Effect of Drying on Total Phenolic Compounds, Antioxidant Activity, and Kinetics Decay in Pears

Abstract

The polyphenols have been identified as food components sensitive to high temperatures; therefore, the application of heat treatments can lead to a significant reduction in the phenolic content and also on antioxidant capacity. The objectives of the present work were to investigate the decrease in total phenolic compounds and antioxidant activity in pears during air drying at different temperatures and to model the kinetics of those variations. The pears (cv. D. Joaquina) were dried at 60°C and 70°C in an electrical drying chamber with hot air at 0.5 m/s. Along drying several samples were collected for analysis, being submitted to multiple extractions with methanol and acetone solutions. The phenolic compounds were determined by the Folin-Ciocalteu method and the antioxidant activity was determined by the ABTS method. The results showed that three successive extractions with methanol followed by three extractions with acetone solution was necessary for an efficient quantification of the total phenolic compounds and antioxidant activity. The decrease along drying was found to be of about 40% for both parameters and for the two temperatures studied. Furthermore, a relatively strong relation was observed between total phenols and antioxidant activity. The mathematical modeling of the kinetics showed that a 3-parameter exponential decay function was the best function to describe the experimental data, and the kinetic constants were found to vary in the range 0.0136–0.0444 min−1.