Milk raw materials from retrovirus infected cows: questions of safety and quality of produced products

Abstract

The questions of quality control and safety of milk raw materials has always been relevant for the dairy industry. One of the most common cattle infection is bovine leukemia (causative agent - BLV), which often occurs in conjunction with a closely related infection -bovine immunodeficiency (causative agent - BIV). These retroviruses are considered to be species-specific, so the key issue for the dairy industry is the nutritional and raw value of milk of infected cows (without clinical signs). Milk of infected with leukemia cows has changed physical and chemical properties and microbiological parameters, but it is allowed to be processed after a single pasteurization. Thus, there is a possibility of getting of the infected with retroviruses cow's milk into the bulk milk, which can affect the quality of the processed products. Characteristics of BlV-positive cow's milk have not yet been studied. The aim of the research was the study of influence of BLV- and BLV- BIV-infected cows' milk impurities (10, 30 и 50%) on organoleptic, physicochemical and microbiological parameters of produced kefir drink. It is revealed that with increasing the mass fraction of infected with retroviruses cows' milk, acidity of composite samples increased of 1-3 °T and total viable bacteria's count rose by 1-3 orders of magnitude, while the total protein in milk decreased by 0.05-0.95% contrasted with an increasing of milk fat content by 0.3-0.9%. However, these characteristics were within normal limits. In samples containing 50% of milk infected with retroviruses cows, coliforms were detected in 0.1 ml, and the rate of total viable bacteria's count exceeded the permissible limits. Therefore, microbiological characteristics are determination markers of dairy raw materials with the high content of milk of the infected with retroviruses cows. The kefir drink was produced from pasteurized samples. It was found that the acidity of the product was lower by 1-10 °T, while the processing time increased by 4-50%, correlating with the mass fraction of infected with retroviruses cows' milk, compared to control. When the mass fraction of infected with retroviruses cows' milk was 30 and 50%, the processed product had a heterogeneous consistency with flake clots. At the same time, the lactic-acid-producing bacterium count in kefir drink decreased by 2-3 orders, and mold and coliforms were found in it. Thus, the presence more than 10% of milk from infected with retroviruses cows in raw materials leads to a decrease in its technological properties, and dose 30 and 50% leads to non-compliance of the processed product with hygienic standards.