Dried berry pomace as a source of high value-added bioproduct: drying kinetics and bioactive quality indices

Abstract

Drying kinetics and bioactive quality indices (total phenolics, flavonols, anthocyanins, and antioxidant activity) of fermented Merlot grape, cranberry, highbush blueberry, and wild lowbush blueberry pomace were evaluated. Thin layer drying experiments were performed at two loading densities (kg m−2) at 50, 60, and 70°C in a cabinet convection air dryer. Phenolics composition and antioxidant activity of both cabinet convection air dried pomace and freeze dried pomace were assessed. The effective moisture diffusivity (Deff) and activation energy (Ea) values were calculated for each pomace type subjected to cabinet convection air drying and experimental drying data from these experiments were modeled with the Newton/Lewis, Henderson-Pabis, and Page equations. This work showed that levels of phenolic compounds and antioxidant activity in pomace subjected to cabinet convection air drying at certain conditions were generally comparable to levels in freeze dried pomace. Results indicated that subjecting the berry pomace to shorter processing times upon cabinet convection air drying (half load density at 70°C) results in better bioactive quality retention. Thus this method could be used to generate dried berry pomace which could be a source of bioactive compounds with potential use as a value added product in the food industry and other industries.

Keywords

• merlot grape
• cranberry
• blueberry pomace
• cabinet convection air drying
• effective diffusivity
• activation energy
• phenolic compounds
• antioxidant activity