P-002. Impact of Dispersing Agents on Radical Scavenging Activity and Inhibitory Properties of Natural Cold Pressed Terpenless Valencia Orange Oil against Foodborne Microorganisms

V. I. Chalova, P. G. Crandall, C. O’Bryan, S. C. Ricke;
Univ. of Arkansas, Fayetteville, AR.

Due to their low solubility in water, oil-based boactive compounds require dispersion in a surface active agent to ensure maximum contact with microorganisms. This act, however, may change their physical and/or chemical characteristics and consequently alter the desired functionality. The objective of this study was to determine the impact of selected dispersing agents, ethanol, DMSO (dimethyl sulfoxide) and Tween-80, on cold pressed terpeneless Valencia orange oil to function in the dual role as a free radical scavenger and as an antimicrobial food additive. Salmonella Typhimurium ATCC 14028 (ST), Listeria monocytogenes ATCC 19115 (LM) and Lactobacillus plantarum WCFS1 (LP) were tested as representatives of gram negative and gram-positive foodborne pathogens and a probiotics respectively. Dilution techniques were used to determine the minimum inhibitory concentration (MIC) of the orange oil. The MIC was defined as the lowest concentration of the oil capable of inhibiting the growth of the microorganism as evidenced by no changes of the optical density. The radical scavenging activities of the orange oil in different dispersing agents were determined by using a DPPH (2,2-Diphenyl-1-picryl hydrazyl) radical photometric assay. When dissolved in ethanol or DMSO, the orange oil fraction had similar MICs for LM (0.3% and 0.25% v/v respectively) which were significantly lower than the MIC for ST (1% v/v). Both ethanol and DMSO oil dispersion systems exhibited an intermediate MIC (0.75% v/v) for LP. Tween-80 when used at 0.1% in an aqueous solution with and without the orange oil yielded no inhibitory activities against any of the bacteria. However, the 1% natural orange oil dispersed in Tween-80 gave a radical inhibition of 56.86% versus 18.37 and 16.60% when the same level of orange oil was dissolved in DMSO or ethanol respectively. In conclusion, these findings suggest that Tween-80 is an appropriate dispersing agent if only the antioxidant functionality is desired. If both antimicrobial and antioxidant properties are needed the orange oil must be dispersed in either DMSO or ethanol.