Influence of processing parameters on the techno-functional properties of berry coagulants

Introduction. The aim of the research is to determine the influence of the parameters of hydrothermal treatment and rubbing of berry raw materials on the content of soluble pectins in berry purees. Attention is paid to the compliance of the purees with the requirements for berry coagulants, which can be used to obtain milk-protein co-precipitates from the buttermilk. Materials and methods. Fresh cranberries and viburnum berries were chosen as the subjects of study. The treatment of the berries with acute vapor was made with the help of the electric steam-convection oven of the injector type at a temperature of 105-107 degrees. during 5-60 seconds. The berries rubbing was made with the help of a crushing-rubbing machine using sieves with hole diameters of 0.4-1.2 mm. Results and discussion. The content of pectin substances in both berry purees increases in direct proportion to the extension of hydrothermal treatment from 5 s to 60 s. The viburnum puree is characterized by the slower increase in the amount of pectin substances comparing to the cranberry puree, which can be explaned by the difference in the structure of protopectin molecules. The losses of vitamin C for both berry purees are relatively low in the first 15 s of treatment, while then they are increasing rapidly due to the acceleration of hydroxyl bonds breaking in the ascorbic acid structure. Processing berry raw materials with an acute vapor is considered rational at a temperature of 105-107 degrees. for 15-30 seconds for cranberries and 5-15 seconds for viburnum berries, which corresponds to an increase in the amount of pectin substances on 19-22% and 11-19% in cranberry and viburnum purees respectively. The largest outcome of cranberry puree was achieved using a sieve with a holes diameter of 0,8-1,2 mm, whereas for the production of viburnum puree it is rational to use a sieve with a holes diameter of 0.6-0.8 mm. The need to use sieves with larger holes to increase the yield of cranberry puree can be explaned by the more pronounced susceptibility of the coarse viburnum fibre towards mechanical stress compared to the finer cranberry fibre with regard to particle size reduction. The chemical composition of obtained purees comparing to the berry raw materials is characterized by an increase in the content of pectin substances by 20 and 21%, and a decrease in the content of vitamin C by 30 and 29 for cranberry and viburnum purees, respectively. The obtained coagulants are characterized by an organic acid content of 2.0 and 1.7% for cranberry and viburnum purees, respectively. Conclusions. The significant increase in the content of soluble pectins and the presence of organic acids allow to use the obtained berry purees as coagulants in the technology of milk-protein co-precipitates from the buttermilk.