• Journal of Dairy Science and Biotechnology
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• v.34 no.4
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• pp.263-270
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• 2016

This study was carried out to evaluate the antioxidant activity and total polyphnol content of Greek-style yogurt in 12% solid content with added stevia leaf extracts. Stevia leaf extracts used as sweetener in preparing Greek-style yogurt were prepared in hot water ($100^{\circ}C$ for 6 h 3 times, and by 70% fermented ethanol for 24 h at room temperature 3 times). The antioxidant activities were measured by assessing the radical scavenging effect through DPPH, ABTS, and FRAP assays. To identify the compounds present, total polyphenol content was evaluated using a Folin-Dennis assay. The capability to scavenge free radicals and total polyphenolic content were the highest in Greek-style yogurt containing 1% stevia extract and fermented in 70% ethanol. According to the results, antioxidant activities significantly increased when high concentration of stevia extracts were added to the yogurt (p<0.05). Therefore, these results suggest that stevia leaf extracts can be used as a source of functional compounds in Greek-style yogurt. We also suggest that fermented ethanol extraction can be used to obtain stevia leaf extracts.

• Journal of Dairy Science and Biotechnology
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• v.34 no.1
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• pp.51-57
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• 2016

In this study, the fermentation and quality characteristics of Greek-style yogurt supplemented with stevia leaf extract during storage were examined. Stevia leaf extract was extracted from dried leaves with hot water and 70% ethanol. The pH decreased significantly in all samples over time during fermentation (p<0.05). In particular, the sharpest decrease was detected in the group in which the hot water extract of stevia was added. Acidity increased significantly over time during fermentation (p<0.05). Lactic acid bacteria counts increased in all samples up to 9 h after the start of fermentation, but decreased after 12 h. The sugar content decreased over time, and there were no major differences between samples. Based on the results of a sensory evaluation, the group treated with stevia extract was rated high in sweetness, but was rated somewhat low in color and flavor. Accordingly, it was rated low in overall acceptability. In a storability experiment, as the days of storage increased, the pH gradually decreased, and acidity showed a tendency to increase. The sugar content showed a tendency to decrease and then increase.