Laboratory Pasteurization Count Research Articles

Troubleshooting high laboratory pasteurization counts in organic raw milk requires characterization of dominant thermoduric bacteria, which includes nonsporeformers as well as sporeformers

Laboratory Pasteurization Count (LPC) enumerates thermoduric bacteria and is one parameter used to assess raw milk quality. While there is currently no regulatory limit for LPC, LPC data are used by some dairy processors and cooperatives to designate raw milk quality premiums paid to farmers and may also be used for troubleshooting bacterial contamination issues. Despite occasionally being used as a proxy for levels of bacterial spores in raw milk, there is limited knowledge of the types of organisms that are enumerated by LPC in contemporary raw milk supplies. While historical studies have reported that thermoduric bacteria quantified by LPC may predominantly represent Gram-positive cocci, updated knowledge on microbial populations enumerated by LPC in contemporary organic raw milk supplies is needed. To address this gap, organic raw milk samples from across the United States (n = 94) were assessed using LPC, and bacterial isolates were characterized. LPC ranged from below detection (<0.70 log cfu/mL) to 4.07 log cfu/mL, with a geometric mean of 1.48 log cfu/mL. Among 380 isolates characterized by 16S rDNA sequencing, 52.6%, 44.5%, and 2.4% were identified as Gram-positive sporeformers, Gram-positive non-sporeformers, and Gram-negatives, respectively, and 0.5% that could not be categorized into those groups because they could only be assigned a higher level of taxonomy. Isolates identified as Gram-positive sporeformers were predominantly Bacillus (168/200) and Gram-positive non-sporeformers were predominately Brachybacterium (56/169) and Kocuria (47/169). To elucidate if the LPC level can be an indicator of the type of thermoduric (e.g., sporeforming bacteria) present in raw milk, we evaluated the proportion of sporeformers in raw milk samples with LPC of ≤100 cfu/mL, 100 to 200 cfu/mL, and ≥200 cfu/mL (51%, 67%, and 35%), showing a trend for sporeformers to represent a smaller proportion of the total thermoduric population when LPC increases, although overall linear regression showed no significant association between the proportion of sporeformers and the LPC concentration. Hence, LPC level alone provides no insight into the makeup of the thermoduric population in raw milk and further characterization is needed to elucidate the bacterial drivers of elevated LPC in raw milk. We therefore further characterized the isolates from this study using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), a rapid microbial identification tool that is more readily available to dairy producers than 16S rDNA PCR and sequencing. While our data indicated agreement between 16S and MALDI-TOF MS for 66.6% of isolates at the genus level, 24.2% and 9.2% could not be reliably identified or were mischaracterized using MALDI-TOF, respectively. This suggests that further optimization of this method is needed to allow for accurate characterization of thermoduric organisms commonly found in raw milk. Ultimately, our study provides a contemporary perspective on thermoduric bacteria selected by the LPC method and establishes that the LPC alone is not sufficient for identifying the bacterial drivers of LPC levels. Further development of rapid characterization methods that are accessible to producers, cooperatives, and processors will support milk quality troubleshooting efforts and ultimately improve outcomes for dairy industry community members.

The Association between Socioeconomic Profiles, Attitudes, and Knowledge of Dairy Farmers Regarding Somatic Cell Count and Milk Quality.

The primary objective of this study was to investigate the association between the bulk tank somatic cell count (SCC) and dairy farmers' knowledge about milk quality, mastitis control, and their socioeconomic characteristics. Additionally, we estimated the association between the bulk tank SCC and bulk tank milk hygienic quality in dairy herds. Bulk tank milk samples from 120 dairy herds enrolled in the milk quality payment program were collected for the determination of the SCC, the total bacterial count (TBC), the preliminary incubation count (PIC), the laboratory pasteurization count (PC), and the coliform count (CC). Based on the bulk tank SCC results, 63 herds were selected and categorized into three groups: (a) low SCC: ≤250,000 cells/mL (n = 16); (b) medium SCC: >250,000 ≤ 400,000 cells/mL (n = 24); and (c) high SCC: >400,000 cells/mL (n = 23). Socioeconomic profiles, attitudes, and knowledge of somatic cell count and milk quality were assessed using previously tested questionnaires, which were used to interview the herd managers of the 63 selected dairy herds. Among the findings, 87.0% of the dairy herds had an SCC < 400 × 103 cells/mL, and presented milk production as the main economic activity of the farm, whereas only 47.0% of dairy herds with an SCC > 400 × 103 cells/mL had milk production as the main economic activity of the farm (p < 0.031). In a total of 95% of the selected herds (n = 60), milking machines were used, with pipeline milking machines being more predominant, accounting for 70.8% in herds with a medium somatic cell count (SCC) and 78.3% in herds with a high SCC, as opposed to herds with a low SCC at 50% (p < 0.031). The frequency of dairy producers' awareness of the maximum legal requirements for the bulk tank SCC and TBC was higher in herds with a higher SCC than in herds with a medium SCC. In conclusion, the results of this study indicate a significant association between the bulk tank somatic cell count (SCC) and dairy farmers' knowledge about milk quality, mastitis control, and socioeconomic characteristics. These findings emphasize the importance of knowledge and the socioeconomic profiles of dairy farms in maintaining and enhancing milk quality in dairy herds.

Evaluation of a new qPCR test to identify the organisms causing high total bacterial count in bulk tank milk

Milk quality in bulk tank milk (BTM) is measured by flow cytometry technology as total bacterial count (TBC) and somatic cell count (SCC). To investigate SCC problems, culture or PCR can be used to identify mastitis causing bacteria, e.g., Mastit 4, a commercially available qPCR test. TBC in BTM can be investigated further using culture-based methods such as standard plate count, laboratory pasteurization count, coliform count, and spore counts. To our knowledge, no qPCR addressing the bacteria involved in TBC has been commercially introduced. The aim of this study is to evaluate a recently introduced 3-h qPCR test, TBC 4. The TBC 4 qPCR detects four target groups, Pseudomonas, Streptococci, Enterobacteriacea/Enterococcus, and Bacillus/Clostridia. These target groups relate to problems on the farm such as cooling, mastitis, environment, and silage. We will continue with new research to compare the TBC 4 qPCR test with traditional culture. For this study, BTM samples from different TBC intervals were selected based on BactoCount results found at routine payment investigation at Eurofins laboratory (Vejen, Denmark). These samples were analyzed using TBC 4 qPCR assay within 24 h. In total, 346 BTM samples were divided into six different intervals of colony forming units (CFU). For all four targets in each of the different intervals of CFU, the percent of positive samples, the average Ct-value, the percent of positive samples with Ct<30 and Ct<25 were calculated. For Pseudomonas, Streptococci, and Enterobacteriacea/Enterococcus, the number of positive samples with lower Ct-values (high bacteria content) correlated with the CFU mL−1. We found Enterobacteriacea/Enterococcus, Pseudomonas, and Streptococci in high number of bacteria (Ct<25) in 25, 19 and 56% of samples with CFU mL−1 between 50 001–100 000 and 53, 44, and 39% in samples with CFU mL−1>100 000. The TBC 4 qPCR test showed to be a strong and fast tool for farmers, advisors and service technicians to address problems with high TBC and ensuring the delivery of good quality milk to the dairy.

Seasonal Variations of Raw Milk Hygienic Quality in Saudi Arabia Dairy Herds

This study was conducted to evaluate current bacterial quality of raw milk in Saudi Arabia dairy farms, to determine correlation among milk quality tests and to investigate seasonal variations in raw milk bacterial counts. Farm records on bacterial quality of raw milk were obtained from one of the largest dairy processor in Saudi Arabia over one year period (January to December 2013). Bulk tank milk samples were tested for total bacterial (TBC), coliform (CC) and laboratory pasteurization (LPC) counts by dairy plant on daily basis. The results showed that the mean and median values were 5,234 and 1,700 cfu/ml for TBC, 738 and 160 cfu/ml for CC, and 87 and 11 cfu/ml for LPC, respectively. There was low to moderate correlation among bacterial counts, indicating different sources of contamination. Seasonal data indicate higher counts during late fall and early winter compared to other months. In conclusion, this study provide insight on the current level of raw milk bacterial quality in Saudi Arabia and emphasize the importance of using multiple quality parameters for evaluation of raw milk hygienic quality.

Discrepancies in Evaluating Farm Management Routines as Risk Factors of Raw Milk and Udder Hygiene in Selected Dairy Farms of Fars Province, Iran

The management practices relevant to bulk tank milk quality were studied in 29 dairy farms of Fars Province, Iran. Farm management practices were obtained by completion of a questionnaire and direct observation. Bulk milk was evaluated by performing standard plate count (SPC), preliminary incubation count (PIC), laboratory pasteurization count (LPC), coliform count (CC), somatic cell count (SCC) and detection of the contagious mastitis agents. The farms were divided into low and high SPC groups (below and above 100,000 CFU/mL) based on Iranian standards. Comparisons of the laboratory results between groups were done using two independent samples t-test. The relationships between the laboratory results were studied by Pearson’s correlation coefficients, all after logarithmic transformation. Associations of managerial risk factors (obtained by the questionnaire and one time of observation) with laboratory results were investigated using two independent samples t-test. P-values 0.05). Strong correlations were detected between SPC and PIC, SPC and CC, and PIC and CC, but many of the well explained risk factors of undesired milk quality lacked any relation with high bacterial counts of raw milk. This could be due to the small number of the studied farms, almost similar faults in the farms, wrong answers of the employees to the questions and modification of the milking practices in the presence of an inspector. Infections with Staphylococcus aureus and Mycoplasma bovis could be potential problems in the studied farms, contributing to the elevation of SCC and/or SPC levels. Veterinary interventions could not be based on the questionnaire results. Direct and frequent observations of farm routines could be recommended.

The effect of storage temperature and duration on the microbial quality of bulk tank milk

The dairy industry in Ireland is currently undergoing a period of expansion and, as a result, it is anticipated that milk may be stored in bulk tanks on-farm for periods greater than 48 h. The objective of this study was to investigate the effects of storage temperature and duration on microbial quality of bulk tank milk when fresh milk is added to the bulk tank twice daily. Bulk tank milk stored at 3 temperatures was sampled at 24-h intervals during storage periods of 0 to 96 h. Bulk tank milk samples were analyzed for total bacterial count (TBC), psychrotrophic bacterial count (PBC), laboratory pasteurization count (LPC), psychrotrophic-thermoduric bacterial count (PBC-LPC), proteolytic bacterial count, lipolytic bacterial count, presumptive Bacillus cereus, sulfite-reducing Clostridia (SRC), and SCC. The bulk tank milk temperature was set at each of 3 temperatures (2°C, 4°C, and 6°C) in each of 3 tanks on 2 occasions during two 6-wk periods. Period 1 was undertaken in August and September, when all cows were in mid lactation, and period 2 was undertaken in October and November, when all cows were in late lactation. None of the bulk tank bacterial counts except the proteolytic count were affected by lactation period. The proteolytic bacterial count was greater in period 2 than in period 1. The TBC and PBC of milk stored at 6°C increased as storage duration increased. The TBC did not increase with increasing storage duration when milk was stored at 2°C or 4°C but the PBC of milk stored at 4°C increased significantly between 0 and 96 h. The numbers of proteolytic and lipolytic bacteria, LPC, or PBC-LPC in bulk tank milk were not affected by temperature or duration of storage. Presumptive B. cereus were detected in 10% of all bulk tank milk samples taken over the two 6-wk periods, with similar proportions observed in both. In bulk tank milk samples, a greater incidence of SRC was observed in period 2 (20%) compared with period 1 (3%). Milk produced on-farm with minimal bacterial contamination can be successfully stored at 2°C and 4°C for up to 96h with little effect on its microbial quality.

Seasonal trends in milk quality in Ireland between 2007 and 2011

The objectives of this study were to evaluate annual and seasonal trends in bulk tank somatic cell count (SCC), total bacterial count (TBC), and laboratory pasteurization count (LPC) in Ireland between 2007 and 2011 (inclusive), and to compare trends based on herd type and herd size. The unadjusted median SCC and TBC of all records were 266,000 and 17,000 cfu/mL, respectively. Data were transformed to log values and analyzed using a mixed model. Fixed effects included milk processor, year, month, and total monthly milk volume; milk producer was fitted as a random variable. After analysis, means were back transformed for interpretation. Annual SCC increased slightly from 259,000 cells/mL in 2007 to a peak of 272,647 cells/mL in 2009 and then declined slightly thereafter. Although statistically significant changes in annual TBC are probably not biologically relevant, values ranged between 23,922 and 26,290 cfu/mL. Annual LPC peaked in 2008 (265 cfu/mL), declined in 2009, and increased thereafter. Monthly mean SCC of all records increased from April onward, with the greatest increases seen from October to December, when the majority of cows entered late lactation. Monthly mean TBC exhibited a seasonal trend, whereby TBC was greatest at the beginning and end of the year, coinciding with winter housing. Seasonal milk production herds (n=8,002 herds) calve all cows in spring (February to April), whereas split-calving herds (n=1,829 herds) calve cows in the spring and autumn. From February to September, monthly SCC was lower for seasonal herds than for split-calving herds, whereas SCC was lower for split-calving herds for the remaining months. During winter (October to March), split-calving herds had lower monthly TBC than seasonal herds, most likely because of stricter regulations imposed upon them. Herd size was approximated using total annual milk production figures. Across all months, larger herds had lower SCC and TBC compared with smaller herds. No obvious improvements in milk quality were seen between 2007 and 2011. Farmers have the opportunity to improve milk quality by reducing bulk tank SCC in late lactation and by imposing stricter hygiene practices at the beginning and end of the year to overcome the seasonal variation of bulk tank TBC.

Effects of UV irradiation in a continuous turbulent flow UV reactor on microbiological and sensory characteristics of cow's milk.

The dairy industry under current pasteurization conditions (15 s at 72°C) and sanitary standards achieves a safe product with excellent quality. In an ever-competitive market there is still a need to improve product quality and extend shelf life of dairy products to increase competitiveness and open up new markets. In an attempt to test the effect of UV irradiation on microbiota of fluid milk, a continuous flow UV system at 254 nm was used to treat 3.5 and 2% fat milk at two UV doses (880 and 1,760 J liter(-1)). Milk was obtained from three processors, and two lots from each processor were assessed. To assess the impact on the most descriptive native microbiota in pasteurized milk after UV illumination, the product was held at two storage temperatures (4 and 7°C) and tested weekly for 5 weeks for aerobic plate counts (psychrotrophic and mesophilic bacteria), laboratory pasteurization counts, aerobic sporeformers, coliform organisms, and titratable acidity. Microbial counts for all tested microorganisms were lower in UV-treated milk when compared with control throughout storage at 4 and 7°C in both 3.5 and 2% fat milk. Sensory analysis indicated that there is a sensory defect associated with UV treatment at the wavelength used.

A comparative microbiological quality assessment of rural and urban milk samples

The present study deals with the comparative microbiological quality assessment of raw cow milk samples procured from rural and urban farms of Sambalpur City, Odisha, India. The bacterial load of both the rural and urban milk samples in terms of total viable count was observed to be much higher than the acceptable limits. The average total viable count of urban sample was observed to be 8.756 ± 0.803 log CFU/ml. The preliminary incubation count was significantly higher in urban samples (8.889 ± 0.424 log CFU/ml) indicating un-hygienic milk production / handling practices. However, the laboratory pasteurization count of the rural milk samples was noted to be comparatively higher than the urban samples (8.083 ± 0.081 log CFU/ml). The enteric microorganisms isolated from both rural and urban milk samples were identified to beEscherichia coli, Enterobacter sp., Klebsiella sp. and Shigella. Salmonella andPseudomonas sp. were present in urban samples alone, indicating the urban samples to be highly contaminated in comparison to that of the rural ones. Key words: Contamination, enteric bacteria, health, quality, raw milk.

Short communication: Evaluation of bulk tank milk microbiological quality of nine dairy farms in Tennessee

The purpose of this study was to evaluate the bulk tank milk (BTM) quality of 9 East Tennessee dairy farms and to determine its relationship with selected quality milk parameters. Bulk tank milk samples (n=1,141) were collected over a 42-mo period (June 2006 through November 2009) from farms, based on their preliminary incubation count (PIC) history. Parameters of BTM quality evaluated in this study included somatic cell count (SCC), standard plate count (SPC), PIC, laboratory pasteurization count (LPC), Staphylococcus spp. count, Streptococcus spp. count, and coliform count. Strong correlations between SPC and Streptococcus spp. counts (0.72) and between SPC and PIC (0.70) were found. However, moderate correlations were seen among other milk quality parameters. In addition, seasonal variations for some milk quality parameters were noted. For example, milk quality parameters such as SCC, SPC, LPC, and coliform count were significantly higher in summer, whereas Streptococcus spp. counts were significantly higher in winter. No seasonal variation in PIC or Staphylococcus spp. counts was observed. Summarizing, results from this investigation showed the importance of using several bacterial counts (SCC, SPC, PIC, LPC, Streptococcus spp. count, Staphylococcus spp. count, and coliform counts) as simultaneous indicators of milk quality.

Effects of season, milking routine and cow cleanliness on bacterial and somatic cell counts of bulk tank milk

The aim of the study was to investigate the effects of season, cow cleanliness and milking routine on bacterial and somatic cell counts of bulk tank milk. A total of 22 dairy farms in Lombardy (Italy) were visited three times in a year in different seasons. During each visit, samples of bulk tank milk were taken for bacterial and somatic cell counts; swabs from the teat surface of a group of cows were collected after teat cleaning and before milking. Cow cleanliness was assessed by scoring udder, flanks and legs of all milking cows using a 4-point scale system. Season affected cow cleanliness with a significantly higher percentage of non-clean (NC) cows during Cold compared with Mild season. Standard plate count (SPC), laboratory pasteurization count (LPC), coliform count (CC) and somatic cell count, expressed as linear score (LS), in milk significantly increased in Hot compared with Cold season. Coagulase-positive staphylococci on teat swabs showed higher counts in Cold season in comparison with the other ones. The effect of cow cleanliness was significant for SPC, psychrotrophic bacterial count (PBC), CC and Escherichia coli in bulk tank milk. Somatic cell count showed a relationship with udder hygiene score. Milking operation routine strongly affected bacterial counts and LS of bulk tank milk: farms that accomplished a comprehensive milking scheme including two or more operations among forestripping, pre-dipping and post-dipping had lower teat contamination and lower milk SPC, PBC, LPC, CC and LS than farms that did not carry out any operation.

Effect of cleaning procedure and hygienic condition of milking equipment on bacterial count of bulk tank milk

The aim of the study was to describe the characteristics of cleaning procedures for milking equipment applied in intensive dairy farms in Lombardy (Italy) and to study their relationships with bacterial count of bulk milk and hygienic condition of milking machine components. A group of 22 dairy farms was visited twice (winter and summer) in order to collect bulk tank milk and post-rinse water samples and swabs from liners and milk receiver. Samples were analysed to determine: standard plate count (SPC), laboratory pasteurization count (LPC), psychrotrophic bacteria count (PBC), coliform count (CC) and Escherichia coli. Cleaning procedures were monitored using electronic milk flow meters with specific software for the measurement of the duration of each cleaning phase, circulating solution temperature and electrical conductivity, turbulence and water filling percentage of pipelines. The results showed that farms classified as high and low milk total bacteria count significantly differed both in terms of liners and receiver bacterial contamination and in terms of water temperature reached during the detergent phase of cleaning milking equipment. Significant positive correlations were found among total bacteria count in milk and bacterial contamination of the liners. Maximum water temperature reached during the cleaning cycle of milking equipment was very low (34.4±8.9°C on average); most of the observations (88.6%) corresponded to water temperatures <45°C. Cleaning temperature was related to psychrotrophic bacteria count of milk and post-rinse water and coliform count in liners. Routine check and regulation of water temperature during the washing phase of the milking machine can be a simple and effective way to control one of the main risk factors for bacteriological quality of bulk tank milk.

Results from raw milk microbiological tests do not predict the shelf-life performance of commercially pasteurized fluid milk

Analytical tools that accurately predict the performance of raw milk following its manufacture into commercial food products are of economic interest to the dairy industry. To evaluate the ability of currently applied raw milk microbiological tests to predict the quality of commercially pasteurized fluid milk products, samples of raw milk and 2% fat pasteurized milk were obtained from 4 New York State fluid milk processors for a 1-yr period. Raw milk samples were examined using a variety of tests commonly applied to raw milk, including somatic cell count, standard plate count, psychrotrophic bacteria count, ropy milk test, coliform count, preliminary incubation count, laboratory pasteurization count, and spore pasteurization count. Differential and selective media were used to identify groups of bacteria present in raw milk. Pasteurized milk samples were held at 6°C for 21 d and evaluated for standard plate count, coliform count, and sensory quality throughout shelf-life. Bacterial isolates from select raw and pasteurized milk tests were identified using 16S ribosomal DNA sequencing. Linear regression analysis of raw milk test results versus results reflecting pasteurized milk quality consistently showed low R2 values (<0.45); the majority of R2 values were <0.25, indicating small relationship between the results from the raw milk tests and results from tests used to evaluate pasteurized milk quality. Our findings suggest the need for new raw milk tests that measure the specific biological barriers that limit shelf-life and quality of fluid milk products.

Bulk Tank Milk Quality in California

Bulk tank milk (BTM) is tested to assure compliance with the national, state, and local milk plants. Testing BTM helps to ensure the safety and quality of dairy products. The following tests are routinely performed: somatic cell count (SCC), standard plate count (SPC), laboratory pasteurization count (LPC), and coliform count (Coli). Information about BTM quality parameters can be used by dairy producers to compare their milk quality to industry-wide benchmarks, and to define achievable goals for their operations. The objective of this study is to describe BTM quality for the California dairy industry.

The association between bulk tank milk analysis for raw milk quality and on-farm management practices

Our objective was to determine the risk factors associated with bacteriological quality of bulk tank milk. Bulk tank milk samples were collected from all Prince Edward Island dairy herds (n=235) from March 2005 to March 2007. Biweekly total bacterial, preliminary incubation, laboratory pasteurization, and coliform counts were conducted using a Petrifilm culture system. Data for on-farm risk factors were collected via a mail-out survey which consisted of 4 main sections: (1) general farm demographics and management, (2) cow cleanliness and hygiene, (3) milking procedures and mastitis control, and (4) equipment maintenance and cleaning.Of 235 producers, 153 completed the mail-out survey giving a response rate of 65%. Both total aerobic and preliminary incubation counts were positively associated with the amount of soiling on the teats prior to udder preparation, manual cleaning of the bulk tank, and the use of a specific type of detergent. Additionally, various methods of premilking udder preparation were important, with pre-dip followed by drying being superior to other methods in reducing the bacterial counts. The laboratory pasteurization count was positively associated with the presence of a plate cooler and inadequate frequency of acid wash, whereas having a water purification system was negatively associated with laboratory pasteurization count. Finally, coliform count was negatively associated with clipping udder hair and automated washing of the bulk tank, whereas increasing herd size and inadequate frequency of acid wash were risk factors. Season was a significant predictor for all bacterial counts with the lowest counts tending to occur in winter.

Associations among milk quality indicators in raw bulk milk

The objective of this study was to determine characteristics and associations among bulk milk quality indicators from a cohort of dairies that used modern milk harvest, storage, and shipment systems and participated in an intensive program of milk quality monitoring. Bulk milk somatic cell count (SCC), total bacteria count (TBC), coliform count (CC), and laboratory pasteurization count (LPC) were monitored between July 2006 and July 2007. Bulk milk samples were collected 3 times daily (n = 3 farms), twice daily (n = 6 farms), once daily (n = 4 farms), or once every other day (n = 3 farms). Most farms (n = 11) had direct loading of milk into tankers on trucks, but 5 farms had stationary bulk tanks. The average herd size was 924 cows (range = 200 to 2,700), and daily milk produced per herd was 35,220kg (range = 7,500 to 105,000kg). Thresholds for increased bacterial counts were defined according to the 75th percentile and were >8,000cfu/mL for TBC, >160cfu/mL for CC, and ≥310cfu/mL for LPC. Means values were 12,500 (n = 7,241 measurements), 242 (n = 7,275 measurements), and 226cfu/mL (n = 7,220 measurements) for TBC, CC, and LPC, respectively. Increased TBC was 6.3 times more likely for bulk milk loads with increased CC compared with loads containing fewer coliforms. Increased TBC was 1.3 times more likely for bulk milk with increased LPC. The odds of increased TBC increased by 2.4% for every 10,000-cells/mL increase in SCC in the same milk load. The odds of increased CC increased by 4.3% for every 10,000-cells/mL increase in SCC. The odds of increased CC increased by 1% for every 0.1°C increase in the milk temperature upon arrival at the dairy plant (or at pickup for farms with bulk tank). Laboratory pasteurization count was poorly associated with other milk quality indicators. Seasonal effects on bacterial counts and milk temperature varied substantially among farms. Results of this study can be used to aid the interpretation and analysis of indicators of milk quality intensively produced by dairy processors’ laboratories.

Microbiological quality of bulk tank raw milk in Prince Edward Island dairy herds

The objectives of this study were to evaluate microbiological quality of bulk tank milk in Prince Edward Island, to evaluate correlation among milk quality criteria, and to determine seasonal effects on milk quality parameters. Bulk tank raw milk quality was evaluated on all Prince Edward Island dairy herds (n = 235) over a 2-yr period (March 2005 to March 2007). Biweekly total aerobic (TAC), preliminary incubation (PIC), laboratory pasteurization, and coliform (CC) counts were determined using a Petrifilm culture system. Additionally, bulk tank somatic cell count was determined weekly. The mean and median values were 12.8×103 and 4.9×103cfu/mL for TAC, 29.6×103 and 13×103cfu/mL for PIC, 87 and 12cfu/mL for laboratory pasteurization count, 21 and 5cfu/mL for CC, and 218×103 and 187×103cells/mL for somatic cell count. There was moderate correlation (0.57) between TAC and PIC. All other correlation coefficients were low (<0.26). Correlation results suggest that a single quality parameter could not predict others used in this study. Seasonal data indicate that 1) in general, all counts tended to be low in winter, 2) the CC and somatic cell count were always high in summer, and 3) TAC tended to be high during summer.

A Survey of Bacteriological Quality and the Occurrence of Salmonella in Raw Bovine Colostrum

In recent years, bovine colostrum has gained popularity as a human food because it is an excellent source of bioactive proteins, which have been claimed to inhibit viral and bacterial pathogens, improve gastrointestinal health, and enhance body condition. A study was conducted to determine bacteriological quality and occurrence of Salmonella in colostrum collected from dairy herds (n = 55) in Pennsylvania. Colostrum samples were analyzed for standard plate count, preliminary incubation count, laboratory pasteurization count, Staphylococcus aureus, Streptococcus agalactiae, coagulase negative staphylococci, streptococci, coliforms, and non-coliforms. A standardized polymerase chain reaction assay was used for detection of Salmonella in colostrum. Salmonella were detected in 8 of 55 (15%) of colostrum samples. Streptococcus agalactiae (1000 colony-forming units [CFU]/mL) was detected in one colostrum sample. The mean standard plate count (977,539 CFU/mL), preliminary incubation count (12,094,755 CFU/mL), laboratory pasteurization count (615 CFU/mL), Staphylococcus aureus (306 CFU/mL), coagulase negative staphylococci (164,963 CFU/mL), streptococci (256,722 CFU/mL), coliforms (323,372 CFU/mL), and non-coliforms (111,544 CFU/mL) counts in colostrum were considerably higher than raw bulk tank milk counts reported previously from Pennsylvania. Analysis revealed that farm size did not influence the bacteriological quality of colostrum. Collection, handling, and storage of colostrum need to be addressed to improve bacteriological quality of colostrum intended not only for feeding calves but also for human consumption.

Bulk Tank Raw Milk Quality

Raw bulk tank milk (BTM) quality (SCC and bacteria burden) is used to quantify the health and safety of milk. Laboratory-based studies have demonstrated that milk with lower bacteria and somatic cell count produces milk products with superior quality attributes and shelf-life. Raw BTM is subjected to a number of tests to indicate udder health, milk harvest hygiene and storage conditions on the farm. These tests include; total bacterial count (TBC) (or standard plate count (SPC)), preliminary incubation count (PIC), laboratory pasteurization count (LPC) and coliform count (CC), as well as SCC. The objective of this study was to examine the relationship between raw BTM quality and consumer experience with fluid milk products and to survey on-farm risk factors for bacterial milk quality.

Guidelines for Monitoring Bulk Tank Milk Somatic Cell and Bacterial Counts

This study was conducted to establish guidelines for monitoring bulk tank milk somatic cell count and bacterial counts, and to understand the relationship between different bacterial groups that occur in bulk tank milk. One hundred twenty-six dairy farms in 14 counties of Pennsylvania participated, each providing one bulk tank milk sample every 15 d for 2 mo. The 4 bulk tank milk samples from each farm were examined for bulk tank somatic cell count and bacterial counts including standard plate count, preliminary incubation count, laboratory pasteurization count, coagulase-negative staphylococcal count, environmental streptococcal count, coliform count, and gram-negative noncoliform count. The milk samples were also examined for presence of Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma. The bacterial counts of 4 bulk tank milk samples examined over an 8-wk period were averaged and expressed as mean bacterial count per milliliter. The study revealed that an increase in the frequency of isolation of Staphylococcus aureus and Streptococcus agalactiae was significantly associated with an increased bulk tank somatic cell count. Paired correlation analysis showed that there was low correlation between different bacterial counts. Bulk tank milk with low (<5000 cfu/mL) standard plate count also had a significantly low level of mean bulk tank somatic cell count (<200,000 cells/mL), preliminary incubation count (<10,000 cfu/mL), laboratory pasteurization count (<100 cfu/mL), coagulase-negative staphylococci and environmental streptococcal counts (<500 cfu/mL), and noncoliform count (<200 cfu/mL). Coliform count was less likely to be associated with somatic cell or other bacterial counts. Herd size and farm management practices had considerable influence on somatic cell and bacterial counts in bulk tank milk. Dairy herds that used automatic milking detachers, sand as bedding material, dip cups for teat dipping instead of spraying, and practiced pre-and postdipping had significantly lower bulk tank somatic cell and/or bacterial counts. In conclusion, categorized bulk tank somatic cell and bacterial counts could serve as indicators and facilitate monitoring of herd udder health and milk quality.