Physical and thermal properties of various ajwain (Trachyspermum ammi L.) seed varieties as a function of moisture content

Ajwain seeds are used as spice and have high medicinal values. The ajwain seed varieties selected were set at 8, 12, 16, and 20% moisture content on dry basis (db) for this study. The geometrical dimensions showed linear increment with the increase in moisture content of ajwain seeds. The true density and porosity increased from 1,069 to 1,697 kg m⁻³ and 15.84–42.88%, respectively, across the three varieties of ajwain seeds with the increasing moisture content. The bulk density showed a decreasing trend of 1049.81–857.14 kg m⁻³ with the increasing moisture content. The coefficient of friction was also found to increase for all the varieties, but the maximum friction was found for the cardboard surface and the minimum friction was observed in case of aluminium sheet. The thermal diffusivity of seeds decreased from 4.09 to 2.46 m² s⁻¹ with the increasing moisture content. Thermal conductivity and specific heat showed a marked increase with increasing moisture content. Varietal differences among the ajwain seeds of variety AA‐1, AA‐2, and AA‐93 were also studied at 5% significance level. Significant differences were observed between the three ajwain varieties, namely AA‐1, AA‐2, and AA‐93 in context to their physical and thermal properties. PRACTICAL APPLICATIONS: The physical and thermal properties of ajwain seeds will be useful in designing of processes and equipment required for its processing. These properties give detailed information about the quality of the seeds, its acceptability to consumers and the behavior of the ajwain post production, during storage and consumption and post consumption. The knowledge on physical properties such as seed size, shape, volume, surface area, mass, density, porosity helps in designing the separating, storing, handling, and drying systems. The grading and sizing machineries will be based on the size and shape of the ajwian seeds. The density and porosity of the ajwain seeds will help in sizing the hoppers and storage containers. The density of seeds will also play role in separation based on density or specific gravities. The frictional properties like coefficient of friction and angle of repose will help in designing the storage bins, chutes, hoppers, screw conveyers, threshers, and forage harvesters. Thermal properties of ajwain seeds will be useful in analyzing and designing of equipment involving heat transfer, such as in case of cooking, sterilizing and drying.