Coffee silver skin as a functional ingredient in sponge cake: Effects on nutritional quality, antioxidant properties and in vitro digestibility

In this study, wheat flour was partially replaced with coffee silver skin (CSS), a by-product of the coffee bean roasting process, in sponge cake formulations. Increase in CSS proportion in the sponge cake formulation significantly improved dietary fibre and phenolic contents of the product as well as its antioxidant activities. When the CSS level increased from 0 to 25%, the pGI of the sponge cake decreased from 71.8 to 45.0; the released total phenolic content increased from 11.47 to 25.25 mg GAE/100 g at the small intestinal stage and from 5.87 to 11.07 mg GAE/100 g at the colonic stage. Nevertheless, higher CSS incorporation modified the physical properties of the sponge cakes, resulting in lower specific volume, slightly reduced hardness and a darker color. CSS powder can therefore be considered a sustainable functional ingredient for sponge cake making, contributing to improved health-promoting properties of the final product.