Effect of spent coffee grounds addition on the microstructure and quality characteristics of protein-fortified bread

This study aimed to develop bread fortified with dietary fiber and protein using spent coffee grounds (SCG) and soy protein isolate and to analyze the effects of SCG addition on bread quality and microstructure. The addition of SCG led to a significant reduction in both the volume and specific volume of bread. Scanning electron microscopy revealed the development of a denser and more irregular crumb structure, with smaller cells and thicker cell walls observed at higher SCG levels. Texture profile analysis showed increased hardness and chewiness in samples with higher SCG addition, reflecting reduced crumb porosity. A 15% addition of SCG led to 7.1%, 10.7%, and over 40-fold increases in crude protein, crude ash, and crude fiber content, respectively, compared to the control. Sensory evaluation showed that breads containing 1–5% SCG exhibited comparable acceptability to the control, with some panelists preferring the enhanced coffee aroma and flavor complexity. • Spent coffee grounds (SCG) were incorporated (1–15%, w/w) into soy protein–fortified bread. • Increasing SCG levels reduced bread volume and produced a denser, irregular crumb structure. • SCG addition enhanced crude protein, ash, and fiber contents, with >40-fold increase in fiber at 15%. • Sensory evaluation indicated that 3–5% SCG breads maintained consumer acceptability. • SCG shows potential as a sustainable ingredient for nutritional and functional bakery applications.