Effect of substitution of wheat flour by sourdough and whey proteins on the properties of sponge cake

Abstract

As a result of consumer preferences, including the demand for healthier and high protein and high dietary fibre plant-based food, there is a trend towards fortifying or completely replacing refined wheat flour with whole grains or alternative ingredients. Redesign of traditional foods in order to create optimal nutritional value becomes a common practice thus offering consumers a wider and healthier choice. Incorporation of proteins and/or fibres from different sources in food formulations present one of the most used approaches. Recently, the application of sourdough technology has gained research interest due to its complexity as well as its ability to promote beneficial modifications on sensory, technological and nutritional properties of bakery products. The technological application of sourdough can offer several advantages such as improving texture and palatability of cereal based products, stabilizing or increasing levels of various bioactive compounds, retarding starch bioavailability and improving mineral bioavailability. This study aims to investigate the effects of substitution of wheat flour by sourdough from whole wheat flour (at levels 20% and 30%) and whey protein concentrate (at level 10%) on the quality of sponge cakes. The characterization of sponge cakes included the evaluation of chemical composition, specific volume, colour and texture properties. The sensory evaluation of sponge cake samples was carried out by a panel of ten trained sensory assessors who evaluated following attributes: shape irregularity, density, pores uniformity, cohesiveness, elasticity, adhesiveness, crumbliness, odour (overall intensity, on eggs), flavour (overall, on eggs), taste (sweet and bitter) and sweet aftertaste. All experimental data were subjected to one-way analysis of variance (ANOVA). To the aim, a Tukey's honestly significant difference (Tukey's HSD) test was carried out to determinate significance differences (P < 0.05) between samples. Regarding the proximate composition and colour measurements, results were, as expected, strongly dependent on the raw materials used in the formulation. Generally, the incorporation of proteins resulted in creation of product which can be labelled as protein source since more than 12% of their energy value is provided by protein. Compared to the control sample, reduction of wheat flour by sourdough and whey proteins caused a significant decrease in specific volume while values of hardness of tested samples were significantly higher. Regarding the sensory analysis, samples with sourdough and proteins exhibited much denser structure with a noticeable number of non-uniform large pores. Reduction of wheat flour by sourdough and whey proteins caused the loss of bitter taste, flavour and odour on eggs while the sweetness for these samples was significantly pronounced. The results indicate that this combination of used ingredients have a potential to be considered as an alternative valueadded food ingredients for bakery products but further research should be conducted in this area.