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Inhibition of Listeria monocytogenes by monoacylglycerols synthesized from coconut oil and milkfat by lipase-catalyzed glycerolysis

Wang, L.L., Yang, B.K., Parkin, K.L., Johnson, E.A.
Journal of agricultural and food chemistry 1993 v.41 no.6 pp. 1000-1005
Listeria monocytogenes, antibacterial properties, monoacylglycerols, milk fat, coconut oil, hydrolysis, triacylglycerol lipase, food preservatives, pasteurized milk
Monoacylglycerols (MAGs) synthesized from coconut oil and milkfat were evaluated in brain heart infusion (BHI) broth and in pasteurized milk for antimicrobial activity against the Scott A strain of Listeria monocytogenes. MAGs were produced by solid-phase glycerolysis catalyzed by lipase PS-30 from Pseudomonas sp. and purified by hexane fractionation. The purities of MAGs from coconut oil and milkfat before hexane fractionation were 74.6% and 54.5% and after were 97.5% and 95.7%, respectively. Fractionated coconut MAGs were slightly more inhibitory against L. monocytogenes than unfractionated MAGs. L. monocytogenes was inactivated by hexane-fractionated coconut MAGs at 250-400 micrograms/mL in pasteurized skim, at 500-750 micrograms/mL in 2% milk, and at 750-1000 micrograms/mL in whole milk at 4 degrees C, but the MAGs were less inhibitory at 13 degrees C and at room temperature. MAGs prepared from coconut oil were more effective than monolaurin against L. monocytogenes in BHI and pasteurized milk, whereas MAGs made from milkfat did not inhibit L. monocytogenes in pasteurized milk. The composition of fatty acids present in the coconut MAGs was associated with the anti-listerial activity, and lauric acid (C12) was the most active fatty acid of the series C8-C14. Certain combinations of the MAGs, particularly monocaprin and monolaurin, showed synergistic activity against L. monocytogenes. Our results indicate that MAGs synthesized from coconut oil could be used to control L. monocytogenes in certain dairy products or in other foods that contain reduced fat.