Sequential Disinfection of Escherichia Coli O157H7 Inoculated Alfalfa Seeds Before and During Sprouting
Sequential Disinfection of Escherichia coli O157:H7 Inoculated Alfalfa Seeds Before and During Sprouting Using Aqueous Chlorine Dioxide, Ozonated Water, and Thyme Essential Oil
Volume 36, Issue 2 , March 2003, Pages 235-243
N. Singha, R. K. Singha and A. K. Bhuniab
a Department of Food Science and Technology, University of Georgia, Food Science Building, Athens, GA 30602-7610, USA
b Department of Food Science, Purdue University, West Lafayette, IN 47907-1160, USA
Several outbreaks of human illness have been documented in the United States associated with alfalfa sprouts. This study was done to evaluate the efficacy of aqueous chlorine dioxide (ClO2) (10, 25, and 50 mg/L), ozonated water (4.60, 9.27, and 14.3 mg/L) and thyme oil (1.0, 2.5, and 5.0 mL/L), for 3, 5, and 10 min, respectively, alone or their sequential washing (thyme oil followed by ozonated water and aqueous ClO2) for eliminating Escherichia coli O157:H7 from alfalfa seeds prior and during sprouting.Alfalfa seeds were inoculated with a three-strain E. coli O157:H7 mixture and dried to attain approximately 106 cfu/g of seed. No single washing treatment was able to ensure complete elimination of E. coliO157:H7 from alfalfa seeds. Germination of seeds was not adversely affected by any of the treatments. A membrane-transferring surface-plating method was evaluated to recover uninjured and injured E. coli O157:H7. Direct surface-plating on selective media, Sorbitol MacConkey-cefixime-tellurite (SMac-CT) showed significantly (P<0.05) low populations recovered, thus indicating a large population of injured cells for each washing treatments in comparison to membrane-transferring surface-plating method tryptic soy agar/membrane/Sorbitol-MacConkey agar-cefixime-tellurite (TSA/M/SMac-CT). Regardless of different washing treatments, populations of E. coli O157:H7 increased to 7.8-8.2log10 cfu/g after sprouting (72 h). Results of this study also showed that sequential washing treatments (as irrigation water) during sprouting process have greater lethality than other sanitizer treatments alone.