Investigation of the use of whey powder and buttermilk powder instead of skim milk powder in yogurt production.

The aim of this study was to determine some physical, chemical, microbiological and organoleptic properties of set-type yogurts made with six different skim milk powder (SMP), whey powder (WP) and buttermilk powder (BMP) during a 21-day period. Samples were taken from yogurts on day 1, 7, 14 and 21. Analyses were carried out on the total solids, fat, non-fat solids, protein, ash, viscosity, syneresis, pH, titratable acidity values. The counts of Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and yeasts-molds were enumerated. Also, sensory evaluations were performed at the same times. The substitution effect of WP and BMP for SMP on ash, viscosity, syneresis and titratable acidity values of yogurts were found to be significant (p < 0.05), while total solids, non-fat solids, protein contents, pH value and S. thermophilus, L. bulgaricus and yeasts-molds counts were not statistically significant. The effect of storage period on protein, ash, viscosity, and titratable acidity values, and L. bulgaricus and yeasts-mold counts was found to be significant (p < 0.05) statistically. However, it was observed that the changes of total solids, fat, non-fat solids, syneresis, pH values, and S. thermophilus counts were insignificant during the storage period. The sensory evaluations showed that sample D was most preferred by panelists.