Storage Of Raw Milk Research Articles

Optimization of Preservation Methods Allows Deeper Insights into Changes of Raw Milk Microbiota.

The temporal instability of raw milk microbiota drastically affects the reliability of microbiome studies. However, little is known about the microbial integrity in preserved samples. Raw cow milk samples were preserved with azidiol or bronopol and stored at 4 °C, or with dimethyl sulfoxide (DMSO) or a mixture of azidiol and DMSO and stored at −20 °C for up to 30 days. Aliquots of 5-, 10-, and 30-day post-storage were treated with propidium monoazide (PMA), then analyzed by sequencing the 16S rRNA gene V3-V4 and V6-V8 regions. The V6-V8 gave a higher richness and lower diversity than the V3-V4 region. After 5-day storage at 4 °C, the microbiota of unpreserved samples was characterized by a drastic decrease in diversity, and a significant shift in community structure. The treatment with azidiol and DMSO conferred the best community stabilization in preserved raw milk. Interestingly, the azidiol treatment performed as well for up to 10 days, thus appearing as a suitable alternative. However, neither azidiol nor bronopol could minimize fungal proliferation as revealed by PMA-qPCR assays. This study demonstrates the preservative ability of a mixture of azidiol and DMSO and provides deeper insights into the microbial changes occurring during the cold storage of preserved raw milk.

Development and Implementation of the HACCP System on the Production Line of Kefir from Goat's Milk

The purpose of this work is to develop a HACCP plan with the subsequent implementation of the HACCP system to ensure the safety of production of kefir from goat's milk produced in the in the Akmola region. When implementing HACCP defined policy and security of products, the scope of the HACCP system, the appointment of working group HACCP, identified hazards, identified Critical Control Points (CCP) for certain operations of the process and developed the cautionary measures to eliminate risks or reduce them to an acceptable level and the proposed corrective actions. Stages of hazard analysis are the basis of the HACCP system. The first stage of this analysis is to identify threats to human health and assess the identified hazard. Hazards are usually divided into three categories: Biological, chemical and physical. The second stage is the selection of critical control points. To select critical control points on the line for the production of kefir from goat's milk produced in LLP Breeding farm Zerenda of Akmola region, the method of Decision Tree was used, which allows to determine critical control points at the stage of the technological process. The implementation of Decision Tree method proves that the stages of raw milk storage, pasteurization and fermentation, are critical control points in relation to the identified preliminary threats to the safety of the dairy product - kefir from goat's milk produced in LLP.

Determination of some element levels in various kinds of cow's milk processed in different ways.

This study aimed to measure zinc (Zn), selenium (Se), copper (Cu), iron (Fe), chromium (Cr), nickel (Ni), lead (Pb), cadmium (Cd), arsenic (As), and aluminum (Al) in whole, semi-skimmed, skimmed, organic, fruit-flavored (strawberry, banana, and cocoa), pasteurized, and raw cows' milk. The samples were collected from sterilized and pasteurized milk processed in different ways in Ankara; the milk was kept in refrigerated raw milk storage tanks on dairy farms. Ninety samples were collected, and there were ten samples in each group. Analyses were performed using inductively coupled plasma-mass spectrometry. Lead and Cd were not found in any samples, while Zn was observed in all samples. The element with the highest frequency of occurrence was Zn, followed by Cr = As> Al > Se > Fe > Ni > Cu > Pb = Cd, in decreasing order. The lowest concentration among the essential elements was seen in Cu. Aluminum and As were found in 85% and 94.45% of the samples, respectively. However, the present concentrations were below the level of a probable negative effect. It was found that the concentrations of elements in milk showed statistically significant differences, depending on the milk type. It is recommended that low-quality materials not be used in the preparation of milk; the element concentrations in milk and the feed and water consumed by animals should be controlled regularly, and the animals should not be pastured near industrial and traffic sites to protect public health.

Evaluation the Efficacy of Lysozyme Hydrolysates-Loaded Chitosan Against Food Borne Pathogens in Raw Milk During Cooling Storage

Milk preservation is closely related with its microbiological quality. The spoilage may occur at any stages from production till consumption and during milk processing. Many potent antimicrobials discovered recently but, it is important to test their efficacy against undesirable bacteria inside the food materials that help to improve food safety and validity. Our research was focused on comparative antibacterial activities between chitosan, lysozyme and their different mixtures against different undesirable bacterial strains by agar well diffusion assay. Then apply the selected antibacterial substances in raw cow milk contaminated with food borne pathogens and spoilage bacteria with monitoring the bacterial growth or inhibition. Our preliminary investigation showed that, chitosan at concentration 0.5% exhibited the largest inhibition zones diameter followed by LZHC complex against Salmonella enteritidis and Bacillus subtilus in-vitro by agar well diffusion method. During application in raw cow milk, LZHC complex exhibited powerful bactericidal effect followed by chitosan especially against Clostridium perfringens, Staphylococcus aureus and Listeria monocytogenes after 24h from cooling storage of raw cow milk. We found that, the bactericidal activity of LZ and LZH were greatly enhanced upon combination with chitosan. But, the bactericidal activity of LZHC complex exhibited great killing power than the conjugation between native LZ and chitosan (LZC) complex at same concentrations. This may be attributed to the chitosan oligomers and lysozyme peptides acting in a synergistic manner in penetrating and killing undesirable bacteria. Although chitosan was effective in inhibiting the growth of spoilage microorganisms but, It is induce changes in raw milk pH. Accordingly, we suggest LZHC complex will be a promising antibacterial additive to produce highly safe raw milk without heat treatment and recommended further future studies to explore its antibacterial mechanism. Also we recommend chitosan to be applied in fermented dairy products to produce safe and good quality product.

Changes in stability and shelf-life of ultra-high temperature treated milk during long term storage at different temperatures

In the ultra-high temperature (UHT) process, milk is subject to temperatures above 135 °C for few seconds giving a product with a shelf-life of several months. The raw milk quality, UHT process and storage conditions affect the stability. In this study, the stability of UHT milk produced in an indirect system was evaluated by studying changes in taste, colour, fat separation, fat adhesion to the package, sedimentation, gelation, heat coagulation time, pH and ethanol stability during storage for up to one year at different temperatures. UHT milk stored at 4 and 20 °C had the longest shelf-life of 34–36 weeks, limited by sediment formation. Storage at 30 and 37 °C considerably decreased the shelf-life of UHT milk to 16–20 weeks, whereby changes in sediment formation, taste and colour were the limiting factors. Our results suggest that the changes observed at the different storage temperatures can be explained by different known mechanisms.

Multiplicação de Pseudomonas fluorescens em temperaturas de refrigeração e seu potencial proteolítico

A multiplicação de estirpes de Pseudomonas fluorescens 07A e 041 em condições de refrigeração foi avaliada neste trabalho, bem como seu potencial proteolítico usando-se ágar-leite e azocaseína como substrato. Foi possível observar a multiplicação dos isolados nas temperaturas de refrigeração, sendo que ocorreu um aumento da multiplicação na medida em que se aumentou a temperatura e o período de estocagem. A atividade proteolítica dos isolados foi demonstrada pelo ágar-leite, sendo que a do isolado 07A foi superior à de 041, o que também foi observado pela técnica de azocaseína. Esse resultado se deve à variabilidade genética entre os microrganismos psicrotróficos e a expressão de suas enzimas proteolíticas. A legislação brasileira preconiza o uso de temperaturas de refrigeração para o armazenamento do leite cru na propriedade rural e no estabelecimento processador. Entretanto, as temperaturas estabelecidas não inibem a multiplicação de microrganismos psicrotróficos. Portando, é imprescindível assegurar a adoção de boas práticas de produção para evitar contaminações, além do controle efetivo do tempo e da temperatura de estocagem do leite cru para se evitar a sua contaminação durante a produção e não comprometer a sua qualidade e de seus derivados.

N2 Gas-Flushing Prevents Bacteria-Promoted Lipolysis and Proteolysis and Alleviates Auto-Oxidation in Bovine Raw Milk During Cold-Storage

Worldwide, tremendous amounts of food, including milk and dairy products, are lost or wasted. Although refrigeration permits longer storage of raw milk, low temperatures still do not prevent the action of other abiotic and biotic factors that promote biochemical, chemical, microbial, sensorial and nutritional changes in raw milk, which also affect milk-derived dairy products. Treatment by N2 gas flushing showed great potential in preserving the microbiological quality of raw milk during storage at low and milder temperatures. Here, we examined the impact of cold storage (at 6°C up to 7 days), on the ascorbic acid content, extent of auto-oxidation, and on levels of lipolysis and proteolysis along with bacterial growth, in three raw milk samples in the presence or absence of N2. When N2 gas was applied, lower levels of lipolysis and proteolysis were found to coincide with the detection of lower numbers of bacterial lipase and protease producers in raw milk. Furthermore, lower auto-oxidation was detected in N2-treated samples than in only cold stored controls. By demonstrating that key components of milk were better preserved during cold storage, the present study further highlights the advantages of the N2 flushing treatment in terms of preserving the quality and safety of raw milk and its derived dairy products.

Strategies for raw sheep milk storage in smallholdings: Effect of freezing or long-term refrigerated storage on microbial growth

We assessed the effects of freezing and refrigeration over long periods on the microbiological quality of sheep milk. The raw milk was frozen in 1-L plastic bags or 5-L milk buckets and, after 1 mo, thawed at 7 or 25°C. We evaluated these samples immediately after thawing (d 0) and after 1 d of storage at 7°C. Furthermore, we stored fresh raw milk at 7°C for 10 d in the same packages and in a bulk milk cooler at 4°C (adding 10% of fresh raw milk daily). The total bacterial, total psychrotolerant, and proteolytic psychrotolerant counts were evaluated before and after thawing (for previously frozen milk) and daily (for refrigerated milk). The frozen-thawed milks showed no significant increase in bacterial counts immediately after thawing for all samples (<0.7 log cfu/mL), but only the samples packaged in 1-L bags and thawed at 7°C remained microbiologically adequate after 1 d of storage. Findings of the refrigerated samples were modeled using a modified Gompertz equation, obtaining a lag phase of around 0.5 (5-L bucket), 2.6 (1-L bag), and 7.0 (bulk milk cooler) d for total bacterial and total psychrotolerant counts. Maximum growth rates (µmax) were 1.0 and 1.0 (5-L bucket), 1.2 and 1.3 (1-L bag) and 3.0 and 1.5 (bulk milk cooler) ln(cfu/mL) per day for total bacteria and total psychrotolerant counts, respectively. Compared with total bacteria and total psychrotolerant bacteria, psychrotolerant proteolytic bacteria grew slowly, reaching unacceptable counts only after 9 to 10 d of storage. The studied methods are interesting alternatives for preserving raw sheep milk on smallholdings.

The Environmental Life Cycle Assessment of Dairy Products

Dairy products such as processed milk, cheese, yoghurt and butter are produced and consumed globally. While having several dietary and economic benefits, their production and consumption also have many environmental impacts of various nature. In this study, a comprehensive review of studies that focus on the life cycle environmental impact analysis of dairy products has been conducted. A total of 31 studies that satisfy certain filtering criteria have been analysed, covering 6 different products and 17 different impacts. Cheese was observed as the most widely studied dairy product whereas global warming potential was the most commonly calculated impact, as it appeared in all 31 of the reviewed studies. The contributions of different stages (raw milk production, factory processes, storage and use, transportation, waste treatment) have been investigated. For many impacts, raw milk production was found to be the main contributor regardless of the product type. Fertiliser use, agricultural material production and use and on-site emissions were the main drivers associated with the raw milk production stage, leading to several impacts such as global warming potential, acidification and eutrophication. As far as the production processes are concerned, energy use emerged as the main cause of environmental footprint. Transportation, storage/use and waste treatment were found to have slightly significant to negligible contributions to almost all the impacts except for ozone layer depletion. Butter appeared as the dairy product with the highest environmental footprint, followed by cheese. The most common recommendations in order to reduce the environmental footprint of dairy products were as follows: using more energy-efficient equipment for production, optimising transportation routes and using more environmentally friendly vehicles, modifying the feed content for the farm animals, and using renewable energy sources.

Comparison of real‐time PCR and cultural method for detection of bacterial load in pasteurized milk

AbstractIn this study, we used a TaqMan® probes through the real‐time polymerase chain reaction (PCR) technique as a rapid and sensitive way to detect bacterial load of pasteurized milk. The reaction was optimized for enumeration of bacteria in pasteurized milk samples. In parallel, the same milk samples were assessed by conventional cultural‐based method. The correlation between methods was evaluated by Bland Altman analysis. The minimum and maximum value for conventional culture‐based method were 0 and 10,000 cfu/ml while qPCR gave us 55 and 7,071 (Bacteria/ml of pasteurized milk), respectively. Results indicated that Taq Man real‐time PCR provides a useful tool for rapid and accurate quantification of bacterial load.Practical applicationsDairy industries are required to determine total bacterial load in farmer's raw milk before collection based on legal standard methods for microbial detection. Moreover, the result of total bacterial counting is the major pricing criterion of raw milk. Despite the storage of raw milk from large farms in separate tanks, raw milk from small‐ and medium‐size farms are mixed in other tanks resulting in total bacterial load alteration. Traditional cultural‐based methods are common to determine total bacterial load in raw milk. However, these techniques are laborious and time‐consuming. Recent molecular‐based methods are easily applicable to ensure that perishable raw milk could be monitored precisely under national rules and legislation in the shortest possible time. This report provides the details of a TaqMan real‐time PCR (qPCR) that can be used in factory sites for accurate monitoring of raw milk bacterial load before transferring the raw milk into pasteurization line.

Detection of pathogenic bacteria from raw, pasteurized and UHT milk available in the local market of Gazipur District

The present study was undertaken with the aim of investigating the bacteriological quality of locally available raw, pasteurized and UHT milk in Gazipur District. A total 5 raw, pasteurized and UHT milk samples were collected during November to December 2016. All the pasteurized and UHT milk samples showed the total aerobic heterotrophic bacterial (TAHB) level above the standard acceptable range (i.e. &gt; 104 cfu/ml for pasteurized milk and &gt; 0 for UHT milk). Both Gram positive and Gram negative pathogenic bacteria viz. Staphylococcus aureus, S. epidermidis, Bacillus sp., Pseudomonas sp. and Enterobacter sp. were isolated from studied samples. API 20 E was used for confirmation of Pseudomonas sp. This study indicates that most of the pasteurized and UHT milk samples were not satisfactory in terms of public health standard. Therefore, care must be taken to avoid possible health risk in every step involving collection, transportation, storage and post pasteurization handing of raw milk.&#x0D; Jahangirnagar University J. Biol. Sci. 7(2): 13-19, 2018 (December)

The contribution of fast growing, psychrotrophic microorganisms on biodiversity of refrigerated raw cow's milk with high bacterial counts and their food spoilage potential

Storage of raw milk in the bulk tank creates an environment which selects for psychrotrophic bacteria. Results from earlier studies suggested that the microbiota of bulk tank milk with high bacterial counts is dominated by single, cold-adapted species with high growth rates at low temperatures. We checked this assumption in more detail and analyzed the microbial diversity of 48 samples from bulk tank raw cow's milk with bacterial counts >100,000 cfu/mL from different geographic regions by culture-dependent and –independent methods.Contrary to presumptions from earlier studies, only the minority (24%) of samples was dominated by a single bacterial species and diversity was not correlated with bacterial counts. The dominating species in this group of samples were identified as psychrotrophic Acinetobacter and Pseudomonas species, related to poor hygiene and spoilage, or mesophilic, mastitis-related Streptococcus species and Escherichia coli. This shows that storage of raw milk under refrigeration does not always lead to a selection of cold-adapted bacteria.Approximately half of the raw milk isolates showed either lipolytic or proteolytic activity at 10 °C or 4 °C. Consistent or increased enzymatic activity at cold temperatures was detected for Acinetobacter spp. and Pseudomonas spp., but also for genera with minor abundance, e.g. Carnobacterium and Arthrobacter.

CONFORMITY OF REFRIGERATED RAW MILK FROM FAMILY PRODUCTION UNITS OF SOUTHERN ESPÍRITO SANTO

Abstract Dairy farming is an important activity in Brazil and Espírito Santo state, with small properties accounting for 80% of production. Despite of this economic importance, data about quality of the milk produced and the hygienic-sanitary conditions are still scarce. Then, the objective of this study was to evaluate the characteristics of refrigerated raw milk produced in family production units in southern Espírito Santo to verify compliance with Brazilian legal standards. Three collections were carried out in 29 community expansion tanks, for a total of 87 samples of refrigerated raw milk. Analysis of standard plate count (SPC), psychrotrophic bacteria count (PBC), somatic cell count (SCC), titratable acidity, density, fat, total dry extract (TDE), non-fat dry extract (NFDE), residues of antibiotics (β-lactam and tetracycline), cadmium and lead levels were performed. Of the 87 samples, 66% presented non-standard values for SPC, and 38% had non-standard values for SCC. Eighty five percent of the samples presented non-standard results for NFDE, 10.3% for density and 2.3% for titratable acidity. All samples complied with the legislation regarding residues of antibiotics, Cd and Pb levels. These results indicated failures in the raw milk obtainment and storage chain from family production units of southern Espírito Santo, Brazil.

Impact of immediate and delayed chilling of raw milk on chemical changes in lipid fraction of pasteurized milk

BackgroundIn many developing countries, milk chilling facilities are not available on the farm where milk is produced, rather these are located at the distance of 10–12 km. After milking, it takes about 2–3 h to reach milk to the chilling facilities. The milk is then chilled and transported to the milk processing plants for thermal processing and value addition. In developing countries, shelf life of pasteurized milk is only 3 days, as compared to 7–10 days in developed countries. The factors which are responsible for the shorter shelf life of pasteurized milk should be discovered for the improvement of dairy sectors of these countries. The magnitude of chemical changes which takes place in un-chilled milk and their effect on fatty acids profile, antioxidant status and lipid oxidation is not previously studied.MethodsRaw milk samples of the same farm were either rapidly chilled to 4 °C immediately or held at room temperature (35 ± 2 °C) for 2 h followed by rapid chilling to 4 °C. Immediately and delayed chilled raw milk samples were stored at 4 °C for 72 h. Both milk samples were pasteurized at 65 °C, filled in 250 ml transparent PET bottles and stored at 4 °C for 6 days. Fatty acid profile, selenium, zinc, total antioxidant capacity, total flavonoid content and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, free fatty acids, peroxide value and anisidine value were determined at different stages of the experiment. This experiment was repeated with milk of same farm for at least five times.ResultsStoring raw milk at ambient temperature (35 ± 2 °C) significantly influenced the pH and lactose content of milk. The loss of short-chain fatty acids in delayed chilled milk was 1.19%, 3.27% and 1.60%, as compared to immediately chilled raw milk. In delayed chilled milk, loss of C18:1 and C18:2 after 3 days of storage period was 6.67% and 01.22. In delayed chilled milk after 6 days of storage, loss of C18:1 and C18:2 was 7.7% and 1.39%, respectively. In immediately chilled milk loss of C18:1 and C18:2 after 3 days of storage was 3.48% and 0.64%. In immediately chilled milk loss of C18:1 and C18:2 after 6 days of storage was 4.57% and 0.9%. Almost 41% vitamin E was lost when raw milk was stored at ambient temperature for 2 hrs. About 21% and 7% vitamin E was lost in delayed and immediately chilled milk, when samples were analyzed immediately after pasteurization. Loss of selenium and zinc contents after 2 h of ambient storage of raw milk were 0.43 and 224 μg/100 g. After 2 h of storage of milk at ambient temperature, free fatty acids increased by 0.03% (p < 0.05). After 6 days of storage, rise of free fatty acids in immediately and delayed chilled milk was 0.06% and 0.14%, respecitively. Rise of 0.13(MeqO2/kg) was recorded, when un-chilled raw milk was stored at ambient temperature for 2 h. After 3 and 6 days of storage, peroxide value of pasteurized milk (delayed chilled) was 0.88 and 1.56 (MeqO2/kg). After 3 and 6 days of storage, peroxide value of pasteurized (immediately chilled) was 0.39 and 0.42(MeqO2/kg). After 2 hrs of ambient storage, 18.41% flavonoids were lost. After 2 hrs of ambient storage of raw milk, loss of total antioxidant capacity and DPPH free radical scavenging activity was 29.31% and 44.53%. After 6 days of pasteurization, loss of total antioxidant capacity and DPPH free radical scavenging activity in delayed chilled raw milk was 72.1% and 89.57%.ConclusionsThe findings of this investigation showed that delayed chilling of raw milk leads to several undesirable chemical changes in lipid fraction of milk.

Spoilage potential of psychrotrophic bacteria isolated from raw milk and the thermo-stability of their enzymes.

The storage and transportation of raw milk at low temperatures promote the growth of psychrotrophic bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy products. Though many studies have been carried out on the spoilage potential of psychrotrophic bacteria and the thermo-stabilities of the enzymes they produce, further detailed studies are needed to devise an effective strategy to avoid dairy spoilage. The purpose of this study was to explore the spoilage potential of psychrotrophic bacteria from Chinese raw milk samples at both room temperature (28 °C) and refrigerated temperature (7 °C). Species of Yersinia, Pseudomonas, Serratia, and Chryseobacterium showed high proteolytic activity. The highest proteolytic activity was shown by Yersinia intermedia followed by Pseudomonas fluorescens (d). Lipolytic activity was high in isolates of Acinetobacter, and the highest in Acinetobacter guillouiae. Certain isolates showed positive β-galactosidase and phospholipase activity. Strains belonging to the same species sometimes showed markedly different phenotypic characteristics. Proteases and lipases produced by psychrotrophic bacteria retained activity after heat treatment at 70, 80, or 90 °C, and proteases appeared to be more heat-stable than lipases. For these reasons, thermo-stable spoilage enzymes produced by a high number of psychrotrophic bacterial isolates from raw milk are of major concern to the dairy industry. The results of this study provide valuable data about the spoilage potential of bacterial strains in raw milk and the thermal resistance of the enzymes they produce.

Phospholipolysis Caused by Different Types of Bacterial Phospholipases During Cold Storage of Bovine Raw Milk Is Prevented by N2 Gas Flushing.

Cold storage aims to preserve the quality and safety of raw milk from farms to dairies; unfortunately, low temperatures also promote the growth of psychrotrophic bacteria, some of which produce heat-stable enzymes that cause spoilage of milk or dairy products. Previously, N2 gas flushing of raw milk has demonstrated significant potential as a method to hinder bacterial growth at both laboratory and pilot plant scales. Using a mass spectrometry-based lipidomics approach, we examined the impact of cold storage [at 6°C for up to 7 days, the control condition (C)], on the relative amounts of major phospholipids (phosphatidylethanolamine/PE, phosphatidylcholine/PC, phosphatidylserine/PS, phosphatidylinositol/PI, and sphingomyelin/SM) in three bovine raw milk samples, and compared it to the condition that received additional N2 gas flushing (N). As expected, bacterial growth was hindered by the N2-based treatment (over 4 log-units lower at day 7) compared to the non-treated control condition. At the end of the cold storage period, the control condition (C7) revealed higher hydrolysis of PC, SM, PE, and PS (the major species reached 27.2, 26.7, 34.6, and 9.9 μM, respectively), compared to the N2-flushed samples (N7) (the major species reached 55.6, 35.9, 54.0, and 18.8 μM, respectively). C7 samples also exhibited a three-fold higher phosphatidic acid (PA) content (6.8 μM) and a five-fold higher content (17.3 μM) of lysophospholipids (LPE, LPC, LPS, and LPI) whereas both lysophospholipids and PA remained at their initial levels for 7 days in N7 samples. Taking into consideration the significant phospholipid losses in the controls, the lipid profiling results together with the microbiological data suggest a major role of phospholipase (PLase) C (PLC) in phospholipolysis during cold storage. However, the experimental data also indicate that bacterial sphingomyelinase C, together with PLases PLD and PLA contributed to the degradation of phospholipids present in raw milk as well, and potential contributions from PLB activity cannot be excluded. Altogether, this lipidomics study highlights the beneficial effects of N2 flushing treatment on the quality and safety of raw milk through its ability to effectively hinder phospholipolysis during cold storage.

A raw milk service platform using BP Neural Network and Fuzzy Inference

An important index for raw milk storage in a dairy farm is the raw milk storage temperature which directly reflects the raw milk quality. Meanwhile, it’s hard to centrally manage numerous dairy farms which are not distributed in the same place. We aim to build a kind of raw milk monitoring and warning equipment, gateway and cloud service platform to solve these problems. The raw milk monitoring and warning equipment and service platform were designed to monitor the raw milk temperature in the refrigerated storage tank and provide a warning alarm if an exception occurred. Data-driven modeling was used for acquiring, cleaning, and utilizing data to solve the raw milk storage problems. The raw milk monitoring and warning management system provided a way of predicting and warning for raw milk storage using BP Neural Network and Fuzzy Inference. The test showed that the BP Neural Network and Fuzzy Inference model built in this paper had a good performance in predicting the raw milk storage temperature and reflecting the variation of raw milk temperature in raw milk storage process. The platform and models provided a method to manage the raw milk in dairies and prevent the raw milk from deteriorating caused by the rising temperature.

Occurrence and growth of Listeria monocytogenes in packaged raw milk

The increased availability of packaged raw drinking milk necessitates the investigation of the occurrence and growth of Listeria monocytogenes in raw milk during distribution and storage. The occurrence of L. monocytogenes in 105 retailed raw milk bottles, 115 bulk tank milk samples, 23 in-line milk filter socks and in 50 environmental samples collected from an on-farm dairy establishment were investigated. Growth of inoculated low-level L. monocytogenes contamination was also investigated in two types of raw milk packaging, namely in 1-litre plastic bottles and 3-litre bag-in-boxes, both stored at three different storage temperatures of 6, 8 and 10°C. The occurrence of L. monocytogenes was higher (4.8%) in bottled raw milk stored until the use-by-date of the package compared to fresh bulk tank milk (1.7%). L. monocytogenes counts were ≤13CFU/ml in bottled raw milk and ≤1CFU/ml in bulk tank milk. L. monocytogenes was not detected in the packaging facility, but occurred very frequently (39%) in the milk filter socks. Subtyping of L. monocytogenes isolates using pulsed-field gel-electrophoresis revealed seven pulsotypes, of which two occurred in multiple samples. Targeted inoculum levels of 1–2CFU/ml yielded L. monocytogenes counts≥100CFU/ml within seven days of storage in 22% of the raw milk packages stored at 6°C, and in all of the raw milk packages stored at 8°C. The frequent occurrence of L. monocytogenes in raw milk and the ability of a low-level L. monocytogenes contamination to grow at refrigeration temperatures highlight the importance of consumer education regarding the appropriate raw milk storage and handling.

N2 Gas Flushing Limits the Rise of Antibiotic-Resistant Bacteria in Bovine Raw Milk during Cold Storage.

Antibiotic resistance has been noted to be a major and increasing human health issue. Cold storage of raw milk promotes the thriving of psychrotrophic/psychrotolerant bacteria, which are well known for their ability to produce enzymes that are frequently heat stable. However, these bacteria also carry antibiotic resistance (AR) features. In places, where no cold chain facilities are available and despite existing recommendations numerous adulterants, including antibiotics, are added to raw milk. Previously, N2 gas flushing showed real potential for hindering bacterial growth in raw milk at a storage temperature ranging from 6 to 25°C. Here, the ability of N2 gas (N) to tackle antibiotic- resistant bacteria was tested and compared to that of the activated lactoperoxidase system (HT) for three raw milk samples that were stored at 6°C for 7 days. To that end, the mesophiles and psychrotrophs that were resistant to gentamycin (G), ceftazidime (Ce), levofloxacin (L), and trimethoprim-sulfamethoxazole (TS) were enumerated. For the log10 ratio (which is defined as the bacterial counts from a certain condition divided by the counts on the corresponding control), classical Analyses of Variance (ANOVA) was performed, followed by a mean comparison with the Ryan-Einot-Gabriel-Welsch multiple range test (REGWQ). If the storage “time” factor was the major determinant of the recorded effects, cold storage alone or in combination with HT or with N promoted a sample-dependent response in consideration of the AR levels. The efficiency of N in limiting the increase in AR was highest for fresh raw milk and was judged to be equivalent to that of HT for one sample and superior to that of HT for the two other samples; moreover, compared to HT, N seemed to favor a more diverse community at 6°C that was less heavily loaded with antibiotic multi-resistance features. Our results imply that N2 gas flushing could strengthen cold storage of raw milk by tackling the bacterial spoilage potential while simultaneously hindering the increase of bacteria carrying antibiotic resistance/multi-resistance features.

Extended storage of cold raw milk on yogurt manufacturing

Abstract: The objective of this work was to evaluate the effect of the extended cold storage of raw milk on the kinetics of fermentation on yogurt production, as well as on the product’s microbiological and physicochemical properties during shelf life. Three treatments were evaluated: yogurts made with raw milk stored for 4, 72, and 168 hours. Kinetics of fermentation was assessed through the lactic acid production rate, growth rate of Streptococcus thermophilus and Lactobacillus bulgaricus, and time to reach pH 5.0 and 4.5. The physicochemical and microbiological characteristics of raw milk and yogurts were also analyzed during cold storage at 4°C. The microbial quality of raw milk was affected by the storage time of 168 hours, with a decreasing tendency in the mesophiles:psychrotrophs ratio. Extended storage of raw milk beyond 72 hours negatively affects yogurt production, despite the low initial bacterial count, decreasing lactic acid production, S. thermophilus growth rate, pH, and protein content. Therefore, to optimize fermentation and yogurt shelf life, the maximum storage time for raw milk at 4oC should not exceed 72 hours.