The optimisation of biscuit formulation with grape and aronia pomace powders as cocoa substitutes

Abstract

By-products of fruit processing, such as grapes and aronia pomace, are rich in fibre and polyphenols, and their application in bakery products could significantly improve nutritional value, bioactive potential and shelf life of final product. This research aimed at optimising wholemeal biscuit formulation with grape and aronia pomaces as partial substitutes for cocoa powder, using the desirability function. Ten formulations with the mixture of cocoa powder, grape and aronia pomace powders in different ratios (0-100%) were tested. The physical properties (texture, colour, thickness, diameter, spread factor), the sensory acceptability of biscuits, and microbiological safety were investigated. The interaction of all three mixture components significantly affected the instrumentally measured redness a* and liking of texture. Biscuit diameter, yellowness b*, and liking of flavour were affected by the interaction of aronia and grape pomace. Biscuit height, spread ratio, hardness, flexibility, toughness, appearance, and odour were not significantly influenced by the mixture composition. The optimized mixture composition contained cocoa, grape pomace, and aronia pomace in the ratio 76.4 : 17.5 : 6.1 (respectively), with the desirability of 0.78. After confirmation, biscuits with that mixture were proven better than the control, that contained 100% cocoa, in terms of decreased hardness (-23%) and toughness (-19%), having the same sensory acceptability, and were microbiologically safe for 5 months. The findings of this study indicate that aronia and grape pomace could be used as partial substitutes for cocoa powder up to 24.3% in the production of wholemeal biscuits.