Disinfection of Radish and Alfalfa Seeds Inoculated withEscherichia coliO157:H7 andSalmonellaby a Gaseous Acetic Acid Treatment

Abstract

The majority of seed sprout-related outbreaks have been associated with Escherichia coli O157:H7 and Salmonella. Therefore, we aimed to find an effective method to inactivate these organisms on seeds before sprouting. Treatment with 8.7% (v/v) acetic acid at 55°C for 2-3 h reduced the population of E. coli O157:H7 and Salmonella inoculated on alfalfa (Medicago sativa L.) and radish seeds (Raphanus sativus L.) by more than 5.0 log CFU/g, and a longer treatment time completely eliminated the E. coli O157:H7 population. The E. coli O157:H7 populations were reduced to an undetectable level with a gaseous acetic acid treatment for 48 h. After enrichment, no E. coli O157:H7 were found in the alfalfa and radish seeds (25 g). However, these treatments were unable to eliminate Salmonella in both seed types. No significant difference between the germination rates of treated alfalfa seeds and control seeds was found, and germination rates greater than 95% were obtained for the radish seeds. Although chlorine washing is commonly used for seed decontamination, chlorine washing at 200 and 20,000 ppm resulted in a reduction of pathogens by less than or equal to 3 log CFU/g. Therefore, these results suggested that gaseous acetic acid is more effective than chlorine washing in controlling pathogenic bacteria on sprout seeds.

A gaseous acetic acid treatment to disinfect fenugreek seeds and black pepper inoculated with pathogenic and spoilage bacteria

“…Previous studies have indicated the effectiveness of gaseous acetic acid to inactivate E. coli and Salmonella in alfalfa seeds (Medicago sativa L.) and radish seeds (Raphanus sativus L.) (Nei et al, 2011(Nei et al, , 2014. In addition, other research groups reported high bactericidal effects of gaseous acetic acid on Salmonella and E. coli O157:H7 inoculated on mung bean seeds (Delaquis et al, 1999).…”

“…Within individual rows, the values followed by different letters are significantly different (p < 0.05). by Delaquis et al (1999) and Nei et al (2011). Delaquis et al (1999) reported that 5.0e6.0 log reduction of E. coli O157:H7 and Salmonella inoculated on mung bean seeds was obtained by the gaseous acetic acid at 242 mL/L for 12 h at 45 C. Nei et al (2011) also indicated the more than 5.0 log CFU/g reduction of E. coli O157:H7 and Salmonella inoculated on alfalfa and radish seeds after the treatment with 8.7% of gaseous acetic acid for 3e48 h at 55 C. On the other hand, Weissinger et al (2001) showed that the population of Salmonella was reduced from approximately 3.6 log CFU/g to 2.1 log CFU/g by the treatment at 50 C with 100e300 mg/L of gaseous acetic acid for 6 h. The lower reduction than that of the present study might be due to experimental conditions such as inoculation level, test strains and fumigation device.…”

“…Sholberg and Guance (1995) studied the effect of gaseous acetic acid on bacteria for several types of fruits. Nei et al (2011) reported the effectiveness of the gaseous acetic acid to inactivate E. coli O157:H7 and Salmonella inoculated on alfalfa seeds and radish seeds. Weissinger et al (2001) also reported decreases in Salmonella population on mung bean seeds (Vigna radiata) by gaseous acetic acid without affecting germination percentage.…”

Antibacterial effect of sprouts against human pathogens in vitro

“…Many researchers have published the methods how sprouts could be decontaminated and secure to eat (BAri et al, 2008(BAri et al, , 2009WAje et al, 2009;Nei et al, 2011).…”

Current Intervention Strategies for the Microbial Safety of Sprouts

“…Treatment of alfalfa and radish seeds with 8.7% acetic acid in the gaseous phase at 55°C for 3 h resulted in greater than 5-log reductions of E. coli 0157:H7 and Salmonella, with 96 to 98% germination (119). Malic acid is a low-cost, effective organic acid antimicrobial.…”