From Brewing By-Products to Next-Generation Food Ingredients: Processing, Functionality, Safety, and Industrial...

Brewing generates several by-products with high potential for conversion into food in-gredients, including brewer's spent grain, brewer's spent yeast, spent hops, and hot trub. These streams contain dietary fibre, proteins, β-glucans, phenolics, minerals, and others with nutritional and technological value. This review evaluates their suitability for food applications by linking composition, processing routes, techno-functional behaviour, safety, sensory quality, and industrial readiness. A structured literature search covering publications from 2015 to 2026 was conducted in Web of Science, Scopus, PubMed, and Google Scholar to support a critical narrative synthesis of food-relevant applications of brewing by-products. The review shows that brewer's spent grain is the most suitable by-product for wider food use, mainly in bakery, snacks, pasta, and cereal-based products, due to its high availability and fibre-rich composition. Brewer's spent yeast is more appropriate for fraction-based applications involving proteins, peptides, β-glucans, and mannoproteins, especially in dairy products, savoury foods, beverages, and encapsula-tion systems. Spent hops and hot trub are less suitable for direct incorporation, but they may be used for selective recovery of phenolic-rich, antioxidant, flavour-active, or pro-tein-containing fractions. The conversion of these materials into food ingredients depends strongly on stabilization, drying, milling, extraction, fermentation, enzymatic treatment, debittering, and fractionation. Main limitations include high moisture content, short shelf-life, microbial spoilage, compositional variability, bitterness, dark colour, high nucleic acid content in yeast-derived fractions, regulatory uncertainty, and limited pilot-scale validation. Overall, brewing by-products can support the development of up-cycled ingredients when processing, safety, sensory quality, and product compatibility are controlled. Future progress requires standardized recovery protocols, stronger quality control, sensory validation, legal assessment, and scale-up studies to support their use in commercial food production.