrees C during the heating cycle. For the cheeses containing fat (full fat and Neufchatel), G' values steeply decreased during heating up to 40 degrees C; the decrease was greater for full-fat cream cheese compared with Neufchatel cheeses. In full-fat cream cheese, one maximum in the LT profile was observed during heating at temperatures below 40 degrees C. In Neufchatel cheeses, a smaller maximum in LT was observed at temperatures below 40 degrees C, whereas fat-free cream cheeses showed no noticeable maximum LT in this temperature region. Most full-fat cream cheeses had greater values of hardness as determined by penetration or spreadability compared with Neufchatel or fat-free cheeses. Sensory analysis indicated that full-fat cream cheeses were firmer, more cohesive, more difficult to dissolve and spread, and less sticky than Neufchatel or fat-free cheeses. The high hardness of full-fat cream cheese is presumably due to its greater fat content because after homogenization of the cream cheese mix, fat globules are partly covered with casein and participate in the aggregation of casein particles, reinforcing the structure of this product. These results indicate that there are significant differences in the textural properties of cream cheese made with different fat contents.

Influence of emulsifying salts on the textural properties of nonfat process cheese made from direct acid cheese bases.

The objective of this study was to investigate the influence of several types of emulsifying salts (ES) on the texture of nonfat process cheese (NFPC). Improperly produced nonfat cheese tends to exhibit several problems upon baking including stickiness, insufficient or excessive melt, pale color upon cooling, formation of a dry skin (skinning) often leading to dark blistering, and chewy texture. These attributes are due to the strength and number of interactions between and among casein molecules. We propose to disrupt these interactions by using suitable emulsifying salts (ES). These ES chelate Ca and disperse caseins. Stirred curd cheese bases were made from skim milk using direct acidification with lactic acid to pH values 5.0, 5.2, and 5.4, and ripened for 1 d. Various levels of trisodium citrate (TSC; 0.5, 1, 1.5, 2, 2.5, 3, and 5%), disodium phosphate (DSP; 1, 2, 3, and 4%), or trisodium phosphate (TSP; 1, 2, 3, and 4%) were blended with the nonfat cheese base. Cheese, ES, and water were weighed into a steel container, which was placed in a waterbath at 98 degrees C and then stirred using an overhead stirrer for 9 min. Molten cheese was poured into plastic containers, sealed, and stored at 4 degrees C for 7 d before analysis. Texture and melting properties were determined using texture profile analysis and the UW-Melt-profiler. The pH 5.2 and 5.4 cheese bases were sticky during manufacture and had a pale straw-like color, whereas the pH 5.0 curd was white. Total calcium contents were approximately 400, 185, and 139 mg/100 g for pH 5.4, 5.2, and 5.0 cheeses, respectively. Addition of DSP resulted in NFPC with the lowest extent of flow, and crystal formation was apparent at DSP levels above 2%. The NFPC manufactured from the pH 5.0 base and using TSP had reduced melt and increased stickiness, whereas melt was significantly increased and stickiness was reduced in NFPC made with pH 5.4 base and TSP. However, for NFPC made from the pH 5.4 cheese and with 1% TSP, the pH value was >6.20 and crystals were observed within a few days. Use of TSC increased extent of flow up to a maximum with the addition of 2% ES for all 3 types of cheese bases. Addition of high levels of TSC to the pH 5.2 and 5.4 cheese bases resulted in increased stickiness. Similar pH trends for attributes such as extent of flow, hardness, and adhesiveness were observed for both phosphate ES but no consistent pH trends were observed for the NFPC made with TSC. These initial trials suggest that the pH 5.0 cheese base was promising for further research and scale-up to pilot-scale process cheese making, because cheeses had a creamy color, reasonable melt, and did not have high adhesiveness when TSC was used as the ES. However, the acid whey produced from the pH 5.0 curd could be a concern.

Use of cold microfiltration retentates produced with polymeric membranes for standardization of milks for manufacture of pizza cheese.

Pizza cheese was manufactured with milk (12.1% total solids, 3.1% casein, 3.1% fat) standardized with microfiltered (MF) and diafiltered retentates. Polymeric, spiral-wound MF membranes were used to process cold (<7 degrees C) skim milk, and diafiltration of MF retentates resulted in at least 36% removal of serum protein on a true protein basis. Cheese milks were obtained by blending the MF retentate (16.4% total solids, 11.0% casein, 0.4% fat) with whole milk (12.1% total solids, 2.4% casein, 3.4% fat). Control cheese was made with part-skim milk (10.9% total solids, 2.4% casein, 2.4% fat). Initial trials with MF standardized milk resulted in cheese with approximately 2 to 3% lower moisture (45%) than control cheese ( approximately 47 to 48%). Cheese-making procedures (cutting conditions) were then altered to obtain a similar moisture content in all cheeses by using a lower setting temperature, increasing the curd size, and lowering the wash water temperature during manufacture of the MF cheeses. Two types of MF standardized cheeses were produced, one with preacidification of milk to pH 6.4 (pH6.4MF) and another made from milk preacidified to pH 6.3 (pH6.3MF). Cheese functionality was assessed by dynamic low-amplitude oscillatory rheology, University of Wisconsin MeltProfiler, and performance on pizza. Nitrogen recoveries were significantly higher in MF standardized cheeses. Fat recoveries were higher in the pH6.3MF cheese than the control or pH6.4MF cheese. Moisture-adjusted cheese yield was significantly higher in the 2 MF-fortified cheeses compared with the control cheese. Maximum loss tangent (LT(max)) values were not significantly different among the 3 cheeses, suggesting that these cheeses had similar meltability. The LT(max) values increased during ripening. The temperature at which the LT(max) was observed was highest in control cheese and was lower in the pH6.3MF cheese than in the pH6.4MF cheese. The temperature of the LT(max) decreased with age for all 3 cheeses. Values of 12% trichloroacetic acid soluble nitrogen levels were similar in all cheeses. Performance on pizza was similar for all cheeses. The use of MF retentates derived with polymeric membranes was successful in increasing cheese yield, and cheese quality was similar in the control and MF standardized cheeses.