Food Protection Trends - June 2009 - 345

products after 1–9 months of storage at room temperature (74), in peanut butter products after 6 months of storage at room temperature and after storage for more than 6 months at refrigeration temperature (6). Salmonella enteritidis pt 30, a strain associated with an outbreak from raw almonds, was isolated from an almond farm over a period of 5 years (76). although storage of high fat low-moisture products at low temperatures (e.g., refrigeration) may be beneficial in preventing oxidative rancidity, low temperatures may enhance the survival of Salmonella. setting process parameters based on d- and z-values would be a more conservative approach than setting them on the basis of the nonlinear Weibull model. because of variations in these parameters, it is important, when published heat resistance data are applied to certain food processes, that the conditions under which the values were obtained not be significantly different from the product or process conditions used by the processor. HEAT RESISTAnCE oF Salmonella heat resistance of Salmonella is greatly increased at reduced water activities in food matrices (exceptions to this trend observed in laboratory media are discussed in a later section). Salmonella typhimurium was reported to have a d-value of 816 min at 66 oc in molten chocolate (41) and was more heat resistant than Salmonella Senftenberg 775W evaluated in the same product. Serovars of Salmonella (agona, enteritidis and typhimurium) in peanut butter showed no significant differences in heat resistance (70). When heat resistance parameters were determined based on the linear portion of the inactivation curve for Salmonella on oil-roasted almonds, the d-value was 0.85 min at 121°c and the z-value was 27°c (46). the nonlinear Weibull model was also used to fit inactivation curves for Salmonella in heated peanut butter and on oil-roasted almonds. based on this model, 42 ± 8 min at 90°c was needed to give a 5-log reduction of a mixture of three outbreak-associated S. tennessee strains in peanut butter (29), and more than 260 min was needed to reduce Salmonella by 7 log cFu/g at 70oc in peanut butter (70). For oil-roasted almonds, 2.06 ± 0.57 min at 121°c was needed to achieve a 5-log reduction of S. enteritidis pt 30 based on the Weibull model (1), in comparison to 4.25 min at 121°c needed for 5-log reduction based on the d-value (46). increasing solids level in dried milk increased the heat resistance of Salmonella alachua (28). at 57 o c, the d-value was 38, 12.5, and 1.6 min for S. alachua in 51%, 42% and 10% milk solids concentrate, respectively. the z-value likewise increased as the solids level in the milk was increased. the z-value for S. alachua was reported as 4.1, 6.2 and 6.9 oc at 10, 42 and 51% milk solids, respectively. the heat resistance of Salmonella is affected by many factors, including strain and serotypes tested, growth and storage conditions, food composition, test media and the media used to recover heat damaged cells. in some cases, A REVIEW oF EXISTInG InduSTRY PRACTICES a survey was conducted in may 2007 to obtain information from gma members on current practices and measures the industry employs to control Salmonella in manufacturing low-moisture products, i.e., foods with aw below 0.85, including products such as cereal, chocolate, spraydried milk, infant formula, and peanut butter. a total of 17 companies/plants responded to the survey. all respondents (100%) had standard operating procedures (Sops) to eliminate or minimize cross contamination from raw ingredients or from the environment. Sixteen of 17 respondents (94%) required “Salmonella-sensitive” ingredients (those that could be potentially contaminated) to be sourced from an approved supplier. While 16 respondents (one did not respond to this question) had an environmental monitoring program for Salmonella on non-product contact surfaces, 2 of the 16 respondents (12.5%) monitored Salmonella on product contact surfaces on a routine basis. Fifteen of 17 respondents (88%) had an environmental monitoring program for non-product contact surfaces. the majority of respondents (80–90%) implemented the following practices: testing of “Salmonella-sensitive” ingredients (either in house or by the supplier); inclusion of equipment sanitary design review in the Salmonella control program; and vali-dation of the lethality of thermal processes for Salmonella. half or more of the respondents (50–70%) routinely analyzed finished products for Salmonella as part of quality assurance, established “high hygiene” zones with particularly stringent hygiene requirements and procedures, and analyzed the air systems (hVac) for Salmonella as part of the environmental monitoring program. Fifty-three percent of respondents had manufacturing periods for the dry portion of their operations that extended 7 days or longer (several companies run production for 28 to 35 days) prior to shutting down for sanitation. Forty-seven percent of respondents had a captive shoes policy (i.e., shoes worn solely within the facility) in place for employees, including temporary contractors. in addition to being asked about industry practices, respondents were asked about situations that could introduce water into the facility, and 56% of them reported roof leaks or other water leak incidents into the production area. another survey was conducted several years ago by the Food industry microbiology round table (56) on industry practices of environmental monitoring for non-meat products. among 20 respondents with programs to monitor the process environment for pathogens, 15 monitored for Salmonella weekly or monthly. Four companies monitored daily, two respondents monitored quarterly, and one monitored twice a year. For the number of samples taken at these frequencies, a slight majority (11 out of 20) obtained 10–20 samples, while others took either fewer than 10 or 21–50 samples. more than half of the respondents (12 out of 20) divided the process environment into zones, with samples being taken during production (6 out of 20), after sanitation (2 out of 20), or after sanitation and during production (6 out of 20 respondents). Some companies preset the sampling sites (8 out of 20), others randomly selected sites (9 out of 20), and still others did both (3 out of 20). the vast majority of the sampling was done by plant personnel (18 out of 20) but occasionally it was done by corporate personnel (1 out 20) or both (1 out of 20 respondents). an expert meeting convened by the Food and agriculture organization and the World health organization (Fao/ Who) issued a report on Enterobacter sakazakii and Salmonella in powdered infant formula (32). a detailed description on the management of Salmonella and E. sakazakii (Cronobacter spp.) in powdered infant formula was also published recently (22). these reports included a summary of risk-reduction strategies the infant formula industry has taken for the past 30–40 years. triggered by outbreaks or isolated cases associated with Salmonella and E. sakazakii in infant formula, the industry has implemented specific control measures to prevent contamination of products with Salmonella. the general principles described in the reports are as follows: 1. avoid entrance of Salmonella into the processing facilities, particularly the zones from drying to filling that are considered as high hygiene areas. 2. prevent Salmonella growth in case of entry and prevent the establishment of Salmonella niches in the facility. 3. use hygienic design for high hygiene zones and equipment in these zones. 4. use “Salmonella-negative” drymixed ingredients based on a sampling plan such as the icmSF JUNE 2009 | FOOD PROTECTION TRENDS 345

Food Protection Trends - June 2009

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