Investigation of drying kinetics of heat pump drying and post-drying quality parameters of mango by using gliding arc plasma discharge (GAPD) pre-treatment

Abstract

Drying has proven to be an efficient technique to extend shelf-life of fresh produce such as fruits. Over the years various pre-treatment techniques have been employed to enhance the drying performance and to improve post-drying quality parameters. Cold plasma pre-treatment is such technique that has shown great potential. Furthermore, heat pump drying has garnered attention with regards to enhancing drying performance through energy efficient operation which is achieved through recirculation of a closed loop of air for drying and condensing moisture. This study investigated the effect of pre-treatment time and distance of GAPD on the drying kinetics and quality parameters (i.e., colour, rehydration parameters and tensile strength) of Tom, Ellawala, and Juan Carlos (TJC) mango. Samples were dried for periods of 5 minutes and 10 minutes at pe-treatment distances of 8 cm and 4.5 cm. Reduction of 35.6% and 70% in time to reach moisture level of 10% from initial moisture level were observed in 3 mm mango samples when pre-treated with CP at a distance of 8 cm for 5 min and 10 min respectively. Similarly, reductions of 46.7% and 66.2% reduction in drying times were observed when 3 mm mango samples were pre-treated at a distance of 4.5 cm for durations of 5 min and 10 min respectively. No significant improvements were observed in terms of post-drying quality parameters such as colour, tensile strength, rehydration parameters and water activity.