Effective acidification of traditional fermented foods.

Abstract

This study was carried out to investigate the survival rates of strains of enteropathogenic Escherichia coli in lactic and acetic acids and to compare them with their survival rates in sour porridge. The fermented and unfermented porridges were prepared in the laboratory. The fermented porridge had both lactic and acetic acids; unfermented porridge was adjusted to the pH of sour porridge with lactic and acetic acids. The sour porridge, the unfermented porridge adjusted to the pH of sour porridge with lactic and acetic acids and the unfermented porridge were inoculated with six strains of enteropathogenic E. coli. The inoculated porridges had a final concentration of 10(6)-10(7) colony-forming units (c.f.u.) per ml of food. Few of the strains of enteropathogenic E. coli were detected 48 hours after inoculation in sour porridge. All the strains were detected 48 hours after inoculation in unfermented porridges adjusted to the pH of sour porridge with lactic and acetic acids but decreased in numbers of surviving cells by about 2 log10 c.f.u. per ml of food. All the strains survived in unfermented porridge for 48 hours and increased in numbers. These results show that lactic and acetic acids have antimicrobial properties but they are not as effective as sour porridge in inhibiting the growth and survival of enteropathogenic E. coli. The inhibitory property of sour porridge is due to a combination of many substances including lactic and acetic acids.