Enzymatic browning in marula fruit 1: Effect of endogenous antioxidants on marula fruit polyphenol oxidase

Abstract

Spectrophotometric assays of marula fruit polyphenol oxidase showed a pronounced lag phase due to the presence of endogenous antioxidants. ne total antioxidant capacity (TAC) was quantified in terms of the equivalent concentration of L-ascorbic acid (L-ASC. eq). Freeze-dried marula fruit juice had 2960 mg L-ASC.eq. per 100 g (pH 4.5) or 1872 mg L-ASC.eq per 100 g of sample (PH 7 0) assayed with ABTS. The values compare with the known L-A SC content of 2017 mg per 100 g. The vitamin C content of marula fruit accounts for about 70 % of the TAC. The TAC estimate for marula fruit was 20-40 times greater than levels reported in most other fruits.