Reduction of Escherichia coli O157:H7 and Salmonella on laboratory-inoculated alfalfa seed with commercial citrus-related products
U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA. Journal of food protection
(Impact Factor: 1.85).
Alfalfa sprouts contaminated with the bacterial pathogens Escherichia coli O157:H7 and Salmonella have been the source of numerous outbreaks of foodborne illness in the United States and in other countries. The seed used for sprouting appears to be the primary source of these pathogens. The aim of this study was to determine whether the efficacy of commercial citrus-related products for sanitizing sprouting seed is similar to that of high levels of chlorine. Five products (Citrex, Pangermex, Citricidal, Citrobio, and Environné) were tested at concentrations of up to 20,000 ppm in sterile tap water and compared with buffered chlorine (at 16,000 ppm). Alfalfa seeds were inoculated with four-strain cocktails of Salmonella and E. coli O157:H7 to give final initial concentrations of ca. 9.0 and 7.0 CFU/g, respectively. Treatments (10 min) with Citrex, Pangermex, and Citricidal at 20,000 ppm and chlorine at 16,000 ppm produced similar log reductions for alfalfa seed inoculated with four-strain cocktails of E. coli O157:H7 and Salmonella (3.42 to 3.46 log CFU/g and 3.56 to 3.74 log CFU/g, respectively), and all four treatments were significantly (P<0.05) more effective than the control treatment (a buffer wash). Citrobio at 20,000 ppm was as effective as the other three products and chlorine against Salmonella but not against E. coli O157:H7. Environné was not more effective (producing reductions of 2.2 to 2.9 log CFU/g) than the control treatment (which produced reductions of 2.1 to 2.3 log CFU/g) against either pathogen. None of the treatments reduced seed germination. In vitro assays, as well as transmission electron microscopy, confirmed the antibacterial nature of the products that were effective against the two pathogens and indicated that they were bactericidal. When used at 20,000 ppm, the effective citrus-related products may be viable alternatives to chlorine for the sanitization of sprouting seed pending regulatory approval.
Available from: Hao Feng
- "Effect of malic acid and TDS on E. coli on sprouts . . . explored include ozone (Sharma and others 2003,), calcinated calcium (Fransisca and others 2011), oxychloro complex (Kumar and others 2006), electrolyzed water (Kim and others 2003; Stan and Daeschel 2003; Kim and others 2006), and organic acids (Fett and Cooke 2003), among others. A number of physical treatments have also been investigated for seed and sprout decontamination, including hot water (Bari and others 2008), dry heat (Bari and others 2009a), heat-and-chill treatment (Bari and others 2009b), gamma irradiation (Thayer and others 2003a,2003b; Kim and others 2006), infrared radiation (Erdo˘ gdu and Ekiz 2011), power ultrasound (Scouten and Beuchat 2002; Kim and others 2006), and ultraviolet light (Sharma and Demirci 2006). "
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ABSTRACT: It has been reported that washing seeds with a 20000 ppm Ca(OCl)2 solution as recommended by the U.S. Food and Drug Administration is unable to eliminate E. coli cells attached to seed surfaces, and the bacterial cells that have survived a sanitation wash can proliferate during sprouting to a high population. The objectives of this research were to examine the efficacy of malic acid (MA) and thiamine dilauryl sulfate (TDS) combined treatments on the inactivation of E. coli O157:H7 on alfalfa seeds, to study the growth of the remaining E. coli cells during sprouting, and to evaluate the sprout quality. When 10 g of inoculated alfalfa seeds were washed in a 10% MA-1% TDS solution, a complete elimination of E. coli was achieved. The same result was observed by washing the seeds in a 20000 ppm Ca(OCl)2 solution. However, when the seed size was increased to 50 g while maintaining the same seed-to-sanitizer ratio, both the MA + TDS and the 20000 ppm chlorine washes failed to completely inactivate the E. coli cells on the seeds. Nevertheless, the 10% MA-1% TDS solution was significantly more effective in E. coli count reduction compared to the 20000 ppm chlorine wash. The E. coli O157:H7 cells remaining on the seeds after treatments with both sanitizers grew up to 7 to 8 log CFU/g sprout after 96 h of sprouting. Under the treatment conditions used in this study, none of the treatments resulted in significant differences in germination rate, yield, or quality of the sprouts.
Practical Application: The malic acid (MA) and thiamine dilauryl sulfate (TDS) combined treatment may provide a new solution to secure the microbial safety of seeds and sprouts. An important finding of this study is that seed sample size has a significant impact on the inactivation of E. coli O157:H7 on alfalfa seeds. The microbial inactivation results obtained in a laboratory set-up cannot be directly applied to a large scale operation. A validation test on the large scale has to be performed to evaluate the efficacy of the sanitizer.
Available from: Cristina Martinez-Villaluenga
- "In this sense, several methods such as heat treatment (Jaquette et al., 1996; Weiss and Hammes, 2003), exposure to ionizing radiation (Thayer et al., 2006), chemical disinfectans (Beuchat et al., 2001; Proctor et al., 2001; Fett and Cooke, 2003; Sharma et al., 2002) and high hydrostatic pressure (Wuytack et al., 2003; Peñ as et al., 2008) have been described for reducing the microbial flora on seeds achieving P5 log reductions recommended by the National Advisory Committee on Microbial Criteria for Foods (NACMCF, 1999). However, studies have demonstrated that although seed decontamination can reduce the populations of human pathogens present, it cannot ensure the production of pathogen-free sprouts (Thomas et al., 2003 "
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ABSTRACT: Three cultivars of broccoli seeds (Brassica oleracea var. italica), cv. Tiburon, cv. Belstar and cv. Lucky, and two cultivars of radish seeds (Raphanus sativus), cv. Rebel and cv. Bolide, were germinated for three and five days and safety aspects such as microbiological counts and biogenic amines were investigated. Cytotoxicity evaluation was also carried out. Broccoli and radish sprouts contained numbers of mesophilic, psychrotrophic, total and faecal coliform bacteria which are the usual counts for minimally processed germinated seeds. Putrescine, cadaverine, histamine, tyramine, spermidine and spermine increased during sprout production although these levels were below those permitted by legislation (5 mg/100 g of edible food). Broccoli and radish sprouts demonstrated no toxic effects on proliferation and viability of HL-60 cells and should be included in our diets as healthy and safe fresh foods.
Available from: Hao Feng
- "(single chemical compound, and/or combination of several chemicals ) (Taormina and Beuchat 1999; Lang and others 2000; Weissinger and Beuchat 2000; Soylemez and others 2001; Beuchat and Scouten 2002), natural antimicrobials (Fett and Cooke 2003), ozone (Sharma and others 2003; Wade and others 2003), electrolyzed water (Kim and others 2003), ultraviolet light (Sharma and Demirci 2003), irradiation (Thayer and others 2003; Bari and others 2003a), high pressure processing (Wuytack and others 2003; Ariefdjohan and others 2004), and ultrasound (Scouten and Beuchat 2002). It has been recognized that it is difficult to achieve a complete elimination of pathogens without compromising the viability of the seeds using treatments with a single lethal factor (hurdle). "
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ABSTRACT: The ability of power ultrasound, acidic electrolyzed water (AEW), and gamma irradiation to inactivate Escherichia coli O157:H7 inoculated onto alfalfa and broccoli seeds was examined. The treatment conditions under which the alfalfa and broccoli seeds treated with sterile deionized water (SW), AEW, ultrasound cleaning tank (UST), ultrasound probe (USP), and irradiation (IR) would retain a germination percentage of >85% were first determined for each disinfection hurdle. E. coli O157:H7 inactivation tests were then conducted with the experimental conditions determined in the germination tests to find out the maximum inactivation ability of each disinfection hurdle. AEW treatment at 55 oC for 10 min reduced E. coli O157:H7 population by 3.4 and 3.3 log CFU/g for the alfalfa and broccoli seeds, respectively. IR at 8 kGy resulted in a 5-log reduction with seed germination of >85% for both seed types, but a reduction in the length and thickness of the sprouts was observed. None of the ultrasound treatments achieved over a 2-log reduction in E. coli O157:H7 population without lowering the germination to below 85%. The results of this study demonstrated that AEW and ultrasound, when applied individually or in combination with thermal treatment at 55 oC, were not able to deliver a satisfactory inactivation of E. coli O157:H7. A combination of several hurdles must be used to achieve a complete elimination of E. coli O157:H7 cells on alfalfa and broccoli seeds.
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