Introduction: The enzymatic activity of lactic acid microorganisms (LAM) plays a decisive role in shaping the amino acid composition and functional properties of fermented dairy products. However, direct relationships between the enzymatic profile of individual strains and the antioxidant potential of the product remain insufficiently studied.

Purpose: To determine the effect of Lactobacillus acidophilus, Lactobacillus bulgaricus, and Streptococcus thermophilus strains on the amino acid profile and antioxidant properties of fermented dairy products.

Materials and methods: The study involved 12 LAM strains from the collection of VNIMI. Enzymatic activity was assessed using the API ZYM test system; amino acid composition was determined by capillary electrophoresis; glutathione content was measured by titrimetric analysis; antioxidant activity was evaluated amperometrically.

Results: L. acidophilus strains demonstrated the highest proteolytic activity, which was associated with an increased content of sulfur-containing amino acids (cystine, methionine) and higher antioxidant activity. L. bulgaricus exhibited moderate values, whereas S. thermophilus showed low antioxidant activity but ensured significant accumulation of glutamic acid, a precursor of glutathione.

Conclusion: A direct relationship between the amino acid profile and antioxidant potential of fermented dairy products and the enzymatic activity of LAM strains was established. The findings confirm the potential of specific strains for targeted enhancement of the functional properties of fermented dairy products and for the selection of starter cultures with predictable biotechnological potential.

Introduction: Postharvest storage of cherry fruits is accompanied by biochemical changes that can significantly reduce their nutritional and technological value. Although previous studies have examined the dynamics of major metabolites during the storage of fruit and berry crops, the varietal-specific variability of sugars, organic acids, and ascorbic acid content under the conditions of southern regions of Russia remains insufficiently explored.

Objective: To determine the optimal storage duration of varietal cherry fruits by monitoring their chemical composition, with subsequent differentiation according to intended use, processing, preservation, and consumption.

Materials and Methods: The study involved fruits of the common cherry varieties Alexa, Aphrodite, Kazachka, Krasnodarskaya Sladkaya, and Khutoryanka, grown during the 2024–2025 seasons. Storage was conducted at 0 °C. Fruits designated for 10-day storage were gradually transferred to higher temperatures from the 7th day, while those intended for 20-day storage underwent a temperature increase beginning on the 16th day. At the end of the storage period, the temperature reached 5 °C. The experimental samples were analyzed for soluble solids (GOST ISO 2173–2013), sugars (GOST 8756.13–87), titratable acidity (GOST ISO 750–2013), and ascorbic acid concentration (GOST 24556–89).

Results: The study demonstrated that the dynamics of the chemical composition of cherry fruits during storage are varietal-specific. The levels of sugars and titratable acids varied with storage duration, while ascorbic acid content declined. The sugar–acid index revealed distinct differences in taste profiles: Aphrodite was most suitable for fresh consumption, Krasnodarskaya Sladkaya for drying and baby food production, and Alexa for winemaking.

Conclusions: The findings confirmed that varietal-specific changes in the chemical composition of cherries during storage can serve as a criterion for technological differentiation. The practical significance lies in enabling the selection of optimal varieties for various processing and consumption purposes, based on sugar–acid balance and vitamin C content. These data provide a basis for developing varietal-specific storage recommendations and broaden current understanding of postharvest changes in cherries under the conditions of southern Russia

Introduction. The key factor determining the quality of cheeses is the balance of the starter microflora composition; the variability of the microorganism ratio can significantly affect the organoleptic profile of the product. An imbalance towards the predominance of leuconostocs over diacetyl lactococci can provoke defects: lack of a pattern, uncontrolled gas formation, taste defects. However, clear criteria for the optimal ratio of gas- and aroma-forming microorganisms have not yet been developed, which complicates the standardization of technological processes for the production of cheeses.

Objective. Establishing the influence of varying the ratio of Lc. lactis subsp. lactis biovar diacetylactis and Leuconostoc in the composition of a polyspecies starter culture on the formation of the organoleptic profile of semi-hard cheeses, and determining the zone of optimal concentrations that minimizes the risks of defects.

Materials and methods. The objects of the research were monospecific bacterial starters (Lc. lactis subsp. lactis, Lc. cremoris, Lc. lactis subsp. lactis biovar diacetylactis, Leuconostoc subsp.); Dutch cheese after pressing, during maturation and at the stage of conditioned maturity. The mass fraction of total and water-soluble protein was measured by the Kjeldahl method. The degree of proteolysis was estimated by the ratio of water-soluble protein to total protein. The molecular weight distribution of soluble nitrogen compounds in the aqueous extract was determined by gel filtration. The mass fraction of lactose, galactose, glucose and lactic acid was determined using a capillary electrophoresis system. The flavor profile of cheeses was determined by the content of volatile aroma-forming substances in the vapor phase of cheese of conditioned maturity.

Results. The use of Leuconostoc subsp. culture slows down the intensity of glycolysis at the production stage and proteolysis during the ripening process, and also reduces the total amount of volatile flavor and aroma substances and their diversity in cheeses of conditioned maturity, while increasing the amount of low-molecular peptides and amino acids in cheeses aged 60 days.

Conclusions. It has been established that when introducing Leuconostoc subsp. in the composition of the polyspecies bacterial concentrated starter culture more than 20.0%, there are risks of deterioration of organoleptic indicators such as insufficient expression of cheese taste and aroma, smearing consistency, the appearance of a nest-like pattern and small cracks up to 15 mm and, as a consequence, a decrease in the grade of cheeses based on the overall score. The obtained results can be used by biofactories for scientifically based design of multispecies bacterial concentrated starters for cheese making.