Assessment of trans-cinnamaldehyde and eugenol assisted heat treatment against Salmonella Typhimurium in low moisture food components

Increased thermal resistance of Salmonella at low water activity (aw) is a significant food safety concern in low -moisture foods (LMFs). We evaluated whether trans-cinnamaldehyde (CA, 1000 ppm) and eugenol (EG, 1000 ppm), which can accelerate thermal inactivation of Salmonella Typhimurium in water, can show similar effect in bacteria adapted to low aw in different LMF components. Although CA and EG significantly accelerated thermal inactivation (55 degrees C) of S. Typhimurium in whey protein (WP), corn starch (CS) and peanut oil (PO) at 0.9 aw, such effect was not observed in bacteria adapted to lower aw (0.4). The matrix effect on bacterial thermal resistance was observed at 0.9 aw, which was ranked as WP > PO > CS. The effect of heat treatment with CA or EG on bacterial metabolic activity was also partially dependent on the food matrix. Bacteria adapted to lower aw had lower membrane fluidity and unsaturated to saturated fatty acids ratio, suggesting that bacteria at low aw can change its membrane composition to increase its rigidity, thus increasing resistance against the combined treatments. This study demonstrates the effect of aw and food components on the antimicrobials-assisted heat treatment in LMF and provides an insight into the resistance mechanism.

Automated summary

Increased thermal resistance of Salmonella at low water activity (aw) is a significant concern in low-moisture foods (LMFs). This study evaluated the effect of trans-cinnamaldehyde (CA) and eugenol (EG) on Salmonella Typhimurium adapted to low aw in different LMF components. The results showed that CA and EG accelerated thermal inactivation of S. Typhimurium in certain LMF components at 0.9 aw, but not in bacteria adapted to lower aw (0.4). The resistance mechanism may be related to changes in bacterial membrane composition.