Irradiation and chlorination effectively reduces Escherichia coli O157:H7 inoculated on cilantro (Coriandrum sativum) without negatively affecting quality

Abstract

Cilantro (Coriandrum sativum) inoculated with Escherichia coli O157:H7 at levels approximating 107 CFU/g was dipped in 200 ppm chlorine solution followed by low-dose gamma irradiation. Samples were plated on tryptic soy agar containing 50 μg/ml nalidixic acid (TSAN) as well as TSAN plates with two 7-ml layers of basal yeast extract agar (TSAN-TAL). Levels of E. coli O157:H7 recovered from both types of media were determined over 11 days. Chlorination alone reduced counts by just over 1.0 log cycle, whereas irradiation at 1.05 kGy resulted in a 6.7-log reduction, and a combination of irradiation and chlorination reduced counts more than 7 log cycles. Trained panels performed analytical sensory tests at time intervals for 14 days to detect changes in yellowing, tip burn, browning, black rot, sliminess, off-aroma, and off-flavor. Sensory tests found no significant differences among attributes over time or dose in samples irradiated at 1.08 to 3.85 kGy. This study showed that combination treatments of chlorination and low-dose irradiation can significantly reduce levels of E. coli O157:H7 in fresh cilantro while maintaining product quality.