Inactivation of Cronobacter sakazakii in reconstituted infant milk formula by plant essential oils

Abstract

This study aimed to screen the in vitro antimicrobial activity of 10 plant essential oils (EOs) against 4 Cronobacter sakazakii strains, and use these oils or their combination to control C. sakazakii cocktail at low (3 log₁₀ CFU/ml) and high (6 log₁₀ CFU/ml) contamination levels in reconstituted infant milk formula (RIMF). Cinnamon and fir oils were the most inhibitory to C. sakazakii strains with inhibition zone of 32 to 40 mm at 20 µl/disc (the minimum inhibitory concentrations were 0.16 and 0.625 µl/ml, respectively). The addition of each of cinnamon or fir oil at 1% (v/v) reduced the C. sakazakii numbers in RIMF by 0.7-0.8 log₁₀ CFU/ml when inoculated with high contamination level and by 2.5-3.1 log₁₀ CFU/ml when inoculated with low contamination level. However, the combination of cinnamon and fir oils reduced C. sakazakii numbers at both inoculum levels to undetectable levels after 3 h of incubation at 37°C. The results of the current study indicated that a combination of cinnamon and fir oils has a potent antimicrobial activity which may potentially be used to control C. sakazakii in RIMF.