91E-30 |
Efficacy of different sanitizer treatments for eliminating Escherichia coli O157:H7 from alfalfa seeds prior and during sprouting |
N. SINGH1, R. K. Singh2, A. K. Bhunia1, and R. L. Stroshine3. (1) Department of Food Science, Purdue University, West Lafayette, IN 47907, (2) Department of Food Science and Technology, University of Georgia, Athens, GA 30602, (3) Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907 Numerous outbreaks of foodborne illness have been linked to the consumption of raw sprouts. This study was undertaken to evaluate different sanitizers, alone or in combination for their effectiveness in killing mixed strains of E. coli O157:H7 on alfalfa seeds prior and during sprouting process. Immersing inoculated seeds in sanitizer solutions containing aqueous ClO2 (25 mg/l, 5 min), ozonated water (14.0 mg/l, 5 min), and thyme oil suspension (0.5 %, 5 min) alone or in combination [(Thyme oil(0.5 %, 5 min) followed by ozonated water(14.0 mg/l,5 min), and aqueous ClO2 (25 mg/l,5 min)] resulted in reduction of 0.54, 0.43, 2.17, and 3.76 log10cfu/g respectively. Germination of seeds was not adversely affected by any of the treatments. Population of E.coli O157:H7 on alfalfa sprouts peaked at 6 to 8 log10 cfu/g 24 h after initiation of the sprouting process and remained stable despite spraying with sanitizers {(aqueous ClO2 (25 mg/l, 5 min), and ozonated water (14.0 mg/l, 5 min)} during sprouting process. However, thyme oil (0.5%, 5 min), and sequential treatments of thyme oil (0.5%, 5 min), followed by ozonated water (14.0 mg/l, 5 min) and aqueous ClO2 (25 mg/l, 5 min) significantly (p£0.05) reduced the population. None of the sanitizer treatment evaluated, alone or in combination was able to eliminate E.coli O157:H7 on alfalfa seeds, and also during sprouting process. The efficacy of these washing treatments was also studied after inoculating alfalfa sprouts with mixed strains of E. coli O157:H7. Washing with thyme oil (0.5%,5 min) followed by ozonated water(14.0 mg/l, 5 min), and aqueous ClO2 (25 mg/l, 5 min), enhanced inactivation by 0.53 log 10 cfu/g compared to treatment with these sanitizers alone. The inaccessibility of E.coli O157:H7 cells in crevices, cracked regions of the seeds, between the cotyledon and testa of seeds as well as in the inner tissues of cotyledon, and sprouts are thought to be reason for the lack of effectiveness of these sanitizers.
Session 91E, Nonthermal Processing: Nonthermal processing of foods
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