Improvment of the microbial safety of fresh produce using chemical or alternative treatments.

Consumption of contaminated fresh produce is responsible for numerous outbreaks of gastrointestinal infections annually in the United States. Controlling Salmonella and pathogenic E. coli, the major causative agents in these outbreaks remains challenging. This study evaluated the effectiveness of calcium hypochlorite (Ca(OCl)2) and peroxyacetic acid (PAA) on control of different strains of Salmonella, E. coli O157:H7, and E. coli O104:H4 on alfalfa seeds and sprouts. Results showed that average Salmonella and E. coli counts were ca. 5 log CFU/g lower on sprouts grown from Ca(OCl)2-treated seeds compared to the controls. PAA treatment of sprout seeds reduced Salmonella by ca. 5 log CFU/g, but only reduced E. coli by about 1.25 - 1.52 log CFU/g, on sprouts. The sanitizer efficacy was strain-dependent, with robust strains being more challenging to control. No adverse effects on germination percentage or sprout yield were observed. Under a different objective, the efficacy of ascaroside (ascr)#18, an immunity modulator from plant parasitic nematodes, was used to control E. coli O157:H7 on spinach. Spinach was grown either from seeds that received ascr#18 treatment alone or from ascr#18 treated seeds plus ascr#18 foliar spray for 3 or 4 to 6 or 7 weeks, and harvested spinach was stored at 4°C for 4 weeks. Mature spinach grown from ascr#18 treated seeds had higher pathogen counts than the younger plants. However, the opposite phenomenon was noticed when ascr#18 foliar spray was added to the top of the seed treatment. E. coli counts decreased as storage time passed, but elimination of the pathogen was not achieved. The study suggests that Ca(OCl)2 and PAA treatments were effective in controlling Salmonella and E. coli on alfalfa seeds and sprouts. While the ascr#18 treatment has the potential to control E. coli in spinach, additional research is needed to determine the optimal concentration of ascr#18 foliar spray. The information obtained from this study may help in improving the microbial safety of sprouts and spinach.