Determination of Total Phenolic Content. A slightly modified Folin-Ciocalteu (FC) reagent method (20) was used to measure the total phenolic content. Briefly, 0.2 mL of sample or solvent blank, 1.0 mL of FC reagent, and 0.8 mL of Na2CO3 (7.5% aqueous solution) were mixed in a 20-mL vial and allowed to stand at room temperature spectrophotometer (Varian Analytical Instruments, Harbor City, CA). Gallic acid solutions were prepared for the generation of a standard curve. Results were expressed as micrograms of gallic acid equivalent (GAE) per milliliter of solution, from which the total phenolic contents
in fresh apple samples were calculated. Concentrations beyond the highest point (500 µg/mL) of the linear range of the standard curve were diluted before final analysis.