Dynamics of 17β-estradiol under influence of technological operations during production of dairy products

Safety of milk can decline because of high concentrations of steroid hormones like 17β-estradiol, which is associated with the development of some oncological diseases and reproductive disorders. We studied the effects of thermal processing of raw milk and technologies of production of butter and yogurt on the concentration of 17β-estradiol. For this purpose, we determined the amount of 17β-estradiol in raw milk, after pasteurization under different regimes, boiling and during the production of butter and yogurt. Content of 17β-estradiol was determined using the method of immunoenzymatic analysis. We determined that low-temperature processing of milk at the temperature of 77.0 ± 1.0 °С for 1 min caused no changes in the structure of the estrogenic hormone 17β-estradiol, resulting in practically no changes in its amount in pasteurized milk. We determined that 17β-estradiol in milk is a temperature-stable hormone with no tendencies towards significant decrease when subject to high-temperature processing (85.0 ± 1.0 °С for 1 min) and during boiling, because the amount of the hormone decreased on average by 5%. Therefore, we may state that after pasteurization or sterilization, the concentration of 17β-estradiol in drinkable milk would not be significantly different from its initial amount in raw milk. We determined significant increase in 17β-estradiol in butter (3896.1 ± 67.5 pg/g), as compared with the concentration in raw milk (189.4 ± 12.5 pg/mL), and its insignificant content in buttermilk was insignificant (29.3 ± 1.8 pg/mL). The concentration of 17β-estradiol in milk decreased by 25% during 9-month storage at the temperature of –18 °С and by 20% at the temperature of –9 °С. This process can be applied to butter made from milk of cows at late stages of lactation, which contains high level of estrogen. We determined that the steroid hormone 17β-estradiol did not break down under the influence of dairy acid that accumulates as a result of lactic acid fermentation, both with the participation of mixed microflora of raw milk and pure lactic-acid bacteria of fermentation starter for yogurt. The prospects of the studies are the development of a safe maximum allowable level of 17β-estradiol in raw milk and methodological evaluation at a milk-processing factory.