Effectiveness of chlorine, organic acids and UV treatments in reducing Escherichia coli O157:H7 and Yersinia enterocolitica on apples.

This study assessed the effectiveness of 200 and 500 ppm of chlorine and organic acids (0.5% lactic acid and 0.5% citric acid) in wash solutions, and UV radiation for reducing Escherichia coli O157:H7 and Yersinia enterocolitica on apples contaminated by two different methods. Residual levels of these pathogens after different treatments were compared. On dip inoculated apples, Y. enterocolitica reductions of 2.66 and 2.77 logs were obtained with 200 and 500 ppm chlorine combined with 0.5% lactic acid, respectively. The E. coli O157:H7 population decreased 3.35 log with 0.5% lactic acid wash solution, and 2.72 and 2.62 logs after 500 ppm chlorine and 500 ppm chlorine plus 0.5% lactic acid treatments, respectively. Similar reductions were obtained with UV radiation. On spot inoculated apples, significant (p < 0.05) decreases of 4.67 and 4.58 logs were observed in E. coli O157:H7 and Y. enterocolitica levels, respectively, after 500 ppm chlorine plus 0.5% lactic acid treatment as compared with the control. In sectioned apples, microorganisms infiltrated in inner core region and pulp were not significantly (p < 0.05) affected by disinfection treatments. No pathogens were detected in the natural microflora on apples. Reductions such as those obtained with 500 ppm chlorine plus 0.5% lactic acid solution were very proximal to the 5-log score required by FDA for apple disinfection.

Effect of chlorine, sodium chloride, trisodium phosphate, and ultraviolet radiation on the reduction of Yersinia enterocolitica and mesophilic aerobic bacteria from eggshell surface.

Eggshell sanitizing practices are necessary to improve microbiological safety of fresh hen eggs and their products. In this work, the effects of 100 mg/liter free chlorine (chl), 3% sodium chloride (NaCl), 1, 5, and 12% trisodium phosphate (TSP) in wash solutions, and UVR (ultraviolet radiation; 4.573 microW/cm2) were studied at different times on uninoculated and Yersinia enterocolitica-inoculated eggs. On uninoculated eggs, the best results were obtained with 100 mg/liter chlorine and UV exposure for >25 min, with reductions of 1.28 and 1.60 log cycles, respectively, compared to the average bacterial count (4.55 log CFU/egg) on the control (untreated eggs). On Y. enterocolitica-inoculated eggs, highest reductions of the average bacterial count (7.35 log CFU/egg) were obtained with 5 and 12% TSP and 100 mg/liter chl. The decrease obtained with 12% TSP (3.74-log reduction) was significantly higher (P < 0.05) than those obtained with the remaining treatments. Y. enterocolitica was more resistant to UVR than the eggshell natural mesophilic aerobic microflora, except when low inoculum (4.39 log CFU/egg) was assayed. Changes in eggshell microstructure were measured by the blue lake staining method. The presence of Yersinia and Salmonella in eggshell natural flora was also investigated.

Atividade fotoprotetora do alcalóide boldina em culturas de enterobactérias / Photoprotective activity of boldine alkaloid in enterobacteria cultures

A boldina é um alcalóide aporfina geralmente encontrado nas plantas das famílilas Magnoliaceae, Annonaceae, Rhamnaceae e Monimiaceae. No presente trabalho foi proposta a realizaçäo de alguns ensaios com o objetivo de avaliar a açäo protetora da boldina em culturas de Yersinia enterocolitica e Escherichia coli HB 101 submetidas a açäo fotoprotetora desse alcalóide somente quando as células foram mantidas em condiçöes de liquid holding.