Introduction. The feasibility of using fermented concentrates of reсonstitutd demineralized sweet whey as a source of whey proteins and monosaccharides in ice cream was proved. Materials and methods. Physicochemical parameters of reconstituted fermented and unfermented concentrates of demineralized sweet whey with dry matter content from 10 to 40% were studied. The lactose content was determined by the accelerated colorimetric method, water activity – on the water activity analyzer. Results and discussion. Rational regimes of enzymatic hydrolysis of lactose in concentrates of reconstituted demineralized sweet whey with dry matter content from 10 to 40% are temperature of 40–43 °C and a pH of 6.1–6.6, the recommended dose of liquid enzyme preparation GODO-YNL2, obtained from the yeast Kluyveromyces lactis, for concentrates with a lactose content of 7.5–30.0% ranges from 0.1 to 0.4%. The duration of enzymatic hydrolysis under these conditions for 4±2 h ensures the degree of lactose hydrolysis not less than 70%. In order to increase the degree of lactose hydrolysis simultaneously with the enzyme preparation in certain quantities single-strain lyophilized probiotic culture «L. acidophilus LYO 50 DCU-S» was used. During the first 4 hours of incubation, the active acidity of the whey concentrates samples reaches values not lower than pH=5.7– 5.9. At the specified acidity, the enzyme preparation GODO-YNL2 shows sufficient activity. The presence of lactose hydrolysis products to some extent stimulates the development of L. acidophilus. Due to the joint hydrolyzing action of enzyme and starter culture preparations for 6–8 hours, the degree of lactose hydrolysis can be achieved at the level of 80–85%. The prospect of further research is the development of scientifically sound ice cream formulations based on hydrolyzed concentrates of reconstituted fermented whey. Ice cream enriched with whey proteins and probiotic culture of L. acidophilus will also have a lower content of disaccharides – sucrose and lactose. Conclusions. The possibility of increasing the efficiency of lactose enzymolysis in concentrates of reconstituted demineralized whey to 80–85% by combining the specific action of the enzyme preparation GODO-YNL2 and starter based on L. acidophilus has been proved. The product of enzymolysis is of technological interest as a multifunctional ingredient in ice cream.