Survival, Growth, and Thermal Resistance of Listeria monocytogenes in Products Containing Peanut and Chocolate

Abstract

Outbreaks of listeriosis associated with the consumption of ready-to-eat foods have raised interest in determining growth, survival, and inactivation characteristics of Listeria monocytogenes in a wide range of products. A study was undertaken to determine the thermal tolerance of L. monocytogenes in a peanut-based beverage (3.1% fat), whole-fat (3.5%) milk, wholefat (4.0%) and reduced-fat (1.0%) chocolate milk, a chocolate-peanut spread (39% fat), and peanut butter (53% fat). The D60 degrees C value (decimal reduction time at 60 degrees C) in peanut beverage (3.2 min) was not significantly different (P > 0.05) than the D60 degrees C value in whole-fat milk (3.3 min) or whole-fat chocolate milk (4.5 min) but significantly lower (P < or = 0.05) than the D60 degrees C value in reduced-fat chocolate milk (5.9 min). The pathogen was significantly more resistant to heat when enmeshed in chocolate-peanut spread (water activity [aw] of 0.46; D60 degrees C = 37.5 min) and peanut butter (aw of 0.32; D60 degrees C = 26.0 min) than in liquid products. At 10 degrees C, the pathogen grew most rapidly in whole-fat chocolate milk and slowest in peanut beverage. At 22 degrees C, populations increased significantly within 12 and 16 h in whole-fat milk and reduced-fat chocolate milk, respectively, and within 8 h in whole-fat chocolate milk and peanut beverage. Initial populations (3.37 to 4.42 log CFU/g) of L. monocytogenes in chocolate-peanut spread and peanut butter adjusted to an aw of 0.33 and 0.65 declined, but the pathogen was not eliminated during a 24-week period at 20 degrees C. Survival was enhanced at reduced aw. Results indicate that a pasteurization process similar to that used for full-fat milk would be adequate to ensure the destruction of L. monocytogenes in peanut beverage. The pathogen survives for at least 24 weeks in chocolate-peanut spread and peanut butter at an aw range that encompasses that found in these products.

Peanut and peanut products: A food safety perspective

“…A 3-strain cocktail of Salmonella tennessee inoculated in peanut butter survived for 2 weeks at 4 and 22 C (Park, Oh, & Kang, 2008). Further, Kenney and Beuchat (2004) reported that another pathogen, Listeria monocytogenes could also survive for 24 weeks in peanut butter at 20 C with an initial inoculation level of 4 log CFU/g. Although no illness was reported, potential contamination by L. monocytogenes also prompted nationwide recalls of certain brands of peanut butter, and peanut butter & jelly sandwiches in 2010 and 2011 respectively (US FDA, 2010; US FDA 2011a).…”

Methods to reduce pathogen microorganisms in manure

“…The decimeration times can increase in dry or fat containing mixture (Kenney and Beuchat, 2004), but the decimeration times for the non-sporing bacteria like Salmonella, Escherichia or Listeria cannot be more than 1 min in manure pasteurization at 70 8C and this treatment would also give final bacterial number of Turner et al (2000). 10 9-60 CFU/g = 10 À 51 CFU/g, which is still very low number and clearly less than any detection limit or infective dose, which could cause infections.…”

Minimal Effects of High‐Pressure Treatment on Salmonella enterica Serovar Typhimurium Inoculated into Peanut Butter and Peanut Products

“…Contamination of peanut butter can occur in raw ingredients or introduced through processing. Research has shown that microorganisms, S. enterica serovars and Listeria monocytogenes , are not completely inactivated by heat typical in the processing of peanut butter and thus can be present in the consumer product (Keeney and Beuchat 2004; Shachar and Yaron 2006; Ma and others 2009). Clean raw ingredients are insufficient to ensure final product safety due to possible recontamination during processing.…”