Drying behaviour of French marigold Tagetes patuala Linn flowers

The study was conducted to analyze the drying behaviour of French marigold flowers (variety Jafri) while drying in mechanical drier. The drying curves for moisture content of drying sample (db) vs drying time (min) and drying rate (dM/dt) vs drying time (min) at different air velocities were drawn. The experimental flowers had initial moisture content of 84 ± 1% (wb) and the samples were dried up to 19 to 20 per cent moisture content (wb). There was a non-linear decrease of moisture with drying time for all the air velocities as well as temperatures. The effect of temperature on the drying time was more significant as compared to drying air velocities. The drying time required for reaching a moisture content of 19 to 20 per cent at 45°C was more than three times the time required at 55°C. Total drying time for flowers under control conditions was also noted for air velocity of 2.5 m/s and it was higher than the drying time for pretreated flowers. The drying time did not change with increase in the level of sulphitation. The initial drying rate of flowers was very high due the presence of free moisture in the flowers particularly the ones which had been pre-treated. The EMC data were used to determine the relation between moisture ratio and drying time. The correlation coefficient revealed that the Page model better describes the drying data as compared to one term exponential model.