Implication of food safety measures on microbiological quality of raw and pasteurized milk

The effects of implementing food safety measures including pre-requisite programs (PRPs) and/or Hazard Analysis Critical Control Points (HACCP) on the microbiological quality of raw and pasteurized milk during four years was investigated in one of the biggest diary plant in Serbia. On the dairy farm, the measures included training of farmers, investments in the infrastructure of gathering points for the collection of raw milk and transportation, improvement of hygiene and decrease of the number of small farmers. As a result of these measures, the contribution of raw milk with of lower total plate count (TPC) in total raw milk quantity decreased over time.As a result of HACCP system implementation in the dairy plant, TPC of pasteurized milk decreased from 3.32 ± 0.48 till 3.11 ± 0.30 log CFU/ml. Eight months after HACCP system was implemented, a significant decrease in TPC from 3.11 ± 0.30 till 2.18 ± 0.54 log CFU/ml in pasteurized milk which could be related to the additional investments covering pasteurisation unit and automated cleaning and disinfection system. The research confirmed constrains of a solely HACCP system without adequate PRPs.Food safety improvements through PRPs and HACCP both on farm level and in the dairy plant present a basis for the production of dairy products.     

Farm to consumption risk assessment for Staphylococcus aureus and staphylococcal enterotoxins in fluid milk in China

The objective of this study was to conduct a risk assessment to determine the food poisoning risk from the consumption of milk in China that might be contaminated by Staphylococcus aureus. Data related to prevalence and concentration of S. aureus in fluid raw milk in China were collected from the literature and used to calculate the initial contamination levels. Two main consumption routes were considered and the results of the Monte Carlo simulation model indicated that the storage temperature in the processing plant and heat processing of milk in the home were the primary factors affecting the S. aureus concentration at the processing plant and the home before consumption, respectively. Other important factors were distribution of log (D)-value's for S. aureus, storage temperature and time on farm, temperature of the thermal treatment of milk, and treatment time at the dairy processing plant. To minimize the risk of milk-borne staphylococcal intoxication in China, the key step appears to be the control of storage conditions during the period after heat treatment and before consumption. The risk assessment model developed in present study provides valuable information for Chinese government and dairy processors to improve milk safety. It also could provide valuable recommendations for Chinese consumer education on safe handling of milk products.     

Seasonal variation of aflatoxin M1 contamination in industrial and traditional Iranian dairy products

This study aimed to determine the occurrence of aflatoxin M₁ (AFM₁) contamination in 682 dairy product samples consisting of raw milk of cow, goat and sheep; Lighvan cheese; and industrial and traditional yoghurt, Kashk and Doogh samples collected from popular markets and dairy ranches in four large Iranian cities. Thin layer chromatography (TLC) technique was used for analysis of the samples. Results showed that the incidence and levels of AFM₁ contamination in raw cow milk and industrial products (manufactured from cow milk) were higher than raw goat or sheep milk, and traditional products (made from goat and sheep milk), respectively. Moreover, seasonal variations influenced the concentration of AFM₁ in most of the analyzed dairy products. Owing to the abundance and popularity of the industrial products, contamination of these products in such a level could be a potential hazard for public health.     

A survey on the milk chemical and microbiological quality in dairy donkey farms located in NorthWestern Italy

There is a growing interest in donkey's milk as food for sensitive consumers, such as infants with cow's milk protein allergy and elderly people. The aim of this study was to carry out a survey on the dairy donkeys farming in Piedmont, Italy. The research was conducted in order to analyze the farm characteristics as well as the chemical and microbiological quality of milk. All the farms were small-sized, family-run, and, in most cases, animals were farmed semi-extensively. The donkey milk from Piedmont farms was characterized by a protein content around 1.5 g/100 mL and a fat content lower than 0.1 g/100 mL. Lysozyme activity was considerably higher than that reported in raw cow milk. The milk microbiological profile greatly differed among the farms. Milk sampled in the farm that performed hand milking showed total viable counts significantly lower than milk collected in the farms equipped with automatic milking. Samples were tested for several pathogens and negative results were observed, except for the detection of Bacillus cereus in one sample. The survey provided useful data for the laying down of recent regional regulation for the production and commercialization of donkey's milk. The results of the survey indicate that further research is needed in order to define the best management and nutritional strategies for the improvement of the quali-quantitative production of dairy donkeys.     

Behavior of Salmonella spp. and Listeria monocytogenes throughout the manufacture and shelf-life of dry-cured formed ham

In contrast to traditional raw ham produced from a whole muscle or from a combination of different parts, dry-cured formed ham consists of many small meat pieces and thus has a high surface area. As a result, foodborne pathogens originating from contamination could grow if they would be transferred into the interior of the formed product. The aim of this study was to evaluate the behavior of Salmonella spp. and Listeria monocytogenes during the manufacture and shelf-life of dry-cured formed ham. The potential origins of pathogens could be from contaminated raw meat, added ingredients, processing equipment, and post-processing. The results of this study showed that the combination of the intrinsic (pH, water activity, and microflora) and the extrinsic properties (fermentation and drying conditions) prevented the growth and lead to reduction of the foodborne pathogens during manufacturing of dry-cured formed ham as well as during the shelf-life of 35 days at 4 °C.     

Prevalence and antimicrobial resistance of Staphylococcus aureus isolated from raw milk and dairy products

The objectives of this study were to determine the prevalence and antimicrobial resistance of Staphylococcus aureus isolated from raw milk (cow and sheep) and dairy products (traditional cheese and kashk) in Mazandaran Province, Iran. A total of 2650 samples, including 1930 raw milk and 720 dairy products were purchased from retail stores. Out of 2650 samples, S. aureus was detected in 328 samples (12.4%) in which 53 (16.2%) were positive for methicillin-resistant S. aureus. The S. aureus isolates showed resistance to tetracycline (56.1%), followed by penicillin G (47.3%), oxacillin (16.2%), lincomycin (11.9%), clindamycin (11.3%), erythromycin (7.9%), streptomycin (5.8%), cefoxitin (5.5%), kanamycin (4%), chloramphenicol (3.7%), and gentamicin (2.1%). A high frequency of blaZ (46%) and tetM (34.8%) resistance genes was found in S. aureus isolates. The findings of this study revealed consumption of raw milk and dairy products as a potential risk of foodborne infection in this region.     

Raw milk hygiene at farms,processing units and local markets in Burkina Faso

The aim of this study was to investigate raw milk hygiene and composition along the dairy chain in Burkina Faso. Milk samples were taken during the rainy and dry seasons from individual cows, farm tanks, milk collectors’ churns, dairy processing unit tanks and at local markets. The results showed lower total bacteria count (10–10⁴ cfu/ml) in individual cow milk than later in the dairy chain. The total bacteria count in farm tank milk was 10⁶ cfu/ml and 10⁷ cfu/ml in tank milk at dairy processing units, in milk collectors’ churns and in market buckets. Somatic cell count (100,000–150,000 cells/ml) did not show significant variation between individual cow milk and in the rest of the chain. Higher pH and lower milk fat and lactose contents were found in market bucket milk than in farm and processing unit tank milks.It was concluded that milk from the cow is of good hygienic quality, but milk is often contaminated after milking, and the hygienic quality is very low when it reaches the consumers. Also, milk sold at local markets had low fat and lactose contents and high pH during the rainy season, indicating that the milk may have been diluted, which may further increase the hazards for human health.     

Aflatoxin M1 in raw,pasteurized and powdered milk available in the Syrian market

The incidence of contamination of aflatoxin M1 (AFM1) in milk samples collected from the Syrian market was investigated by using the competitive enzyme linked immunosorbent assay (ELISA) technique. A total of 126 samples composed of raw cow milk (74 samples), raw sheep milk (23), raw goat milk (11), pasteurized cow milk (10) and powdered milk (8) showed that 80% of tested samples were contaminated with various levels of AFM1 ranging from >20 to 765 ng/l. Percentages of AFM1-contaminated samples exceeding the American, Syrian and European tolerance limits were 22%, 38% and 52%, respectively.The range of contamination was relatively higher in pasteurized milk than in raw cow and sheep milk. 80% of AFM1-contaminated pasteurized cow milk samples exceeded the European tolerance limit with a range of contamination between 89 and 765 ng/l. Percentages of contaminated raw cow, sheep and goat milk exceeding the European tolerance limit were 59%, 24% and 14%, respectively.Milk powder was almost free of AFM1 contamination with only one sample containing a concentration lower than the European tolerance limit (12 ng/l).Extrapolation of aflatoxin B1 (AFB1) from AFM1 levels of contamination in milk samples indicates that contamination in dairy cattle feeds may range from 0.5 to 47.8 μg/kg.     

Quantitative risk assessment of Mycobacterium avium subsp. paratuberculosis survival in pasteurized milk in three dairy plants in Italy

The objective of this study was to carry out a quantitative risk assessment (QRA) of Mycobacterium avium subsp. paratuberculosis (MAP) survival in pasteurized milk produced by industrial dairy plants. Data were collected in three dairy plants (A, B and C) located in three different Italian regions and processing 38.75 (plant A), 89.29 (plant B) and 190.56 million litres (Plant C) of milk yearly. Plants A and plant C produce pasteurized milk, soft and hard industrial cheeses and yogurt; plant B produces only pasteurized milk. In-line milk filter (ILMF) samples and/or bulk milk samples were collected from all 569 herds delivering milk to the three dairy plants. Samples were analysed by quantitative real-time PCR (qPCR). The QRA considered the presence of MAP in ILMF and in bulk milk of all the dairy herds delivering milk to the three investigated dairy plants, estimating MAP concentration in raw milk on the basis of these data, the dilution effect due to mixing milk in collecting trucks and in plant silos, and the effect of pasteurization in reducing the MAP load. The expected fraction of litres of pasteurized milk with 0 MAP would be 99.02%, 99.45% and 99.12%, in plants A, B and C respectively, and an overall percentage 0.55% to 0.98% of pasteurized milk having a MAP contamination >0 colony forming units (CFU)/l and 0.04%–0.11% of pasteurized litres with a MAP contamination > 100 CFU/l was predicted. A daily variation was observed in the proportion of MAP-contaminated litres of milk. The study demonstrated that milk in the dairy plants investigated may be a source of MAP exposure for humans. The between-herd and within-herd MAP apparent prevalence in the investigated areas are likely comparable to those in other areas in Italy, Europe and North America, and the results are applicable to other geographical areas.     

Contamination of milk with Bacillus cereus by post-pasteurization surface exposure as evaluated by automated ribotyping

Over the last decade, increased transportation of refrigerated raw milk from farms to factories has raised concerns over Bacillus cereus contamination in the Brazilian dairy industry. Twelve isolates from pasteurized milk and 30 isolates from the post-pasteurization equipment surfaces of a dairy processing unit were characterized as B. cereus. Seven ribotypes were identified, demonstrating the genetic variability of this microorganism. Most of the isolates belonged to the same ribogroup (RIBO1222-73-S4), and they were found on four surfaces and also in the milk, indicating the role of the equipment surfaces as reservoirs for milk recontamination.     

Determination of microbiological contamination sources during Turkish white cheese production

This study has been conducted to determine the microbiological contamination sources during production of white cheese in a local dairy plant, Bursa, Turkey. Twenty nine different control points or sample types (raw milk, pasteurized milk, milk in cheese vat, curd, moulded cheese before salting, moulded cheese after salting, cheese at cold holding and vacuum packaged cheese; samples from starter culture, rennet, calcium chloride solution, brine, cheese vat, cheese cloth, polyethylene separator sheet, milk stirrer, curd cutting knife, side pressure plate, upper pressure plate, moulded cheese cutting knife, cheese tray, packaging material used during production; workers’ hands, cold room and production room air, floor, wall, and potable water) have been examined for the enumeration of total aerobic mesophilic bacteria, staphylococci, coagulase positive staphylococci, Enterobacteriaceae, enterococci, coliforms, Escherichia coli, psychrophilic bacteria, and yeast and molds.We determined: starter culture as the possible contamination source of coagulase positive staphylococci, enterococci and psychrophilic bacteria; brine and upper pressure plate as the contamination source for staphylococci; floor and packaging material as the contamination source of psychrophilic bacteria; cheese vat, cheese cloth and curd cutting knife as the contamination source of total aerobic mesophilic bacteria; cold room and production room air as the contamination sources for yeast and molds.     

Assessment of foodborne pathogen presence in the peach supply chain and its potential risk to the end consumer

Peaches are popular, nutritious and widely consumed. Being a tree crop, it is considered a low risk fruit, with no direct water contact, and no previous foodborne disease outbreaks associated with its consumption. However, in 2014 the pioneer association between stone fruit and a foodborne illness was reported, linking Listeria monocytogenes to stone fruit. This highlights the need for better understanding of risk associated with contaminated fresh stone fruit, in order to implement adequate preventative measures. No information is available on the presence of foodborne pathogens on peaches in the supply chain. A case study approach was therefore followed to assess foodborne pathogen presence on the farm, focusing on the impact of irrigation water, facility sanitation and hygiene by collecting various fruit and environmental samples (n = 428). This study demonstrates the effectiveness of integrating basic microbial testing with safety management and risk assessment tools that can be collectively used to improve the food safety management system. No Salmonella Typhimurium was detected from samples, however, Escherichia coli O157:H7, Listeria spp. and Staphylococcus aureus were detected on fruit and environmental samples. Despite the GlobalG.A.P. certification status of the farm, livestock frequented water sources which lead to E. coli O157:H7 contamination. This conclusion was based on positive detection of foodborne pathogens from the water sources and subsequent removal of livestock which resulted in a definite decrease in pathogen detection. A number of E. coli O157:H7 and S. aureus were detected during the second year of monitoring from environmental samples and it was observed that the personal hygiene and facility sanitation was not adequately enforced. Based on feedback given to the farmer, enforcement was improved and a definite decrease in foodborne pathogens was observed in the following sampling cycle. Areas of risk that were still identified following the fourth year of monitoring included the water source used for irrigation and poor sanitation in the production and processing facilities. Limited foodborne pathogen prevalence on peaches over the full study period as well as the extended export supply chain at controlled temperatures resulted in low-to-medium calculated consumer risk. The correct and meticulous implementation of integrated and holistic pre- and post-harvest food safety management systems is therefore essential to prevent produce contamination, reduce the consumer risk and therefore ensure overall product safety.     

Influence of climate conditions on aflatoxin M1 contamination in raw milk from Minas Gerais State,Brazil

Aflatoxin M1 (AFM1) contamination in milk is a potential risk for animal and human health. The occurrence of AFM1 in raw milk from Minas Gerais State, Brazil, in different climate conditions was evaluated. A total of 129 milk samples were collected from dairy farms in three distinct periods (dry period, transition period and rainy period), and analyzed by enzyme-linked immunoabsorbent assay (ELISA) as screening test. Samples with AFM1 at concentrations above 0.05 μg/L were analyzed by liquid chromatography with fluorescence detection (HPLC-FD) as confirmatory method. All the analyzed samples showed contamination with AFM1. In the three periods, AFM1 was detected at concentrations below the permitted limit of 0.50 μg/L in milk, according to the Brazilian legislation, and 18 samples (13.95%) showed contamination with AFM1 above the permitted limit of 0.05 μg/L established by Codex Alimentarius and European Commission. Milk contamination with AFM1 was significantly affected by climatic conditions, and the highest values were verified in dry period. The AFM1 contamination was lower than the acceptable daily intake (ADI) estimated for Latin America, indicating that milk from this region is safe for human consumption. Control measures to monitor AFM1 in milk are mandatory in tropical climate countries especially in dry periods.     

Incidence of Listeria monocytogenes and Escherichia coli O157:H7 in two Kasar Cheese processing environments

This study was designed to determine the presences of two environmental pathogens in two dairy factories in Sakarya, Turkey. A total of 264 environmental samples, raw milk and cheese samples were taken at four different seasons. According to the results, Listeria monocytogenes or Escherichia coli O157:H7 was isolated from 26 or 2.7% of the samples collected from both factories, respectively. None of the cheese or curd samples were found to be positive for Listeria or E. coli O157:H7. However, 50% of raw milk samples contained Listeria innocua. Listeria was mostly isolated from the swap samples taken from the drains or the floors in processing or packaging areas. However, E. coli was also isolated from the swap samples taken from the workers’ hands and gloves as well as the drains and the floor. Only one raw milk sample contained E. coli O157:H7. A higher prevalence of both pathogens was observed in the summer months than in the other months.     

Detection of verocytotoxin-producing Escherichia coli (VTEC) in minced beef and raw milk by colony blot hybridization

Verocytotoxin-producing Escherichia coli (VTEC) are foodborne pathogens that cause outbreaks linked to consumption of meat and raw milk. In this note the authors report results obtained from a survey conducted on minced beef and raw bovine milk samples using a Multiplex PCR (M-PCR) for the detection of eae, stx₁, stx₂ and hlyA genes as a screening step followed by a colony blot hybridization (CBH) technique for the isolation of the VTEC. Of 100 minced beef and 123 raw milk samples, 13 (13%) and 7 (5.7%) were positive in the M-PCR and among these 9 and 3 strains were isolated using CBH, respectively. All isolates showed the presence of the stx₂ gene, single or in association with the other investigated genes. None of the isolates belonged to the O157, O26, O91, O103, O111 and O145 serogroups. The study showed that the use of M-PCR for the screening of samples coupled with a sensitive and specific detection technique, could improve the possibility of detection of VTEC strains in foods. Moreover, the presence of VTEC in minced beef and in raw milk confirms their important role as putative vehicles of infection to humans. Stringent control of these foodstuffs is essential for food safety purposes.     

Internalization of Salmonella enterica by tomato fruit

Since 1990, several outbreaks of foodborne illness have been associated with the consumption of raw tomatoes. Various serovars of the bacterial pathogen, Salmonella enterica, were responsible for these illnesses. Fruits and vegetables are not a normal niche for mammalian pathogens. Hypotheses concerning introduction of Salmonella into tomatoes range from contamination in the field or greenhouse to direct or cross-contamination during harvest, handling and preparation of tomato as a raw agricultural commodity. Many different reports have shown that Salmonella can not only survive in tomato fruit but also proliferate from small, relatively inconsequential populations to numbers known to incite illness even in healthy individuals.Herein, production, harvest and handling of fresh market tomatoes are evaluated in terms of how Salmonella might contaminate this crop. Physical principles are emphasized, whereas biological factors are included where appropriate. Salmonella is viewed as a bacterium that is affected by the same physical principles affecting bacteria naturally occurring in the environment surrounding tomato fruit as well as tomato plants during production, harvest and handling.     

Delphi expert elicitation to prioritize food safety management practices in greenhouse production of tomatoes in the United States

Most of fresh tomatoes sold in the United States (US) are grown using protected agriculture. The risk of contamination and severe disease outbreaks in humans due to foodborne pathogens linked to fresh produce are a constant threat to the public and the industry. To date, there are limited tools to prioritize food safety management practices in commercial greenhouses to reinforce food safety in a timely manner. One rapid cost effective approach, originally applied in education and healthcare, is the Delphi method that uses expert opinion to quantify and rank priorities.An iterative systematic Delphi expert elicitation approach was used to prioritize management factors for the reduction of foodborne pathogen contamination in tomato greenhouses in the US. A validated online survey addressing eight thematic areas (water management, workers, environment and greenhouse design, equipment sanitation, waste management, animal intrusion, traceability, and propagation) was discussed among 20 individuals internationally recognized as experts in fresh produce production in protected agriculture, foodborne pathogens, and food safety theory and practice. Consensus rankings of activities and practices most likely contributing to microbial contamination and its mitigation were determined.Food safety priorities to prevent contamination of greenhouse tomatoes, in order of significance (i.e, ranking scale, weighted average; 1 lowest, 5 highest), included handwashing (4.67), environmental controls (4.32), enforceable worker health policy (3.94), cleaning and sanitation of reusable plastic containers (3.94), reused retail-ready containers (3.89), and irrigation water testing for human pathogens (3.84) to prevent contamination of greenhouse tomato.The majority of experts indicated that contaminated greenhouse surfaces that are in contact (direct or indirect) with the fruits are important sources of pathogen transfer to fresh tomatoes, highlighting the need for environmental controls in greenhouses. Importance of adequate worker management practices including handwashing and health policy highlights the role of worker education in reducing the risks of foodborne outbreaks linked to greenhouse grown produce. This report illustrates the benefits of using Delphi approach to improve food safety in greenhouses. The provided priority list can be used by growers to guide the routine food safety practice implementation procedures.     

Aflatoxin M1 in milk and traditional dairy products from west part of Iran: Occurrence and seasonal variation with an emphasis on risk assessment of human exposure

In the present study, a total of 358 samples consisting of raw milk of cow (n = 64), goat (n = 56) and sheep (n = 52); traditional cheese (n = 40), yoghurt (n = 42), Kashk (n = 40), Doogh (n = 44) and Tarkhineh (n = 20) were analyzed for aflatoxin M₁ (AFM₁) by using an enzyme linked immunosorbent assay (ELISA). Frequency of AFM₁ and its concentration ranges in the ELISA positive samples were determined by high performance liquid chromatography with fluorescence detection (HPLC-FD). AFM₁ contamination was 84.3%, 44.6% and 65.3% for cow, goat and sheep raw milks, respectively. Moreover, AFM₁ was in 65.5%, 23.8%, 14%, 13.6% and 35.0% of cheese, yoghurt, Kashk, Doogh and Tarkhineh samples, respectively. Percentages of cow milk, goat milk, sheep milk and cheese samples exceeding the EU limit were 35.9%, 11.1%, 26.9% and 10%, respectively. HPLC analyses confirmed the ELISA results although the percentages of AFM₁ contamination in raw milk and dairy products were lower than that of ELISA. There were significant differences (P < 0.05) between the mean AFM₁ contents of raw milk, cheese and yoghurt samples during winter and summer seasons. Our study demonstrated that there is a potential risk for liver cancer due to the consumption of milk and dairy products in Iranian consumers.     

Metabolites produced during the growth of probiotics in cocoa supplementation and the limited role of cocoa in host-enteric bacterial pathogen interactions

Cocoa contains various compounds that can significantly affect the growth of a broad range of bacteria, and have multiple human health-promoting properties. In this study, the effects of cocoa powder on the growth of Lactobacillus, common milk resident bacteria, and three major foodborne enteric bacterial pathogens; enterohemorrhagic Escherichia coli O157:H7 (EHEC), Salmonella enterica serovar Typhimurium, and Listeria monocytogenes, were investigated in vitro. Significant (p < 0.05) growth stimulation on beneficial bacteria including Lactobacillus and other resident bacteria in milk was observed in the presence of 3% cocoa powder. In contrast, growth of three foodborne enteric pathogens was significantly (p < 0.05) inhibited within 9 h, but no stimulation was found with longer incubation. In addition, cocoa powder significantly (p < 0.05) inhibited adhesion to and invasion of INT407 cells by these bacterial pathogens in a dose dependent manner. These results suggest that addition of cocoa into dairy products could improve the beneficial effect of probiotics by stimulating their growth, without raising the risk of cross-contamination with enteric pathogens.     

Matching portable NIRS instruments for in situ monitoring indicators of milk composition

The real time knowledge of dairy milk composition can be used as a tool to guarantee milk quality and safety, offering additional information for dairy producers and consumers. To carry out these in situ analyses, methodologies based on Near Infrared (NIR) portable sensors have a great potential as an advisory tool. The main goals of the present work have been to develop a methodology using a hand-held portable NIR spectrophotometer to collect raw milk spectra, including the development of calibration models for the analysis of protein, fat and solids-non-fat (SNF) of raw milk and further to transfer the developed models to another portable unit. A total of 542 fresh milk samples were scanned over the NIR spectral range (1600–2400 nm) using a hand-held MicroPhazir™ (MP) NIR spectrometer and different instrumental configurations. The best results for repeatability and reproducibility calculated as root mean squared (RMS) were obtained using a 17 mm cuvette thickness. The displayed predictive ability of calibration models measured as Standard error of prediction/Standard error of cross validation were 0.96; 0.72 and 0.83 for fat, protein and SNF contents, respectively. For cloning purposes an additional MP unit (satellite) has been used. A standardization set of 10 samples enabled standardization of both instruments. After applying standardization matrix, Standard error of differences between master and satellite reached great reduction, 68% for fat, 66% for protein and 54% for SNF. Moreover, the demonstrated ability of sharing calibration models among several units is essential for implementation of portable instruments for in-situ analysis to provide indicators of milk composition at farm level.