Alginate-based antimicrobial coating reduces pathogens on alfalfa seeds and sprouts

Foodborne illness associated with the consumption of contaminated sprouts has been a significant food safety risk. While seed disinfection with chemical sanitizers has been used as an intervention approach, its efficacy to reduce bacterial load has not been always satisfactory. In this study, a newly developed alginate-based, antimicrobial seed coating treatment was evaluated for its efficacy to reduce foodborne pathogens from alfalfa seeds and sprouts. Alfalfa seeds were inoculated with Listeria monocytogenes or Salmonella enterica serovar Typhimurium, air-dried, and thereafter subjected to different treatments. The treated seeds were analyzed for bacterial cell populations over 28 days of storage. Meanwhile, treated seeds after one day of storage were sprouted for three days and the populations of pathogens on sprouts were determined. The results showed that the alginate coating in the presence of lactic acid (alginate coating/LA) reduced both pathogens to an undetectable level one day after the treatment. With sprouts, alginate coating/LA resulted in significantly lower (P < 0.05) populations of Listeria and Salmonella than chlorine or lactic acid treatment. While the germination rate of seeds was reduced due to the use of lactic acid, the impact of alginate coating on germination was not significant. In general, this study indicated the effect of alginate coating on reducing the bacterial load from alfalfa seeds and sprouts, and further study is needed to select antimicrobial compounds and coating materials to reduce the adverse impact on germination rate.