Reduced-fat soft-dough biscuits : multivariate effects of polydextrose and resistant starch on dough rheology and biscuit quality

The aim of this work was a multivariate study of polydextrose and resistant starch (high amylose maize starch; Hi-Maize™ 260) effects on reduced-fat soft-dough biscuits. Design of Experiments and Response Surface Methodologies were applied to model the effects on dough rheology and biscuit quality of a partial substitution of fat with polydextrose (0e50%) and of flour with resistant starch (0e80%). The calculated models evidenced highly significant effects (p < 0.001) of the experimental factors on dough density and rheological behaviour and on most biscuit characteristics (colour, milk absorption, and fracture strength). With the increase of shortening reduction, higher density and lower complex modulus of dough were observed. The biscuit quality characteristics most influenced by shortening and flour substitution were fracture strength and strain, redness (a*), heterogeneity, and milk absorption. The obtained models were used in a desirability function for the optimization of the reduced-fat formulation based on the following constraints: 25e50% shortening reduction; 41e44 g/100 g milk absorption; 100 e160 kPa fracture strength. The optimized product (17.54 ± 0.05 g/100 g fat), obtained with 46.3% shortening reduction and 12.5% flour replacement, had quality characteristics similar to those of full-fat biscuits (31.1 ± 0.4 g/100 g fat).