Monolaurin is the glycerol monester of lauric acid. Derived from coconut oil, it has been generally recognised as safe in the US since the 1960s, but its use in the global food industry has been limited, with benzoates, sorbates and nitrites used more commonly. Monolaurin has seen more take up to date by the cosmetics and personal care industry.
One of the barriers to monolaurin in food has been that high concentrations over 500µg/ml can result in a soapy odour and taste that affects sensory acceptability. For this reason, it may be combined with other microbials “to establish a series of hurdles that microorganisms could not overcome”, report the authors of the new study.
The team from Zhejiang University in China wanted to increase understanding of its potential use and limitations in foods. They obtained monolaurin from Hangzhou Kangyuan Food Science and Technology with a 99 per cent monoester content.
This material was tested in combination with nisin, sodium lactate, sodium dehydroacetate, calcium propionate and ethylenediamenetetraacetic acid (EDTA), against E coli, Staphylococcus aureaus and Bacillus subtilis using microtiter plate assay. Their findings have been published in the Journal of Food Science.
The minimum inhibitory concentrations for the monolaurin were 25µg/ml against E.coli, 12.5µg/ml against S.aureaus and 30µg/ml. When combined with nisin, it was seen to be affected against all three of the bugs.
However when used with sodium dehydroacetate or EDTA it was effective only against the E.coli and B.subtitlis. Neither use with sodium lactate nor with calcium propionate showed any action against the bugs.
Food matrix tests
The researchers then went on to investigate how the monolaurate’s action could be affected by the composition of certain food products.
They looked at its effect in fat by comparing growth in treatments containing liquid soybean cooking oil at concentrations of 0, 10 and 20 per cent to which E.coli was then added; to test the effect with protein and starch the agar dilution method was used, with TSA plates containing 0, 1 and 3 per cent soy protein or water soluble starch respectively.
They observed that the effectiveness of the monolaurin in combating the E.coli was reduced by fat or starch, while its action was unaffected by protein.
Journal of Food Science Volume 74, Issue 7, M418-M421
Antibacterial Interactions of Monolaurin with Commonly Used Antimicrobials and Food Components
Authors: Hui Zhang, Hewen Wei, Yinan Cui, Guoqun Zhao, Fengqin Feng