Biochemical content, minerals, and antioxidant activity of fruit jiaosu obtained by natural fermentation
2021
Y. C. Kam | P. A. Hnin | N. W. Sit
This study was conducted to determine the pH, protein concentration, mineral, phenolic, flavonoid, and organic acid contents, as well as the antioxidant activity of three batches of fruit jiaosu (F1B3, F1B4, and F1B5). The jiaosu was prepared by mixing ten types of fresh fruits, raw honey, and water (3:1:10, w/w/w), and fermented at room temperature for six months. All fruit jiaosu had low pH (2.96–3.69), and the protein concentration was ranged from 8.45 to 16.2 µg/mL. Potassium (605.0–657.2 mg/L) was found to be the most abundant mineral in all the samples, followed by magnesium, calcium, and sodium. The total phenolic and flavonoid contents were 183.1–210.5 µg gallic acid equivalent/mL and 45.2–53.8 µg quercetin equivalent/mL, respectively. Acetic acid was the major organic acid in the F1B4 and F1B5 samples (6.58 g/L and 20.7 g/L, respectively) while the F1B3 sample contained the highest amount of lactic acid (12.1 g/L). Ascorbic and citric acids were present in small amounts in all samples. All the samples showed stronger scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radicals (half-maximum inhibitory concentration, IC₅₀: 13.6–16.8% v/v) than against hydrogen peroxide (IC₅₀: 47.2–50.6% v/ v). The ferric reducing antioxidant power and oxygen radical absorbance capacity values for the samples were 14.9–20.9 µg ascorbic acid equivalent/mL and 23.9–25.4 mg Trolox equivalent/mL, respectively. The results indicated that the fruit jiaosu is a complex acidic solution containing proteins, minerals, phenolic compounds, and organic acids with antioxidant activities. Natural fermentation may cause variations in the organic acid content of the fruit jiaosu.
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