Optimizing volatile oil retention in ajwain (Trachyspermum ammi L.) through cryogenic grinding techniques

Abstract: The therapeutic benefits of seed spices have long been acknowledged, and there is growing interest in their potential biological activity in human health. Ajwain (Trachyspermum ammi L.), a significant seed spice from the Apiaceae family, is characterized by its distinct aroma and taste, attributed to its volatile oil content (2.5-5%). In postharvest processing, grinding is a crucial stage requiring careful handling to preserve flavor and aroma constituents. However, conventional grinding methods can lead to volatile oil loss due to varying grinding temperatures. To address this, a study was conducted using cryogenic grinding of ajwain seeds with liquid nitrogen on a laboratory-scale cryogenic grinder. The grinding was performed at temperatures ranging from 0°C to -100°C, with feed rates of 8, 9, and 10 kg/h and sieves of 0.8 and 1.0 mm. The study focused on liquid nitrogen consumption and the volatile oil content of the ground powder. The optimal conditions for producing high-quality ajwain seed powder were determined to be a feed temperature of -60°C, a feed rate of 8 kg/h, and a sieve size of 0.8 mm, achieving the highest retention of volatile oil at 2.9%. This approach highlights the effectiveness of cryogenic grinding in preserving the volatile oil content in ajwain seeds, offering a promising method for maintaining the quality of spice powders.