EFFECT OF MILK FAT CONTENT ON THE GROWTH AND ACTIVITY OF STARTER CULTURES AND QUALITY OF YOGHURT

Effect of milk fat content on the growth and activity of starter cultures during fermentation of yoghurt was studied. Sensory assessment and syneresis of yoghurt samples were also determined. In this study pH, acidity, count of starter bacteria (Streptococcus thermopiles and Lactobacillus bulgaricus) during fermentation and syneresis percentage and sensory attributes of final product were measured. Experiments were done in three replications and analysed in two factorial completely block designe. Statistical analysis showed that increase of milk fat content from 1% to 4%, increased pH of product from 4.01 to 4.44 and decreased acidity from 0.8 to 0.66. Increasing of fat percentage from 1% to 4% excited the growth of Streptococcus thermopiles and number of these bacteria increased from 226x10⁶ cfu/ml to 395x10⁶ cfu/ml but had no effect on the growth of Lactobacillus bulgaricus.
Increasing fat from 1% to 4%, not only decreased syneresis from 36% to 27%, but sensory acceptability of the final product was also decreased.