Cheese pH Research Articles

Modeling the effects of ripening at refrigeration and ambient temperatures on physic-chemical and microbiological parameters of artisanal Minas cheese

This study aimed to assess the effects of ripening at refrigeration and ambient temperatures on physic-chemical and microbiological parameters of artisanal Minas cheeses (made from raw milk) and to model the kinetics of lactic acid bacteria – LAB, Escherichia coli – Ec, and coagulase-positive staphylococci – Sa along the ripening. Cheese pH, acidity, and moisture, fat, and protein contents were quantified, as well as LAB, Ec, and Sa concentrations. Richards and simplified Lotka-Volterra models were used to describe the microbial kinetic data. The fits were assessed by statistical indices, and the Monte-Carlo method was applied to identifiability analysis. Cheese moisture was reduced along the ripening, increasing protein concentration and acidity values. Cheese pH showed a reduction followed by an increase. LAB concentration increased to the stationary phase after a few days; Ec and Sa concentrations increased and then decreased due to interactions with LAB and low moisture content. Mathematical models successfully described the kinetics of LAB, Ec, and Sa in cheese throughout ripening. Most parameters were not correlated to each other and were estimated with narrow confidence intervals.

Psychrotrophic Bacteria and Yeast Populations in Turkish White and Tulum Cheeses

In this study, pH and microbiological (psychrotrophic bacteria and yeast) properties of White and Tulum cheeses were investigated. According to the results of our study, the lowest pH value identified was 4.42, and the highest pH was 5.84 in the cheese samples. Psychrotrophic bacteria counts ranged from 4.15 to 6.21 log CFU/g for White cheese and 4.02 to 6.15 log CFU/g for Tulum cheese. Psychrotrophic yeast counts ranged from 2.98 to 7.58 log CFU/g for White cheese and 2.99 to 6.77 log CFU/g for Tulum cheese. The highest values of psychrotrophic yeast were detected in the Tulum cheese samples. As a result, it was determined that the numbers of psychrotrophic bacteria and yeast were high in both Tulum and White cheese samples. These high numbers of psychrotrophic microorganisms during cheese storage in the refrigerator may increase even further and reduce shelf life. To extend the shelf life of these cheeses, it is recommended to ensure hygienic handling practices and explore the use of natural preservatives or modified atmosphere packaging.

Zinc Supplementation Improves Texture, Oxidative Stability of Caciotta Cheese and Reduces Biogenic Amines Production.

Zinc is essential for animals, playing a vital role in enzyme systems and various biochemical reactions. It is crucial to ensure a sufficient intake of zinc through the diet to maintain efficient homeostasis. Only few studies on zinc effect in cow lactating diet evaluated the effects on milk and cheese quality, with conflicting findings. 24 cows of the Friesian breed were divided into two groups (CTR: control and TRT: treated group). Cows were selected for age, body weight, parity and phase of lactations (mid lactation, 140-160 days). CTR diet contained 38 mg/kg of Zn and TRT diet was supplied with 120 mg/kg of complete feed for 60 days. The objective of current investigation was to evaluate the impact of a dietary Zinc Oxide (ZnO) integration of lactating Friesian cows on chemical composition, zinc content, fatty acid and proteic profile, ammine content, pH, aw, texture, and sensory profile of cheese and to improve the chemical-nutritional quality of milk and cheese. The results showed that ZnO supplementation reduced mesophilic aerobic bacteria and Presumptive Pseudomonas spp. growth, proteolysis, biogenic amines content, lipid oxidation, odour intensity and sour and increased hardness, gumminess, chewiness, elasticity of cheese. Biogenic amines are considered an important aspect of food safety. ZnO integration in cow diet could represent a promising strategy for improving the quality, the safety and shelf-life of caciotta cheese.

Use of high-pressure processing and low-temperature storage to extend the performance shelf life of 2 types of string cheese

The manufacturing method of string cheese is similar to mozzarella, but the hot curd is extruded through narrow tubes or pipes, which align the protein fibers that provide the characteristic ability for consumers to pull strings from this cheese. Firmness is another important performance attribute for consumers who just bite into the string cheese without peeling off strings. There have only been a few studies on string cheese, but it is known that stringiness and firmness decrease during prolonged storage, which is a particular challenge for exporting string cheese. We explored 2 treatments to try to retain the stringiness and firmness of string cheese for longer storage periods. The techniques used were high-pressure processing (HPP; 600 MPa for 3 min) and reduced storage temperature (0°C). In other cheese varieties, these techniques have helped extend the performance shelf life. We tested these techniques using the 2 main types of commercial string cheese: direct acid string cheese (DASC) and cultured string cheese (CSC), which were obtained from 2 different manufacturing facilities. The DASC had higher fat (∼2.2%) and higher pH values (∼0.2 units) compared with the CSC. The CSC had higher protein content (∼3.4%), higher insoluble calcium content (∼8 mg insoluble Ca/g protein) and higher texture profile analysis (TPA) hardness values (∼4 N) compared with the DASC. Due to the compositional differences, the 2 varieties were statistically analyzed separately for all other attributes. In both cheese types, HPP caused an immediate reduction in stringiness, some solubilization of insoluble calcium, and a slight increase in the cheese pH values. High-pressure processing also caused a slight increase in TPA hardness of the CSC samples until 14 d (possibly due to a slight increase in cheese pH). The use of the 0°C storage temperature reduced proteolysis and helped retain firmness during storage. Low-temperature storage could help extend the performance shelf life of string cheese by a couple of months, but HPP was not suitable, as the process caused an immediate reduction in stringiness due to the disruption of the matrix induced by the HPP treatment.

Artichoke extract and human bifidobacteria to attain symbiotic sheep milk cheeses

There is a growing interest for healthy non-bovine functional dairy products. Therefore, in the present study, an aqueous polyphenol-rich artichoke extract (AE) and two Bifidobacterium strains of human origin (B. pseudolongum INIA P2 and B. longum INIA P132) were added, alone or in combination with AE, for the manufacture of six sheep milk cheeses. In general, addition of 1.25 g of lyophilized AE per 100 g of curd did not affect cheese pH, dry matter, lactoccci starter counts or organic acid levels during ripening. Bifidobacterial strains showed good viability in cheeses with AE during ripening and after simulated major gastrointestinal conditions. Cheeses with AE showed improved functional properties, with significantly (P < 0.01) higher total polyphenol content and, especially, antioxidant activity The cheese with AE and strain INIA P2 fulfil the definition of a symbiotic cheese. It contains prebiotic compounds and Bifidobacterium at adequate levels to sustain a therapeutic effect, which are able to survive major gastrointestinal conditions. This cheese could confer beneficial effects on consumers’ health by contributing to the host antioxidant capacity and increasing polyphenol bioavailability.

Utilization of Whey for Eco-Friendly Bio-Preservation of Mexican-Style Fresh Cheeses: Antimicrobial Activity of Lactobacillus casei 21/1 Cell-Free Supernatants (CFS).

Using whey, a by-product of the cheese-making process, is important for maximizing resource efficiency and promoting sustainable practices in the food industry. Reusing whey can help minimize environmental impact and produce bio-preservatives for foods with high bacterial loads, such as Mexican-style fresh cheeses. This research aims to evaluate the antimicrobial and physicochemical effect of CFS from Lactobacillus casei 21/1 produced in a conventional culture medium (MRS broth) and another medium using whey (WB medium) when applied in Mexican-style fresh cheese inoculated with several indicator bacteria (Escherichia coli, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Listeria monocytogenes). The CFSs (MRS or WB) were characterized for organic acids concentration, pH, and titratable acidity. By surface spreading, CFSs were tested on indicator bacteria inoculated in fresh cheese. Microbial counts were performed on inoculated cheeses during and after seven days of storage at 4 ± 1.0 °C. Moreover, pH and color were determined in cheeses with CFS treatment. Lactic and acetic acid were identified as the primary antimicrobial metabolites produced by the Lb. casei 21/1 fermentation in the food application. A longer storage time (7 days) led to significant reductions (p < 0.05) in the microbial population of the indicator bacteria inoculated in the cheese when it was treated with the CFSs (MRS or WB). S. enterica serovar Typhimurium was the most sensitive bacteria, decreasing 1.60 ± 0.04 log10 CFU/g with MRS-CFS, whereas WB-CFS reduced the microbial population of L. monocytogenes to 1.67 log10 CFU/g. E. coli and S. aureus were the most resistant at the end of storage. The cheese's pH with CFSs (MRS or WB) showed a significant reduction (p < 0.05) after CFS treatment, while the application of WB-CFS did not show greater differences in color (ΔE) compared with MRS-CFS. This study highlights the potential of CFS from Lb. casei 21/1 in the WB medium as an ecological bio-preservative for Mexican-style fresh cheese, aligning with the objectives of sustainable food production and guaranteeing food safety.

Determination of different spice powder levels for soft cheese based on milk

This study aims to evaluate and determine the most optimal level of addition spice powder to soft cheese based on milk. The spice powders used are cinnamon (Cinnamomum burmannii), lemongrass (Cymbopogon citratus), and turmeric (Curcuma longa L.) with the following treatment; T0: soft cheese without added spices powder; T1: soft cheese + 1% cinnamon powder; T2: soft cheese + 2% cinnamon powder; T3: soft cheese + 3% cinnamon powder; T4: soft cheese + 1% lemongrass powder; T5: soft cheese + 2% lemongrass powder; T6: soft cheese + 3% lemongrass powder; T7: soft cheese + 1% turmeric powder; T8: soft cheese + 2% turmeric powder; T9: soft cheese + 3% turmeric powder. The study design used a completely randomized design with three replications. Variables measured including pH, color (L*, a*, b*), total solids, and antioxidant activities using/via DPPH scavenging activity (2,2-diphenyl-picrylhydrazyl). The soft cheese pH ranged from 5.60–6.26, with T0 was the lowest and T3 had the highest value. Total solids ranged from 38.87–66.77%, with T1 was the lowest and T3 had the highest value. Antioxidant activities ranged from 37.96–72.43%, with T0 was the lowest and T9 had the highest value. Soft cheese showed L* value 66.58–80.31, with T9 was the lowest and T0 had the highest value; a* value 3.47–12.44, with T6 was the lowest and T9 had the highest value; b* value 12.35–25.95, with T0 was the lowest and T9 had the highest value. Results were analyzed using analysis of variance and Duncan’s Multiple Range Test. Based on the results, it can be concluded that the level addition of 3% spice powder was the most optimal level for soft cheese, with the highest pH, total solids, antioxidant activity, redness, and yellowness.

Determination of Thermotolerant Yeast Population in Dairy Products

Thermotolerant yeasts constitute a critical indicator for the effective management of product quality, food safety, and production processes in the dairy industry. This study aims to investigate the presence of thermotolerant yeasts in diverse dairy products within the context of Turkiye. In this study, pH and thermotolerant yeast properties of Turkish white cheese, butter, cream (Kaymak), and Tulum cheese were investigated. Thermotolerant yeast counts in butter samples ranged between 4.30 and 4.82 log CFU/g, with pH values ranging from 4.91 to 6.68. Thermotolerant yeast counts of Tulum cheese, white cheese and cream samples were &lt;2 log CFU/g. The pH values of cream and Tulum cheese were ranged from pH 5.07-6.79 and pH 4.91-6.68, respectively. The mean pH value for white cheeses was 4.98. As a results, thermotolerant yeast counts of Tulum cheese, white cheese and cream samples were below the detectable value; however, a high number of thermotolerant yeasts were determined in butter samples. In conclusions, these findings offer valuable insights for evaluating the microbiological quality of different dairy products, aiding producers in enhancing safety and quality for consumers.

Effect of purified Calotropis gigantea latex protease on the cheese quality

Cheesemaking has been relying solely on chymosin for so long. But factors like increased cheese production, diminishing supply of chymosin as well as religious and dietary limitations have been hindering the demand-production balance of cheese in the world. Hence, the primary objective of this study was to utilize the three-phase partitioning (TPP) purified Calotropis gigantea latex protease in cheesemaking. The cheese prepared using purified protease was compared with chymosin cheese for physicochemical, sensorial, textural, and microbiological evaluation. The optimum conditions for purified protease from response surface methodology (RSM) analysis were 6.25 milk pH and 45℃ milk temperature. The physicochemical parameters (moisture content, protein, ash, calcium, salt content, and pH) of cheeses prepared from latex protease and chymosin were significantly different (p&lt;0.05). The yield of latex protease cheese was significantly higher (p&lt;0.05) than chymosin cheese. In terms of texture and aftertaste, the cheese made with latex protease had significantly lower (p&lt;0.05) mean scores than chymosin cheese. Compared to chymosin cheese, the latex protease cheese had a generally inferior textural character, with significantly (p&lt;0.05) lower values for hardness, chewiness, gumminess, cohesiveness, and resilience. The total viable count and Lactobacilli count of the cheeses produced with chymosin and latex protease showed a significant (p&lt;0.05) difference. Hence, this study highlighted that the TPP purified C. gigantea latex protease could be used as a plant coagulant for cheesemaking.

Use of Raw, Thermized and Pasteurized Cow’s Milk for Making Siirt Herbed Tulum Cheese.

In this study, Siirt herby tulum cheese was produced using raw, thermalized and pasteurized forms of cow milk taken from a farm. Production and packaging were completed within 24 hours. The pasteurization was made at 72˚C for 1 min, and the termization at 68˚C for 1 min. Cloth formation was made at 32˚C for 90 min. The clot was broken into a 1x1x1 cm pieces, left for 45 min, and then filtered for 15 min. First pressure was applied to the strained curd, to which 1% salt was added, under half the weight of milk for 12 hours. Sirmo (Allium sp.) was added to the curd and a second pressure was applied for 12 hours under a weight equal to the weight of the milk used. Chickpea-sized cheese samples were tightly pressed in a plastic screw cap package, and then ripened at 4 °C for 120 d. The curd efficiency was calculated using the ratio of the amount of curd to the milk. The % yield of raw, thermized and pasteurized milk curds was determined as 26.7, 38.6 and 21.1, respectively. Similar dry matter levels (average 45%) were detected in all three cheeses. It was observed that pasteurized milk cheeses reached appropriate microbiological quality on the first d, pureed milk cheeses on the 60th d, and raw milk cheeses on the 90th d. During the process, the pH of raw milk cheeses increased from 5.4 on the first d to 7.1 on the 120th d. In pasteurized milk, these values were measured as 6.1 and 5.9. Adequate acidity and pH improvement was observed by using pasteurized cow's milk. It was seen that Siirt herby tulum cheese can be produced using pasteurized cow's milk, with a minimum of 20% fat, 20% protein, 45% dry matter and a maximum of 2% salt. The proposed method may be useful for more standard, hygienic and economical production. Further research on the subject and development of the ideal industrial production process can be achieved.

Safety assurance assessment of palmito cheese: A Mesoamerican pasta filata unripe artisanal cheese

Use of acidification and kneading/stretching steps to ensure the safety of palmito cheese was evaluated. The pH (acidification) and temperature (kneading/stretching) kinetics were recorded during processing for three cheese batches from each of three artisanal producers and a pilot plant-produced cheese. The pH and water activity of cheeses were used to estimate the growth potential of pathogens of concern. F65 °C equivalent values for Coxiella burnetii were calculated using temperature kinetics. Theoretical logarithmic reductions for other foodborne pathogens were also estimated based on D and z values reported in literature. According to their pH and water activity, all produced cheeses may support the growth of Listeria monocytogenes, Salmonella, Escherichia coli O157:H7, and Staphylococcus aureus. Calculated F65 °C values for C. burnetii confirmed that the kneading/stretching operation cannot substitute milk pasteurisation. In no case was a 5-log reduction of all pathogens achieved. Hence, both steps should not be used as sole safety-assuring hurdles.

Inulin Functionalized "Giuncata" Cheese as a Source of Prebiotic Fibers.

The development of functional foods in the dairy sector represents a flourishing field of technological research. In this study, an Italian fresh cheese as "giuncata" was enriched with inulin, a dietary fiber, with the aim of developing a product with improved nutritional properties in terms of prebiotic action on intestinal microbiota. An inulin concentration of ~4% w/w was determined in the fresh cheese after the fortification process, enabling the claim of being a "source of dietary fiber" (inulin > 3 g/100 g) according to the European regulation. The addition of inulin has no effect on the pH of cheese and does not relevantly influence its color as well as the total fat content (fat reduction ~0.61%) in comparison to the control. Mechanical properties of the cheese were also not markedly affected as evidenced from rheological and tensile testing analyses. Indeed, the incorporation of inulin in "giuncata" only exerts a slight "softening effect" resulting in a slightly lower consistency and mechanical resistance in comparison to the control. Overall, this study demonstrates the feasibility of producing a fiber-enriched dairy functional food from a large consumed fresh and soft cheese as "giuncata".

Dynamic Modelling to Describe the Effect of Plant Extracts and Customised Starter Culture on Staphylococcus aureus Survival in Goat's Raw Milk Soft Cheese.

This study characterises the effect of a customised starter culture (CSC) and plant extracts (lemon balm, sage, and spearmint) on Staphylococcus aureus (SA) and lactic acid bacteria (LAB) kinetics in goat's raw milk soft cheeses. Raw milk cheeses were produced with and without the CSC and plant extracts, and analysed for pH, SA, and LAB counts throughout ripening. The pH change over maturation was described by an empirical decay function. To assess the effect of each bio-preservative on SA, dynamic Bigelow-type models were adjusted, while their effect on LAB was evaluated by classical Huang models and dynamic Huang-Cardinal models. The models showed that the bio-preservatives decreased the time necessary for a one-log reduction but generally affected the cheese pH drop and SA decay rates (logDref = 0.621-1.190 days; controls: 0.796-0.996 days). Spearmint and sage extracts affected the LAB specific growth rate (0.503 and 1.749 ln CFU/g day-1; corresponding controls: 1.421 and 0.806 ln CFU/g day-1), while lemon balm showed no impact (p > 0.05). The Huang-Cardinal models uncovered different optimum specific growth rates of indigenous LAB (1.560-1.705 ln CFU/g day-1) and LAB of cheeses with CSC (0.979-1.198 ln CFU/g day-1). The models produced validate the potential of the tested bio-preservatives to reduce SA, while identifying the impact of such strategies on the fermentation process.

Effect of basil seed and xanthan gum on physicochemical, textural, and sensory characteristics of low-fat cream cheese.

This study aims to produce fat-reduced cream cheese using the different levels (0.25%-0.5%) of basil seed and xanthan gum by a RSM method. The basil seed, xanthan gum, and fat levels did not significantly influence the cream cheese's pH and acidity. With the fat reduction, textural properties were lost; for example, hardness, gumminess, and adhesiveness increased, and cohesiveness decreased. In addition, low-fat cream cheese's sensory score (taste, mouthfeel, and overall acceptance score) was lower. However, adding basil seed and xanthan gum could improve water holding capacity (WHC), hardness, gumminess, cohesiveness, adhesiveness and scores of mouthfeel, and overall acceptance. Basil seed gum had a better impact than xanthan on fat-reduced cream cheese properties among the two gums. In general, results showed that adding 0.5% basil and 0.5% xanthan into cream cheese could manufacture a product with a reduced-fat level (19.04%). At the same time, its physicochemical, sensory, and textural attributes were similar to cream cheese with high fat (24%). In addition, the price of the obtained product was lower.

Some properties of semi-hard cheese made from cow’s and goat’s milk

Goat's milk has been among the priority milk in consumer preferences, in recent years. It is an excellent food for children and adults due to its chemical composition and functional properties, and it can be easily consumed by individuals with cow's milk allergy. In the study, semi-hard type cheese was produced from cow’s and goat’s milk. Acidity, pH, fat, dry matter, ash, water activity, salt, color, protein, yield, organic acid and textural properties of cheeses were investigated. As a result of the analysis, it was determined that the titration acidity (% lactic acid), ash, total protein and value of cheese produced from goat's milk were higher. In terms of color, goat's cheese has a more matte appearance than cow's cheese, a* values are higher in semi-hard type cheese produced from goat's milk, and b* value is lower. The study determined that the firmness value of cheese produced from cow's milk was higher than that of goat cheese. In the study, 6 organic acids (oxalic acid, tartaric acid, formic acid, lactic acid, acetic acid and succinic acid) were determined. Formic, succinic and tartaric acid amounts were found higher in cheeses produced from goat milk. It was determined that the lactic acid level was designated the highest organic acid in cheese produced from both milk types. Cheeses produced from goat milk are more appreciated in terms of cross-sectional appearance and taste in sensory analysis. It is thought that semi-hard type cheeses can be produced from goat's milk can be an alternative to cheeses produced from cow's milk.

Microencapsulation of presumptive probiotic bacteria Lactiplantibacillus plantarum CCMA 0359: Technology and potential application in cream cheese

Microencapsulation appears to be a promising technique for protecting probiotics against conditions found in gastrointestinal digestion. Therefore, the survival of free and microencapsulated Lactiplantibacillus plantarum CCMA 0359, a potential probiotic strain, into cream cheese during storage and simulated gastrointestinal digestion was evaluated. The influence of the microencapsulated probiotic on the physicochemical and sensory properties of the cream cheese was also evaluated. Microencapsulation significantly enhanced the protection of cells against simulated gastrointestinal digestion, regardless of the storage time, and the cell count was slightly higher (8.31 log cfu g−1) compared with the free cell count (8.07 log cfu g−1). The addition of the probiotic (notably microencapsulated cells) increased the acidity and decreased the pH of cream cheese during storage and did not affect consumer acceptance. Findings indicate cream cheese as an alternative vehicle for the potential probiotic L. plantarum CCMA 0359, without affecting the acceptance of the product.

Growth Kinetics of Bacteria Isolated from Laboratory Prepared Cheese Made From Different Milk Sources

Background: Dairy food products constitute a major part of our routine diets and it is fundamental to the food industry globally. However, the need for quality control cannot be over-emphasized. A microbiological guideline must be used to define the differences between unacceptable and acceptable food products as food-borne related diseases have been associated with milk and dairy products. Aim of Study: The study aims to evaluate the growth kinetics of cheese prepared in the laboratory from different milk types over a 96 hour period in order to determine its bacteriological quality and assess the effect of storage time on the pH of the various cheeses. Methods: The laboratory cheese was prepared from fresh Goat, cow, sheep and soybeans using the traditional method. Thereafter, 10g of the cheese samples were stored in sterile 250 ml conical flasks at temperature of 28±2 oC for duration of 96 h. The samples were analyzed every 12-24 h interval using Nutrient Agar, MacConkey Agar, Mannitol Salt Agar and De Mann Rogosa and Sharpe Agar for their bacterial, coliform, staphylococcal and lactobacilli load respectively. Results: At 96 h the highest heterotrophic bacterial load, coliform, staphylococcal and lactic acid bacteria counts were observed in sheep milk cheese (8.27 ± 0.02 Log10cfu/g), (7.10 ± 0.33 Log10cfu/g), (7.40 ± 0.34 Log10cfu/g) and cow milk cheese (8.19 ± 0.05 Log10cfu/g) respectively. At 0 h the highest pH was recorded in Soybean milk cheese (5.76±0.01) while the least was cow milk cheese (4.97±0.11). The highest pH at 96 h was Soybean milk cheese (6.96±0.01) while the least pH was recorded in sheep milk cheese (6.12±0.00). Comparing results of this present study with that of the European Union microbiological regulations (EUMR) and the Gulf Standards Organization (GSO) for foods, the bacteria load of all cheese samples at 12 h was within the acceptable or permissible limit. Conclusion: The present study indicates that laboratory prepared cheese contains a repertoire of significant public health microorganisms in numbers above the permissible limit. It is recommended that appropriate aseptic procedures should be strictly upheld by dairy handlers across the entire chess production value chain.

Survival Behavior of Escherichia coli O157:H7 during over 60-Day Aging of Camembert Cheeses Manufactured from Unpasteurized Raw Milk

Although many developed countries (USA, Canada, and several EU countries) allow raw milk cheese to be aged more than 60 days, these countries have strict standards for the aging conditions, such as temperature, of raw milk cheese. Spiking experiments were conducted with Camembert cheese made from raw milk, to assess the microbiological safety of raw milk cheese aged for more than 60 days. We spiked Escherichia coli O157:H7 into raw milk with different inoculation levels (high, medium, and low). Camembert cheese was prepared from the inoculated raw milk, then aged in an incubator for up to 9 weeks (63 days). There were no significant differences in pH and water activity (aW) between uninoculated cheese and cheese samples inoculated with E. coli O157:H7 (p&lt;0.05). The pH and aW of the Camembert cheese decreased throughout the storage period. In conclusion, E. coli O157:H7 did not affect the pH and aW of the cheese samples. Cell counts were conducted every week using the agar-plating method. Inoculated cells were completely eliminated, especially in Camembert cheese, after 60 days, and the reduction rate of cells was much faster in Camembert cheese.

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.

Growth Behavior of Listeria monocytogenes during over 60-Day Ripening of Camembert Cheeses Produced by Unpasteurized Raw Milk

Although the USA, Canada, and several EU countries allow raw milk cheese to be aged more than 60 days, these countries have strict standards for its aging conditions, such as temperature. Many developed countries have employed standards of identity which effectively prevent the manufacture and sale, of cheese made from unpasteurized milk (i.e., raw milk) in interstate commerce, unless such cheese has been aged for a minimum of 60 days. The microbiological safety of raw milk Camembert cheese, aged for more than 60 days, was evaluated using spiking experiments. We spiked Listeria monocytogenes into raw milk with different inoculation levels (high, medium and low). Camembert cheese was prepared from the inoculated raw milk, then aged in an incubator for up to 9 weeks (63 days). The number of cells was determined every week using the agar-plating method. Inoculated cells were completely eliminated, especially in Camembert cheese, after 60 days, and the reduction rate of cells was much faster in Camembert cheese. There were no significant differences in pH and water activity (aW) between the uninoculated cheese and the cheese samples in which Listeria monocytogenes was inoculated (p&lt;0.05). The pH and aW of the Camembert cheese decreased throughout the storage period. In conclusion, the pathogenic bacteria used in this study did not affect the pH and aW of the Camembert cheese samples.