Key issues and challenges in spice grinding

Spices are ubiquitous in the daily diet and gained more attention as preservatives, flavor, aroma, and therapeutic agents in the food and pharmaceutical industry. The quality standards of spices are closely associated with processing techniques. In spice processing, grinding plays an important role and needs special emphasis considering the problems of significant quality loss due to heat generation. Grinding is a simple unit operation but interlinked with crop parameters, machine parameters, and pre-treatments. Several techniques and methods are being applied in the spice grinding process like conventional grinding (hammer, plate, pin mill), superfine grinding (ball, jet, roller mill), improved grinding (cryogenic, dry ice, pre-chilling, chilled air, water jacket, stage grindings). Convectional methods follow several challenges like more energy consumption, material stability, cost economics, etc. Among improved grinding methods, cryogenic grinding has proved a superior method for spice grinding. Although proven technology, it has till certain challenges in design, optimization in liquid nitrogen use, initial and operational costs. The major objective of this paper is to identify critical factors associated with the quality retention of spices during grinding and a comprehensive understanding of their cause-effect relationships. Attribute coding and the DEMATEL approach were applied for determining the cause-effect relationship of identified factors. The review highlights the challenges, opportunities, and perspectives of each grinding technique. The findings of the study intended to guide researchers, processors, and manufacturers in reducing quality loss during spice processing and also to serve as a ready reckoner for developing efficient and novel spice grinding technologies.