Inactivation of Cronobacter spp. (Enterobacter sakazakii) in infant formula using lactic acid, copper sulfate and monolaurin

Aims: To investigate the effect of lactic acid (LA), copper (II), and monolaurin as natural antimicrobials against Cronobacter in infant formula. Methods and Results: The effect of LA (0 center dot 1, 0 center dot 2 and 0 center dot 3% v/v), copper (II) (10, 50 and 100 mu g ml-1) and monolaurin (1000, 2000, and 3000 mu g ml-1) suspended into tween-80 (TM) or dissolved in ethanol against Cronobacter in infant formula was investigated. Reconstituted infant formula and powdered infant formula were inoculated with five strains of Cronobacter spp. at the levels of c. 1 x 106 CFU ml-1 and 1 x 103 CFU g-1, respectively. LA at 0 center dot 2% v/v had a bacteriostatic effect on Cronobacter growth, whereas 0 center dot 3% v/v LA resulted in c. 3 log(10) reduction. Copper (II) at the levels of 50 mu g ml-1 and 100 mu g ml-1 elicited c. 1 and 2 log(10) reductions, respectively. The combination of 0 center dot 2% LA and 50 mu g ml-1 copper (II) resulted in a complete elimination of the organism. Monolaurin exhibited a slight inhibitory activity against Cronobacter (c. 1 center dot 5 log(10) difference) compared to the control when ethanol was used to deliver monolaurin. Conclusions: A complete elimination of Cronobacter was obtained when a combination of sublethal concentrations of LA (0 center dot 2%) and copper (II) (50 mu g ml-1) was used. Significance and Impact of the Study: The use of the synergistic interactive combination of LA and copper (II) could be beneficial to control Cronobacter in the infant formula industry.