Abstract: Bismuth sulfide（Bi₂S₃）precipitation has emerged as a novel quality and safety concern in the dairy industry. It manifests as grayish-black precipitates when dairy products are stored in an inclined position,severely compromising the sensory quality and commercial value of the products. This study systematically investigated the molecular formation mechanism of Bi₂S₃ precipitation,traced its risk sources across the entire dairy industry chain,and conducted an in-depth analysis of key control points in raw milk collection,processing technologies and end-product storage. Based on these findings,a full-chain risk management framework was established,encompassing raw material traceability management,processing parameter optimization,online monitoring technology upgrading and regulatory standard improvement. Finally,the limitations of current research are identified, including the lack of long-term toxicological data on bismuth residues,the absence of precipitation kinetic models for complex milk matrices,and the underdevelopment of intelligent real-time monitoring technologies. Future research directions are proposed,such as precise traceability,development of novel inhibitors and the application of intelligent packaging. This study provides a scientific basis for the dairy industry to prevent and control such quality defects and ensure product quality and safety.

Key words: bismuth sulfide, dairy products, precipitation mechanism, risk management, veterinary drug residues