Food Applications, Composition, and Sustainability Trade‐Offs of Bourbon Distillers’ Spent Grain: A Critical Review

Bourbon distillers’ spent grain (DSG‐B) is a protein‐ and fiber‐rich coproduct generated during bourbon production that has emerging potential as an upcycled food ingredient. Unlike conventional corn distillers’ dried grains with solubles and brewer's spent grain, DSG‐B arises from bourbon‐specific processing conditions, including multigrain mash bills, on‐grain fermentation, and variable post‐distillation handling, all of which may influence its composition, functionality, and consistency. This critical review evaluates the current state of knowledge on DSG‐B with emphasis on composition, functional properties, safety considerations, food applications, and selected sustainability implications relevant to food use. Available bourbon‐specific studies indicate that DSG‐B contains approximately 25%–34% crude protein and 29%–70% total dietary fiber on a dry basis, with insoluble fiber predominating and lysine availability likely limited by the corn‐based protein matrix and thermal processing history. Among reported food applications, extrusion has the strongest bourbon‐specific evidence, with particle size and inclusion level shown to significantly affect expansion, porosity, hardness, and fiber enrichment; formulations containing up to 10% DSG‐B at about 300 µm have demonstrated acceptable product quality. In contrast, bakery applications remain less developed and are supported largely by older or non‐bourbon‐specific literature. Major gaps persist in food safety data, contaminant surveillance, sensory validation, phenolic characterization, and protein‐quality assessment using methods such as the Digestible Indispensable Amino Acid Score or reactive lysine analysis. Overall, DSG‐B represents a promising value‐added ingredient, but broader food applications will require compositional standardization, targeted functionality studies, safety validation, and product‐specific optimization.