Effect of incorporation of pomegranate peel powder on the phyiscochemical and sensory characteristics of sponge cakes

Pomegranate peel, a waste generated from fruit processing industry, is known as a potential source of bioactive ingredients such as polyphenols, minerals and fibers. In this study, the chemical composition and functional properties of pomegranate peel powder (PPP) were determined and it was applied as a substitute of wheat flour in formulation of sponge cake at five levels of 1.5, 3, 4.5, 6 and 7.5% and two particle sizes of 210 and 500 microns. Then, the physical properties of the batter and the chemical, physical and sensory properties of the resulting sponge cake were examined. The chemical analysis of PPP showed that this powder was high in fiber, minerals especially potassium and calcium, and phenols. By increasing the PPP level and decreasing its particle size, batter consistency and density, as well as cake specific volume and symmetry index were significantly increased, while the porosity of the cake decreased. The chemical analysis of the cakes also showed a significant increase in the moisture content, ash, total fiber, and the decreasing trend of the protein, carbohydrate and energy content by increasing the percentage of PPP. In addition, samples containing higher levels of PPP had a lower L * index and higher a * and b * indices and were, therefore, darker, more reddish and yellowish. According to texture analysis, cakes with a higher percentage of PPP had more hardness and gumminess, and less cohesiveness. Based on the sensory analysis, the closest sample to the control was a cake containing 1.5% PPP with a particle size of 500 microns. Overall, it can be concluded that replacing less than 4.5% PPP can produce a cake with good quality properties and higher nutritional value.