Study of antioxidant characteristics of stirred yogurt incorporated with African bitter leaf (vernonia amygdalina del.) extract

Mardjuki, Karina Indriani (2018) Study of antioxidant characteristics of stirred yogurt incorporated with African bitter leaf (vernonia amygdalina del.) extract. Bachelor thesis, Universitas Pelita Harapan.

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Abstract

Vernonia amygdalina Del. commonly known as African bitter leaf. Has been traditionally consumed as soup and vegetables. The leaf is known to have many benefits related to human health since it is very high in phytochemical compounds that act as antioxidant, namely flavonoid. Yogurt on the other hand is one a rising-in-consumption product. The objective of this research was to study the antioxidant characteristics of bitter leaf extract added to stirred yogurt. Two types of blanching methods were applied to the African bitter leaf and the result shows that steam blanching was the best method in exhibiting high phenolic content (166.968±3.309 mg GAE/100mL), high flavonoid content (40.143±3.309 mg QE/100mL) and high antioxidant activity (37.187±0.840 ppm). Further, extraction with different solvents showed that there was a significant difference (p£0.05) of the extraction solvents and antioxidant characteristics. Ethanol exhibited the best extraction result in obtaining high phenolic content (168.6.849±6.849mg GAE/g dry weight), high flavonoid content (50.700±1.135 mg QE/100ml) and high antioxidant activity (361.118±15.411 ppm). Different African bitter leaf extract ratio was added to milk (85:0, 83.75:1.25, 82.5:2.5, 80:5) and the product was fermented at different incubation time (12, 15 and 18 h) to see their antioxidant characteristics. Based on its antioxidant characteristics and pH of each yogurt, the results showed the three yogurts with fresh milk and bitter leaf extract ratio of 83.75:1.25 had the highest antioxidant characteristics and were further given to 70 panelists to see their acceptance towards the sample. The results shown that yogurt with ratio 83.75:1.25 with incubation time of 12 h were selected by the panelists with its total phenolic content of 298.211±9.974 mg GAE/g, total flavonoid content of 59.718±1.081 5mg QE/g and antioxidant activity of 58.930±0.289 ppm).

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