Evaluations of Disinfectants for Control of Pathogens in Alfalfa Seeds

Evaluationsof Disinfectants for Control of Pathogens in Alfalfa Seeds & Sprouts

ReferenceType: Conference Proceedings
Record Number: 5955
Author: Beuchat, Larry R.; Taormina, P. J. ; Weissinger, W. R.
Year of Conference: 2001
Title: (Paper 91-7)
Conference Name: IFT Annual Meeting
Conference Location: New Orleans, LA
Date: June 23-27, 2001

Abstract:Outbreaks of infections associated with raw fruits and vegetables have occurredwith increased frequency during the past decade. At least fourteen outbreaks ofSalmonella and Escherichia coli O157:H7 infections linked to the consumption ofalfalfa sprouts, clover sprouts, and mungbean sprouts have been documented since1995. The level of safety risk associated with sprouts that are not cookedbefore eating has raised interest in evaluating a wide range of chemicals fortheir efficacy in killing pathogens on seeds intended for sprout production andon mature sprouts. Test chemicals have included chlorine (hydochlorous acid),chlorine dioxide, acidified sodium chlorite, various organic acids, trisodiumphosphate, calcium hydroxide, hydrogen peroxide, ethanol, volatile plantcompounds, and several commercial formulations. While treatment with some ofthese chemicals has been shown to reduce populations of Salmonella and E. coliO157:H7 by more than 6 log10 CFU/g, substantial loss of seed viability alsooften occurs. Treatment of alfalfa seeds with 20,000 ppm chlorine (as calciumhypochlorite), 1% calcium hydroxide, 500 ppm acidified sodium chlorite, and aprototype produce wash (Fit7) are most effective in reducing pathogens withoutsacrificing germination percentage. The delicate nature of alfalfa sproutsrenders them extremely sensitive to chemical treatment. Gaseous acetic acid (500ppm) and allyl isothiocyanate (200 ppm) reduce the number of Salmonella onalfalfa sprouts by about 7 log10 CFU/g but also adversely affect color, turgor,and overall appearance. Among the aqueous chemical treatments applied to alfalfasprouts, acidified sodium chlorite shows the most promise. Disinfection of seedsbefore sprout production remains a unique challenge in terms of developinginterventions for eliminating pathogenic bacteria without reducing yield orcompromising sensory quality of mature sprouts. Combinations of chemical andphysical treatments are currently being investigated on the assumption thatmultiple assaults will enhance lethality to pathogens that apparently areoccasionally present in low numbers on alfalfa seeds.