Reduced-fat biscuits: interplay between food structure, nutritional and sensory properties

In recent years, interest towards the impact of food structure on nutritional functionality has grown, revealing new perspectives in the design of products with improved nutritional features. Extrusion-cooking and double emulsification processes may offer new ingredients for fat reduction, but the impact on food structure, nutritional profile and sensory properties must be assessed. The aim of this work was to evaluate the interplay between structure, nutritional functionality and sensory properties of reduced-fat soft-dough biscuits obtained with different ingredients. A standard full-fat formulation (STD) with 31.1±0.4 g/100g fat was considered as reference. Experimental biscuits were prepared based on a previously optimized reduced-fat formulation (OPT; fat, 17.5±0.2 g/100g) containing polydextrose as fat substitute (46.3% shortening replacement) and resistant starch (4.8 g/100 g) as structuring agent. In particular, two biscuit samples contained bean flour (BEAN) or extruded bean flour (BEAN_EXTR) instead of resistant starch, while the third sample contained a water-in-oil-in-water double emulsion (WOW) to substitute shortening (fat, 14.9±0.1 g/100g). Rheological properties and density of the biscuit doughs were analysed. Biscuits were characterized in terms of proximate composition, colour, milk absorption, texture, microstructure, starch and protein digestibility, as well as sensory properties. Samples STD and OPT were comparable for texture parameters, while the use of raw and extruded bean flours implied a significant increase of protein content and fracture strength, coupled with a significant decrease of fracture strain in sample BEAN. Shortening substitution with WOW led to a worsening of all the studied macrostructural features and the biscuits resulted definitely harder than STD and OPT samples. SEM images revealed differences in internal structure of the biscuits and the gummy aspect of starch granules. In conclusions, the results of this study allowed to understand how the different ingredients affected structure, nutritional properties, consumers’ perception and acceptability of reduced-fat foods obtained with innovative ingredients.