99E-12

M. WIHODO¹, Y. Han¹, T. L. Selby¹, P. Lorcheim², M. Czarneski², G. Huang³, and R. H. Linton¹. (1) Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Dr., West Lafayette, IN 47907-2009, (2) ClorDisys Solutions, Inc., 5 Concord Rd., PO Box 549, Lebanon, NJ 08833, (3) Almond Board of California, 1150 9th St., Ste. 1500, Modesto, CA 95354

Salmonella spp. contamination and salmonellosis have been associated with raw almonds. Chlorine dioxide (ClO₂) gas may provide an alternative for almond decontamination due to its high effectiveness in reducing pathogens on other surfaces. Our objective was to determine the efficacy of different ClO₂ gas treatments in reducing Salmonella spp. on raw almond surfaces. Almonds (25g) were spot-inoculated on the surface with 8-9 log cfu of a mixture of five Salmonella strains, stored for 24 hr at 4^o C or dried for 24 hr at 22^o C in a biosafety hood. Inoculated almonds were then treated with 5-10 mg/L ClO₂ gas for 10-30 min at 22^o C and 80-90% relative humidity under atmosphere pressure or vacuum conditions (20kpa-80kPa). Salmonella were recovered by either a stomaching or a washing procedure, and enumerated using a membrane-transferring plating technique on tryptic soy agar and xylose lysine desoxycholate agar. No significant difference (P>0.05) between recovery methods (stomaching vs. washing) was observed. The efficacy of ClO₂ gas increased with increasing concentrations and treatment time. Under atmosphere pressure condition, a treatment with 10 mg/L ClO₂ gas for 10 min led to a 2.54 log cfu/25g reduction on refrigerated almonds and a 2.67 log cfu/25g reduction on dried samples. After 10 mg/L ClO₂ gas treatment for 30 min, a 5.29 log reduction on refrigerated almonds was achieved; however, a bleaching effect was observed on almond surface. Under the vacuum conditions, 2.22, 2.32, and 4.50 log reductions were obtained after treatments with 5 mg/L ClO₂ gas for 10 min, 5 mg/L ClO₂ gas for 15 min, and 10 mg/L ClO₂ gas for 10 min, respectively. No obvious color changes were noticed after these treatments. Gaseous ClO₂ treatment led to significant reductions in Salmonella. Vacuum conditions enhanced reduction and therefore show a greater potential for reducing Salmonella on raw almond surfaces.

Session 99E, Nonthermal Processing: General II
8:30 AM - 12:00 PM, Wednesday AM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana