FOOD. Science. Technology. Quality

Food. SCIENCE. Technology. Quality

Food. Science. TECHNOLOGY. Quality

Food. Science. Technology. QUALITY




Effect of selected factors on water activity and microbiological quality of ewe’s milk soft cheeses


The materials investigated constituted an ewe’s milk and soft rennet cheeses. In the milk, the following contents were determined: total solids; fat; total nitrogen compounds; as were the titratable acidity; pH; and density. The milk was divided in two portions; one portion was pasteurised at 72 °C, and the second portion was not pasteurised. Rennet was added to the two milk portions (rate 1:1000). The curd produced was cut into cubes and cheeses were moulded. 24 hours later, one cheese made from pasteurized milk and one cheese from non-pasteurised milk were placed in 16 % brine for 1 hour. The remaining cheeses (one from raw and one from pasteurised milk) were scalded in water at 70 °C for 3 minutes. Fresh cheeses, raw and pasteurised, were assessed in order to determine: total solids; pH; water activity, texture profile/ Microbiological analyses were also performed in order to determine the total count of micro-organisms, coliform count, acidifying bacteria count, and yeast and mould. After storing the cheeses for 14 days at 4 ºC, once more the same parameters were determined, i.e.: content of total solids, water activity, pH, texture parameters; microbiological analyses were performed, too. The results obtained were statistically analysed and elaborated. It was found that the pasteurisation caused all the examined parameters in cheeses to decrease; statistically significant was the decrease of pH, cohesiveness, chewiness, and counts of micro-organisms (total count, coliform, and moulds). The brining process significantly reduced water activity in cheeses. The microbial count (total, coliforms, and moulds) was also reduced, but not statistically significantly. The scalding process significantly increased the content of total solids and the values of texture parameters: hardness, cohesiveness, springiness, and chewiness. Correlation coefficients between water activity and other examined cheese parameters varied depending on the experimental factor applied.


ewe’s milk, cheeses, pasteurization, brining, scalding, water activity, microbiological quality