29F-14

S. G. SEGURA, P. M. Davidson, and J. Weiss. Dept. of Food Science & Technology, Univ. of Tennessee, 2605 River Dr., Knoxville, TN 37996-4500

Phytophenols are antimicrobials that can inhibit growth of foodborne pathogens. However, their activity in food systems is reduced because of low solubility and/or interference from food components. Encapsulation in nanoparticles may offer a new method to increase solubility and antimicrobial activity.

The objective of this study was to determine the antimicrobial activity of phytophenols encapsulated in nanoparticles against Listeria monocytogenes and E. coli O157:H7 strains.

Eugenol and carvacrol were encapsulated in Surfynol 465 and 485W to produce nanoparticle solutions ranging from 0.025 to 2wt%. A microbroth dilution assay was used to determinate the minimum inhibitory concentrations (MIC) of nanoparticles against Listeria monocytogenes (Scott A, 101, 108, 310) and Escherichia coli O157:H7 (H1730, F4546, 932 E0019). Microtiter plates were filled with 120µl nanoparticle solutions and 120µl inoculated TSB (~10⁴CFU/ml) and the optical density (OD) was recorded after 0, 3, 6, 12 and 24 hr. MIC was defined as the lowest concentration of antimicrobial causing complete inhibition (OD<0.07) in 24hrs.

Surfactant–phytophenol nanoparticles exhibited antimicrobial activity at low concentrations. Table 1 illustrates the lowest concentrations of antimicrobial-surfactant combinations that inhibited growth of pathogens. Nanocapsules from Surfynol 485W were more efficient than particles that consisted of Surfynol 465, e.g. 0.025wt% carvacrol encapsulated in 1wt% Surfynol 485W inhibited growth of E. coli while 0.15wt% carvacrol encapsulated in 2.5wt% surfactant was required for Surfynol 465. Similar results were observed for other microorganisms. The concentration of nanoparticles that was effective in preventing growth was below the maximum amount of antimicrobial that could have been incorporated (2.8wt%). Solutions were transparent and did not contain any free oil. No inhibition was found in controls that consisted of empty nanoparticles.

Encapsulation in nanoparticles offers a promising new method to improve the antimicrobial activity and application characteristics of phytophenols which may provide another tool to improve food safety.

Session 29F, Food Microbiology: Control of foodborne microorganisms by antimicrobials
2:00 PM - 5:30 PM, Sunday PM

2003 IFT Annual Meeting - Chicago,