Resource utilization of spent grains, an underutilized by-product from Chinese Baijiu brewing: Recent advances and prospects

Abstract

Spent grains, as a by-product of Chinese Baijiu brewing, are increasing with the industrial development of Chinese Baijiu. The resource utilization of spent grains is crucial for the sustainable development of Chinese Baijiu enterprise and the realization of the dual carbon goal. This review firstly introduced the brewing process of solid-state fermented Baijiu, as well as the sources and composition of spent grains. Subsequently, the research progress of main twenty distinct methods for the resource utilization of spent grains was comprehensively summarized and evaluated based on recent studies, and categorized into three aspects: (1) direct utilization methods of nutrients and functional components in spent grains, (2) applications of spent grains in functional materials and energy supply, and (3) extraction and utilization methods of high value-added functional components in spent grains. Further, the latest progress in the industrial-scale resource utilization of spent grains implemented by Chinese Baijiu enterprises was reviewed. Finally, the challenges hindering the scaled-up production of spent grains resource utilization technologies were discussed, along with proposed future research directions. Only by integrating methods from diverse studies, optimizing high-value component extraction processes, and establishing multi-level cascading resource utilization systems-while minimizing waste emissions and resource loss during processing-can the full value of spent grains be realized. Coupled with policy incentives and market-driven promotion, such an integrated framework can drive the green and sustainable development of Chinese Baijiu industry and serve as a replicable model for global distilled spirits sectors.