DETERMINATION OF THE PATTERNS OF CHANGES IN WATER ACTIVITY AND MOISTURE-BINDING CAPACITY OF PLANT SUBSTRATES IN THE PROCESS OF LACTIC ACID FERMENTATION

Abstract

The study investigates the patterns of changes in water activity and water-binding capacity of plant substrates during lactic acid fermentation to substantiate their technological use as functional ingredients in food products. The relevance of the study is due to the need for a deeper understanding of the transformation of the state of water in plant raw materials under the influence of biotechnological processes that determine their structural, mechanical, and moisture-retaining properties.
The objects of the study were plant substrates of different biochemical nature: spelt, flaxseed, Laminaria, and oyster mushroom fruiting bodies. Fermentation was carried out using a Lactiplantibacillus plantarum culture under controlled conditions for 24 hours with periodic sampling. Water activity was determined by a hygrometric method, while water-binding capacity was assessed using a pressing method.
It was established that during lactic acid fermentation, a gradual decrease in water activity occurs in all studied substrates, indicating a redistribution of the water phase and a reduction in the proportion of free water. The most pronounced decrease was observed in the flaxseed substrate, which can be explained by the high hydrophilicity of its mucilage polysaccharides. At the same time, changes in spelt and oyster mushroom substrates were less intensive.
It was proven that the water-binding capacity of all substrates increases during fermentation; however, the intensity of this process significantly depends on their chemical composition. The highest increase was observed for flaxseed (up to 120%), a substantial increase for Laminaria (75.4%), while changes in spelt and oyster mushroom were moderate. The obtained dependencies are nonlinear and are well described by polynomial models (R² > 0.99).