DEVELOPMENT OF A METHOD FOR DETERMINING THE ACIDITY OF DAIRY PRODUCTS BY FREEZING POINT

One of the most important safety indicators of milk and its processed products is acidity, which determines the freshness and shelf life of the products. At the same time, increasing the accuracy and speed of acidity measurement is currently limited by the capabilities of the titrimetric method and pH-metry. In this regard, the task was set to search for alternative measurement methods. A cryoscopic method was tested as such a method - determining the freezing point of a liquid product. Laboratory-prepared curdled milk from normalized cow's milk with a fat content of 2.5% was chosen as the object of study. For four prepared samples of curdled milk, titratable acidity (TA) was measured using an automatic titrator and freezing point (FP) was measured using a cryoscope-milliosmometer during fermentation - from fresh milk to finished curdled milk. The data obtained made it possible to establish a linear relationship between these physical quantities of the form: TA = (- FP - 0.4701) / 0.0023 at R2 = 0.9879. The method enables a reliable express assessment of the acidity of a dairy product: the accuracy of temperature measurement is better than 0.1% (a temperature of 0.5°C is measured with an accuracy of 0.001°C), while the error of pH meters is, as a rule, 1%, and the titrimetric method gives results with a tolerance of ±1°T. The data obtained make it possible to recommend the use of the cryoscopic method in laboratory practice in the dairy industry.

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