Abstract
Today increasing population has led to higher demands for healthy processed foods, and yogurt is considered as one of the fermented dairy products with high demand. Therefore, studying microbial contamination of such products seems to be very important. In this study, 18 samples of yoghurt were collected from market of Iran, and the samples were evaluated in terms of yeast, mold and phage contamination. Also, natamycin was measured as a common preservative used in dairy products. Yeast and mold were counted using yeast extract-dextrose chloramphenicol agar media after incubation the plates at 25 °C for 3 days. Phage experiments were carried out using inhibition test and plaque assay. Also measurement of natamycin was done using high performance liquid chromatography by c18 column and UV detector. All experiments were carried out in triplicate benefiting from ANOVA method. Results of the current study showed that, just 2 yogurt samples had significant yeast and mold contamination. However, other samples contained microbial load had no significant difference with each other. Phage experiment showed that, just 1 sample of yogurt had significant phage contamination (P < 0.05). Results of natamycin measurements showed that 88 % of samples contained natamycin preservative in different amounts. It was concluded that mold, yeast and phage contaminations were very low in Iranian yogurt samples. However, use of natamycin preservative in high dosage is common as found in yogurt samples collected from the market of Iran.
Published Version
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