Low-moisture Part-skim Mozzarella Research Articles

Using 1H and 23Na NMR relaxometry as a novel tool to monitor the moisture and salt distribution in commercial low-moisture part skim mozzarella

Zonal variations in 1H or 23Na content in commercial low-moisture part-skim mozzarella with a uniform salt distribution, obtained by dry-salting, or with a salt gradient, obtained by dry-salting and brining, were profiled using a combined 1H and 23Na NMR relaxometry procedure. 1D concentration–distance profiles were constructed in all cheeses from the surface to the core. Rapid, non-invasive, (∼21 min) distinction between dry-salted and brined cheese was enabled. Uptake of salt in cheese brined for 0–24 h was determined, and the derived effective diffusion coefficient of 23Na (3.23 × 10−10 m2 s−1) compared favourably with values reported for other semi-hard cheeses during brining; the 23Na concentration–distance profiles of brined cheese stored for 2–44 d at 4 °C corresponded to an effective diffusion coefficient of about 5.21 × 10−10 m2 s−1. Small variations in moisture content in the cheese could not be distinguished from the random fluctuations in 1H signal intensity.

Low-moisture part-skim mozzarella cheese made from blends of camel and bovine milk: Gross composition, proteolysis, functionality, microstructure, and rheological properties.

Camel (CM) milk is used in variety of ways; however, it has inferior gelling properties compared with bovine milk (BM). In this study, we aimed to investigate the physicochemical, functional, microstructural, and rheological properties of low-moisture part-skim (LMPS) mozzarella cheese, made from BM, or BM mixed with 15% CM (CM15%) or 30% CM (CM30%), at various time points (up to 60 d) of storage at 4°C after manufacture. Low-moisture part-skim mozzarella cheeses using CM15% and CM30% had high moisture and total Ca contents, but lower soluble Ca content. Compared with BM cheese, CM15% and CM30% LMPS mozzarella cheese exhibited higher proteolysis rates during storage. Adding CM affected the color properties of LMPS mozzarella cheese manufactured from mixed milk. Scanning electron microscopy images showed that the microstructure of CM15% and CM30% cheeses had smooth surfaces, whereas the BM cheese microstructures were rough with granulated surfaces. Low-moisture part-skim mozzarella cheeses using CM15% and CM30% showed significantly lower hardness and chewiness, but higher stringiness than BM cheese. Compared with BM cheese, CM15% and CM30% cheeses showed lower tan δ levels during temperature surges, suggesting that the addition of CM increased the meltability of LMPS mozzarella cheese during temperature increases. Camel milk addition affected the physicochemical, microstructural, and rheological properties of LMPS mozzarella cheese.

Impact of sodium orthophosphate, sodium pyrophosphate or sodium citrate addition via dry-salting on the properties of low-moisture part skim mozzarella

Low-moisture part-skim mozzarella was dry-salted with sodium orthophosphate, sodium pyrophosphate or sodium citrate to examine the impact on its functional properties after 14 d of storage at 4 °C. Relative to the control, dry-salting the cheese with sodium pyrophosphate impaired flow and extensibility after heating, whereas those dry-salted with sodium orthophosphate or sodium citrate had greater flow and required less work to extend after heating. Elevated levels of insoluble Ca and P were found in all cheeses except for the cheese with sodium citrate that had lower insoluble P. The findings suggested that the addition of sodium pyrophosphate enhanced the interactions between Ca, P and para-casein, possibly by formation of Ca-caseinate phosphate complexes, whereas the effects of sodium orthophosphate may be explained by displacement of colloidal Ca-P and subsequent re-association to the casein micelle, and those of sodium citrate by solubilisation of colloidal Ca-P and formation of insoluble Ca-citrate complexes.

Effects of reducing milk pH to 6.2 by CO2 injection or by addition of lactic acid on the biochemical and functional properties of commercial low-moisture part-skim mozzarella

The effects of adjusting milk pH to 6.2 by CO2 injection or by addition of lactic acid solution on the properties of commercial low-moisture part-skim mozzarella stored for 15 or 30 d at 4 °C were investigated. Relative to the control, cheese from milk adjusted to pH 6.2 using CO2 had a slightly-reduced total Ca content, a lower melting temperature, and required less work to stretch (extend) to 38 cm following heating to 95 °C. Reducing milk pH to 6.2 using lactic acid resulted in a greater decrease in total Ca content, higher moisture content and reductions in cheese firmness, melting temperature and work to stretch. The results indicate that CO2 injection of milk to 6.2 may be used to promote subtle changes in functionality of Mozzarella without altering gross composition.

An approach to improve the baking properties and determine the onset of browning in fat-free mozzarella cheese

Compared with low-moisture part-skim mozzarella and mozzarella cheese, bake performance of low-fat and fat-free mozzarella on pizza has a lot to desire. We hypothesized that a water-soaking pretreatment step of low-fat and fat-free cheese shreds before baking would improve pizza baking performance. The study also examined the correlation of the onset of cheese browning with the rate of moisture loss, changes in cheese surface temperature, and 3-dimensional (3D) plot L* a* b* CIELAB color analysis. The pretreatment of soaking cheese shreds in water improved the baking properties of fat-free mozzarella cheese on pizza. Compared with the control sample, which demonstrated significant shred identity, poor shred melt, fusion, and stretch during a pizza bake with fat-free mozzarella, the soaked cheese (SC) sample demonstrated satisfactory cheese melt, fusion, and stretch. In addition, the SC sample had desired browning as opposed to the control sample's excessive browning. The additional moisture from the soaking pretreatment aided in delaying the onset of cheese browning in the SC sample when compared with the control sample. For both the control and SC samples, there was a strong correlation between the onset of cheese browning with the peak of moisture-loss rate, and an increase in cheese surface temperature (>100°C). The color analysis of the 3D plot confirmed the relationship between the onset of cheese browning and the shift in L* (lightness), a* (red-green color), and b* (blue-yellow) values. According to the study's findings, soaking cheese shreds before baking can help improve bake performance on pizza. Furthermore, 3 measurement tools used in the study, (1) moisture-loss rate, (2) cheese surface temperature, and (3) 3D plot CIELAB color, were useful in determining the onset of cheese browning and can be applied to different intervention strategies to control cheese browning during pizza baking.

Seasonal variations in the functional performance of industrial low-moisture part-skim mozzarella over a 1.5-year period

Seventy-five blocks of low-moisture part-skim mozzarella cheese were procured from an industrial cheese plant, and the relationships between the physicochemical and functional properties were evaluated during refrigerated storage. In total, cheeses were obtained from 1 cheese vat on 7 different production dates, at 2 to 4 monthly intervals, over a 1.5-yr period; all cheeses were made using a standard recipe. The cheeses were held at 4°C for 0, 1, 2, 4, 8, 16, or 32 d and assayed for composition, primary proteolysis, serum distribution, texture profile analysis, heat-induced changes in viscoelastic behavior, cheese extensibility, and melt characteristics. The results demonstrated a substantial increase in serum uptake by the calcium-phosphate para-casein matrix between 1 and 16 d of storage with a concomitant improvement in the functional performance of the cheese. Extending the storage time to 32 d resulted in further changes in the functional quality, concurrent with ongoing increases in protein hydration and primary proteolysis. Differences in the measured characteristics between the cheeses obtained on different sampling occasions were evident. Principal component analysis separated the cheeses based on their variance in functional performance, which was found to be correlated mainly with the calcium content of the cheese. The results indicate that the manufacturing process should be tightly controlled to minimize variation in calcium content and enhance the quality consistency of the cheese.

Short communication: Influence of intramuscular injection of vitamin B12 in early-lactation dairy cows on Mozzarella cheese quality and vitamin B12 stability

The current study explored the effect of intramuscular injection of vitamin B12 (VB12) in early-lactation dairy cows on subsequent low-moisture part-skim Mozzarella cheese quality and VB12 levels during cheese processing and storage. Twenty-four peripartum dairy cows were blocked based on parity and milk yield and randomly assigned into 2 treatments: basal diet (CON) and basal diet with an intramuscular injection of 10 mg of VB12 per cow per week (VB12). Raw milk was collected to determine VB12 content and then used to make low-moisture part-skim Mozzarella cheese 8 wk after injection. The VB12 content of raw milk and cheese was determined using ultra-performance liquid chromatography coupled with tandem mass spectrometry. We found that VB12 content was significantly increased in milk (15.43 vs. 3.30 ng/mL) and fresh cheese (3.72 ng/g vs. undetectable) from the VB12 group compared with the CON group. However, approximately 70% of VB12 was lost in the whey during cheese making, and no VB12 was detectable in either cheese treatment after 8 wk of storage. Furthermore, no significant differences were observed in fat and protein contents in the cheese between the 2 groups. For cheese color, the b* value increased and the a* value decreased slightly in fresh VB12 cheese. Functional properties of stretchability, flowability, and meltability of VB12 cheese were initially comparable to that of CON cheese, but higher flowability and meltability was observed in VB12 cheese after 8 wk of storage. In summary, intramuscular injection of VB12 in early-lactation dairy cows increases the content of VB12 in milk and fresh cheese with no adverse effect on cheese quality, but substantial VB12 is lost during cheesemaking and declines rapidly during storage.

Impact of freezing on the physicochemical and functional properties of low–moisture part–skim mozzarella

Low–moisture part–skim (LMPS) mozzarella cheeses were held at 4 °C for 0, 2 or 8 d before freezing to −20 °C. The cheeses were frozen at a rate of 0.6, 2.0 or 8.0 °C h−1 and held frozen at −20 °C for 1, 6, 12 or 44 weeks. After freezing, cheeses were stored at 4 °C for 16–37 d, resulting in a total storage time at 4 °C (before and after freezing) of 24–37 d (frozen–thawed mozzarella). Control mozzarella was stored at 4 °C for 25–37 d. The control and frozen–thawed cheeses were assayed for composition, primary proteolysis, moisture distribution, texture profile analysis and melting characteristics after similar storage times at 4 °C. Freezing under the evaluated conditions resulted in reduced firmness of the unheated cheese but did not significantly affect the properties of the heated cheese. The results suggest that freezing may be effectively applied to control or extend the functional shelf–life of LMPS mozzarella shipped to long–distance markets.

Grazing of dairy cows on pasture versus indoor feeding on total mixed ration: Effects on low-moisture part-skim Mozzarella cheese yield and quality characteristics in mid and late lactation

This study investigated the effects of 3 dairy cow feeding systems on the composition, yield, and biochemical and physical properties of low-moisture part-skim Mozzarella cheese in mid (ML; May-June) and late (LL; October-November) lactation. Sixty spring-calving cows were assigned to 3 herds, each consisting of 20 cows, and balanced on parity, calving date, and pre-experimental milk yield and milk solids yield. Each herd was allocated to 1 of the following feeding systems: grazing on perennial ryegrass (Lolium perenne L.) pasture (GRO), grazing on perennial ryegrass and white clover (Trifolium repens L.) pasture (GRC), or housed indoors and offered total mixed ration (TMR). Mozzarella cheese was manufactured on 3 separate occasions in ML and 4 in LL in 2016. Feeding system had significant effects on milk composition, cheese yield, the elemental composition of cheese, cheese color (green to red and blue to yellow color coordinates), the extent of flow on heating, and the fluidity of the melted cheese. Compared with TMR milk, GRO and GRC milks had higher concentrations of protein and casein and lower concentrations of I, Cu, and Se, higher cheese-yielding capacity, and produced cheese with lower concentrations of the trace elements I, Cu, and Se and higher yellowness value. Cheese from GRO milk had higher heat-induced flow and fluidity than cheese from TMR milk. These effects were observed over the entire lactation period (ML + LL), but varied somewhat in ML and LL. Feeding system had little, or no, effect on gross composition of the cheese, the proportions of milk protein or fat lost to cheese whey, the texture of the unheated cheese, or the energy required to extend the molten cheese. The differences in color and melt characteristics of cheeses obtained from milks with the different feeding systems may provide a basis for creating points of differentiation suited to different markets.

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 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.

Sodium content in retail Cheddar, Mozzarella, and process cheeses varies considerably in the United States

Reducing the sodium content in cheese is expected to contribute to reducing the overall intake of sodium by US consumers. The purpose of this study was to measure the sodium levels in cheeses that are most commonly purchased by US consumers in the retail market, including brand and private label. A secondary purpose of the study was to generate data that can enable the dairy industry to adopt best practices regarding sodium levels in cheeses. The sodium content of a total of 1,665 samples of Cheddar (650 samples), low moisture part skim (LMPS) Mozzarella (746 samples), and process cheese singles (269 samples) from 4 geographical regions were collected over a period of 3 wk, and were analyzed over a 1-mo period. Process cheese contained the highest mean level of sodium (1,242mg/100g), followed by string cheese (724mg/100g). Across Cheddar cheese forms and brands, the mean analytical sodium was 615mg/100g, with 95% between 474 and 731mg/100g; label sodium ranged from 600 to 800mg/100g (mean 648mg). Across all LMPS Mozzarella forms and brands, the mean analytical sodium was 666mg/100g, with 95% between 452 and 876mg/100g; label sodium ranged from 526 to 893mg/100g (mean 685mg). Across all process cheese forms and brands, the mean analytical sodium was 1,242mg/100g, with 95% between 936 and 1,590mg/100g; label sodium ranged from 1,185 to 1,740mg/100g (mean 1,313mg/100g). These findings demonstrate that manufacturers tended to be conservative with their reporting of sodium on labels. Manufacturers need to reduce variability to better target desired sodium levels, which is an opportunity for better process control, and will enable them to label sodium more accurately.

Activation energy measurements in rheological analysis of cheese

Activation energy of flow ( E a) between 30 and 44 °C was calculated from temperature sweeps of cheeses with contrasting characteristics to determine its usefulness in predicting rheological behavior upon heating. Cheddar, Colby, whole milk Mozzarella, low-moisture part-skim Mozzarella, Parmesan, soft goat, and Queso Fresco cheeses were heated from 22 to 70 °C, and E a was calculated from the resulting Arrhenius plots. Protein and moisture content were highly correlated with E a. The E a values for goat cheese and Queso Fresco, which did not flow when heated, were between 30 and 60 kJ mol −1. Cheddar, Colby, and the Mozzarellas did flow upon heating, and their E a values were between 100 and 150 kJ mol −1. Parmesan, the hardest cheese, flowed rapidly with heat and had an E a > 180 kJ mol −1. E a provides an objective means of quantitating the flow of cheese, and together with elastic modulus and viscous modulus provides a picture of the behavior of cheese as it is heated.

Comparison of the level of residual coagulant activity in different cheese varieties

The coagulant retained in cheese curd is a major contributor to proteolysis during ripening. The objective of this study was to quantify residual coagulant in 9 cheese varieties by measuring its activity on a synthetic heptapeptide (Pro-Thr-Glu-Phe-[NO2-Phe]-Arg-Leu) assayed using reversed-phase HPLC. The level of residual coagulant activity was highest in Camembert cheese, probably due to its low pH at whey drainage and the high moisture content of the cheese, followed in order by Feta=Port du Salut=Cheddar>Gouda>Emmental=Parmigiano Reggiano=low-moisture part-skim Mozzarella=Mozzarella di Bufala Campana. The high cooking temperature (50-54 degrees C) used during the manufacture of Emmental and Parmigiano Reggiano cheeses and the cooking and stretching step in hot water during the manufacture of Mozzarella cheese may be the reasons for the lowest residual coagulant activity in these cheeses. The level of residual coagulant activity was higher in Feta cheese made from milk concentrated by ultrafiltration than in conventional Feta.

Effect of pH on Characteristics of Low‐Moisture Mozzarella Cheese during Refrigerated Storage

This study evaluated the effect of cheese pH on proteolysis, calcium distribution, and functional characteristics of Mozzarella cheese. On 4 occasions, cultured low-moisture part-skim Mozzarella cheeses were obtained from a commercial producer on the day after manufacture. Cheese blocks were randomly assigned to 2 groups. One group was shredded, subdivided, and exposed to either ammonia vapor to increase the pH or HCl vapor to decrease the pH. Samples were vacuum packaged, stored at 4 degrees C, and analyzed for pH 4.6 and 12% TCA soluble nitrogen, apparent viscosity, free oil, and water-soluble calcium on days 5, 12, 22, and 40. The 2nd group was sectioned into 23-mm thick slabs and similarly exposed to either ammonia vapor to increase the pH or HCl vapor to decrease the pH. The slabs were vacuum packaged, stored at 4 degrees C, and analyzed for pH 4.6 and 12% TCA soluble nitrogen, TPA hardness, springiness and cohesiveness, and meltability on days 17, 29, and 41. Data were analyzed by ANOVA according to a spilt-plot design. Experimentally induced pH differences persisted and significantly affected TPA hardness, apparent viscosity, meltability, and water-soluble calcium throughout 40 d of storage, but did not affect soluble nitrogen changes. Thus, cheese pH affected functional characteristics and calcium distribution but did not affect proteolysis rates. Higher cheese pH resulted in a harder cheese that required longer aging to develop desirable melting characteristics, whereas cheese with lower pH developed desirable melting characteristics more quickly but had a shorter functional shelf life.

Vatless Manufacturing of Low-Moisture Part-Skim Mozzarella Cheese from Highly Concentrated Skim Milk Microfiltration Retentates

Low-moisture, part-skim (LMPS) Mozzarella cheeses were made from concentration factor (CF) 6, 7, 8, and 9, pH 6.0 skim milk microfiltration (MF) retentates using a vatless cheese-making process. The compositional and proteolytic effects of cheese made from 4 CF retentates were evaluated as well as their functional properties (meltability and stretchability). Pasteurized skim milk was microfiltered using a 0.1-μm ceramic membrane at 50°C to a retentate CF of 6, 7, 8, and 9. An appropriate amount of cream was added to achieve a constant casein:fat ratio in the 4 cheesemilks. The ratio of rennet to casein was also kept constant in the 4 cheesemilks. The compositional characteristics of the cheeses made from MF retentates did not vary with retentate CF and were within the legal range for LMPS Mozzarella cheese. The observed reduction in whey drained was greater than 90% in the cheese making from the 4 CF retentates studied. The development of proteolytic and functional characteristics was slower in the MF cheeses than in the commercial samples that were used for comparison due to the absence of starter culture, the lower level of rennet used, and the inhibition of cheese proteolysis due to the inhibitory effect of residual whey proteins retained in the MF retentates, particularly high molecular weight fractions.

Functionality and Physico-Chemical Characteristics of Bovine and Caprine Mozzarella Cheeses During Refrigerated Storage

Low moisture part-skim Mozzarella cheeses (MC) were manufactured using fresh bovine and caprine milk to study melting, physico-chemical, textural, and microstructural properties of the cheeses during 8 wk of refrigerated storage. Structural changes in cheese matrix were evaluated by scanning electron microscopy and by proteolytic patterns using nitrogen solubility, SDS-PAGE, and Gel-pro analyzer. Meltability of ripened cow and goat MC were not different when fat content of both milks were standardized, whereas bovine MC formed a significantly larger amount of free oil throughout the experiment. The results of the proteolytic patterns, texture attribute (cohesiveness), and microstructure revealed that bovine MC had a greater structural degradation of cheese matrix than caprine MC during the storage. Elevated protein degradation in bovine MC led to more intense brown color formation than the goat counterpart when the cheeses were baked. The melting characteristics showed high positive correlation (r=0.51 to 0.80) with proteolysis, whereas it was negatively correlated with textural characteristics. Among textural attributes, cohesiveness was highly inversely correlated with melting characteristics (r=−0.69 to −0.88). High negative correlations were also observed between proteolytic parameters and textural attributes (r=−0.48 to −0.81).

Effect of Calcium and Water Injection on Structure-Function Relationships of Cheese

Our objectives were to determine the effect of calcium and water injection on cheese structure and to relate changes in structure to changes in functional properties of cheese. Cheese with fat and moisture content similar to that of low-moisture part-skim Mozzarella was made according to a direct-acid, stirred/pressed-curd procedure. The cheese was then cut into blocks that were high-pressure-injected from one to five times, with either water or a 40% calcium chloride solution. Successive injections were performed 24h apart. After 42 d of refrigerated storage, cheese microstructure and functionality were analyzed. When injected three or more times, water tended to increase cheese weight. The control, uninjected cheese, had the typical structure of a stirred/pressed-curd cheese: protein matrix interspersed with areas that originally contained fat and/or serum. Injecting water increased the area of cheese matrix occupied by protein, but it did not affect textural properties or melting of cheese. In contrast, when calcium was injected, a decrease in cheese weight was observed that was manifested through syneresis. The moisture content and pH of the cheese decreased as well. Calcium injection also decreased the area of cheese matrix occupied by protein. Cheese hardness increased, and cohesiveness and melting of cheese decreased upon calcium injection. We concluded that adding calcium to cheese alters how the proteins interact, which is manifested as changes in cheese microstructure. Such changes in cheese structure provide an understanding of changes in functional attributes of the cheese.

Proteolytic Specificity of Lactobacillus delbrueckii subsp. bulgaricus Influences Functional Properties of Mozzarella Cheese

Low-moisture part-skim Mozzarella cheeses were manufactured from 2% fat milk and aged for 21 d. Treatments included cheeses made with one of three different strains of Lactobacillus delbrueckii ssp. bulgaricus in combination with a single strain of Streptococcus thermophilus. A fourth, control treatment consisted of cheeses made with only S. thermophilus. Although total proteolytic ability of these strains, as indicated by the o-phthaldialdehyde analysis, was similar in each of the three strains of L. bulgaricus, these strains exhibited different proteolytic specificities toward the peptide, αs1-CN (f 1-23). On the basis of their αs1-CN (f 1-23) cleavage patterns and a previously described classification, these strains were assigned to the groups I, III, and V. The objective of this study was to investigate the influence of lactobacilli proteolytic systems, based on specificity toward αs1-CN (f 1-23), on functionality of part-skim Mozzarella cheese. Moisture, fat, protein, salt-in-moisture, and moisture in nonfat substances content of cheeses made with groups I, III, and V strain were similar. Control cheese had a lower moisture content than did other treatments. Significant differences were observed in functional properties between cheeses manufactured using groups III and V strains. Cheeses made with groups I and III strains were similar in their meltability, hardness, cohesiveness, melt strength, and stretch quality. Meltability and cohesiveness increased with age, while melt strength and stretch quality decreased with age for all cheeses. Additionally, HPLC showed that total peak areas of water-soluble peptides derived from cleavage of αs1-CN (f 1-23) by different strains of lactobacilli could be highly correlated to meltability and stretch characteristics of cheeses made with those strains.

Effect of manufacturing treatments on the rheological character of Mozzarella cheese made from microfiltration retentate depleted of whey proteins1

Low‐moisture, part‐skim (LMPS) Mozzarella cheeses were made from highly concentrated skim milk microfiltration (MF) retentate and butteroil. Differing combinations of rennet concentration, coagulation temperature and post‐coagulation curd cutting time were used, with comparisons made of the rheological and functional characteristics of cheeses during ageing. Lubricated squeezing flow, stress relaxation, melt and stretch measurements demonstrated that commercial LMPS Mozzarella had substantial textural and functional change between 7 and 30 days of age, while the rheological and functional behaviour of LMPS MF Mozzarella (MFM) exhibited substantial change between 30 and 60 days of age. Rennet concentration was the only experimental factor to significantly affect MFM rheological and functional development. The delayed development of MFM was partially attributed to inhibition of normal cheese proteolysis via whey protein (WP) incorporation, lack of starter culture protease, and homogenization of MF cheesemilk. Use of starter culture in MFM led to improved rheological and functional behaviour.