Comparison of antibacterial effect of seven 1-monoglycerides on food-borne pathogens or spoilage bacteria

The aim of this study was to compare under the same conditions in vitro the inhibitory effects of seven 1-monoglycerides (MAG) containing fatty acids with a medium chain on ten strains of food-borne pathogens or spoilage gram-positive and gram-negative bacteria (Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Micrococcus luteus, Staphylococcus aureus, Citrobacter freundii, Escherichia coli, Proteus mirabilis, Salmonella enterica ser. Enteritidis and Pseudomonas aeruginosa) and on their growth indicatos. The inhibitory effect of MAGs (monocaprylin, monocaprin, monolaurin, monomyristin, monopalmitin, MAG of undecanoic and 10-undecenoic acids) at a concentration of 25 – 1500 mg·l -1 was observed. Growth of bacteria in the presence of MAG was studied by means of optical density of bacteria for 24 h. The data were modelled through a Gompertz equation and the lag-time, the maximum specific growth rate and the maximal value reached were calculated. MAGs inhibited mainly the growth of gram-positive bacteria, which was shown by the extended lag-time, decrease in specific growth rate and decrease in cell density. Inhibitory effects of tested MAGs could be ranked from point of view of the minimum inhibitory concentration: MAG-C12:0 > MAG-C11:0 > MAG-C10:0 > MAG-C14:0 > MAG-C11:1 > MAG-C8:0 > MAG-C16:0. In vitro, no significant inhibitory effects of 1-monoglycerides, with the exception of the highest concentrations applied, on the growth of gram-negative bacteria were detected. The main contribution of this study is to compare the effects of several MAG containing fatty acids with a medium chain under the same conditions on the growth indicators of bacteria. Inhibition effect, esters of glycerol, microorganism, Gompertz model, specific growth rate, lag-time In the environment of foodstuffs, many food-borne pathogens, animal pathogens or spoilage microorganisms that can be transmitted to humans may be proliferated. Undesirable growth of microorganisms on the surface and inside animal products may be health hazardous. Therefore, preservation of food and its ingredients has become an important issue nowadays. In the food processing industry, antimicrobial substances belong to the most important groups of additives (Davidson and Branen 2005; Kacaniova et al. 2009). Antimicrobial substances should be an integral part of foodstuffs and could even improve their functional properties. These substances include monoglycerides (MAG) (Kabara and Marshall 2005) that are used for their emulsifying abilities in the food processing industry (Moonen and Bas 2004). Moreover, they can improve rheological properties of many foodstuffs, e.g. dairy or bakery products (Ravi et al. 2000; Buňka et al. 2007). Antimicrobial activity of fatty acids and monoglycerides as their other functional properties depends on the number of carbon atoms and on the presence of double bonds