Abstract

ROJAS, T  and  CASTILLO, Z. Survival of strain of escherichia coli o157:h7 in unpasteurized orange juice commercially expended. Rev. Soc. Ven. Microbiol. [online]. 2003, vol.23, n.1, pp.16-20. ISSN 1315-2556.

    In this study the survival of strain of Escherichia coli O157:H7 was evaluated in unpasteurized orange juices commercially expended. The samples were prepared being adjusted their pH at three levels: 3,0; 3,5 and 4,0. An inocula of strain (10⁵ CFU/ml) was prepared and inoculated in the samples to the different pH, being stored at 5 and 10°C. The number of viable cells was determined by surface plating, during four serial days to the inoculation. In levels non detectable of the microorganism by surface plating was used a pre-enrichment technique and detection by ELISA. The results reveal significant differences (p<0,05) in the survival of the microorganism among the utilized storage temperatures, being obtained recounts bigger than viable cells to 5°C. The survival of the microorganism to the different pH treatments, presented differences statistically significant (p<0,05) as much to 5 as to 10°C. To pH 3,0 and 3,5, the population decreases in 4 logarithmic cycles, while to pH 4,0 the reduction was of 2,5 cycles, as much to 5°C as to 10°C. The data indicate that the survival of the microorganism was observed until for 8 days post-inocula, and in the first 4 days the levels of viable cells are in the order from 10² to 10⁴ CFU/ml of juice.

Keywords : Escherichia coli O157:H7; jugo de naranja; supervivencia.