ABSTRACT
Microorganisms play signifi cant role in the development of well-balanced aroma/fl avor and texture in cheese and therefore give cheese a dynamic nature. Cheese contains a complex microfl ora including bacteria, yeasts and molds. Cheese microfl ora is divided into two basic groups namely starter cultures and secondary fl ora (Cogan 2002). Both groups basically contribute to the formation of desired aroma/fl avor and textural characteristics in cheese. Cheese starters ferment milk sugar (lactose) to yield lactic acid and other organic acids which reduce the milk pH (Beresford 2003). Lactococcus lactis, Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus delbrueckii are the most common lactic acid bacteria used in the manufacture of cheese. At the early stages of ripening, the counts of starter lactococci are around 106-1010 cfu g-1. However, these fi gures decline rapidly within the fi rst weeks of ripening at 2-16°C. Among the factors affecting the counts of starter lactococci are salt level of cheese, low pH, insuffi cient level of fermentable carbohydrate and low ripening temperature. Autolytic properties of starter bacteria, salt tolerance and resistance against phage attacks determine the level of decrease in the counts of starter bacteria.
