Food Protection Trends - March 2009 - 151

ing 100 CFU/g; and a S. aureus count in raw milk cheeses not exceeding 1000 CFU/g (39). RESULTS A total of 61 cheeses were ordered via online shopping, and were delivered to the Virginia Dept. of Agriculture Lynchburg Regional Animal Health Laboratory (VDACS Lynchburg RAHL) in Lynchburg, VA. The 61 cheeses tested came from 39 different farmstead dairies in 24 different states within the United States. Of the 61 cheeses tested, 30 from raw cow’s milk, 15 from pasteurized cow’s milk, 2 from raw goat’s milk, 13 from pasteurized goat’s milk, and 1 from pasteurized sheep’s milk. Some of the cheeses were ordered directly from the farm that produced them, and the others were ordered from third party gourmet food companies. Most of the samples (86.9%) arrived in insulated coolers with frozen or partially frozen ice packs. Two samples (3.3%) arrived in insulated coolers with completely thawed ice packs, and 6 samples (9.8%) arrived in non-insulated boxes with no ice packs. Most samples (68.9%) were in transit (from the point of shipment to the delivery destination) for two days. Some samples (21.3%) were in transit for only one day, and a few (9.8%) for four days. Standard delivery (as defined by the seller) was requested for all orders. Packaging and labeling of received cheeses was noted. A summary of the test results on the 61 samples tested, grouped by the type of cheese tested (pasteurized or raw milk, and species of animal) and results obtained, can be found in Table 1. Of the 61 samples tested, 54 (88.5%) were found to be acceptable with regard to microbiological safety. Of the 30 cheeses made from raw cow’s milk, 4 (13.3%) were found to be unacceptable with regard to microbiological safety. Of the 15 cheeses made from pasteurized cow’s milk, 2 (13.3%) were found to be unacceptable. Only one of the 13 pasteurized goat’s milk samples (7.7%) was found to be unacceptable. The two raw goat’s milk cheeses were found to be microbiologically safe, as was the one pasteurized sheep’s milk cheese. Only one sample, a pasteurized cow’s milk cheese, was found to be contaminated with Salmonella. None of the 61 samples tested were found to be contaminated with L. monocytogenes or E. coli O157:H7. Three samples (one raw cow’s milk cheese, one pasteurized cow’s milk cheese, and one pasteurized goat’s milk cheese) had coliform counts that exceeded Virginia’s legal limit. Three samples (all raw cows’ milk cheeses) exceeded the legal limit for S. aureus organisms. DISCUSSION This brief study was conducted to evaluate the microbiological safety of farmstead cheeses selected from those that are produced in the United States, and that are available for purchase via online shopping to consumers in other states. Internet searches for farmstead cheeses revealed that there are hundreds of farmstead cheese producers across the US, and many of these producers offer their cheeses for sale over the Internet. Dairy products, including cheeses, are perishable products known to be potential carriers of pathogenic bacteria when care is not taken to prevent contamination with such bacteria. The farmstead dairy environment, where the animals that produce the milk used in production are raised in close proximity to the site where the dairy products are made, presents additional challenges to the prevention of contamination, compared with non-farmstead dairies, because the animals and their immediate environment are natural reservoirs of the foodborne pathogens associated with dairy products (33). Often, the same individuals who care for the animals also make the cheeses, so in the absence of adequate attention to sanitation, contamination of the cheeses could easily occur. Additionally, many of these farmstead cheeses are made from raw milk rather than from pasteurized milk, which calls for an even greater need to be certain of the microbiological safety of the milk being used. This last point can be a challenge even to the most attentive producer, because it is known that animals can be asymptomatic or subclinical carriers of Salmonella, L. monocytogenes, E. coli O157:H7, and S. aureus. The results of this brief and limited study indicate that the majority of the farmstead cheeses produced in the United States and available for purchase online are microbiologically safe for consumers. With such a small number of unacceptable samples in this study, it is difficult to make substantive speculations based on the results, but for the sake of discussion, some comments can be made. The seven unacceptable samples were from six different states, so no correlation between unsafe farmstead cheeses and the state in which they were produced could be found. Interestingly, none of the seven unacceptable samples were found to exceed the limits for more than one type of bacteria. This was an unexpected result, especially with regard to coliform counts, since coliform counts are very commonly used as an indicator of the sanitary quality of foods (14). Three of the seven unacceptable samples, including the one sample positive for Salmonella, were made from pasteurized milk (according to the cheese maker’s description of the product), so based on these results, it cannot be said that cheeses made from pasteurized milk are safer that those made from raw milk. One of the limitations of this study should be considered with this last comment: A phosphatase test was not done to detect the presence of alkaline phosphatase, the presence of which indicates the presence of some level of raw milk, since proper pasteurization temperatures inactivate phosphatase. The recovery of Salmonella (determined to be Group B) from one of the cheese samples, regardless of whether or not the sample was made from properly pasteurized milk (as the label indicated), was a significant finding. The symptoms of salmonellosis, one of the most common foodborne illnesses worldwide, can include abdominal pain, nausea, vomiting, diarrhea, and fever, and the illness can become life-threatening in very young, very old, or immunocompromised individuals (15). Cheeses can become contaminated with Salmonella in a number of different ways and at a number of different points in the cheese-making process. Both raw milk cheeses and pasteurized milk cheeses have been associated with outbreaks of salmonellosis (11), and it has been shown that under some circumstances, cheeses made from pasteurized milk contaminated with Salmonella post-pasteurization can still have viable Salmonella organisms after several months of storage (10). Some studies have shown that Salmonella can develop adaptive responses to unfavorable factors in their environments, including increased acidity, increased salinity, and unfavorable temperatures (27). This MARCH 2009 | FOOD PROTECTION TRENDS 151

Food Protection Trends - March 2009

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