Disinfection of Alfalfa Sprouting Seed Using a Treatment Compliant with Organic Production Requirements

Introduction: Sprouting seed disinfection treatments recommended by Canadian regulatory agencies require the application of concentrated chlorine (2,000 ppm) or hydrogen peroxide (8%) solutions. Occupational safety and health risks, environmental concerns, and increasing demand for organically certified products mandate the development of alternative disinfection strategies.

Purpose: The purpose of this study was to evaluate the antimicrobial efficacy of an alfalfa seed disinfection treatment based on the application of mild heat and chemicals compatible with organic production.

Methods: Alfalfa seed, inoculated with five log cfu/g Salmonella enterica, E. coli O157:H7, and Listeria monocytogenes, was treated with: 1) 2,000 ppm chlorine for 20 min; 2) 8% H₂O₂ for 10 min; and 3) 10 min in water at 50°C followed by 10 minutes in 2.0% H₂O₂+0.1% acetic acid. Surviving populations were estimated with selective media and by nonselective enrichment procedures. Seed germination rates and yields were also measured.

Results: Treatment with 2,000 ppm chlorine for 20 min reduced populations of S. enterica (3.19±0.13 log cfu/g), E. coli O157:H7 (3.20±0.07 log cfu/g) and L. monocytogenes (3.83±0.14 log CFU/g). In contrast, treatment with 8% H₂O₂ for 10 min or a 10 min soak at 50°C followed by 10 minutes in 2.0% H₂O₂+0.1% acetic acid consistently reduced populations by five log cfu/g, but all species were recovered by enrichment. Germination rates and yields were not significantly (P>0.05) affected by the treatments.

Significance: Populations of S. enterica,  E. coli O157:H7 and L. monocytogenes on alfalfa seed were reduced by five log cfu/g using a treatment compliant with organic food production principles. In parallel with other seed disinfection strategies that employ aqueous sanitizers, the treatment did not ensure complete pathogen eradication.