Sand frying and sand roasting: A review of their effects on food and health

Sand frying and sand roasting represent ancient dry thermal processing technologies, fundamental in Asian gastronomy and Traditional Chinese Medicine (TCM), which are resurging as sustainable oil-free alternatives. This systematic review consolidates scattered literature to establish the state of the art, outlining trends, transfer mechanisms, and critical control parameters. The mechanisms of direct conductive heating and rapid moisture evaporation are elucidated, which generate high surface conductance and induce significant volumetric expansion, creating unique porous food matrices. The analysis shows key functional impacts: structural changes in starch (gelatinization and retrogradation to resistant starch), improved digestibility, retention of bioactive compounds, and effective detoxification of alkaloids. It is concluded that, although these methods offer superior advantages in sensory and nutritional profiles compared to conventional frying, their industrial scalability requires rigorous standardization of granular medium quality and control of occupational risks from silica. This work highlights the translational potential of sand processing for the development of clean label functional foods, urging future research on the optimization of energy efficiency and micronutrient bioavailability.