Innovative technologies used to convert spent coffee grounds into new food ingredients: Opportunities, challenges, and prospects

Spent Coffee Grounds (SCG) are an abundant by-product of instant coffee and coffee beverage brewing with current estimates being close to 60 million kg generated daily, worldwide. SCG are a promising feedstock to produce new food ingredients. SCG have composed mainly of carbohydrates, dietary fibre, hemicellulose, lignin, lipids, and proteins. SCG are high in potassium and magnesium. SCG also contain bioactive compounds such as chlorogenic acids, caffeine, and melanoidins. The potential health benefits of SCG include its antioxidant, antimicrobial, anticancer, and detoxifying activities. Among innovative technologies applied for SCG are green extractions, hydrolysis to generate prebiotic hydrolysate and fermentable sugars, fermentation and encapsulation. In many cases, several of these innovative technologies are used in sequence to produce new food ingredients. The aim of this systematic review is to detail the main processing unit operations that can be used to transform SCG to produce new food ingredients. There is a significant opportunity to expand understanding of processing technologies, in particular fermentation technologies that might be applied to SCG to enhance its hard-to-digest nature and produce food ingredients suitable for human consumption. SCG have the potential to be used in sustainable food production, providing a range of nutritional and functional benefits.