2.5. Measurement of ascorbic acid content
Ten fruits were randomly selected from each replicate and macerated for 1 min until the tissues were completely homogenized using a home mixer. A 3-g slurry sample from the homogenates was mixed with 30 ml of 3% meta-phosphoric acid in water and homogenized. The homogenate was filtered with a filter paper (Whatman No. 1) and a 20-μl sample was injected into the HPLC system (YL9100, YoungLin, Anyang, Korea), which consisted of a binary pump, an autosampler, and a diode array detector. A μBondapak NH2 column (Waters, 3.9 × 30 mm, 10 μm) with a guard column was used, and the solvent was acetonitrile:water (7:3, v/v) with 0.01 M ammonium dihydrogen phosphate at a flow rate of 1 ml/min. Ascorbic acid was detected at 255 nm. Standard curves were constructed between 0 and 500 μg/ml of ascorbic acid and used to quantify the samples.