Investigation of rosehips dried via microwave, convective and shade drying methods in terms of drying kinetics, color and nutrients content

Rosehip (Rosa canina L.) whose mass is 50.00 ± 0.02 g and initial moisture content is 52.79 % ± 0.05 (w.b.) was dried using shade drying, convective drying at 50°C, microwave drying at 100 W, 300 W, 500 W, 700 W and 1000 W until its final moisture content was 11.14 % ± 0.03 (w.b.). These drying process were completed in 9360, 1080, 364, 162, 77, 45 and 21 minutes, respectively. The obtained data related to drying were modelled with 21 different thin-layer drying models in the relevant literature, and thus the closest estimation results to the experimental data were identified to be Alibas model for shade drying, 50°C, 300 W, 500 W and 700 W. Besides, the best estimation model for 100 W and 1000 W was determined to be Weibull distribution and Modified Henderson and Pabis equations, respectively. It was also concluded that the drying methods showing the closest results to the colour parameters of the fresh product were microwave drying methods at 700 W and 500 W. However, drying at 100 W led to great losses in colour parameters. The drying methods with the highest amount of protein were seen to be the microwave drying methods at 500 and 700 W. Last but not least, the drying method in which K, Mg, Na and Fe content is best conserved was 500 W; on the other, P, Ca, Cu, Mn and Zn content were preserved at a high level at 700 W. The findings suggested that the best drying methods were 700 W and 500 W microwave drying in terms of both drying parameters consisting of drying period, average drying rate, total energy consumption as well as specific energy consumption and quality parameters such as colour and nutrients. Key words: Rosehip, drying, color mathematical models, nutrient elements, drying period