This study was carried out to investigate the quality characteristics and antioxidant activity of yogurt dressing prepared with different amounts (0, 5, 10, 15, and 20%) of black currant (Ribes nigrum L) extract. All samples were evaluated for chemical composition, pH, viscosity, sugar content, color, organic acid content and antioxidant activity. Our findings revealed that with increasing amounts of black currant extract in yogurt dressing, the moisture, crude protein and crude lipid contents decreased. The pH and viscosity gradually decreased, whereas the sugar increased with increase in black currant extract. Further, the lightness (L) value decreased, while the redness (a) and yellowness (b) values increased with increase in added black currant extract. Among the organic acids, the contents of citric acid, malic acid, succinic acid and acetic acid increased, while that of tartaric acid and lactic acid decreased with increasing levels of added black currant extract. The total polyphenol and total anthocyanin contents were 5.90-245.97 mg/100 g and 0.62-190.09 mg/100 g, respectively. In addition, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-thylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities significantly increased with increase in added black currant extract.

The chemical components and anti-oxidant activities of black currant were investigated. The pH, soluble solid and total acidity values were 3.36, 15.11 °Brix, and 1.65%, respectively. The Hunter L, a, and b values were 18.20, 5.13, and 1.08, respectively. The proximate compositions were as follows; moisture, 77.64%; nitrogen free extract, 17.41%; crude fiber, 3.08%; crude protein, 1.28%; crude ash, 0.31%; and crude lipid, 0.28%, respectively. The mineral elements were K (177.36 mg/100 g), P (54.74 mg/100 g), and Ca (26.45 mg/100 g). The free sugar components were glucose (7.71%) and fructose (5.88%). The amino acid contents of the black currant were very rich in glutamic acid (105.73 mg/100 g) and deficient in cystine (5.29 mg/100 g). The ascorbic acid and total phenolic contents were 112.19 mg/100 g and 34.48 mg GAE/g, respectively. The ABTS and DPPH radical scavenging activity levels were 99.48% and 89.03% at the 10 and 1.25 mg/mL concentrations. The reducing power and FRAP of the black currant were dose-dependent. Thus, black currant can be an effective source of functional food substances, i.e., natural anti-oxidants.