Colour and rehydration properties of bay leaves dried by convective and microwave methods

A. Polat, N. Izli

Department of Biosystems Engineering, Agriculture Faculty, Bursa Uludag University, Gorukle Campus, 16059 Nilüfer, Bursa, Turkey

(Manuscript received 26 July 2018; accepted for publication 30 November 2018)

Abstract. This study aims to evaluate the effect of the convective and microwave dying methods on the colour parameters (L*, a*, b*, C,  and ΔE) and rehydration ratio of bay leaves. Drying experiments were conducted using 350 and 460W of microwave powers and air temperatures of 50, 60 and 70C. Different microwave powers show significant effect on colour of dried bay leaves. Increasing microwave power, a* (redness/greenness),  (hue angle) and ΔE (total colour changes) values increased whereas L* (lightness), b* (yellowness/blueness) and C (Chroma) values decreased. For the convective drying, although there are changes in the values of the colour parameters (L*, a*, b*, C and ), there are no significant differences in the values of the total colour changes (ΔE) statistically (P>0.05). The effect of microwave power levels and air temperature on rehydration characteristics was determined. It was found that the rehydration ratio values decreased with an increasing temperature and increasing power levels. The highest rehydration ratio was recorded for the samples dried at 350W and the lowest ratio was seen in a sample dried at 70°C. Microwave drying can be a practical drying process, an alternative to convective drying for drying bay leaves.