Influence of salt concentration on survival of listeria monocytogenes during Domiati cheese ripening

ABSTRACT

Domiati cheese was made from a pasturized mixture of cowbuffalo milk [11], which was inoculated with Listeria monocytogenes and with different ratio of sodium chloride 6 and 9 and 12%. Aportion of the cheese was held in a refrigerator [5-7°] while another portion was held at room temperature [20-22°]. Pickled cheese was analysed microbiologically [aerobic bacterial count, lactic acid bacteria count and numbers of L. monocytogenes], as well as chemically for moisture, total acidity, sald content, soluble nitrogen/total nitrogen and formol ripening index] were done every 15 days for a period of 3 months. Results obtained showed that numbers of total bacteria, lactic acid bacteria, and L. monocytogenes increased in pickled cheese stored at room temperature to a greater extent than in cheese held at 5?7° for all different levels of salt concentration. During holding of cheese, the numbers of L. monocytogenes decreased gradually throughout the entire period of storage. A decrease in the population of L. monocytogenes was correlated with an increased in titratable acidity and also with an increase in salt concentration in cheese milk