Unlocking the potential of oat okara: A review of origins, composition, and upcycling opportunities in plant-based foods

• Oat okara is currently an underutilized side-stream of the plant beverages industry • Oat okara could be up-cycled as a new food ingredient for sustainable food systems • Enzyme pretreatments and fermentation are viable processing approaches for the revalorization of oat okara • A better understanding of oat okara composition and potential is needed for successfully exploiting its nutritional potential As the demand for sustainable plant-based alternatives grows, revalorizing by-products from food production in line with circular economy principles can reduce food waste and create economic value. The production of oat-based beverages generates significant amounts of oat okara, a nutrient-rich but underutilized by-product. This review discusses the composition of oat okara, emphasizing its nutritional profile, while also addressing its limitations, and explores several opportunities for its upcycling beyond traditional uses like animal feed or energy production. By applying chemical, physical, enzymatic, and biological treatments, oat okara's sensory and functional properties can be enhanced, making it suitable for incorporation into commercially viable food products. Enzymatic pretreatments are effective at releasing nutrients and supporting microbial growth, while fermentation further improves sensory qualities, increases nutrient bioavailability, and protects against spoilage. The successful integration of oat okara into food production relies on innovative and cost-effective processing technologies to generate appealing and safe products. Unlocking the full potential of this by-product offers opportunities for the food industry to foster sustainability, improve nutrition, and meet the growing demand for plant-based products.