Combination Treatments for Killing Escherichia coli O157:H7 on Alfalfa, Radish, Broccoli, and Mung Bean Seeds

Abstract

In this study, the effectiveness of prolonged dry-heat treatment (50 degrees C) alone or in combination with chemical treatments (1% oxalic acid, 0.03% phytic acid, 50% ethanol, electrolyzed acidic water, and electrolyzed alkaline water) in eliminating Escherichia coli O157:H7 on laboratory-inoculated alfalfa, radish, broccoli, and mung bean seeds was compared with that of dry-heat treatment in combination with irradiation treatment. Dry-heat treatment for 17 or 24 h alone could reduce E. coli O157:H7 numbers to below detectable levels in radish, broccoli, and alfalfa seeds, but was unable to reduce the pathogen numbers to below the detectable level in mung bean seeds. In addition, dry-heat treatment for 17 h plus sanitizer treatments were effective in greatly reducing pathogen populations on radish, broccoli, and alfalfa seeds, without compromising the quality of the sprouts, but these treatments did not eliminate the pathogen from radish and alfalfa seeds. Seventeen hours of dry heat followed by a 1.0-kGy dose of irradiation completely eliminated E. coli O157:H7 from radish and mung bean seeds, whereas only a minimum radiation dose of 0.25 kGy was required to completely eliminate the pathogen from broccoli and alfalfa seeds. Dry heat in combination with radiation doses of up to 1.0 kGy did not negatively impact the seed germination rate or length of alfalfa, broccoli, and radish seeds or the length of alfalfa, broccoli, and radish sprouts, but did decrease the length of mung bean sprouts.

Inactivation of Escherichia coli O157:H7 on Radish Seeds by Sequential Treatments with Chlorine Dioxide, Drying, and Dry Heat without Loss of Seed Viability

“…To achieve greater reductions in numbers of food-borne pathogens, sequential or simultaneous treatments with chlorine-based sanitizers, organic acids, heat, high pressure, and irradiation have been evaluated (6,13,17,21,23,31). Although most studies using multiple treatments have been shown to result in greater reductions in pathogens than those using a single treatment, with some exceptions (3,4), elimination of pathogens without decreasing the germination rate of seeds has been difficult. Bari et al (4) reported that E. coli O157:H7 was eliminated from alfalfa, mung bean, and radish seeds without decreasing the germination rate and yield by applying dry heat (50°C for 1 h) and irradiation (2.5 kGy).…”

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).…”

Evaluation of Aerated Steam Treatment of Alfalfa and Mung Bean Seeds To Eliminate High Levels of Escherichia coli O157:H7 and O178:H12, Salmonella enterica, and Listeria monocytogenes

“…The bacteria which can be present there (44) are not accessible to various chemical disinfectants such as, e.g., hypochlorite, since these disinfectants are not able to penetrate the seed coat (45)(46)(47). The extent to which aerated steam can be applied to eliminate bacterial loads not only on the outer seed surface but also in the inner parts of the seed needs to be studied in future work.…”