Valorisation of spent coffee grounds in the context of prebiotic potential: a review

Spent coffee grounds (SCGs) are the solid residues generated after coffee brewing and have been widely researched due to their rich carbohydrate content. Beyond energy generation, there is a growing interest in developing functional food ingredients. This review focuses on assessing various extraction methods for SCG-derived compounds in terms of their prebiotic potential.

One common type of functional carbohydrate extracted from SCGs is mannooligosaccharides (MOS), primarily obtained through single-stage and enhanced extraction strategy. Single-stage extraction often uses one method, with integrated mechanism and yields oligosaccharides and monosaccharides. On the other hand, the enhanced extraction combines pre-treatments and enzymatic hydrolysis to increase the SCG extractability and selectively degrade polysaccharides. This method yields fewer undesired by-products and aims to avoid complete hydrolysis of SCG into monosaccharides.

In this review, several research gaps were identified in relation to fully valorise SCG. First, there is a critical gap in standardized analytical methods for accurately determining the profile of extracted oligosaccharides. Developing and adopting validated techniques is essential for a reliable characterization of these compounds. Second, the efficacy of pretreatment processes on SCG remains challenging to assess due to the lack of uniform evaluation criteria. Establishing such criteria would help compare across studies, ensuring more consistent assessment of pretreatment outcomes. Finally, the criteria for confirming prebiotic potential in SCG-derived compounds are not well understood. It is essential to adhere to established definitions of the term ‘prebiotic’ and to apply validated methodologies to assess their prebiotic status.