Purpose: To evaluate the antimicrobial activities of carvacrol and cinnamaldehyde against Salmonella Tennessee K4643 in peanut paste with different aw and fat levels over 5 days at 25°C.
Methods: Low fat (< 5%) peanut pastes were made with defatted peanut flour, glycerol and DI water to achieve aw of 1.0, 0.7, 0.5 and 0.3. High fat (50%) peanut paste was prepared with defatted peanut flour and peanut oil (aw = 0.29). Carvacrol (0, 1250 and 2500 ppm) or cinnamaldehyde (2500 and 5000 ppm) were added to each sample. All samples were then inoculated with 8 log Salmonella Tennessee K4643 and stored at 25°C. Samples were taken at day 0, 1, 3 and 5 and Salmonella were enumerated on tryptic soy agar. Each experiment was performed in triplicate.
Results: In low fat peanut pastes, Salmonella at aw 1.0 increased by 1 log over 5 days in the control. Neither compound reduced viable Salmonella at the maximum concentration at aw 1.0. Lowered aw (0.7 - 0.3) alone reduced Salmonella by 2.58 - 3.45 logs on day 5. Cinnamaldehyde was more effective than carvacrol. On day 5, the population reached an undetectable level with 2500 ppm cinnamaldehyde while 2.69 and 3.08 log remained with 5000 ppm carvacrol at aw 0.5 and 0.3, respectively. Increased fat concentration greatly reduced the effectiveness of both compounds as Salmonella was not affected by either compound after 5 days (P > 0.05).
Significance: Both essential oil components effectively inactivated Salmonella Tennessee in low fat peanut paste at aw ≤ 0.7 with cinnamaldehyde demonstrating better inactivation than carvacrol. The effectiveness of both compounds was dramatically reduced by increased fat level.