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This study reports the effect of psychrotrophs in raw milk on the quality of Mozzarella cheese. Physical, chemical, sensorial and textural characteristics were evaluated, and the indices of lipolysis and proteolysis were assessed. The highest population (7 log cfu/mL vs. 3 log cfu/mL) was associated with a decrease in yield and in primary proteolysis index, higher acidity and free fatty acid index and concentration. Short‐ and medium‐chain free fatty acids increased in all cheeses during storage, being higher in those produced with milk containing a high population of psychrotrophics. No sensory differences between the cheeses were observed. [ABSTRACT FROM AUTHOR]

In this research communication the genetic diversity of Pseudomonas fluorescens (n = 67) and Pseudomonas putida (n = 44) isolated from refrigerated raw milk from bulk tank trucks were verified. The relationship between the genetic profile of the isolates and their lipoproteolytic potential was evaluated using skim milk agar and tributyrin agar (21°C/72 h). The lipoproteolytic potential (low or high), evaluated by the diameter of the halos (cm), was correlated with the number of milk producing properties that contributed to each sample (one sample = one bulk tank truck; 8−80 producers/sample) and the distance between the dairy properties and the processing plant (21−370 km). P. fluorescens was confirmed in all samples, while P. putida in 60% samples. For both species, two clusters (I and II) were observed, and the first one showed lower genotypic diversity and the presence of isolates with 100% similarity. P. fluorescens isolates presenting at least 70% similarity were 83.9% in Cluster I (n = 31) and 44.4% in Cluster II. In both clusters (I and II) observed in the P. fluorescens dendrogram, the occurrence of high proteolytic and lipolytic potential were equivalent. The higher the number of farms per milk sample, the greater the lipoproteolytic intensity of P. fluorescens isolates. In relation to P. putida isolates, 74% presented at least 50% similarity in Cluster I (n = 27) and only 35% in Cluster II (n = 17). The occurrence of high proteolysis linked to P. putida was proportional between both Clusters, but the occurrence of high lipolysis was greater in Cluster II. No significant association was detected between P. putida isolates and the variables studied. The results indicate the circulation of P. putida and P. fluorescens with 100% similarity in different milk producing regions. The level of genetic diversity was related only to the lipolytic capacity of P. putida. [ABSTRACT FROM AUTHOR]

In an age of flexible conditions about mandatory milk pasteurisation, this opinion-based research reflection supports the view that the knowledge and the awareness of milk-borne infections are key requirements to decrease the risks associated with raw milk. Providing an analysis of the current potential risks related to consumption of raw milk and raw milk products, we discuss the main reasons to continue to be vigilant about milk-borne pathogens and the current scenario in relation to the formal and clandestine sale of raw milk. Finally, we select some highly effective strategies to reduce the risks associated with raw milk in food services. Regardless of whether a country regulation allows or prohibits the trade of raw milk and its products, this is not the time to be negligent. [ABSTRACT FROM AUTHOR]

The frequency and possible sources of non-starter lactic acid bacteria (NSLAB) and citrate fermenting bacteria (CFB) at four points of a milk supply chain were evaluated. The relationship between the distance from farms (G1 and G2) to industry with NSLAB, CFB and psychrotrophic bacteria populations was also evaluated. A positive correlation between psychrotrophic and CFB was verified, which points to the need for the correct use of good milking practices to control these bacteria. NSLAB showed a significant increase in the population in raw milk samples collected in industrial silos (4.4 log cfu mL−1). CFB populations showed a significant increase in milk from tank trucks (4 log cfu mL−1). There was no difference between G1 and G2 in microorganisms counts. Even after the pasteurisation process, NSLAB and CFB populations remained high, which points to the occurrence of post-heat treatment recontamination, formation of biofilms and/or the presence of thermoduric microbiota. [ABSTRACT FROM AUTHOR]

BACKGROUND Provolone can be fresh or ripened, with its taste varying from sweet to spicy. The high psychrotrophic density of raw milk is associated with thermoresistant enzymes that can change cheese characteristics such as texture, promote sensory defects and decrease industrial yield. Two batches of provolone‐type smoked cheese were produced from chilled raw milk with 3 log cfu mL−1 (Treatment 1) and 7 log cfu mL−1 (Treatment 2) of psychrotrophs. The psychrotrophic (21 °C for 25 h) and physical‐chemical profile of the raw milk were determined. Cheeses were evaluated by fat level, primary and secondary proteolysis index, yield, protein profile (Urea‐polyacrylamide gel electrophoresis), and texture (hardness, cohesiveness, elasticity, and chewiness) at 14, 30, and 60 days of storage time. Sensorially, the cheeses were evaluated (100 tasters/period) using the triangular test. RESULTS: The treatments did not influence proteolysis index, although maturation influenced the proteolytic depth index after 60 days. The psychrotrophic population influenced αs1‐ and β‐casein fractions, while maturation time influenced αs1‐ and γ‐casein fractions. Treatment 2 induced a 3% reduction in cheese yield. Hardness and chewiness showed a linear and positive relationship with the milk's psychrotrophic load. There was a significant difference in the fat content of the cheeses, with Treatment 2 having a lower level. The triangular test showed no difference between the cheeses. CONCLUSION: Although the larger psychrotrophic population in raw milk was associated with superior values of hardness and chewiness, as well as an increase in protein fractions indicating that proteolysis was observed, the tasters did not identify sensorial differences between the cheeses. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Despite clear health risks associated with consuming unpasteurised milk, a considerable number of people are still consuming these products. We evaluated consumers' behaviour and perceptions about food safety risks related to raw milk and unpasteurised cheese product consumption, associating their awareness of foodborne diseases with the epidemiology of gastro-intestinal disorders. A cross-sectional study in Brazil was conducted using an online standard questionnaire. The consumption of raw milk and dairy products is widespread. Although 66% of consumers are misinformed about regulations, 90% of consumers are conscious about the risks of raw milk consumption. The level of awareness of milk-borne diseases is not equal across age and educational level. Although our results should be generalised with caution, we found that awareness of milk-borne diseases is a protective factor against abdominal pain, concluding that the ability to understand the risks of unpasteurised dairy product consumption was associated with health status of the population. [ABSTRACT FROM AUTHOR]

The aim of this work was to use X-ray diffraction to identify substances used for adulteration of raw milk and to determine if crystallographic analysis can detect extraneous substances in milk. Two unknown substances were sent anonymously by employers linked to the dairy chain, who claimed that they were added directly in milk prior to water addition by truck drivers. The samples were analyzed by X-ray diffraction and submitted to physicochemical analysis. The first substance was identified by X-ray diffraction as sodium citrate, complying with its physicochemical attributes, such as the powerful ability to decrease the freezing point. The second substance was identified by X-ray diffraction as sucrose and this result was also in agreement with its ability to increase the density, decrease the freezing point and finally, to be positive for sucrose in the resorcinol qualitative test. To evaluate if X-ray diffraction can detect extraneous substances already mixed in milk, fresh raw milk samples tampered with urea, sodium hydroxide, sodium citrate and sucrose were freeze dried and analyzed by X-ray diffraction, with no detection of any extraneous substances at any percentage. This is the first report of attempted diagnosis of extraneous substances in milk by X-ray diffraction. However, this technique can be useful only when applied to identify substances used for adulteration prior to its dilution in milk, since the amorphous nature of milk seems to be a limitation for the accurate detection of extraneous substances. [ABSTRACT FROM AUTHOR]

The objective of the work described in this research communication was to determine the lipoproteolytic capacity and potential of Pseudomonas spp. from the microbiota of refrigerated raw milk. The influence of temperature and bacterial population on these activities was also evaluated. Pseudomonas spp. (PS) counts (30 °C/48 h) were confirmed by PCR. Proteolytic (10% milk agar) and lipolytic capacities (PLC) (tributyrin agar) were evaluated (21 °C/72 h). Proteolytic (PP) and lipolytic potential (LP) were assessed by measuring the diameter of the halos and were categorized as low or high. A total of 91.3% PS possessed PLC. The PP of 64.16% isolates was high and was frequently observed in PS from milk samples with higher counts and lower temperatures. The LP of 70.52% isolates was low, and higher LP was associated with low microbiological counts and temperatures. Genetic studies evaluating Pseudomonas spp. strains in the milking environment and investigating the origin of these isolates could be useful to improve the quality and shelf life of dairy products. [ABSTRACT FROM AUTHOR]

This work aimed to assess the inhibitory effect of Lactobacillus rhamnosus against different populations of Pseudomonas fluorescens and Pseudomonas putida, isolated from refrigerated raw milk and the compounds responsible for inhibitory effects over storage time. An initial population of 4 log cfu/ml (50 ml) of L. rhamnosus (working culture) was added to 150 ml of reconstituted powder milk (12%) with P. fluorescens and P. putida, with an initial concentration of 2, 4, and 6 log cfu/ml. After activating at 21°C/72 hr, 200 ml of inoculum was stored at 10°C/48 hr. L. rhamnosus inhibited the growth of P. fluorescens and P. putida for all populations analyzed after inoculation (0 hr), 24, and 48 hr. The inhibitory compounds were organic acids. The average diameter measurement of inhibition zones for P. fluorescens was 1.9 cm and for P. putida was 1.6 cm. Practical applications: This study demonstrated the antibacterial activity of L. rhamnosus against P. fluorescens and P. putida, both of the species isolated from the milk microbiota found in the environment of milk‐processing facilities. Although these findings need further validation on an industrial scale, it was demonstrated that L. rhamnosus can contribute for the improvement of raw milk quality. [ABSTRACT FROM AUTHOR]

Due to their quality, high yield and nutritional value, sheep dairy products have been gaining market space and attracting new producers. Pseudomonas spp. is the most common psychrotrophic genus present in bovine refrigerated raw milk and is characterized by intense lipoproteolytic activity. Metalloprotease aprX is one of the enzymes produced by Pseudomonas spp. which has great industrial importance, since it has specific activity in the deterioration of casein, resulting in significant changes in physicochemical properties and sensorial characteristics of raw milk and dairy products. The aim of this study was to observe the occurrence of Pseudomonas spp. in raw sheep milk and evaluate the influence of storage temperature on the spoilage potential of the strains. Raw sheep milk samples were stored at 4 °C or 9 °C (72 h) and plated in Pseudomonas Agar Base supplemented with CFC (25 ºC / 48 h). The isolates characteristic of Pseudomonas had their genus, species (P. putida , P. fluorescens and P. aeruginosa) , and presence of gene apr X confirmed by Polymerase Chain Reaction (PCR). The lipoproteolytic capacity and the spoilage potential of the isolates were evaluated in Milk Agar (10%) and Tributyrin Agar Base (1%) (21 °C / 72 h). Initial (2 h) populations of Pseudomonas spp. ranged from 1.0 to 4.2 log CFU/mL; after 72 h, the values observed in milk samples stored at 9 °C (3.0–7.0 log CFU/mL) were higher than those obtained in samples at 4 °C (1.6–6.0 log CFU/mL). A total of 255 strains of Pseudomonas spp. were isolated: 30.2% (77) from milk stored at 4 °C and 69.8% (178) from milk at 9 °C. At both temperatures, P. fluorescens was predominant, followed by P. putida. P. aeruginosa strains, isolated only from samples stored at 9 °C, showed high lipoproteolytic capacity and were characterized by higher proteolytic potential than lipolytic. P. fluorescens was the only species to present high proteolytic (halos > 2 cm) potential. Considering a single storage temperature (4 °C and 9 °C), only P. fluorescens showed higher proteolytic potential than lipolytic. The aprX gene was predominant in P. fluorescens and P. putida isolates (4 °C and 9 °C); strains obtained from milk stored at 4 °C showed higher proteolytic potential than those isolated from milk at 9 °C. All strains of P. fluorescens and only 46.42% of P. putida presented proteolytic capacity at 9 °C. The apr X gene was observed in all P. aeruginosa strains, but only 95.65% of them showed proteolytic capacity. The lipolytic potentials of P. fluorescens and P. putida were not influenced by milk storage temperature. P. fluorescens was the only species to present high lipolytic potential. P. putida isolated from milk at 9 °C was the only species to present higher lipolytic potential than proteolytic. According to the microbiota and the storage temperature, there may be a predominance of proteolytic or lipolytic enzymes in milk and consequently, defects in sheep dairy products. It should also be considered that most of the isolates of Pseudomonas spp. presented lipoproteolytic capacity, which emphasizes the importance of low initial populations of this microorganism in raw sheep-chilled milk, mainly when used in the production of dairy products. • P. fluorescens was predominant specie in raw sheep milk. • P. aeruginosa strains were isolated only at 9 °C. • There was a high frequency of aprX gene in P. fluorescens, P. putida, P. aeruginosa. • Most of the isolates of Pseudomonas spp. presented lipoproteolytic capacity. [ABSTRACT FROM AUTHOR]