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

M A Al-Holy, L F Castro, H M Al-Qadiri

Index: Lett. Appl. Microbiol. 50 , 246-251, (2010)

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Abstract

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.