Rapid detection and quantification of melamine, urea, sucrose, water, and milk powder adulteration in pasteurized milk using Fourier transform infrared (FTIR) spectroscopy coupled with modern statistical machine learning algorithms.

There is an evident requirement for a rapid, efficient, and simple method to screen the authenticity of milk products in the market. Fourier transform infrared (FTIR) spectroscopy stands out as a promising solution. This work employed FTIR spectroscopy and modern statistical machine learning algorithms for the identification and quantification of pasteurized milk adulteration. Comparative results demonstrate modern statistical machine learning algorithms will improve the ability of FTIR spectroscopy to predict milk adulteration compared to partial least square (PLS). To discern the types of substances utilized in milk adulteration, a top-performing multiclassification model was established using multi-layer perceptron (MLP) algorithm, delivering an impressive prediction accuracy of 97.4 %. For quantification purposes, bayesian regularized neural networks (BRNN) provided the best results for the determination of both melamine, urea and milk powder adulteration, while extreme gradient boosting (XGB) and projection pursuit regression (PPR) gave better results in predicting sucrose and water adulteration levels, respectively. The regression models provided suitable predictive accuracy with the ratio of performance to deviation (RPD) values higher than 3. The proposed methodology proved to be a cost-effective and fast tool for screening the authenticity of pasteurized milk in the market.

Characterization of Pseudomonas spp. contamination and in situ spoilage potential in pasteurized milk production process.

To investigate the prevalence of Pseudomonas in the pasteurized milk production process and its effect on milk quality, 106 strains of Pseudomonas were isolated from the pasteurized milk production process of a milk production plant in Shaanxi Province, China. The protease, lipase and biofilm-producing capacities of the 106 Pseudomonas strains were evaluated, and the spoilage enzyme activities of their metabolites were assessed by simulating temperature incubation in the refrigerated (7 °C) and transport environment (25 °C) segments and thermal treatments of pasteurization (75 °C, 5 min) and ultra-high temperature sterilization (121 °C, 15 s). A phylogenetic tree was drawn based on 16S rDNA gene sequencing and the top 5 strains were selected as representative strains to identify their in situ spoilage potential by examining their growth potential and ability to hydrolyze proteins and lipids in milk using growth curves, pH, whiteness, Zeta-potential, lipid oxidation, SDS-PAGE and volatile flavor compounds. The results showed that half and more of the isolated Pseudomonas had spoilage enzyme production and biofilm capacity, and the spoilage enzyme activity of metabolites was affected by the culture temperature and sterilization method, but ultra-high temperature sterilization could not completely eliminate the enzyme activity. The growth of Pseudomonas lundensis and Pseudomonas qingdaonensis was less affected by temperature and time, and the hydrolytic capacity of extracellular protease and lipase secreted by Pseudomonas lurida was the strongest, which had the greatest effect on milk quality. Therefore, it is crucial to identify the key contamination links of Pseudomonas, the main bacteria responsible for milk spoilage, and the influence of environmental factors on its deterioration.

Seasonal variation of Salmonella enterica prevalence in milk and cottage cheese along the dairy value chain in three regions of Ethiopia.

Seasonal fluctuations influence foodborne illness transmission and affect patterns of microbial contamination of food. Previous investigations on the seasonality of Salmonella enterica prevalence in dairy products in Ethiopia have been minimal. However, such data are needed to inform strategic development of effective interventions to improve food safety, as seasonal differences may affect intervention strategies. This study was conducted to identify differences in the prevalence of Salmonella in milk and cheese samples between wet and dry seasons. A longitudinal study design was utilized with a random sampling occurring during both dry and wet seasons. A total of 448 milk and cottage cheese samples were collected from Oromia, Sidama, and Amhara regions. Samples were tested for Salmonella using the ISO 6579-1: 2008 method, followed by PCR confirmation. A chi-square test was conducted to assess the significance of differences in the prevalence of Salmonella in the samples between the two seasons. Results from this study showed a higher prevalence of Salmonella in all sample types during the dry season (P < 0.05). Moreover, when comparing raw milk, pasteurized milk, and cottage cheese samples, a significant difference was observed in Salmonella prevalence from raw milk samples (27.08%) collected in the Oromia region. Additionally, data showed a significantly higher prevalence of Salmonella in samples collected from raw milk producers (29.17%) during the wet season (P < 0.05). This study indicates that in order to enhance the safety of dairy products in Ethiopia, comprehensive, long-term awareness building on hygienic milk production and handling that consider seasonal influence is warranted. Supplementary Information: The online version contains supplementary material available at 10.1186/s40550-024-00108-4.

Microbiological Assessment of Dairy Products Produced by Small-Scale Dairy Producers in Serbia.

The microbiological quality of dairy products from small-scale producers in Serbia was analysed. A total of 302 dairy products [raw (n = 111) and pasteurized milk cheeses (n = 79) and kajmak (n = 112)], were collected and tested for the presence of pathogens, Listeria monocytogenes and Salmonella spp., and enumerated for Coagulase-positive staphylococci (CPS), Escherichia coli, and yeasts and moulds. None of the samples tested positive for Salmonella spp., while L. monocytogenes was recovered from one raw milk cheese and five kajmak samples. Raw milk cheese and kajmak also had higher levels of indicator microorganisms, namely E. coli and yeast and moulds. Molecular serotyping grouped L. monocytogenes isolates into serogroups 1 (1/2a and 3a) and 3 (1/2b, 3b, and 7). When exposed to eight antibiotics, L. monocytogenes isolates were mostly sensitive, with the exception of oxacillin and reduced susceptibility to clindamycin, penicillin G, and trimethoprim/sulfamethoxazole, emphasizing the importance of continuous surveillance for antimicrobial resistance. Samples that tested positive for Listeria spp. also had higher loads of indicator microorganisms, namely E. coli and yeast and moulds, suggesting lapses in hygiene practices during production. Collectively, these data emphasize the need for improved food safety and hygiene practices among small-scale dairy producers. This is crucial to reduce the microbial contamination and improve both the quality and safety of dairy products in the Serbian market.

A2 milk: Bioaccessibility of essential minerals and the release of amino groups under static in vitro digestion conditions.

Alternative milk products such as A2 milk are gaining popular stand within consumer market, for their healthy profile and expected greater digestibility characteristics. However, total mineral content and its bioaccessible profile have lacked in studies through the years, even more because of their relevance in public health. The present study aimed to evaluate the mineral profile of commercial A2 bovine milk (AT) and estimate the bioaccessibility of calcium, phosphorus and magnesium using the INFOGEST protocol. Non-A2 samples (NAT) were evaluated for comparison purpose. The determination of Ca, Mg, Na and K was performed by FAAS and total P was quantified by colorimetric method. Total protein content was determined by Kjeldahl method. Free amino acids were quantified by OPA method along the in vitro digestion stages. Total content of Ca, Na and P exhibited equivalent results between samples, although A2 milk showed elevated levels of total Mg and K in the analyzed batches. AT showed protein content equivalent to NAT. In addition, levels of free NH2 were observed 2 times higher in AT, during the first hour of pancreatic phase in the intestinal digestion. Bioaccessibility of Ca showed equivalent percentages for AT (12-42 %) and NAT (10-39 %). The observed low values were possibly derived from interferences with saturated fatty acids and standardized electrolytes during digestion. Similar amounts of bioaccessible Mg were found for all milk samples (35-97 %), while A2 samples evidenced percentages of bioaccessible P exceeding 60 % across the three batches. Despite the health benefits associated to A2 milk, the study did not evidence clear distinction from non-A2 milk in terms of enhanced essential mineral solubility in digestive tract simulation, considering the association of greater digestibility expected for A2 milk.

Improvement of Raw and Pasteurized Milk Quality through the Use of Lactoperoxidase Systems (LPSs) along the Dairy Value Chain, under Real Conditions in Ethiopia.

Lactoperoxidase systems (LPSs) can enhance the microbiological quality of raw milk when there is lack of cooling facilities. In this study, a total of 250 milk samples were collected from farmers, collectors, and factories. Experimental samples were both LPS-activated morning and overnight milk. The samples were tested with several chemical and microbiological tests, such as total bacterial count (TBC), total coliform count (TCC), and Escherichia coli count (EC). Results indicated that all LPS-activated milk samples had a higher quality than all the control samples. For instance, both the morning and overnight farm milk samples had mean TBCs of 5.79 log and 6.55 log cfu/mL, which is significantly (p < 0.05) lower than the control samples' mean TBC of 6.73 log and 7.31 log cfu/mL, respectively. When this was compared with the Ethiopian Standard, 51.4% of morning and 39.5% of overnight farm milk with LPS activation met the acceptable quality, while only 28% of morning and 15.7% of overnight control milk met the standard. Moreover, LPS activation has also significantly improved the shelf life of collectors' raw milk and pasteurized milk at the factories. Therefore, a better hygienic practice with LPS application can be practiced in conditions that lack cooling infrastructure and electricity.

The impact of heat treatment of bovine milk on gastric emptying and nutrient appearance in peripheral circulation in healthy females: a randomized controlled trial comparing pasteurized and ultra-high temperature milk.

BACKGROUND: Heat treatments of dairy, including pasteurization and ultra-high temperature (UHT) processing, alter milk macromolecular structures, and ultimately affect digestion. In vitro, animal, and human studies show faster nutrient release or circulating appearance after consuming UHT milk (UHT-M) compared with pasteurized milk (PAST-M), with a faster gastric emptying (GE) rate proposed as a possible mechanism. OBJECTIVES: To investigate the impact of milk heat treatment on GE as a mechanism of faster nutrient appearance in blood. We hypothesized that GE and circulating nutrient delivery following consumption would be faster for UHT-M than PAST-M. METHODS: In this double-blind randomized controlled cross-over trial, healthy female (n = 20; 27.3 ± 1.4 y, mean ± SD) habitual dairy consumers, consumed 500 mL of either homogenized bovine UHT-M or PAST-M (1340 compared with 1320 kJ). Gastric content volume (GCV) emptying half-time (T50) was assessed over 3 h by magnetic resonance imaging subjective digestive symptoms, plasma amino acid, lipid and B vitamin concentrations, and gastric myoelectrical activity were measured over 5 h. RESULTS: Although GCV T50 did not differ (102 ± 7 min compared with 89 ± 8 min, mean ± SEM, UHT-M and PAST-M, respectively; P = 0.051), GCV time to emptying 25% of the volume was 31% longer following UHT-M compared with PAST-M (42 ± 2 compared with 32 ± 4 min, P = 0.004). Although GCV remained larger for a longer duration following UHT-M (treatment × time interaction, P = 0.002), plasma essential amino acid AUC was greater following UHT-M than PAST-M (55,324 ± 3809 compared with 36,598 ± 5673 µmol·min·L-1, P = 0.006). Heat treatment did not impact gastric myoelectrical activity, plasma appetite hormone markers or subjective appetite scores. CONCLUSIONS: Contrary to expectations, GE was slower with UHT-M, yet, as anticipated, aminoacidemia was greater. The larger GCV following UHT-M suggests that gastric volume may poorly predict circulating nutrient appearance from complex food matrices. Dairy heat treatment may be an effective tool to modify nutrient release by impacting digestion kinetics. CLINICAL TRIAL REGISTRY: www.anzctr.org.au (ACTRN12620000172909).

The Investigation of Changes in Bacterial Community of Pasteurized Milk during Cold Storage.

The quality of pasteurized milk is commonly assessed through microbiological analysis, with variations in storage conditions significantly impacting the suppression of bacterial growth throughout the milk's shelf life. This study investigated the dynamics of total bacterial counts (TBCs) and bacterial community shifts in milk that underwent pasteurization at 80 °C for 15 s. The milk was subsequently stored at 4 °C for varying intervals of 1, 4, 7, 10, 13, and 16 days. Culture-based testing revealed a significant TBC increase during the storage period spanning 1 to 16 days (up to -log10 4.2 CFU/mL at day 16). The TBC in pasteurized milk exhibited accelerated microbial growth from day 13 onwards, ultimately peaking on day 16. Bacillus was detected through 16S rRNA identification. Principal component analysis demonstrated a significant impact of storage time on bacterial communities in pasteurized milk. Analysis of bacterial diversity revealed a negative correlation between the Shannon index and the duration of pasteurized milk storage. Using high-throughput sequencing, Streptococcus and Acinetobacter were detected as prevalent bacterial genera, with Streptococcus dysgalactiae and Streptococcus uberis showing as dominant taxa. The presence of Streptococcus dysgalactiae and Streptococcus uberis in pasteurized milk might be attributed to the initial contamination from raw milk with mastitis. This study offers new evidence of the prevalence of bacterial community in pasteurized milk, thereby adding value to the enhancement of quality control and the development of strategies for reducing microbial risks.

Thermal inactivation kinetics of Listeria monocytogenes in milk under isothermal and dynamic conditions.

Thermal processing is a widely used method to ensure the microbiological safety of milk. Predictive microbiology plays a crucial role in quantifying microbial growth and decline, providing valuable guidance on the design and optimization of food processing operations. This study aimed to investigate the thermal inactivation kinetics of Listeria monocytogenes in milk under both isothermal and dynamic conditions. The thermal inactivation of L. monocytogenes was conducted under isothermal and non-isothermal conditions in sterilized and pasteurized milk, with and without background microbiota, respectively. Furthermore, a secondary model was developed between the shoulder effect and temperature, which was then integrated into the dynamic model. The results showed that L. monocytogenes grown in Tryptic Soy Yeast Extract Broth (TSBYE) prior to thermal inactivation exhibited higher heat resistance compared to cells grown in sterilized milk at isothermal temperatures of 60.0, 62.5, and 65℃. Moreover, the presence of background microbiota in milk significantly enhanced the heat resistance of L. monocytogenes, as evidenced by the increased D-values from 1.13 min to 2.34 min, from 0.46 min to 0.53 min, and from 0.25 min to 0.34 min at 60.0, 62.5, and 65 °C, respectively, regardless of whether the background microbiota was inactivated after co-growth or co-inactivated with L. monocytogenes. For non-isothermal inactivation, the one-step dynamic model based on the log-linear with shoulder model effectively described the microbial inactivation curve and exhibited satisfactory model performance. The model developed contributes to improved risk assessment, enabling dairy processors to optimize thermal treatment and ensure microbiological safety.

Antibacterial Activity and Mechanism of Polygonatum sibiricum Extract Against Bacillus cereus and Its Application in Pasteurized Milk.

The purpose of this study was to reveal the antibacterial activity and mechanism of Polygonatum sibiricum extract (PSE) against Bacillus cereus and further analyze the application of PSE in pasteurized milk (PM). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values and growth curve analysis were used to evaluate the antibacterial activity of PSE against B. cereus. The changes in contents of intracellular adenosine 5'-triphosphate (ATP) and reactive oxygen species (ROS), activities of ß-galactosidase, adenosine triphosphatase (ATPase) and alkaline phosphatase (AKP), cell membrane potential, protein and nucleic acid leakage, and cell morphology were used to reveal the antibacterial mechanism. The effects of PSE on viable count and sensory evaluation of PM during storage were analyzed. The results showed that the MIC and MBC values of PSE against B. cereus were 2 and 4 mg/mL, respectively. Growth curve analysis showed that PSE with a concentration of 2 MIC could completely inhibit the growth of B. cereus. After treatments with PSE, the levels of intracellular ATP and ROS, and activities of ß-galactosidase, ATPase and AKP of B. cereus were significantly reduced (p < 0.05). Cell membrane was depolarized, amounts of protein and nucleic acid leakage were significantly increased (p < 0.05), and cell morphology was destroyed. Furthermore, PSE significantly reduced the viable count of B. cereus in PM and improved the sensory quality of PM during storage (p < 0.05). Together, our findings suggested that PSE had the desired effect as a natural preservative applied in PM.

Seasonal Comparison of Microbial Hygiene Indicators in Raw and Pasteurized Milk and Cottage Cheese Collected across Dairy Value Chain in Three Regions of Ethiopia.

A longitudinal design with a simple random sampling method was used to collect and compare microbial hygiene levels between the dry season (January to April) and wet season (June to August). A total of 456 milk and cottage cheese samples were collected from each site along the dairy value chain from three regions. Enumeration of total aerobic mesophilic bacteria (APC), total coliforms (TCC), and Escherichia coli (EC) was performed according to standard methods. Independent t-tests were employed to assess the significant variation at (p < 0.05) between the two seasons. The cumulative result of APC of 7.61 log cfu/mL and g and TCC of 3.50 log cfu/mL in the dry season were significantly higher than the wet season of 7.15 log cfu/mL and 2.49 log cfu/mL, respectively, whereas generic E. coli count (EC) was significantly higher in the wet season (0.70 log cfu/mL and g) than that in the dry season (0.40 log cfu/mL and g). The results of hygienic indicator microbial load significantly varied with season. Hence, hygienic milk production and handling practices that comprehend seasonal influence should be implemented to improve the safety of milk.

Long short-term memory based quasi-targeted lipidomics reveals propane-1,2-diol expediting the digestion of lipids via mediating the α-helices to a random curl or ß folding of lipase.

Scandal of detecting 1,2-propanediol (PD) in milk brought a crisis to the trust of consumers in dairy industry, and investigations focused effect of PD on digestive behavior of milk were still restricted. Long short-term memory amalgamated to quasi-targeted lipidomics was applied to monitor dynamics changes of lipids during digestion and the pseudo-first-order kinetic model elucidated that PD elevated the digestibility of lipid with the degradation rate (S-1) ranged from 4440.31 to 5665.59 and mediated the transition of α-helices (26.46% to 19.07% of pancreatic lipase and 29.89% to 23.37% of gastric lipase) covering active center in lipase to random curl (48.25% to 51.17% of pancreatic lipase and 41.58% to 44.57% of gastric lipase) and ß folding (9.14% to 4.67% of pancreatic lipase and 6.52% to 10.05% of gastric lipase), ultimately upregulating the lipase activity and further intervening lipid nutrients utilization in milk. This study provided a critical insight about the impact of PD contamination at trace concentrations on the nutritional value of milk fat during digestion.

Ambient 1,2-propanediol exposure accelerates the degradation of lipids and amino acids in milk via allosteric effects and affects the utilization of nutrients containing amide bond.

The scandal of detecting 1, 2-propanediol (PL) in milk brought a crisis to the trust of consumers in the dairy industry, and the potential toxicity of PL has aroused the public concern about dietary exposure. A total of 200 pasteurized milk samples were collected from 15 regions, and the quantity of PL ranged between 0 and 0.31 g kg-1. Pseudo-targeted quantitative metabolomics integrated with proteomics demonstrated that PL enhanced the reduction of κ-casein, ß-casein, and 107 substances (41 amines and 66 amides) containing amide bonds. Pathway enrichment and topological analysis indicated that PL induced the metabolism of lipids, amino acids, oligosaccharide nucleotides, and alkaloids by accelerating the rate of nucleophilic reaction, and acetylcholinesterase, sarcosine oxidase, and prolyl 4-hydroxylase were determined as the vital enzymes related to the degradation of above nutrients. The results of molecular simulation calculation illustrated that the number of hydrogen bonds between acetylcholinesterase, sarcosine oxidase, and substrate increased to 2 and 3, respectively, while the position of hydrogen bonds between prolyl 4-hydroxylase and proline was shifted, indicating the change of conformation and the enhancement of hydrogen bond force were essential factors for the up-regulation of enzyme activity. This study first revealed the mechanism of deposition and transformation of PL in milk, which contributed to the knowledge of the quality control of milk and provided vital indicators to evaluate the adverse risks of PL in dairy products.

Differential behavior of Lactobacillus helveticus B1929 and ATCC 15009 on the hydrolysis and angiotensin-I-converting enzyme inhibition activity of fermented ultra-high-temperature milk and nonfat dried milk powder.

Consumers' growing interest in fermented dairy foods necessitates research on a wide array of lactic acid bacterial strains to be explored and used. This study aimed to investigate the differences in the proteolytic capacity of Lactobacillus helveticus strains B1929 and ATCC 15009 on the fermentation of commercial ultra-pasteurized (UHT) skim milk and reconstituted nonfat dried milk powder (at a comparable protein concentration, 4%). The antihypertensive properties of the fermented milk, measured by angiotensin-I-converting enzyme inhibitory (ACE-I) activity, were compared. The B1929 strain lowered the pH of the milk to 4.13 ± 0.09 at 37°C after 24 h, whereas ATCC 15009 needed 48 h to drop the pH to 4.70 ± 0.18 at 37°C. Two soluble protein fractions, one (CFS1) obtained after fermentation (acidic conditions) and the other (CFS2) after the neutralization (pH 6.70) of the pellet from CFS1 separation, were analyzed for d-/l-lactic acid production, protein concentration, the degree of protein hydrolysis, and ACE-I activity. The CFS1 fractions, dominated by whey proteins, demonstrated a greater degree of protein hydrolysis (7.9%) than CFS2. On the other hand, CFS2, mainly casein proteins, showed a higher level of ACE-I activity (33.8%) than CFS1. Significant differences were also found in the d- and l-lactic acid produced by the UHT milk between the 2 strains. These results attest that milk casein proteins possessed more detectable ACE-I activity than whey fractions, even without a measurable degree of hydrolysis. Findings from this study suggest that careful consideration must be given when selecting the bacterial strain and milk substrate for fermentation.

Nutritional quality and adulterants of cow raw milk, pasteurized and cottage cheese collected along value chain from three regions of Ethiopia.

Milk is a nutritionally rich food for humans. However, fulfilling the quality of milk is a major concern for milk factories, nutrient requirements, and public health. The objective of this research was to assess the composition of raw and pasteurized milk and cheese, evaluate change in milk and cheese composition along the value chain, and identify adulteration of milk. A total of 160 composite samples were determined using lactoscan and conventional approved methods along value chain. Results indicate that there were significant (p < 0.05) changes of in milk composition along the value chain in the study regions. The range values were; total solid (8.41-11.7%), protein (2.25-3.06%), fat (2.16-3.17%), lactose (3.33-4.76%), ash (0.52-0.73%), P (62.7-84.2 mg/100 g) and Ca (78.2-109 mg/100 g) of liquid milk were obtained in all regions. Liquid milk was found to be adulterated by water along the value chains in all regions (ranged from 0 to 24.8%). Formalin (4 samples) and starch (1 sample) were detected at farmer's and collectors' respectively. In all regions, there was no significant (p > 0.05) difference in cheese nutritional quality between farmers and retailers. The grand mean for moisture, protein, fat, total ash, Ca, P and pH values were 77.1%, 17.1%, 1.42%, 1.18%, 37.8 mg/100 g, 88.2 mg/100 g and 3.7 respectively. Comparison of liquid products with the Compulsory Ethiopian Standard (CES) indicates that 80.2% for fat, protein, and SNF in raw and pasteurized milk were below the CES. In conclusion, liquid milk had poor nutritional composition and varied along the value chain in the study regions. Moreover, there is milk fraud where all dairy value chain add water into milk and milk consumers are consuming lower nutrients and paying for substandard liquid milk. Therefore, training should be provided to all value chain to improve the quality of milk products and quantification of formalin and other adulterants need to be further studied.

Quality assessment of raw and pasteurized milk in Gondar city, Northwest Ethiopia: A laboratory-based cross-sectional study.

Milk is a complete and highly nutritious source of food for human beings. However, in many developing countries, including Ethiopia, the quality of milk products has become a major health concern for consumers, particularly for infants and children. Therefore, the aim of the present study was to assess the quality of raw and pasteurized milk marketed in Gondar city, Northwest Ethiopia. A laboratory-based cross-sectional study was conducted on 90 milk samples. The samples were chosen using a simple random sampling technique. For statistical analysis, ANOVA and the Pearson correlation coefficient were used. The specific gravity of pasteurized milk, farm milk, and milk vendors were found to be 1.021, 1.027, and 1.026, respectively. Farm milk, milk vendors, and pasteurized milk had fat contents of 3.38%, 3.22%, and 3.09%, respectively. The total bacterial count in pasteurized milk, farm milk, and milk vendors was found to be 7.08, 6.73, and 6.94 log10 CFU/mL, respectively. In raw milk, hydrogen peroxide (7.7%), formalin (7.7%), and water (3.8%) were found, whereas in pasteurized milk, hydrogen peroxide (50%), formalin (50%), and water (19.8%) were found. Based on the findings of this study, the quality of both raw and pasteurized milk was found to be poor as per the milk quality standards. This may cause significant public health-related problems. Therefore, an appropriate intervention should be conducted to improve the quality of milk.

Prevalence and associated risk factors for Salmonella enterica contamination of cow milk and cottage cheese in Ethiopia.

Animal sourced foods, such as dairy products, are common sources of Salmonella enterica, a foodborne pathogen of increasing global concern, particularly in developing countries. In Ethiopia, most data on the prevalence of Salmonella in dairy products is highly varied and limited to a specific region or district. Furthermore, there is no data available on the risk factors for Salmonella contamination of cow milk and cottage cheese in Ethiopia. This study was therefore conducted to determine the presence of Salmonella throughout the Ethiopian dairy value chain and to identify risk factors for contamination with Salmonella. The study was carried out in three regions of Ethiopia, including Oromia, Southern Nations, Nationalities and Peoples, and Amhara during a dry season. A total 912 samples were collected from milk producers, collectors, processors, and retailers. Samples were tested for Salmonella using the ISO 6579-1: 2008 method, followed by PCR confirmation. Concurrent with sample collection, a survey was administered to study participants to identify risk factors associated with Salmonella contamination. Salmonella contamination was highest in raw milk samples at the production (19.7%) and at milk collection (21.3%) levels. No significant difference in the prevalence of Salmonella contamination among regions was detected (p > 0.05). Regional differences were apparent for cottage cheese, with the highest prevalence being in Oromia (6.3%). Identified risk factors included the temperature of water used for cow udder washing, the practice of mixing milk lots, the type of milk container, use of refrigeration, and milk filtration. These identified factors can be leveraged to develop targeted intervention strategies aimed at reducing the prevalence of Salmonella in milk and cottage cheese in Ethiopia.

Extending the Shelf Life of Raw Milk and Pasteurized Milk with Plantaricin FB-2.

Raw milk and pasteurized milk are characterized by a short shelf life, and drinking expired raw milk and pasteurized milk causes illness. In the study, Plantaricin FB-2 (extracted from Lactiplantibacillus plantarum FB-2) was added to liquid milk. By evaluating the microbial growth, acidity changes, protein content, and sensory changes in raw milk and pasteurized milk during storage, it was found that when Plantaricin FB-2 was added at 0.4 g/kg, the shelf life of raw milk was extended by 3 days (7 days if not added). The shelf life of pasteurized milk with Plantaricin FB-2 was extended to 31 days (25 days in the control group), and the optimal amount was 0.3 g/kg. This confirmed that Plantaricin FB-2 can effectively prolong the shelf life of raw and pasteurized milk. This study provides valuable information for the application of bacteriocins produced by Lactiplantibacillus plantarum in raw milk and pasteurized milk to improve their shelf life.

Correlation Analysis of Microbial Contamination and Alkaline Phosphatase Activity in Raw Milk and Dairy Products.

Microbial contamination in raw milk and dairy products can detrimentally affect product quality and human health. In this study, the aerobic plate count, aerobic Bacillus abundance, thermophilic aerobic Bacillus abundance, and alkaline phosphatase activity were determined in 435 raw milk, 451 pasteurized milk, and 617 sterilized milk samples collected from 13 Chinese provinces (or municipalities). Approximately 9.89% and 2.22% of raw milk and pasteurized milk samples exceeded the threshold values for the aerobic plate count, respectively. The proportions of aerobic Bacillus in raw milk, pasteurized milk, and sterilized milk were 54.02%, 14.41%, and 1.30%, respectively. The proportions of thermophilic aerobic Bacillus species were 7.36% in raw milk and 4.88% in pasteurized milk samples, and no bacteria were counted in sterilized milk. Approximately 36.18% of raw milk samples contained >500,000 mU/L of alkaline phosphatase activity, while 9.71% of pasteurized milk samples contained >350 mU/L. For raw milk, there was a positive correlation between the aerobic plate count, the aerobic Bacillus abundance, and the alkaline phosphatase activity, and there was a positive correlation between the aerobic Bacillus abundance, the thermophilic aerobic Bacillus count, and the alkaline phosphatase activity. For pasteurized milk, there was a positive correlation between the aerobic plate count, the aerobic Bacillus abundance, and the thermophilic aerobic Bacillus count; however, the alkaline phosphatase activity had a negative correlation with the aerobic plate count, the aerobic Bacillus abundance, and the thermophilic aerobic Bacillus abundance. These results facilitate the awareness of public health safety issues and the involvement of dairy product regulatory agencies in China.

UHPLC-Q-Orbitrap-Based Integrated Lipidomics and Proteomics Reveal Propane-1,2-diol Exposure Accelerating Degradation of Lipids via the Allosteric Effect and Reducing the Nutritional Value of Milk.

The scandal of detecting the flavoring solvent propane-1,2-diol (PD) in milk has brought a crisis to the trust of consumers in the dairy industry, while its deposition and transformation are still indistinct. Pseudo-targeted lipidomics revealed that PD accelerated the degradation of glycerolipid (33,638.3 ± 28.9 to 104,54.2 ± 28.4 mg kg-1), phosphoglyceride (467.4 ± 8.2 to 56.6 ± 4.2 mg kg-1), and sphingolipids (11.4 ± 0.3 to 0.7 ± 0.2 mg kg-1), which extremely decreased the milk quality. Recoveries and relative standard deviations (RSDs) of the established method were 85.0-109.9 and 0.1-14.9%, respectively, indicating that the approach was credible. Protein-lipid interactions demonstrated that 10 proteins originating from fat globules were upregulated significantly and the activities of 7 enzymes related to lipid degradation were improved. Diacylglycerol cholinephosphotransferase was the only enzyme with decreased activity, and the molecular docking results indicated that PD adjusted its activity through regulating the conformation of the active center and weakening the hydrogen bond force between the enzyme and substrate. This study firstly revealed the mechanism of deposition and transformation of PD in milk, which contributed to the knowledge on the milk quality control and provided key indicators to evaluate the adverse risks of PD in dairy products.