Exogenous Impurities in Baijiu: Sources, Detection, and Safety Strategies

Baijiu, China’s traditional distilled spirit, is produced through solid-state fermentation and distillation of grains, resulting in a highly complex chemical and sensory profile. However, exogenous impurities introduced via raw materials, water, equipment, packaging, or the surrounding environment pose significant challenges to both safety and quality. These impurities, including heavy metals, plasticizers, pesticide residues, mycotoxins, environmental pollutants, and un-authorized food additives, are associated with neurotoxicity, carcinogenicity, endocrine disruption, and sensory defects. This narrative review synthesizes current knowledge on their sources, reported concentration ranges in Baijiu (generally at trace µg/kg–mg/kg levels), analytical detection methods with sub-mg/kg sensitivity, and control strategies for these substances. Regulatory frameworks, including China’s standards, are critically assessed, with emphasis on gaps such as the lack of explicit limits for certain classes of impurities. Case studies of contamination incidents are discussed to illustrate practical risks and monitoring gaps. Emerging trends, including low- and zero-alcohol Baijiu, are also considered in relation to changing impurity profiles and detection requirements. Recommendations include tightening regulatory limits, adopting portable and real-time detection technologies, and promoting the development of “pure Baijiu” that meets international safety and quality expectations. Future research priorities center on high-resolution mass spectrometry, advanced real-time monitoring, and eco-friendly analytical solutions, ensuring that Baijiu maintains both cultural heritage and global competitiveness.