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Title: Effect of oil and dry roasting of peanuts at various temperatures and times on survival of Salmonella and Enterococcus faecium

item Sanders, Timothy
item CALHOUN, R - American Peanut Council

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2013
Publication Date: 5/23/2014
Publication URL: doi:
Citation: Sanders, T.H., Calhoun, R.S. 2014. Effect of oil and dry roasting of peanuts at various temperatures and times on survival of Salmonella and Enterococcus faecium. Peanut Science. 41:65-71.

Interpretive Summary: Salmonella contamination has caused problems in peanut butter. These studies were conducted to determine if Enterococcus faecium. a non-toxic bacteria, was an acceptable surrogate for Salmonella in studies to determine reduction in Salmonella in the laboratory and in commercial operations. These studies was also conducted to determine the time and temperature required to achieve an acceptable reduction of these organisms. The studies indicated that E. faecium was slightly more heat and time tolerant than Salmonella and thus was a very good surrogate for Salmonella, Further, oil roasting required a very short time to provide an acceptable reduction of both organisms and reduction of both in dry roasting were related to higher temperatures and longer exposure times. These results are important because they proved the value of E. faecium as a surrogate and indicated that temperatures used in commercial oil and dry roasting are in the range to produce an acceptable reduction of both organisms.

Technical Abstract: A number of outbreaks of salmonellosis since 2006 associated with the consumption of Salmonella-contaminated peanut butter have increased concerns about this food and the associated processing methods. Laboratory studies were conducted to determine the level of Salmonella reduction associated with oil and dry roasting of peanuts. After inoculation with either Salmonella or Enterococcus faecium, peanuts were dry roasted for various time durations at 5 temperatures ranging from 129-163 C and oil roasted at 120-160 C for three different time durations. At each dry roast combination of temperature and time in the study, Salmonella and E. faecium reductions were 2.7 log CFU/g or greater. Dry roast temperature of 154 C provided 4.6-4.7 log CFU/g reduction of Salmonella at 10 min and greater than 5.4 log CFU/g reduction at15 min. Oil roasting for 1.5 min at 150 C resulted in greater than a 6.0 log CFU/g reduction of Salmonella. E. faecium log CFU/g reductions were significantly lower than Salmonella reductions in all treatments.