Abstract
The article reveals the data on lead and cadmium content in raw milk samples taken in seven areas located in two districts of Semey Territory of East Kazakhstan Region (Abay and Ayagoz Districts). The authors determined high content of lead (from 0.11 to 0.15 mg/l) in milk samples taken in the populated areas which are located closer to the territory of the former Semipalatinsk Nuclear Test Site. To reduce the content of toxic elements in raw milk the authors developed an experimental filtration unit using natural zeolite brought from Tarbagataysky deposit (East Kazakhstan Region) as sorption-filtering material. Natural zeolite module SiO2/Al2O3 consists of 6.3 units which characterizes it as a high-purity clinoptilolite, highly efficient sorption ion-exchange material. As a result of the experiments the authors determined that natural zeolite taken from Tarbagataysky deposit of East Kazakhstan Region shows sorption properties in relation to lead and cadmium ions. Zeolite application as a sorption-filtering material helps reduce cadmium and lead ion content in milk during filtration. The most suitable processing parameters of milk filtration which help change the content of the considered elements significantly are the following: filtration temperature should be 18–20°C, pump rotation frequency – 300 rpm with filter of the experimental unit which consists of 200 g of natural zeolite. Besides, the authors studied the changes in organoleptic, physical and chemical properties of milk during filtration. The authors determined that organoleptic, physical and chemical properties during milk filtration using natural zeolite as a sorption-filtering material do not change and comply with the regulatory requirements which specify fresh milk quality parameters. Titratable acidity of milk reduces insufficiently.