Milk Cheese Research Articles

Relationship between Volatile Organic Compounds and Microorganisms Isolated from Raw Sheep Milk Cheeses Determined by Sanger Sequencing and GC-IMS.

Recently, the interest of consumers regarding artisan cheeses worldwide has increased. The ability of different autochthonous and characterized lactic acid bacteria (LAB) to produce aromas and the identification of the volatile organic compounds (VOCs) responsible for flavor in cheeses are important aspects to consider when selecting strains with optimal aromatic properties, resulting in the diversification of cheese products. The objective of this work is to determine the relationship between VOCs and microorganisms isolated (Lacticaseibacillus paracasei, Lactiplantibacillus plantarum, Leuconostoc mesenteroides and Lactococcus lactis subsp. hordniae) from raw sheep milk cheeses (matured and creamy natural) using accuracy and alternative methods. On combining Sanger sequencing for LAB identification with Gas Chromatography coupled to Ion Mobility Spectrometry (GC−IMS) to determinate VOCs, we describe cheeses and differentiate the potential role of each microorganism in their volatilome. The contribution of each LAB can be described according to their different VOC profile. Differences between LAB behavior in each cheese are shown, especially between LAB involved in creamy cheeses. Only L. lactis subsp. hordniae and L. mesenteroides show the same VOC profile in de Man Rogosa and Sharpe (MRS) cultures, but for different cheeses, and show two differences in VOC production in skim milk cultures. The occurrence of Lactococcus lactis subsp. hordniae from cheese is reported for first time.

Study on the Characteristics of Cheddar Cheese Prepared from Different Blends of Buffalo and Goat Milk

Cheese is a good food while traveling. It is valuable for its portability, long life, and high content of fat, protein, calcium, and phosphorus. Cheese is a more compact form of nutrition and has a longer shelf life than milk from which it is made. Goat cheese is known as Chevre, after the French word for goat. Goat cheese is often higher in protein and lower in fat than cheese from cow’s milk. Regardless of excellent nutritional profile goat milk has been an ignored commodity; researchers and manufacturers have paid very little attention for its direct consumption and use in product value addition. In our current study Cheese was prepared from goat and buffalo milk and their blends 75:25, 50:50, 25:75, respectively. Samples thus prepared were packed in air-tight polyethylene bags and stored at 4±1ºC. Samples were evaluated for different physicochemical analysis i.e. fat, protein, lactose, ash, total solids, pH, acidity and organoleptic qualities on monthly basis up to 120 days of storage period. All the analysis was conducted in the Laboratories of Department of Animal Products Technology (DAPT) and Department of Food & Nutrition, University of Veterinary and Animal Sciences Lahore and Ravi Campus Pattoki. The data thus obtained from all the parameters was analyzed using analysis of variance technique to determine the level of significance. Statistical analysis showed that the storage and treatments had the non-significant effect on pH, acidity, moisture, protein, lactose of cheddar cheese. The sensory evaluation of different treatments of goat and buffalo milk in cheddar cheese varied non-significantly among each other. However, evaluation during storage varied significantly with respect to color and taste. Furthermore, the interaction between treatments and storage was found non-significant in smell, texture and overall acceptance.

The evolution of antioxidative properties of protein-derived peptides of Mexican Panela goat and cow milk cheese during its shelf life

ABSTRACT In the current study, Mexican Panela cheeses manufactured from cow or goat milk were analyzed in terms of sensory characteristics, peptide concentration, proteolysis and antioxidant activity using the DPPH radical (1, 1-diphenyl-2-picrylhydrazyl) assay during its shelf life at 1, 7, 14, 21, and 28 days. There was no significant difference in sensory rating owing to the influence of the cheese based on a cow or goat milk, with high levels of like seen in both varieties of cheese (from 6 to 7 on average on the hedonic scale of 1 to 9). On the other hand, all cheeses, showed antioxidant activity, which was stronger in goat milk cheeses, which had a DPPH radical inhibition in the range from 11.59 to 83.11%. Additionally, substantial correlations were identified between the studied variables, suggesting that the antioxidant activity is related to the peptides contained in the water-soluble peptides extract by 92%.

Ammi-visnaga extract; a novel phyto-antiviral agent against bovine rotavirus.

The spread of bovine rotavirus has a great impact on animal productivity, milk products, and human public health. Thus, this study aimed to develop a novel, effective and accessible Phyto-antiviral treatment made from methanolic Ammi-visnaga seed extract against rotavirus infection. Rotaviruses were isolated from raw milk and cottage cheese samples randomly collected from Cairo and Qalubia governorates. They were all identified serologically, however, only three of them were both biologically and molecularly confirmed. The methanolic extract derived from Khella seeds (MKSE) was chemically analyzed with mass chromatography. The cellular toxicity of MKSE was tested on Caco-2 cells and its antiviral activity against one of the isolated bovine rotaviruses (BRVM1) was tested by both the cytopathic inhibition assay and the plaque reduction assay. Our results showed that 17.3% of the total collected 150 dairy samples were bovine rotavirus antigen positive. Three representatives of them were phylogenetically identified to be included in group A based on a 379bp coat protein gene. Visnagin, Benzopyran, Khellin, and Benzenepropanoic acid were the major active components found in the MKSE. The maximum non-toxic concentration of MKSE was 5µg/mL and the CC50 value was 417µg/mL. The MKSE exhibited in-vitro antiviral activity against BRVM1 indicated by inhibition of the viral cytopathic effect (SI = 204.5, IP = 98%), causing a 1.5 log decrease in BVRM1 TCID50 and reducing the viral plaques count by the percentage of 93.14% at MNTC (5 ug/ml). In conclusion, our study showed that bovine rotavirus represents a severe health problem that needs attention in Egypt, and it supports using MKSE as a potential natural anti-rotavirus agent.

Descriptive Characteristics and Cheesemaking Technology of Greek Cheeses Not Listed in the EU Geographical Indications Registers

Greece has a variety of cheeses that are registered as protected designation of origin and protected geographical indications, and many others that are produced in a traditional way, without such registration. This article aims to describe the characteristics of these cheeses, which do not bear a certification of geographical indication, in order to increase their significance. Therefore, in this work, the scientific data published about the history, production, composition, and other specific properties of some milk cheeses (Kariki, hard Xinotyri, soft Xinotyri, Kefalotyri, Kashkaval Pindos, Graviera, Manoura Sifnos, Teleme, Tsalafouti, Tyraki Tinou, Ladotyri Zakynthou, Touloumotyri, and Melichloro) and whey cheeses (Anthotyros, Myzithra, and Urda) are presented. This information may contribute to their better promotion and recognition, protecting their heritage, and supporting the local economy.

Colloidal Gold Immunochromatography and ELISA Traceability of Tetracycline Residues from Raw Milk to its Dairy Products.

The presence of tetracycline (TC) and its residues in raw milk and milk dairy products poses a threat to human health due to the induction of antibiotic resistance of bacteria that can be transmitted between animals, humans, and the environment. The aim of this study was to investigate the transfer of TC from raw milk to different dairy products: pasteurized milk, boiled milk, sour milk, skimmed milk, and cottage cheese. We analyzed samples of milk from different sources: household farmers, local farms, and milk factories. The analyses of TC in milk and dairy products were performed using colloidal gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA). The highest content of TC was found in the milk purchased from local household farmers; therefore, these samples were chosen for the study of TC transfer to dairy products. TC was also found in sour milk at levels comparable with those obtained in raw milk. The average TC content decreased following heat treatment of the milk, as follows: for pasteurized milk 22.07% and for boiled milk 29.35%. The highest concentrations were determined in cottage cheese in the range 200-620 μg/kg. TC residues are transferred from milk to dairy products in various amounts depending on the preparation conditions, and due to their chemical properties, they accumulate in concentrated derivatives, such as cheese. Therefore, TC can be identified even in cheeses prepared from milk with undetected antibiotic levels.

КОМПЛЕКСНАЯ МЕТОДИКА ОПТИМИЗАЦИИ АГРОПРОИЗВОДСТВЕННОГО КЛАСТЕРА АДМИНИСТРАТИВНЫХ РАЙОНОВ РЕСПУБЛИКИ БЕЛАРУСЬ

Ensuring the growth of the economy of Belarus provides for sustainable socio-economic development of admin-istrative districts, which significantly increases the level of income and quality of lifeof the population. The main trigger for the development of administrative districts is the increase in the eco-nomic efficiency of the functioning of their agro-production cluster, which consists of agricultural organizations and food and light industry processing enterprises. As a re-sult of the research, a comprehensive methodology for optimizing the agro-production cluster of administrative districts has been developed, including a three-level economic and mathematical model in which all agricultural organizations, on-farm production units and processing enterprises are represented as separate blocks, including components in the form of restrictions of the main and connecting blocks. The objective function of the model is designed to determine the max-imumgross value added. The model was tested on the example of the agro-industrial cluster of the Gorkiadministrative district of the Mogilev region of the Republic of Belarus(hereinafter –Gorki district), which includes 8 agricultural organi-zations and a milk processing enterprise, the butter and cheese plant OJSC Molochny Gorki. During the calculations, the substantiation of the prospective crop yields and annual livestock productivity in the farms of the Gorki district was per-formed using correlation models. The optimal number of livestock and sown areas of commercial crops have been calcu-lated. The reserves for the growth of production volumes and economic efficiency of the functioning of the agro-production cluster and the Gorki district have been determined.

Diagnosis of the impact of Covid-19 on artisanal cheese production in the semi-arid region of Brazil

The objective of this study was to present information on the impacts resulting from Covid-19 on the artisanal coalho cheese production chain about: access to information; socioeconomic; income and government support; healthcare. The interviews were conducted using the Google Forms tool, with milk and artisanal coalho cheese producers in Rio Grande do Norte, Brazil. The producers obtained a lot of information transmitted on television (66%); the majority to adhere to health protocols. There was instability in the production, with an initial need to reduce production resulting from prohibitive measures to trade. The level of demand with regard to the consumer market increased with the quality of milk and cheeses. An allegation of lack of support from the government to maintain the activity was also verified in 78.7% of the interviewees, but 83% had resorted to emergency aid. Therefore, it can be concluded that the challenges imposed by the pandemic are not just sanitary. The study confirmed the need to restructure public services and policies. These results can provide compelling evidence about the rural context in the country.

Campylobacter fetus foodborne illness outbreak in the elderly.

In June 2021, a cluster of seven cases of Campylobacter fetus infections occurred in a rehabilitation center and caused significant morbidity in elderly patients including five with bacteremia and two with osteoarticular medical device infections. The genetic identity identified by whole genome sequencing of the different Campylobacter fetus strains confirms a common source. This foodborne illness outbreak may have resulted from the consumption of unpasteurized dairy products, such as a cow's raw milk cheese resulting from a farm-to-fork strategy.

Comunidades bacterianas em queijos artesanais de leite bovino cru da região sul do Brasil

ABSTRACT: The production of artisanal cheeses made with raw bovine milk has grown in the southern region of Brazil. It is important to obtain information about the risks of this practice, especially concerning food safety. In this study, next-generation sequencing was used to identify and characterize the bacterial communities of artisanal raw milk cheeses. We analyzed one pool of five raw milk samples (control group M1) from different dairy farms and nine pools (M2-M10) of 45 artisanal raw milk cheeses.The characterization of the bacterial communities included 199 species distributed across 59 different genera dispersed among the samples. Among the genera observed, 11 were classified as beneficial to the aroma, flavour, colour, and texture of the cheese. Thirty-one genera were classified as harmful to these characteristics. Another 17 were classified as potential pathogens for animals and humans, including Aeromonas, Bacillus, Cronobacter, Salmonella, Staphylococcus, and bacteria of the coliform group, including E. coli and Klebsiella. There was a significant difference (P < 0.05) in the number of bacterial communities identified between the control group (M1) and the two pools of artisanal raw milk cheeses (M2 and M8). This study demonstrated that next-generation sequencing provides in-depth information on the composition of the microbiota in artisanal raw milk cheeses, characterizing bacterial communities, identifying the wide microbial diversity, and identifying microbial benefits and risks.

Study of Microbial Fuel Cell Technology using Dangke, Whole Milk, and Whey Cheese Substrates

Microbial Fuel Cell technology using dangke, whole milk, and whey cheese as substrates have been done. Dangke, whole milk, and whey cheese were placed in the anode chamber. As for the cathode chamber, KMnO4 electrolyte solution was used. The two chambers were then connected by a membrane made of a salt bridge. The highest voltage measurement results for dangke, whey cheese, and whole milk substrate were respectifley obtained at 659 mV, 998 mV, and 670 mV. As for the current measurement on each substrate, it was 0.29 mA, 0.37 mA, and 0.23 mA. In general, the measurement results show that the MFC made using whey cheese substrate has the best quality with a power density of 9.23 x 10-3 W/m2 . Thus, whey cheese which is an industrial waste can be used as an alternative source of electricity by converting organic compounds using microorganisms.

Microbiological Biodiversity of Regional Cow, Goat and Ewe Milk Cheeses Produced in Poland and Antibiotic Resistance of Lactic Acid Bacteria Isolated from Them.

(1) Unique sensory values of traditional and regional dairy products made them more and more popular among consumers. Lactic acid bacteria naturally occurring in these products can express antibiotic resistance and be a reservoir of antibiotic resistance genes (ARG) in the environment. The aim of the study was to characterize the microbial diversity of twenty regional cheeses produced from non-pasteurized cow, goat and ewe milk, and investigate the phenotypic and genotypic antibiotic resistance (AR) of lactic acid bacteria isolated from these products. (2) Conventional microbiological methods were applied for the enumeration of lactic acid bacteria (lactobacilli and lactococci) and their isolation, and for the enumeration of Enterococcus, Staphylococcus, Enterobacteriaceae and spores. The disc diffusion method was applied for phenotypic AR. The PCR-based methods were used for strain identification, microbiological diversity of cheeses (PCR-DGGE), and for AR gene detection. (3) Among 79 LAB isolates the most frequent species were L. plantarum (n = 18), Leuc. lactis (n = 17), Lc. lactis (n = 11), Leuc. mesenteroides (n = 9) and L. pentosus (n = 8). Additionally, by using the PCR-DGGE method, DNA of L. casei was found in nine products. Lactobacilli (5.63-8.46 log cfu/g) and lactococci (6.15-8.41 log cfu/g) predominated over Enterococcus (max. 4.89 log cfu/g), Staphylococcus (max. 4.18 log cfu/g), and Enterobacteriaceae (mostly up to 4.88 log cfu/g). Analysis of phenotypic resistance to tetracycline (30 µg), erythromycin (15 µg), and chloramphenicol (30 µg) showed that 29% of LAB isolates were resistant to one antibiotic, 8%-to two, and 12%-to all tested antibiotics. Antibiotic resistance genes (AGR) for tetracycline (tet(M), tet(L), tet(W)), erythromycin (erm(B)) and chloramphenicol (cat-TC) were detected in 30 (38%), 29 (36.7%) and 33 (43.4%) LAB isolates, respectively. Among 31 LAB isolates phenotypically susceptible to all tested antibiotics, only 5 (16%) had no ARGs. (4) The results obtained in our work shed light on the potential threat posed by the widespread presence of ARGs in LAB present in regional cheeses.

Identification of Lactobacillus strains from human mother milk and cottage cheese revealed potential probiotic properties with enzymatic activity

The main attempt of this study is to isolate, determine potential probiotic properties and enzyme production of some lactic acid bacteria (LAB). Among all isolates, two LAB strains isolated from human mother milk and cottage cheese revealed antimicrobial activity against some tested pathogenic strains. Both isolates inhibited all the tested pathogens except Escherichia coli. The two isolates were identified by morphological, biochemical properties and then by 16S rRNA gene sequencing technique as Lactobacillus acidophilus SAM1 and Lactiplantibacillus plantarum SAM2. Potential probiotic characters were investigated. Both strains survived in relatively low pH and high bile concentrations and were able to grow at 0.5% of pancreatin concentrations. Their growth decreased by increasing phenol from 0.2% till 0.5%. Both strains did not show hemolytic activity. Coaggregation potential was exhibited by the two strains against Staphylococcus aureus and Candida albicans. Hydrophobicity of Lactobacillus acidophilus SAM1 and Lactiplantibacillus plantarum SAM2, with ethyl acetate; were 88.1% and 82.8%, respectively. Lactobacillus acidophilus SAM1 was susceptible to Ampicillin, Penicillin, Erythromycin, Ciprofloxacin and Tetracycline; on the contrary, it resists Vancomycin and Cefoxitin; while Lactiplantibacillus plantarum SAM2 resists all tested antibiotics. Maximum growth was achieved using glucose as a carbon source and yeast extract as nitrogen source for both strains; however, glucose is the most preferred carbon source for microorganisms and it prevents the uptake of carbon from other sources like yeast by catabolite repression mechanism. Lactobacillus acidophilus SAM1 produces lipase enzyme, while Lactiplantibacillus plantarum SAM2 produces amylase and protease.

Goat production systems of the central highlands of Veracruz, Mexico

Objective: This study was to characterize the goat production units of the central mountain area of the state of Veracruz, Mexico. Disign/methodology/approach: A multiple case study was carried out taking into consideration socioeconomic aspects, type of forage, goat feeding, reproduction, improvement, and health. Results: The results showed that goat and cheese production account for 50-100% of the producers' income. The forages grown and the type of goat feed used in the production units of the mountain area are: King grass, CT-115, maralfalfa, giant star grass, alfalfa, and corn. Animal reproduction is carried out by controlled mating and births take place at the beginning and end of each year. Flocks do not exceed 150 heads; the predominant breeds are Saanen and Alpine. The average daily production of milk ranges from 16 to 90 L, with a production of 0.75-3 L milk animal-1 day-1. Study limitations/implications: None Findings/conclusions: The activity is family-based and involves cultivation, animal management, and milk and artisanal cheese production. Further studies are required to confirm individual milk production.

Polymorphism of the kappa-casein gene in dairy cattle populations of the Kostroma region and its effect on dairy productivity of cows

Relevance. Despite the more than 20-year history of research, the study of the polymorphism of the kappacasein (CSN3) gene in domestic dairy cattle breeds and its effect on the indicators of dairy productivity of cows is still relevant. The largest number of domestic studies on the kappa-casein gene was carried out on the Black-and-White and Yaroslavl breeds, while the Kostroma breed of dairy cattle in this area has not been studied enough.Methods. The source of DNA for analysis was whole blood taken from the tail vein of animals and treated with a set of reagents "Proba-NK" ("NPO DNA Technology" LLC, Russia) according to the manufacturer’s instructions. Genotyping of the single-nucleotide polymorphism of the kappa-casein gene (rs43703017) was implemented by real-time PCF using the "DTprime" amplifier ("NPO DNA Technology" LLC, Russia) and HRM-analysis technology (high resolution melting). The results were processed using methods of zootechnical and statistical studies.Results. As a result of the study, it was found that the population of cows of the Kostroma breed is characterized by a significantly greater consolidation of the gene pool compared to animals of the Blackand-White breed, which suggests a higher efficiency of breeding work with the Kostroma breed using the kappa-casein gene as a genetic marker of suitability of milk for cheese making. The kappa-casein gene has a significant effect on the parameters of dairy productivity and functional longevity of cows.

High Level of Interaction between Phages and Bacteria in an Artisanal Raw Milk Cheese Microbial Community.

Microbial starter cultures are used in the production of many cheeses around the world, such as Parmigiano-Reggiano, in Italy, Époisses, in France, and Canastra, in Brazil, providing many of the unique features of these cheeses. Bacteriophages (phages) are ubiquitous and well known to modulate the structure of bacterial communities, and recent data indicate that cheeses contain a high abundance of naturally occurring phages. Here, we analyze the viral and bacterial metagenomes of Canastra cheese: a traditional artisanal Brazilian cheese produced using an endogenous starter culture and raw milk. Over 1,200 viral operational taxonomic units were recovered using both isolated viral-like particles and complete metagenomic DNA. Common viral families identified included Siphoviridae and Myoviridae, with 40% of putative phage genomes unidentified at the family level of classification. We observed very high phage diversity, which varied greatly across different cheese producers, with 28% of phage genomes detected in only one producer. Several metagenome-assembled genomes were recovered for lactic acid-producing bacteria, as well as nonstarter bacterial species, and we identified several phage-bacterium interactions, at the strain level of resolution, varying across distinct cheese producers. We postulate that at least one bacterial strain detected could be endogenous and unique to the Canastra cheese-producing region in Brazil and that its growth seems to be modulated by autochthonous phages present in this artisanal production system. This phage-host relationship is likely to influence the fermentation dynamics and ultimately the sensorial profile of these cheeses, with implications for other similar cheese production systems around the world. IMPORTANCE Our work demonstrated a dynamic yet stable microbial ecosystem during cheese production using an endogenous starter culture. This was observed across several distinct producers and was marked by genomic evidence of continued phage-bacterium interactions, such as the presence of bacterial defense mechanisms. Furthermore, we provide evidence of unique microbial signatures for each individual cheese producer studied in the region, a fact that may have profound consequences on product traceability. This was the first effort to describe and understand the bacteriophage composition and ecological dynamics within the Brazilian Canastra cheese production system. The study of this prototypical backslopping production system provides a solid background for further mechanistic studies of the production of many cheeses around the world.

Regression trees to identify combinations of farming practices that achieve the best overall intrinsic quality of milk

Many studies over the last 30 years have shown the effects of farming practices on milk compounds. Combinations of practices may have antagonistic or synergistic effects on milk compounds, but these combination effects remain underinvestigated. Research needs to focus on overall intrinsic milk quality (including sensory, technological, health, and nutritional dimensions) and identify the combinations that can optimize it. The aim of this study was to identify which combinations of farming practices achieved the best scores for sensory, technological, health, and nutritional dimensions and for overall intrinsic milk quality. Ninety-nine private farms were visited once each to sample their bulk tank milk and survey their farming practices. The surveyed practices concerned herd characteristics, feeding management, housing conditions, and milking and milk storage conditions on the day of test. Analyses of bulk tank milk were designed to evaluate the overall intrinsic quality of the milk for 2 target products: raw milk cheese and semi-skimmed UHT milk. Regression trees were then used to identify the combinations of farming practices that achieved the best scores on each dimension and on overall intrinsic quality of the milk. Breed and diet (type of forage) were the most influential factors for sensory and health dimensions and for technological and nutritional dimension scores, respectively, in the cheese assessment. Overall cheese quality was highly positively correlated with these 4 dimension scores. Therefore, breed and diet emerged as the most influential practices in the regression tree for overall cheese quality. However, the combinations of practices that resulted in the best quality scores differed according to dimension studied and product targeted. This suggests that advice on farming practices to improve intrinsic milk quality needs to be adapted according to the end-purpose of the collected milk. This innovative approach combining on-farm data and regression trees provides farm managers with a valuable and practical tool to prioritize practices in terms of their role in shaping milk quality, and to identify the combinations of practices that promote good milk quality and practice thresholds or modalities needed to achieve it.

Microbiological Quality and Safety of Traditional Raw Milk Cheeses Manufactured on a Small Scale by Polish Dairy Farms.

Polish raw milk artisanal cheese may pose a threat to consumer safety due to pathogen presence. The aim of this study was to assess the microbiological safety, quality and physicochemical composition of cow’s and goat’s milk fresh cheeses produced by farmers on a small scale. A total of 62 samples of six cheese types were analyzed for Listeria monocytogenes, Salmonella spp., lactic acid bacteria and coliform presence and concentration levels. The physicochemical analysis estimated energy, water, protein, fat, carbohydrate, ash and salt content. The cheeses were also tested for heavy metal contamination. Listeria monocytogenes and Salmonella spp. were not detected in any of the samples. Coliforms were present in all the goat’s milk cheeses and only in two of the cow’s milk cheeses. Low levels of cadmium, below 0.008 ppm, were detected in three of the cows’ milk samples. The raw milk cheeses studied were free of the pathogens examined and were of high nutritional value.

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.

Evaluation of the Bacterial Load in the Raw Dairy Products in Baghdad, Iraq.

Milk and cheese were recognized as highly nutritious food due to their high protein, fat and minerals (calcium, phosphorus, iron, and vitamins). Accidental contamination of food through the handlers could have resulted in many kinds of bacteria especially Staphylococcus aureus in the dairy products. Therefore, this study aimed to study variation in bacterial isolation percentage and the bacterial counts in raw milk and locally produced soft cheese in local markets in Baghdad. A total of 150 samples of raw milk and local soft cheese (75 for each) were collected from different regions of Baghdad city from October 2020 to July 2021 to study the evaluation of bacterial contamination. The isolation percentage of total coliform, Fecal coliform, Escherichia coli and Staphylococcus aureus in the raw milk were 82, 69, 54 and 42%, respectively. While in the soft cheese, the isolation percentage for coliform, Fecal coliform, Escherichia coli and Staphylococcus aureus were 90, 74, 60 and 45%, respectively. Furthermore, high percentages of bacterial isolation were recorded during summer. The recorded data showed significant (P<0.05) variation for both raw and soft cheese according to months, and soft cheese had a higher isolation percentage than the raw milk samples. The average values of bacterial count values that were isolated from October to February in the raw milk of the total coliform, fecal coliform, E. coli and Staph aureus were 5.57, 4.25, 3.77 and 2.94 cfu log10/mL respectively, which were recorded during the cold months. While the recording of the average values from March to July as hot months were 6.02, 5.02, 5.22 and 3.23 CFU log10/mL, respectively. The average bacterial values in the soft cheese were 6.02, 5.03, 4.97 and 3.67cfu log10 /g, respectively, from October to February and were significantly (P<0.05) less than the summer from March to July, which recorded 7.17, 6.32, 5.01 and 4.15cfu log10/g respectively. The high contamination found in the soft cheese and during hot months compared with raw milk and cold months, respectively, is a sign of unsanitary manufacturing conditions such as post-process contamination, high temperature in summer, and lack of refrigeration during long-distance transportation.