Utilization of coffee grounds in dark chocolate: a sustainable approach to fiber enrichment and sensory evaluation

Abstract Growing global coffee consumption has increased the availability of coffee grounds as a major food by-product. This study aimed to enrich dark chocolate with coffee grounds as a natural source of dietary fiber. Chocolate samples were produced with different concentrations of coffee grounds based on Turkish Food Codex fiber criteria. In Phase I, untrained panelists evaluated control and enriched samples using a nine-point Likert scale, and the highest-scoring formulation was selected. Texture analysis was conducted. In Phase II, a larger group of consumers evaluated the samples using the same scale and completed a 12-item perception questionnaire after being informed about the enrichment. Enrichment at 5% and 21% increased fiber by 3.5 g/100 g and 15 g/100 g, respectively. While the higher level negatively affected sensory scores, the 5% formulation maintained overall acceptability comparable to the control. Appearance and odor showed no differences, whereas texture and taste scores were lower for 5% chocolate ( p = 0.001; p = 0.004). Instrumental analysis indicated increased hardness ( p = 0.002) and brittleness ( p = 0.042); however, consumer acceptance remained stable. More than half of the participants liked the coffee flavor ( p < 0.001) and expressed willingness to consume the product to increase fiber intake ( p = 0.009). No significant relationship found between dietary fiber knowledge and attitudes. Adding 5% coffee grounds increased fiber while maintaining acceptability. Higher levels impaired texture and taste, but this formulation balanced nutrition and sensory quality, highlighting coffee grounds as a sustainable functional ingredient where particle size remains crucial. Future studies should focus on optimizing particle size and formulation strategies to further improve sensory acceptance while maintaining fiber-related nutritional claims. Graphical abstract