Effect of blueberry addition on antioxidant activity, textural, microbiological and physicochemical properties of strained yoghurt

In this research, the microbiological, physicochemical, rheological, textural, sensory properties and antioxidant activity of blueberry pulp added (0, 4%, 8% and 12%) strained yoghurt samples were investigated during a 28 day storage period. The Lactobacillus delbrueckii spp. bulgaricus and Streptococcus thermophilus counts in the samples were found to have decreased at the end of the storage period. The lightness, yellowness/blueness and whiteness index values showed a decrease depending on the addition of blueberry, while the redness/greenness values increased. The addition of blueberry had a negative the effects on the fat and protein values, while it had a positive effect on the total solids values. The storage period did not significantly change any of the physicochemical, colorimetric or rheological properties of the strained yoghurt samples. The general acceptability scores of the sample containing 12% blueberry were higher than the other samples. The antioxidant activities and total phenolic content of the strained yoghurt samples increased in accordance with blueberry concentration, while the firmness and work of the shear values decreased. In conclusion, it was determined that the addition of blueberry pulp at a 12% ratio could be used to enhance the nutritional and functional properties of strained yoghurts.