Optimization of Drying of Olive Leaves in a Pilot-Scale Heat Pump Dryer

Abstract

Recently, the interest in olive leaf has increased due to its high phenolic content. It has a high potential for industrial exploitation in food industry and the main process in olive leaf treatment is drying. Drying affects the product quality and is an energy-intensive process, so the use of heat pumps in drying processes that have low operating cost has attracted the attention of the investigators. In this study, response surface methodology was used to optimize operating conditions of drying of olive leaves in a pilot-scale heat pump conveyor dryer. The independent variables were air temperature, air velocity, and process time, and the responses were total phenolic content and antioxidant activity loss, final moisture content, and exergetic efficiency. Optimum operating conditions were found to be temperature of 53.43°C, air velocity of 0.64 m/s, process time of 288.32 min. At this optimum point, total phenolic content loss, total antioxidant activity loss, final moisture content, and exergetic efficiency were found to be 9.77%, 44.25%, 6.0% (w.b.), and 69.55%, respectively.

Keywords:

• Exergy
• Heat pump drying
• Olive leaves
• Optimization
• Response surface methodology

ACKNOWLEDGEMENT

This study is a part of the M.Sc. thesis The Investigation of Modeling, Optimization, and Exergetic Analysis of Dryingof Olive Leaves and is supported by Ege University Scientific Research Project no. 2007/MÜH/30. The heat pump conveyor dryer system used in this study was designed and constructed under the scope of the project Design, Test and Performance Evaluation of a Gas Engine–Driven Solar-Assisted Band Conveyor Heat Pump Drying System (Project no: 106M482) supported by the Scientific and Technological Research Council of Turkey (TUBITAK).

Notes

^a Nominal value was taken as 6.0.

^b Nominal value was taken as 13.14.

^c Nominal value was taken as 45.72.

^d Nominal value was taken as 68.54.