Stability and Antimicrobial Efficiency of Eugenol Encapsulated in Surfactant Micelles as Affected by Temperature and pH
Abstract:Growth inhibition of four strains of Escherichia coli O157:H7 (H1730, F4546, 932, and E0019) and Listeria monocytogenes (Scott A, 101, 108, and 310) by eugenol encapsulated in water soluble micellar nonionic surfactant solutions (Surfynol 485W) adjusted to pH 5, 6, and 7 and incubated at 10, 22, and 32°C was determined. Concentrations of eugenol ranged from 0.2 to 0.9% at a surfactant concentration of 5%. Antimicrobial activity was assessed using a microbroth dilution assay. Eugenol encapsulated in surfactant micelles inhibited both microorganisms at pH 5, 6, and 7. At pH 5, some inhibition occurred in the absence of eugenol, i.e., by the surfactant itself (optical density at 24 h for L. monocytogenes = 0.07 and optical density at 24 h for E. coli O157:H7 = 0.09), but addition of >0.2% eugenol led to complete inhibition of both microorganisms. Inhibition of L. monocytogenes and E. coli O157:H7 decreased with increasing pH, that is, the minimum inhibitory concentration was 0.2, 0.5, and 0.5% of micellar encapsulated eugenol solutions at pH 5, 6, and 7, respectively. The encapsulated essential oil component in surfactant micelles was effective at all three temperatures tested (10, 22, and 32°C), indicating that the activity of encapsulated eugenol was not affected by high or low (refrigeration) temperatures. Overall, strains of E. coli O157:H7 were more sensitive than strains of L. monocytogenes. Improved activity was attributed to increased solubility of eugenol in the aqueous phase due to the presence of surfactants and improved interactions of antimicrobials with microorganisms.
Document Type: Research Article
Affiliations: 1: Department of Food Science, University of Massachusetts, Chenoweth Laboratory, 100 Holdsworth Way, Amherst, Massachusetts 01003 2: Department of Food Science and Technology, The University of Tennessee, 2605 River Road, Knoxville, Tennessee 37996 3: Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, F423 Walters Life Science Building, 1414 West Cumberland Avenue, Knoxville, Tennessee 37996-0840, USA
Publication date: 2005-07-01
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