Antioxidant properties of Philippine Bignay (Antidesma bunius (Linn.) Spreng cv. ‘Common’) flesh and seeds as affected by fruit maturity and heat treatment

Abstract

The effects of maturity (green-unripe, red-ripe, and purple-fully ripe) and heat treatment (blanching at 90±5°C for 2 mins and steaming at 105±5°C for 5 mins) on the antioxidant content and activity of Philippine bignay (Antidesma bunius (Linn.) Spreng cv. ‘common’) flesh and seeds were investigated. The total phenolic content (TPC), total flavonoid content (TFC) and total anthocyanin content (TAC) were determined using the Folin-Ciocalteau assay, aluminum chloride assay, and pH differential technique, respectively, and the antioxidant activity was determined using DPPH, ABTS, and FRAP assays. Results showed that the antioxidant content and activity of bignay increased with maturity. Fully ripe flesh and seeds were found to have the highest antioxidant content and activity regardless of the heat treatment applied. The TPC (8.06±0.15 mg gallic acid equivalents (GAE)/g), TFC (8.10±0.06 mg quercetin equivalents (QE)/g), TAC (4.07±0.03 mg cyanidin-3-glucoside equivalents (CGE)/L extract), and antioxidant activity (ABTS 10.37±0.04 , DPPH 9.60±0.10, FRAP 24.37±0.53 Trolox equivalents (TE)/g) of fully ripe seeds were superior when blanched. On the other hand, the TPC (40.73±0.04 mg GAE/g), TFC (31.54±0.15 mg QE/g), TAC (20.93±0.12 mg CGE/L extract), of fully ripe flesh were superior when not heat-treated while its antioxidant activity (ABTS 34.19±0.19, DPPH 14.01±0.02, FRAP 87.78±1.22 (TE)/g) was highest when blanched but did not vary significantly compared to unheated samples. This study suggested that bignay ‘common’ variety was a good source of antioxidants particularly the flesh at fully ripe stage. Blanching had shown to enhance its antioxidant activities.