[Show abstract][Hide abstract] ABSTRACT: Minor shoot injury to glasshouse celery, Cos lettuce and chive plants significantly increased the persistence of applied Escherichia coli (P<0.05). After 1 week, mean counts of about 5 log(10) CFU/g decreased to fewer than 0.5 log(10) CFU/g on the uninjured plants, compared to 4 log(10) CFU/g or more on injured plants. By the end of the 3-week long experiments, counts from the uninjured plants were 0.21 log(10) CFU/g or fewer, but 2.8, 2.3 and 5.1 log(10) CFU/g on injured Cos lettuce, celery and chive plants, respectively. A field experiment using Cos lettuce also showed that shoot injury increased E. coli persistence. Counts from the injured plants on days 1, 3, and 7 were, 4.2, 4.1 and 3.3 log(10) CFU/g, respectively, whereas the uninjured plants returned significantly (P<0.05) lower counts on those days, and were 2.8, 2.0 and 1.2 log(10) CFU/g, respectively. These findings reveal that increased E. coli persistence on injured tissue is common to different vegetables and can occur in the glasshouse and the field. The implications of this study on vegetable production practices are presented.
International journal of food microbiology 02/2010; 138(3):232-7. DOI:10.1016/j.ijfoodmicro.2010.01.022 · 3.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The survival and growth of Salmonella salford, Escherichia coli and Listeriainnocua on the surface of fruit with inedible skins was investigated. Passionfruit, banana, cantaloupe (rock melon) and honeydew melon were inoculated by immersion in solutions containing two inoculum levels and then stored under normal storage and distribution temperature regimes. A low (ca. 103 cfu ml−1) and high (105–106 cfu ml−1) inoculum concentration was used for each organism. Bananas were stored for 13 days at 18 °C, passionfruit for 6 days at 10 °C, cantaloupes for 7 days at 8 °C and honeydew melons for 1 day at 12 °C then 5 days at 8 °C. Generally, the fruit did not support growth under the conditions employed, although test organisms could usually be recovered either directly or after an enrichment step. The exception was the growth of L. innocua on the skin of cantaloupe. Significant growth was observed for both the low and high inoculum levels during storage at 8 °C. Cantaloupes inoculated with 2.4×106 cfu ml−1 had an initial level of 3.4×103 cfu cm−2 and this increased to 2.9×105 cfu cm−2 during 7 days storage. For the low inoculum (1.3×103 cfu ml−1), levels that could only be detected by enrichment initially increased to 1.4×102 cfu cm−2.
[Show abstract][Hide abstract] ABSTRACT: The effectiveness of calcium hypochlorite on inactivation of Escherichia coli inoculated on fresh produce was investigated. Different exposure times and concentrations of chlorine were studied. Dipping was not effective at eliminating E. coli populations although it significantly reduced the E. coli counts compared with inoculated, undipped lettuce. Dipping inoculated cos lettuce leaves into hypochlorite solutions containing 50 mg/l or greater free chlorine for times of 30 s or greater reduced E. coli cells by approximately 1.9–2.8 log10 CFU/g from an initial population of approximately 6.8 log10 CFU/g. Dipping inoculated broccoli florets into hypochlorite solution reduced E. coli cells by approximately 1.7–2.5 log10 CFU/g, depending on the time and concentration of the free chlorine. Dipping lettuce or broccoli in water alone reduced cell numbers by 1.5–1.8 log10 CFU/g. Dipping broccoli florets for 2 min in a 100 mg/l free chlorine solution at temperatures between 4 and 25°C reduced E. coli cells by approximately 2.4 log10 CFU/g. No significant effect of temperature on the rate of cell reduction was observed.