Raw Milk Samples Research Articles

Risk assessment of antibiotic residues in raw cow’s milk in Bangladesh

ABSTRACT This study evaluated the presence of residual levels of commonly utilised antibiotics, including oxytetracycline (tetracyclines), ciprofloxacin, enrofloxacin, and levofloxacin (fluoroquinolones), in milk samples. Fifty raw milk samples were collected from five farms in Keraniganj, Dhaka. A validated RP-HPLC method was applied to detect and quantify antibiotic residues, demonstrating good linearity with coefficients ranging from 0.999 to 1.0 in the concentration range of 1.25–15.00 µg/mL. The study revealed that oxytetracycline was detected in 90% of the samples, followed by levofloxacin (66%), enrofloxacin (64%), and ciprofloxacin (62%). One farm showed the highest antibiotic prevalence, with oxytetracycline in all samples and levofloxacin, enrofloxacin, and ciprofloxacin in 80% of the samples. About 30% of the oxytetracycline-positive samples exceeded the MRL, while none surpassed the MRL for enrofloxacin and ciprofloxacin. Calculated human health risks appeared to be low, but children might face potential risks due to prolonged exposure.

Metagenomics reveals differences in spore-forming bacterial diversity in raw milk in different regions and seasons in China

The spore-forming bacteria in the dairy industry are notable for their spores resilience and capacity to survive heating processes, allowing them to germinate and enter the vegetative stage, potentially leading to spoilage of the milk. Additionally, these spores can form biofilms, becoming a persistent source of contamination in processing environments. In this study, we collected a total of 165 raw milk from six different parts in China in spring, summer, autumn, and winter, respectively. Metagenomics sequencing method was used to explore and compare the differences in spore-forming bacterial composition and diversity in raw milk samples. Among these samples, four genera and 207 species of spore-forming bacteria were identified, with the genus Bacillus and the species Paenibacillus darwinianus dominant. Seasonal variations had a greater impact on the composition and abundance of spore-forming bacteria in raw milk than regional differences. Notable, raw milk samples collected during the spring and summer exhibited a higher number of unique spore-forming bacterial species compared to those collected in other seasons. Moreover, different regions and seasons have their own dominant bacteria. Metabolism of cofactors and vitamins, energy metabolism, carbohydrate metabolism, and amino acid metabolism were the main metabolic pathways. Hence, specific strategies need to be adopted to prevent and control spore-forming bacteria in raw milk in different regions and seasons.

The paradox of safe milk supply by small-scale dairy farmers in Sub-Saharan Africa: insights based on current practices in Malawi

Abstract This research paper aimed to assess milking and milk handling practices among small-scale dairy farmers and determine the presence of E. coli in raw and processed liquid milk in Malawi. A total of 113 dairy farmers were interviewed across three agroecological zones of Malawi. Eighty-seven (87) processed and raw milk samples were collected from selected food stores and dairy farms and tested for E. coli. Ninety-five percent of small-scale dairy farmers had at most 2 milking cows, with daily average milk production of less than 10 L. Sixty-nine percent cleaned milking utensils using untreated water, and the farmers had no refrigerators. Eighty-eight percent held raw milk for over 6 hours at room temperature. Escherichia coli was found to be widely distributed in raw milk (76%) and pasteurized milk (75%), averaging 5.38 ± 1.82 and 2.47 ± 1.02 log cfu/ml, respectively. In conclusion, this study demonstrates that Malawian small-scale dairy farmers employ poor milking and post-milking practices, which compromise the socioeconomic environment of small-scale dairy farmers.

Assessment of genetic parameters and breeding value of somatic cell score and first lactation 305 days milk yield in crossbred dairy cattle of Kerala

Present study focuses on estimating the genetic parameters and breeding values related to somatic cell score (SCS) and first lactation 305 days milk yield (FL305DMY) in crossbred cattle in Kerala. Mastitis, a common inflammatory condition of the mammary gland, poses significant challenges to dairy production by decreasing milk quality and quantity, resulting in considerable economic losses for farmers. The study involved 200 first-lactation crossbred cows from various locations and 200 raw milk samples were analysed for SCS estimation. Overall least square mean of SCS and 305 DMY were 4.85 and 2409.35 kg, respectively. The heritability estimates for SCS and 305 DMY were 0.003±0.340 and 0.359±0.076. The average breeding value of 200 crossbred cattle sired by 78 bulls for SCS was 4.16 and for 305DMY was 2743.60 kg. The negative genetic correlation between SCS and FL305DMY (-0.113 ± 0.38) further emphasizes the detrimental impact of mastitis on milk production. The results indicate the necessity of incorporating SCS into selection criteria for dairy cattle to enhance both milk yield and overall herd health.

Artificial Neural Network Modeling to Predict Electrical Conductivity and Moisture Content of Milk During Non-Thermal Pasteurization: New Application of Artificial Intelligence (AI) in Food Processing

This study proposed applying artificial intelligence (AI) to predict the actual electrical conductivity (EC) of raw and pasteurized milk using moderate electric field (MEF) based on the electric field strength (EFS) and mass flow rate (MFR) along with modeling moisture content (MC) based on the EC. To this end, an artificial neural network (ANN) was implemented for conventionally (CP) and non-thermally (NP) pasteurized milk. The findings indicated no significant difference (p > 0.05) between the experimental and predicted data for EC and MC. The MFR and EFS affected the actual EC. The raw milk samples had an EC of 0.468812–0.46913 S/m and MC of 87.3218–87.35941%, while these values in NP pasteurized milk were 0.457441–0.638224 S/m and 87.33986–87.40851%. With correlation coefficients (R) of 0.736478106–0.951840323 and mean square errors (MSE) of 0.005539–0.0064, the ANN accurately predicted the raw and pasteurized milk MC based on the EC using the sixth-order polynomial model and the EC based on the EFS and MFR using a quadratic model. The EC of pasteurized milk by NP was significantly (p < 0.05) lower than that of CP and raw dairy by 15.44% and 11.30%, respectively. The results show that the EFS and MFR might be used for the online assessment of milk’s physical attributes (e.g., EC), followed by using the assessed parameter to determine other properties (e.g., MC) by developing AI approaches based on optimized models. These observations showcase the innovative use of ANN-based AI to predict milk’s EC and MC accurately. Integrating such AI platforms into non-thermal food processing could eventually develop more sustainable food production and enhance food security and quality through process innovation and sustainable manufacturing, contributing to the industrial revolution and sustainable development goals.

Characterization of psychrotrophic and thermoduric bacteria in raw milk using a multi-omics approach.

Psychrotrophic and thermoduric bacteria are the main reasons for the spoilage of dairy products. This study aims to address the composition and function of psychrotrophic and thermoduric bacteria in eight groups of raw milk samples obtained from Heilongjiang Province and Inner Mongolia (China). Microbial enumeration showed an average total bacterial count of 4.63 log c.f.u. ml-1 and psychrotrophic bacterial counts of 4.82 log c.f.u. ml-1. The mean counts of mesophilic and thermophilic thermoduric bacteria were 3.68 log and 1.81 log c.f.u. ml-1, respectively. Isolated psychrotrophic bacteria (26 genera and 50 species) and mesophilic thermoduric bacteria (20 genera and 32 species) showed high microbial diversity. Through metagenomic and proteomic analyses, significant disparities in the concentration and community structure of psychrotrophic and thermoduric bacteria were observed among different locations. A large number of peptidases were annotated by metagenomics, which may result in milk spoilage. They mainly come from some typical psychrotrophic and thermoduric bacteria, such as Chryseobacterium, Epilithonimonas, Pseudomonas, Psychrobacter, Acinetobacter, Lactococcus, Escherichia and Bacillus. However, the main proteins detected in fresh raw milk were associated with bacterial growth, reproduction and adaptation to cold environments. This investigation provides valuable insights into the microbial communities and protein profiles of raw milk, shedding light on the microbial factors contributing to milk deterioration.

Digital Holographic Microscopy in Veterinary Medicine-A Feasibility Study to Analyze Label-Free Leukocytes in Blood and Milk of Dairy Cows.

For several years, the determination of a differential cell count of a raw milk sample has been proposed as a more accurate tool for monitoring the udder health of dairy cows compared with using the absolute somatic cell count. However, the required sample preparation and staining process can be labor- and cost-intensive. Therefore, the aim of our study was to demonstrate the feasibility of analyzing unlabeled blood and milk leukocytes from dairy cows by means of digital holographic microscopy (DHM). For this, we trained three different machine learning methods, i.e., k-Nearest Neighbor, Random Forests, and Support Vector Machine, on sorted leukocyte populations (granulocytes, lymphocytes, and monocytes/macrophages) isolated from blood and milk samples of three dairy cows by using fluorescence-activated cell sorting. Afterward, those classifiers were applied to differentiate unlabeled blood and milk samples analyzed by DHM. A total of 70 blood and 70 milk samples were used. Those samples were collected from five clinically healthy cows at 14-time points within a study period of 26 days. The outcome was compared with the results of the same samples analyzed by flow cytometry and (in the case of blood samples) also to routine analysis in an external laboratory. Moreover, a standard vaccination was used as an immune stimulus during the study to check for changes in cell morphology or cell counts. When applied to isolated leukocytes, Random Forests performed best, with a specificity of 0.93 for blood and 0.84 for milk cells and a sensitivity of 0.90 and 0.81, respectively. Although the results of the three analytical methods differed, it could be demonstrated that a DHM analysis is applicable for blood and milk leukocyte samples with high reliability. Compared with the flow cytometric results, Random Forests showed an MAE of 0.11 (SD = 0.04), an RMSE of 0.13 (SD = 0.14), and an MRE of 1.00 (SD = 1.11) for all blood leukocyte counts and an MAE of 0.20 (SD = 0.11), an RMSE of 0.21 (SD = 0.11) and an MRE of 1.95 (SD = 2.17) for all milk cell populations. Further studies with larger sample sizes and varying immune cell compositions are required to establish method-specific reference ranges.

Hygienic Production Practices and Microbiological Quality of Sheep Milk in Ararso District of Jarar Zone, Somali Regional State, Ethiopia

This study was conducted to evaluate the hygienic production practices and microbiological quality of sheep milk in Ararso district of Jarar Zone, Somali Regional State, Ethiopia. A stratified sampling strategy was used to choose 180 households specifically for this investigation. A total of 60 pooled raw sheep milk samples (each containing 200 mL) were collected from the udders and milk handling equipment of selected milk producers in the research area. The samples were examined to determine microbiological quality. The data were gathered via a questionnaire, field observation, key informant interviews, and focus group discussions. The vast majority of respondents in pastoral (86.7%) and agro-pastoral (64.4%) production systems were illiterate. The majority of respondents (70.6%) in the research area cleaned the sheep home (kraal) once every two days. The majority (98.3%) of respondents in the research area milk their sheep in open kraals with no roof or walls. As a consequence, 36.7% of pastoral and agro-pastoral respondents (81.1%) reported cleaning milk vessels on a regular basis. Almost all of the responders in the research area used plastic equipment for milking and handling. The majority of responders in pastoral and agro-pastoralist categories placed barn hygiene first, with indexes of 0.24 and 0.23, respectively. The average total bacterial count (TBC), coiform count (CC) and yeast and mould count (YMC) of raw sheep milk samples were 5.13±0.21, 2.89±0.27, and 0.77±0.21 log10 cfu/mL, respectively. Raw sheep milk samples taken from producers’ milk handling equipment had a substantially higher mean total bacterial count (5.78±0.32 log10 cfu/mL) compared to samples collected from the udder (4.48±0.23 log10 cfu/mL). Milk samples from pastoral and agro-pastoral households had an average coliform count of 3.18 and 2.60 log10 cfu/mL, respectively. The average YMC in milk samples from pastoralists and agro-pastoralists were 0.74 and 0.80 log10 cfu/mL, respectively. In general, pastoralists and agro-pastoralists in the district do not practice hygienic milking and handling. Consequently, the implementation of hygienic milk production and handling practices is essential to enhance the safety and quality of sheep milk in the study area. Additionally, further research should be undertaken to investigate the microbiological aspects and assess the safety and quality parameters of sheep milk in greater detail.

Prevalence, Risk Factors, and Antimicrobial Resistance of Staphylococcus and Streptococcus Species Isolated from Subclinical Bovine Mastitis.

Subclinical mastitis (SCM) is a prevalent serious disease among dairy cows worldwide. It poses a significant challenge to the dairy industry, animal welfare, and a threat to public health. The present study aimed to investigate the molecular detection, prevalence, and antimicrobial resistance of Staphylococcus spp. and Streptococcus spp. isolated from raw composite milk samples obtained from SCM dairy cattle in Bangladesh. A total of 612 quarters milk samples obtained from 153 cows were analyzed for SCM using the California Mastitis Test. Bacterial isolation and identification were carried out and bacterial species were confirmed using molecular polymerase chain reaction methods. Antimicrobial susceptibility testing was performed using disc diffusion method. The findings revealed that the prevalence of SCM was 70.3% (26/37), 35.95% (55/153), and 23.04% (141/612) in the herd, cow, and quarter levels, respectively. Among the positive samples, 92.7% (51/55) were Staphylococcus spp. (S. aureus, S. chromogenes, and S. simulans) and the remaining isolates were 7.3% (4/55) Streptococcus spp. (Streptococcus agalactiae and Streptococcus dysgalactiae). The most prevalent species was S. chromogenes, accounting for 67.3% (37/55). Antimicrobial susceptibility testing showed that 65.5% of isolates were susceptible to cefoxitin, whereas, 89.1% were resistant to penicillin. Overall, 12 isolates (21.8%) out of 55 were resistant to more than three classes of antimicrobials and were defined as multidrug-resistant isolates. Methicillin-resistance gene was detected in 61.1% of the cefoxitin-resistant isolates. A multivariate logistic regression analysis identified five potential risk factors including the lack of post-milking teat disinfection (OR: 3.06), absence of immediate feeding after milking (OR: 9.81), poor udder hygiene (OR: 7.83), tick infestation (OR: 13.76), and absence of dry cow therapy (OR: 3.31). The findings of the current study underscore the urgent requirement for targeted interventions, considering the identified factors to effectively manage and control SCM in dairy cows.

Seroprevalence of Toxoplasma gondii in Cattle in Southern Egypt: Do Milk and Serum Samples Tell the Same Story?

Toxoplasma gondii is an intracellular protozoan parasite of veterinary and public health importance. Infection may lead to abortion in susceptible pregnant animals and women, and potentially fatal health complications in immunocompromised individuals. In this study, we aimed to provide an update on the seroprevalence of, and risk factors for, T. gondii antibodies in cattle from Qena, southern Egypt. Additionally, we investigated if raw milk and serum samples from the same animals reacted similarly in a commercial ELISA, thus potentially reducing the invasiveness of future serosurveillance studies. Cattle serum samples (n = 362) from three locations in the Qena governorate (Qena, Qus, and Al Waqf cities), of both sexes and different ages were collected. From most dairy cows, a corresponding milk sample (n = 154) was additionally obtained. We found that the overall seroprevalence in serum samples was 9.1% (33/362). Increasing age was the sole risk factor identified in our study among all tested parameters (location, age, sex, lactating yes or no). Thus, older cattle (more than 3 years old) exhibited significantly higher rates of T. gondii antibodies (11.7%; p = 0.033, odd ratio = 4.3) in comparison to animals younger than 1 year (2.9%). In the corresponding serum and milk samples, the prevalence was 12.3% (19/154) in serum samples, and 9.7% (15/154) in milk samples, respectively. A high correlation was observed between the two sample types with a concordance of 97.4%, a kappa value of 0.87, and a Pearson r correlation coefficient of 0.85. When the serum ELISA was taken as the gold standard, the milk ELISA had the following characteristics: sensitivity (78.9%), specificity (100%), positive predictive value (100%), negative predictive value (97.1%), and area under the receiver operating characteristic (ROC) curve (0.6, p = 0.0011). In this study, we confirmed the frequent occurrence of T. gondii antibodies in cattle in southern Egypt and demonstrated that non-invasive milk samples may be used instead of serum samples for seroprevalence studies in dairy cows.

Quantitative Risk Assessment of Aflatoxin M1 Related to the Consumption of Raw Cow's Milk in Daloa (Côte d’Ivoire)

Cow's milk represents a potential health risk for consumers. The objective of this work is to assess the sanitary quality of raw cow's milk produced and consumed by the populations of Daloa. For this purpose, a total of 30 raw milk samples were collected from 3 raw cow's milk extraction points in the city of Daloa. Mycotoxins were determined using gas chromatography. The results showed that 100% of the analyzed samples were contaminated with aflatoxin M1 (AFLM1). These results indicated that the aflatoxin M1 levels in the analyzed samples exceeded the maximum limit (ML) set by European regulations. To assess the risk of contamination for the population of Daloa, a survey was conducted among consumers of raw cow's milk. A total of 388 individuals were interviewed to gather their opinions. The survey involved a form with questionnaires related to the objectives of the study. This form provided information on identity, marital status, consumption patterns, frequency, quantity, and the socio-economic characteristics of the consumers. The results showed that the risk of liver cancer related to the consumption of raw cow's milk in the city of Daloa is approximately 36.08% to 36.16%; representing 36,080 to 36,150 cases per 100,000 inhabitants. Thus, to ensure consumer safety, good hygiene practices in the preservation of feed for cattle and the construction of enclosures for them must be implemented.

Investigation of Various Toxigenic Genes and Antibiotic and Disinfectant Resistance Profiles of Staphylococcus aureus Originating from Raw Milk.

This study investigated the toxigenic genes and antimicrobial resistance profiles of Staphylococcus aureus strains isolated from 260 raw milk samples collected from dairy farms in Türkiye. The results indicated that 60.7% of staphylococcal enterotoxin genes (sea, seb, sed, seg, sei, sej, sek, seq, sem, seo, and seu) and 21.4% of the tst and eta genes were positive, with most enterotoxin-positive samples carrying more than one gene. The sec, see, seh, sel, sen, sep, and etb genes were not identified in any samples. The prevalence of antibiotic resistance genes (mecA, blaR, blaI, blaZ, vanA, ermT, tetK, aac/aph, ant, dfrA, tcaR, IS256, and IS257) was high at 89.2%, with bla being the most frequently detected gene (75%). The mecA gene was present in 14.2% of samples, while tcaR was detected in 78.5%. Nevertheless, the mecC was not identified. Disinfectant resistance genes (qacA/B, qacC, qacJ, smr) were detected in 21.4% of the samples. The results of the disk diffusion test showed that 64.2% of strains were resistant to penicillin G and ampicillin, with additional resistance found for cefoxitin, teicoplanin, levofloxacin, norfloxacin, and other antibiotics. These findings highlight a significant public health and food safety risk associated with raw milk due to the presence of S. aureus strains with toxigenic genes and high antimicrobial resistance.

Prevalence, Cross Contamination, Virulence, and Multidrug Resistance Profiles of Staphylococcus aureus Isolates from Four Middle-Scale Dairy Farms in Bareilly, Northern India.

Milk, a nutritious global important food commodity, serves as an excellent medium for microbial growth as well. The foodborne pathogen Staphylococcus aureus is a commensal member of human microflora that enters the food chain through poor hygienic practices and cross contamination and causes various clinical manifestations in humans. During this study, raw milk and swab samples (milker's hand, udder, towel, milking bucket, and farm floor) were collected from four middle-scale buffalo dairy farms. The results revealed S. aureus presence in 11.6% (n = 56/448) bucket raw milk samples and 2.6% (n = 12/448) udder raw milk samples. Contrarily, S. aureus prevalence was significantly higher in farm floors (100%, n = 84/84), towel (35.7%, n = 10/28), milking bucket (11.6%, n = 56/448), milker's hand (10.7%, n = 3/28), and udder swab samples (4.0%, n = 18/448). The chi-square test yielded p values of 0.000, 0.005, and 0.0011 for udder raw milk, udder swab, and milker's hand swab, respectively. The p values of the milking bucket (p = 0.048) and farm floors (p = 0.0183) confirmed their possible role in S. aureus cross contamination. Gene amplifications of nuclease and enterotoxin A indicate potential virulence of S. aureus isolates in collected samples. Antibiotic susceptibility testing revealed multidrug resistance in 44% (n = 239) of S. aureus isolates with the highest resistance of 61% against penicillin. Resistance against ampicillin, streptomycin, and lincomycin was observed. Fewer S. aureus isolates were resistant to kanamycin and erythromycin, whereas the lowest number of resistant isolates was observed against chloramphenicol. A high prevalence of S. aureus in the farm environment and milking equipment suggested the cross contamination of potentially enterotoxin-producing and multidrug-resistant S. aureus to raw milk. Therefore, good hygiene practices should be enforced to avoid foodborne and zoonotic infections.

Investigation of Staphylococcus Spp and Coliform Bacteria Contamination Sources after Cleaning-in-Place in Production Lines of Dairy Factories in Türkiye.

Microorganisms detected on dairy factory surfaces after disinfection can cause product contamination, leading to economic losses and health hazards for consumers. In this study, the presence of Staphylococcus spp. and Coliform in a total of 450 samples taken from food-contact and non-contact surfaces (stainless steel, plastic, cloth, and tiles surfaces), raw milk and final product (white cheese, kashar cheese, butter, yogurt, and cream) samples in five dairy factories was investigated by conventional techniques. The isolates obtained were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry. In this study, a total of 54 Staphylococci (16.7% S. aureus and 81.5% coagulase-negative Staphylococci [CNS]) and 44 coliform isolates were identified at the species level. The most common CNS isolated by samples was S. epidermidis followed by S. saprophyticus, S. capitis, S. succinus S. carnosus. S. xylosus, S. sciuri, S. equorum, S. warneri, and S. hominis. Eighteen of the coliform isolates (41%) were identified as E. coli; 13 (29.5%) as E. cloacae; 3 (6.9%) as E. kobei, C. freundii, and K. oxytoca; 2 (4.5%) as K. pneumoniae; 1 (2.3%) as E. ludwigii and C. farmeri. The contamination rate of non-food contact surfaces (71.3%) was found to be higher than food contact surfaces (10.4%), and contaminated surfaces were found to be effective in product contamination. Study results show that some bacterial species obtained from raw milk, surfaces, and final products are factory specific and surface-associated bacteria are prominent in the product microbial profile.

Phenotypic and Molecular Characterization of Staphylococcus aureus in Dairy Farms from Henan Province and the Inner Mongolia Autonomous Region, China.

Staphylococcus aureus, a prevalent pathogen associated with infectious and foodborne diseases, is also a significant cause of intramammary infections in dairy farms. This study aimed to determine the phenotypic and molecular characterization of S. aureus in two different stock sizes of dairy farms in Henan province (HN) and the Inner Mongolia autonomous region (IM), China, through biofilm formation, antimicrobial resistance, virulence, and molecular type of S. aureus isolates. In HN, 74 S. aureus isolates (60.7%) were recovered from 122 bulk tank milk samples, while in IM, 24 S. aureus isolates (17.4%) were detected from 161 samples soured from various origins. Notably, 25.7% (19/74) of isolates in HN and 20.8% (5/24) in IM exhibited multidrug-resistant (MDR) phenotypes. Molecular typing revealed distinct patterns: ST97 (n = 32) and spa type t189 (n = 20) predominated in HN, whereas ST50 (n = 13) and spa type t518 (n = 11) were prevalent in IM. Additionally, three isolates harbored both tsst-1 and lukF-PV genes, and two MRSA strains displayed a MDR phenotype in raw milk samples from HN. Biofilm formation was observed in 91.8% strains. Phylogenetic analysis identified two subpopulations (lineages 1 and 2). Among them, cluster 6 in lineage 2 comprised S. aureus strains from three sources within a farm, suggesting potential cross contamination during different stages in IM. Remarkably, among 19 MDR isolates in HN, ST398 MSSA strains exhibited a higher multidrug resistance compared to non-ST398 MSSA strains. This study underscores the high prevalence and diverse characteristics of S. aureus in raw milk, necessitating enhanced surveillance and control measures to mitigate associated risk.

Insights into the microbiota of raw milk from seven breeds animals distributing in Xinjiang China.

Owing to its high nutritional content, raw milk contains a rich microbiota. Thus, to study microorganisms present in raw milk available in Xinjiang China, 142 raw milk samples from seven animal breeds (cow, sheep, goat, donkey, horse, camel, and yak) and four regions (Hami, Tarbagatay, Kashgar, and Ili) were analyzed by high-throughput DNA sequencing. These microorganisms were characterized by 10 dominant phyla. Proteobacteria (68.33%) was the major phylum, followed by Firmicutes (18.80%) and Thermi (3.16%). Horse milk contained more Bacteroidetes, sheep milk contained more Gammaproteobacteria, and donkey milk contained more unclassified sequences. Camel and donkey milk contained the highest and lowest bacterial diversity compared with that contained by the remaining milk samples, respectively. Additionally, spoilage microorganisms, including Chryseobacterium, Propionibacterium, and Flavobacterium, and pathogenic bacteria, including Ochrobactrum anthropi and Sphingomonas, were more prevalent in horse and yak milk, whereas probiotic lactic acid bacteria (LAB), such as Leuconostoc, Lactococcus, or Lactobacillus, were more prevalent in goat, donkey, and camel milk. Furthermore, Moraxella was abundantly present in goat, camel, and yak milk, Acinetobacter was more abundant in camel milk, and Pseudomonas was relatively abundant in sheep and donkey milk. Overall, specific harmful microorganisms and probiotic lactic acid bacteria were found in the raw milk samples obtained from different animals, which provided a basis for preventing and controlling the growth of harmful bacteria, as well as investigating probiotic resources in raw milk.

Shiga toxin-producing Escherichia coli in the milk production chain: Evaluation of virulence genes and clonal diversity of O157:H7 strains

Microbial contamination of milk and dairy products is a significant issue due to sensory changes and the risk of foodborne diseases. Shiga toxin-producing Escherichia coli (STEC), particularly the O157:H7, are major pathogens transmitted by dairy products. This study aimed to evaluate the microbiological quality of bovine milk at various stages of the production chain in a dairy cooperative and its suppliers in Rio de Janeiro, Brazil. Additionally, the presence of STEC in milk and faeces from dairy cattle was investigated, along with the isolation of STEC O157:H7 strains and the evaluation of virulence genes and clonal diversity. These findings were compared with previously isolated STEC O157:H7 strains from the same region. A total of 100 raw milk samples (54 farm gallon (FG) samples, 25 community bulk tank milk (CBTM) samples, 14 isothermal car-tanker milk (ICTM) samples, and 7 industry tank milk (ITM) samples) and 10 pasteurized milk samples, along with 63 bovine faeces samples, were analysed. The stx gene, a marker for STEC, was detected in 65% of raw milk samples and 88.9% of faecal samples, indicating a high risk of contamination throughout the production chain. None of the pasteurized milk samples tested positive for the stx gene. The prevalence of stx in faeces and raw milk underscores the need for rigorous controls to prevent contamination. While pasteurization was effective, the microbiological quality of raw milk remained unsatisfactory, highlighting the importance of good hygiene practices and continuous monitoring to ensure dairy safety.

The inactivation of Shiga toxin-producing Escherichia coli (STEC) and Listeria monocytogenes using isochoric freezing in raw milk and carrot juice

Isochoric freezing is a novel food preservation method that may maintain the quality and safety of products by simultaneously applying low temperatures and high pressures. This work aims to determine whether isochoric freezing can improve food safety by inactivating Shiga toxin-producing Escherichia coli (STEC) and Listeria monocytogenes in raw milk and carrot juices. Raw milk and carrot juice samples were inoculated with cocktails of either STEC or L. monocytogenes and then subjected to isochoric freezing conditions in pressurized chambers set at −5, −10, and −15 °C and treated for 1, 5, 7, or 10 days. Following treatment, the product was sampled for surviving pathogens. The results demonstrated that a 5-log reduction of both STEC and L. monocytogenes can be achieved for raw milk and carrot juice without adversely affecting quality. For STEC inoculated in raw milk, both the linear and Weibull models suggest that 10 days is required to achieve 5-log reduction at −10 °C. Decreasing the temperature to −15 °C led to accelerated log reduction but induced phase separation in the milk. Listeria in raw milk demonstrated a biphasic reduction, indicating 1.3 days is required for a 5-log reduction at −10 °C. In comparison, pathogens demonstrated faster log reduction in carrot juice due to its intrinsic properties. The survival curves for STEC-inoculated carrot juice demonstrated that the 5-log reduction times were 6.9 days at −10 °C and 3.8 days at −15 °C. L. monocytogenes in carrot juice required 1.5 days at −10 °C for a 5-log reduction and was eliminated (7 log cfu/ml) within 24 h at −15 °C. Isochoric freezing could be an option for milk and carrot juice processors wishing to improve food safety without applying heat. This method is not a one-size-fits-all solution, and the time and temperature will need further optimization depending on the target pathogen and intended commodity.

Detection of antibiotic residues by a novel rapid test in cow’s milk from north Algeria

Detection of antibiotic residues by a novel rapid test in cow’s milk from north Algeria Veterinary treatments, particularly antibiotics used for therapeutic or prophylactic purposes in dairy cattle, can be the cause of antibiotic residues in raw milk. The aim of this study is to investigate the use of antibiotics in the dairy cattle industry and to detect the presence of antibiotic residues in raw milk at collection centers using the SNAPduo ST Plus Test in the Bouira and Bordj Bou Arreridj (BBA) regions of Algeria. The results of the survey of 114 breeders showed that the Montbeliarde and Holstein breeds are the most dominant in the farms studied, the frequency of veterinary interventions in cattle farming is always, the curative veterinary intervention represents the highest rate and the beta-lactam is the most family used with 46.25% in Bouira and 85% in BBA, then the oxytetracycline was 22.5% and 15% respectively. Regarding the use of antibiotics by breeders, the majority of them use antibiotics for their animals, with 76.25% in the region of Bouira and 91% in the province of BBA. The antibiotic test of 122 samples of raw milk showed that 19.67% (24/122) of the samples were positive for antibiotic residues with the beta-lactam showing the highest value (79.16%) followed by tetracycline residues with 20.83%. This study showed the presence of antibiotic residues in raw milk in the study area, which may affect the health of dairy consumers.

Temperature correction of near-infrared spectra of raw milk

Accurate milk composition analysis is crucial for improving product quality, economic efficiency, and animal health in the dairy industry. Near-infrared (NIR) spectroscopy can quantify milk composition quickly and nondestructively. However, external factors, such as temperature fluctuations, can alter the molecular vibrations and hydrogen bonding in milk, altering the NIR spectra and leading to errors in predicting key constituents such as fat, protein, and lactose. This study compares the effectiveness of Piecewise Direct Standardization (PDS), Continuous PDS (CPDS), External Parameter Orthogonalization (EPO), and Dynamic Orthogonal Projection (DOP in correcting the impact of temperature-induced variations on predictions in milk long-wave NIR spectra (LW-NIR, 1000–1700 nm).A total of 270 raw milk samples were analyzed, collecting both reflectance and transmittance spectra at five different temperatures (20 °C, 25 °C, 30 °C, 35 °C, and 40 °C). The experimental setup ensured precise temperature control and accurate spectral measurements. PLSR models were calibrated at 30 °C to predict milk fat, protein, and lactose content. The performance of these models was assessed before and after applying the temperature correction methods, with a primary focus on reflectance spectra.Results indicate that EPO and DOP significantly enhance model robustness and prediction accuracy across all temperatures, outperforming PDS and CPDS, especially for lactose prediction. These orthogonalization methods were compared against PLSR models calibrated with spectra from all temperatures. EPO and DOP showed comparable or superior performance, highlighting their effectiveness without requiring extensive temperature-specific calibration data. These findings suggest that orthogonalization methods are particularly suitable for in-line milk quality measurements under farm conditions where temperature control is challenging. This study highlights the potential of advanced chemometric techniques to improve real-time, on-farm milk composition analysis, facilitating better farm management and enhanced dairy product quality.