Color, microbiological and sensory properties of low–fat probiotic yogurt supplemented with Spirulina platensis and Ferulago angulata hydroalcoholic extracts during cold storage

The aim of this study was to investigate the effects of Ferulago angulata and Spirulina platensis extract at 0.1 to 1% (v/v) on the color parameters, survivability of starter cultures and Lactobacillus acidophilus and sensory characteristics in low–fat yogurt during 1, 7, 14 and 21 d. The results showed that by increasing the extract concentration, average values of b* and light intensity (L*) was declined and control, showed the highest lightness during storage. Treatments containing F. angulata extract had a higher a* and b* values and color intensity (C*) in compartion with S. platensis extract. The mean values of total color difference (∆E*) at the first week and last two weeks were higher in the treatments containing S. platensis and F. angulata, respectively. The mean L. bulgaricus count more than St. thermophilus and the mean count of starter cultures in the treatments containing S. platensis extract was significantly higher than F. angulata extract. However, the survivability of starter cultures and L. acidophilus at the end of the refrigerated storage was more than standardized number of bacteria (107–108cfu/ml) in yogurt. The color, flavor, consistency and overall acceptability scores of treatments containing S. platensis extract were significantly higher than the F. angulata extract. Therefore, these additives could be used successfully without having detrimental effects on bio–yogurt.