The effect of adding thyme extracts on microbiological, chemical and sensory characteristics of yogurt

Abstract

This study evaluated the effects of adding alcoholic and aqueous extracts of thyme on microbiological, chemical and sensory characteristics of yogurt. Supplementation of yogurt with thyme extracts during storage time were found to influence on yogurt composition compared to plain yogurt. So, plain yogurt (PY), thyme alcoholic extract yogurt (TCEY) and thyme aqueous extract yogurt (TAEY) moisture content decreased in all yogurt treatments to reach 88.21%, 88.39% and 88.23%, respectively after 28 days of storage. Protein content increased after 28 days of storage and reached to 4.82%, 4.83% and 4.81%, respectively. Fat content tended to increase at the end of study period to reach 0.32%, 0.36 and 0.326% respectively. The ash percentage after 28 days of storage increased to reach 0.71%, 0.72% and 0.71%, respectively. Titratable acidity increased after 28 day to 1.28, 1.17 and 1.2 while the pH decreased to 4.24, 4.31 and 4.29 respectively. For sensory evaluation, (TCEY) was more acceptable followed by (TAEY) and (PY) respectively. Microbial content revealed that all yogurt treatments were close at zero time for lactic acid bacteria (LAB) content and increased gradually to (7.38, 7.31 and 7.32) log (cfu/ml) respectively, there wasn’t any grow during all study periods in (TCEY) and (TAEY) for coliform and yeast & mold content, while there was a grow in (PY) after 14 day for coliform and after 21 day for yeast & mold.