Grinding characteristics and energy consumption in cryogenic and ambient grinding of ajwain seeds at varied moisture contents

Abstract

The study on cryogenic and ambient grinding of ajwain seeds was envisaged to understand the energy consumption pattern during different grinding processes as a function of moisture content 8, 12, 16 and 20% (db) for AA-1, AA-2 and AA-93 varieties of ajwain seeds. The grinding time was found to increase from 57.6 ± 0.01 to 180 ± 0.08 s, whereas feed rate was found to decrease from 6.25 ± 0.07 to 2.00 ± 0.12 kg h−1 with the increasing moisture content. This resulted in more power consumption ranging from 0.012 ± 0.08 to 0.037 ± 0.007 kW h−1 in all the ajwain varieties for the selected moisture range under cryogenic and ambient grinding conditions. But the specific energy consumption was found to be higher in case of ambient grinding conditions. Also, the various energy models such as Kick's, Rittinger's and Bond's work index were found to increase significantly (p < 0.05) with increasing moisture content ranging from 1.02 to 13.22 kJ kg−1, 0.55 to 21.92 kJ kg−1 and 15.31 to 195.31 kJ kg−1, respectively. The cryogenic grinding was found to be more energy efficient than ambient grinding. Moreover, cryogenic grinding results in more yield and good quality product with uniform particle size distribution and lower powder density. This study will help the food processing industries while grinding spices and for designing of appropriate grinder specifically for grinding ajwain seeds.