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IMPACT OF INOCULUM LEVEL ON THE TRANSFER OF SALMONELLA SEROVARS FROM CONTAMINATED ALMOND BUTTER TO FOOD CONTACT MATERIALS
Title
IMPACT OF INOCULUM LEVEL ON THE TRANSFER OF SALMONELLA SEROVARS FROM CONTAMINATED ALMOND BUTTER TO FOOD CONTACT MATERIALS
Creator
Zheng, Yue
Date
2012-11-19, 2012-12
Description
Outbreaks of salmonellosis associated with nut butter have raised public concerns of sanitation issues in nut butter processing. The high fat,...
Show moreOutbreaks of salmonellosis associated with nut butter have raised public concerns of sanitation issues in nut butter processing. The high fat, low-moisture characteristics of nut butters significantly affect the efficiency of regular cleaning and sanitizing programs, allowing cross-contamination issues to persist on processing equipment. Besides organic matter in food soil, microbial load could also be a factor affecting efficacy of chemical sanitizers. The FDA Food Code (2005) require a 5-log bacterial reduction in testing the efficacy of a chemical sanitation method. As a result, evaluation of microbial transfer is essential for establishing methods for equipment sanitation. The first study of this thesis (Section 4.1) evaluated the survival of Salmonella serovars in almond butter at 25 ± 2 oC. This was achieved by investigating the survival of Salmonella Tennessee and Salmonella Oranienburg in inoculated almond butter sample for up to two weeks. These Salmonella serovars were inoculated into creamy almond butter separately and stored at 25 ± 2 oC. Results showed that Salmonella populations decreased slowly and could survive in almond butter for at least two weeks. This study also investigated the effect of initial inoculum level, contact time, food-contact material and bacterial serovar on the subsequent potential for transfer of bacteria to equipment surfaces (Section 4.2). Almond butter inoculated with Salmonella Oranienburg and Tennessee at different inoculums levels (~3, 6, 9 log CFU/g) were spread on 16 cm2 coupons made of polyethylene, polyurethane, Delrin and stainless steel. Microbial analysis was conducted after physically removing all visible nut butter with laboratory wipes. Results for S. Oranienburg and Tennessee followed similar trends of microbial transfer with regards to inoculum level and food-contact surface. The amount x of Salmonella transferred to a food-contact surface was dependent on initial inoculation levels. An average of 0.88 ± 0.22, 1.53 ± 0.15, and 4.59 ± 0.06 log CFU S. Tennessee per 16 cm2 were transferred to the four different food-contact surface types for low, medium, and high inoculum level, respectively. An average of 1.25 ± 0.24, 2.08 ± 0.08, and 4.55 ± 0.35 log CFU S. Oranienburg per 16 cm2 were transferred to the same four different foodcontact surfaces for low, medium, and high inoculum levels, respectively. The third part of this study (Section 4.3) determined the transfer of Salmonella from contaminated food-contact coupon surfaces to almond butter. Uninoculated almond butter was applied on the surface of previously contaminated food-contact coupon surfaces. More than 5 log CFU/16 cm2 Salmonella could transfer to clean almond butter after immediate contact (within 5 min) with the contaminated area. These findings help advance our understanding of factors affecting microbial transfer between nut butters and processing equipment surfaces. This research can be used to support future cleaning and sanitation studies for nut butter processing equipment.
M.S. in Food Safety and Technology, December 2012
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