Total Phenolic Content

Measurement of total phenolic content of apple peel was done using the Folin– Ciocalteu method according to Mditshwa et al. [9], with slight modifications. In triplicates, 50 μL of 4-fold diluted crude extract was added to 450 μL of 50% methanol, followed by 500 μL Folin–C reagent and then sodium carbonate (2%) solution after 2 min. The mixture was vortexed incubated for 40 min in the dark at room temperature, and absorbance was measured at 725 nm using a UV–visible spectrophotometer (Thermo Scientific Technologies, Madison, Wisconsin). Total phenolic content in the extract was extrapolated using a gallic acid calibration curve. Results were expressed as mean (milligrams) of gallic acid equivalents per unit dry matter (mg GAE/g DM) of peel in triplicate samples.
