Environment-friendly mild heat and relative humidity treatment protects sprout seeds (radish, mung bean, mustard, and alfalfa) against various foodborne pathogens

Abstract

The utility of a novel technology based on heat and relative humidity (RH) was examined; the method was used to treat experimentally contaminated radish, mung bean, mustard, and alfalfa seeds. Seeds were inoculated with high (ca. 7 log CFU/g) or low (ca. 3 log CFU/g) levels of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes, and treated at 65 °C/40% RH for 8, 15, or 22 h. The 15 h treatment reduced the numbers of E. coli O157:H7 and S. Typhimurium on all seeds to below the detection limit (10 CFU/g), whereas longer treatment (up to 22 h) was needed for L. monocytogenes. At 8 h, L. monocytogenes on mung bean was significantly less susceptible to combined treatment that L. monocytogenes on other seeds (P < 0.05). Overall, the 22 h treatment eliminated E. coli O157:H7 from radish and mustard seeds, and L. monocytogenes from mustard and alfalfa seeds; the treatment had no significant effect on the viability of radish, mung bean, or alfalfa seeds (P > 0.05). However, the mustard seed viability fell by about 9.8%. These findings indicate that the environmentally friendly technology is a wide spectrum method of decontaminating sprout seeds, with little concomitant reduction in seed quality.