Abstract:
The inhibitory effect of chitosan on the growth of Saccharomyces cerevisiae in the laboratory liquid medium, Potato Dextrose Broth, was investigated at pH 4.5 and 3.5 and at the temperatures of 30 and 4?C, respectively. At 30?C, the growth curves were observed for S. cerevisiae grown in PDB at both pH values. However, longer lag time, slower growth rate and lower maximum cell numbers were found for the growth at pH 3.5. The growth curves were changed to survival curve when chitosan was added to the media. At pH 4.5, the yeast numbers were reduced by 3.43 and 5.07 log10 reduction after 72 h of exposure to 1 and 2 g/l of chitosan. 5.98 log10 reduction and no growth were found for the media containing 1 and 2 g/l of chitosan when the pH was reduced to 3.5. The effect of storage temperature was investigated at 4?C for 17 days. Slow growth was exhibited at the pH 4.5 and slow reduction in cell numbers was found at pH 3.5 (0.54 log10). Adding 1 and 2 g/l of chitosan caused a significant reduction in cell numbers to 1.72 and 3.73 log10 for pH 4.5 and 4.21 and 5.49 log10 for pH 3.5, respectively. This finding illustrated that chitosan may be used as a preservative in combination of temperature and low pH in order to extend the shelf life of specific food products.