Fermentation of skimmed milk in the presence of arabinogalactan

The object of the study are samples of the fermented milk product manufactured from skimmed milk. Arabinogalactan has been added to the test samples as a dry powder. The control samples have been prepared without arabinogalactan. Both control and test samples have been fermented with Streptococcus salivarius thermophilus (StST) starter in the amount of 3% of the total sample volume in the laboratory environment. The fermentation process has been occurring at 35°C for 12 hours. Active acidity, titratable acidity, effective viscosity, syneretic capacity, organoleptic parameters, and the lactic acid germ count have been determined in the samples. Arabinogalactan has imparted a cream-coloured tint and a vegetable taste to the skimmed milk, which has not worsen the overall organoleptic perception. After fermentation, there has been a tendency to increasing the pH value and decreasing the titratable acidity, correlating with the mass fraction of arabinogalactan in the milk-vegetable systems. After fermentation, the number of viable StST cells in both control and test samples has been 1*108 CFU/cm3. Consequently, there has been no inhibition of StST development in the test samples and the starter microorganisms has adapted to the milk-vegetable mixture. The analysis of the experimental data on viscosity and syneresis has revealed a relationship between these parameters and the mass fraction of arabinogalactan. The most stable food system has been represented by the samples with the introduction of 5.0% dietary fiber by weight into the milk base.