The effect of adding olive leaves on starter culture and sensory properties of fermented Doogh

Doogh is considered a good carrier for the transfer of nutritious compounds, and also olive leaf is one of the nutritional requirements of experts, which can be used to enrich food products to improve human health and prevent or reduce disease. The effect of adding olive leaves before and after fermentation on pH, acidity, corrosive microorganisms, Lactobacillus bulgaricus, Streptococcus thermophilus, and sensory evaluation of the samples were evaluated. The enriched specimens were examined in the refrigerator during the 21-day storage time. The results showed that all samples enriched with different concentrations of olive leaves were acceptable and lower concentrations of treatments had more favorable sensory properties and at higher concentrations due to bitter taste and taste, the herb was diminished from sample acceptance. The number of L. bulgaricus colonies were significantly decreased during the maintenance period. The amount of this bacterium on the first day was the highest and did not have a significant effect on the Lactobacillus colonies by increasing the concentration of olive leaves. The survival of S. thermophilus in the enriched samples were not significantly different from that of the control sample and were not affected by the time and concentration of the olive leaves. Also, the addition of them in both the pre- and post-fermentation process did not have a significant effect in the number of L. bulgaricus and S. thermophilus colonies. The addition of olive leaf did not affect the viability and growth of starter microorganisms and was similar to the control sample. The microbial condition of the sample was examined for the presence of corrosive and pathogenic microorganisms during the storage of 21 days in a refrigerator. The addition of olive leaves before and after the process did not affect the microbial status of the sample.