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

To investigate the effect of lactic acid (LA), copper (II), and monolaurin as natural antimicrobials against Cronobacter in infant formula. The effect of LA (0.1, 0.2 and 0.3% v/v), copper (II) (10, 50 and 100 microg ml(-1)) and monolaurin (1000, 2000, and 3000 microg ml(-1)) suspended into tween-80 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 10(6) CFU ml(-1) and 1 x 10(3) CFU g(-1), respectively. LA at 0.2% v/v had a bacteriostatic effect on Cronobacter growth, whereas 0.3% v/v LA resulted in c. 3 log(10) reduction. Copper (II) at the levels of 50 microg ml(-1) and 100 microg ml(-1) elicited c. 1 and 2 log(10) reductions, respectively. The combination of 0.2% LA and 50 microg ml(-1) copper (II) resulted in a complete elimination of the organism. Monolaurin exhibited a slight inhibitory activity against Cronobacter (c. 1.5 log(10) difference) compared to the control when ethanol was used to deliver monolaurin. A complete elimination of Cronobacter was obtained when a combination of sublethal concentrations of LA (0.2%) and copper (II) (50 microg ml(-1)) was used. The use of the synergistic interactive combination of LA and copper (II) could be beneficial to control Cronobacter in the infant formula industry.