Effect of temperature changes on pathogenic microbial population during Lighvan cheese ripening

Cheese ripening is a slow and gradual process and therefore it is costly and expensive. Enhancingripening temperature is the most efficient and cheapest method to shorten ripening period and reducemanufacturing expenses. However, the growth of harmful microorganisms is accelerated with increasing temperature. The aim of this research was to investigate the effect of enhancing temperature in order to accelerate ripening on pathogenic microbial population changes during 120-day ripening period of Lighvan cheese. The experimental cheese samples were stored at 4 temperatures including 9°C, 13°C, 15°C and 19°C during ripening period and analysed for enumeration of total bacteria, coliforms, yeasts and molds and presence of Staphylococcus aureus and E.coli. Microbial population increased in cheese samples with increasing ripening temperatures. Temperature effect was significant (P<0.05) on total and coliform counts in all sampling days and the cheeses stored at temperature of 19°C had significantly higher bacterial counts (P<0.05). Presenceof E. coli was confirmed in samples ripened at 19°C on days 30, 60 and 90 and in other temperatures on days 30 and 60. In all samples Staphylococcus aureus was negative. No significant difference was observed between treatments in mold and yeast count. In all treatments, bacterial count had decreasing trend during ripening. On the basis of results of this research, enhancing temperature to accelerate ripening should be done cautiously while considering sanitary standards. Maximum temperature for accelerated ripening should not be exceeded of 15°C.