Determination of Enterococcus faecium thermal reduction in normal and high oleic peanut products

During processing, peanut butter can become contaminated with pathogenic bacteria (e.g., Salmonella). The introduction of an additional heat treatment step after roasting can help inactivate these microorganisms. In this study, trials were conducted to determine Enterococcus faecium (Salmonella surrogate) reduction rates during the roasting of high oleic (HO) peanuts and heat-treatment of normal oleic (NO) and HO peanut butters. HO peanuts were inoculated with E. faecium and roasted in a convection oven at 190°C. There was a 2 and 6 log CFU/g reduction at 300 and 480 s, respectively. D-values for HO peanut butter at 110, 120, and 125°C were 438.9, 165.1, and 80.6 s, respectively. The z-value was calculated to be 20.8°C. There was no significant difference in D-values and z-values between NO and HO peanut butter. In a pilot scale experiment, HO peanut butter was inoculated with E. faecium and agitated in a heated mixer for 21.5 min. E. faecium was reduced by 5.1 log CFU/g after 16.5 min with no apparent change in viscosity or texture. This study demonstrated that significant reductions in E. faecium can be achieved during roasting and through an additional heat-treatment step.