Influence of Spent Coffee Ground as Fiber Source on Chemical, Rheological and Sensory Properties of Sponge Cake.

Since spent coffee grounds (SCGs) represented the main by-product from instant coffee industry, the aim of the present study was to evaluate the use of these residues as functional food ingredient in sponge cake.Baked control sample (100% wheat flour) and three supplemented blends (98% wheat flour+2% SCGs, 96% wheat flour+4% SCGs and 94% wheat flour+6% SCGs) were subjected to chemical, rheological, texture, freshness, volatile, sensory and color analysis.The SCGs are a promising source for dietary fiber (51.86%), protein (8.97%) and fat (13.89%) with a well-known negligible glycaemic sugar content. Supplemented sponge cake recipes with SCGs (2, 4 and 6%) reduced the degree of browning due to the lower glycaemic sugar content as well as the protein content in comparison to the control sample. A significant difference in the organoleptic properties were showed in all cake samples containing SCGs (p>0.05), which again may belong to the lower content of reduced sugars in SCGs. Volatiles extracted and identified using Solid Phase Micro-Extraction (SPME)/GC-MS have a lower content of furans, furanones and pyrazines in supplemented recipes due to the effect of lower glycemic sugar content. The higher dietary fiber content of SCGs increased volume, weight and the rheological properties of the sponge cake in addition to softened the texture.Innovative sponge cake proved to have excellent nutritional and functional properties to be used for patients with obesity related diseases.