Effect of Fat on Mechanical and Acoustical Properties of Biscuits Related to Texture Properties Perceived by Consumers

This study aims to measure the changes in the mechanical and acoustic properties of biscuits when solid fat was replaced by vegetable oils and to relate these properties to the texture sensations perceived by consumers. Twelve biscuit formulations containing different types of fat (two shortenings and four oil/hydrocolloid systems) and different fat contents (10.6 and 15.6 %) were studied. The mechanical and acoustic properties of the biscuits were measured instrumentally by a three-point bending test and two penetration tests using cylindrical and spherical probes. The values of parameters, such as the maximum peak, distances, slopes and number of events were obtained from the force-distance and sound-distance curves. Results showed that both fat type and content affected instrumental texture of biscuits. When reducing fat content, biscuits presented high force at breaking and at penetration and more fractures during cylinder penetration. When the saturated fat was replaced by the oil/xanthan gum system, the biscuit proved more elastic, resistant to breaking and noisy during penetration. Moreover, when the fat content was decreased or the shortening was replaced with the oil/gel systems, the number of force events (>0.1 N) during sphere penetration was lower. Free-choice profiling was used to determine the differences in texture characteristics perceived by consumers (n = 28), and relationships between the consumers’ perception and instrumental parameters was performed by partial least squares regression analysis. Results show that higher force at breaking values and at penetration and a large amount of fractures during the cylinder penetration were related with hard and crunchy perception in biscuits. Moreover, high values of the resistance to breaking parameter and large amount of sound events were also related with an increased sensation of the hardness. Finally, a high number of microfractures (0.1 N) during the penetration with sphere were found to be related with the perception of mealy, crumbly and brittle sensations. The olive oil/HPMC system at the high fat content conferred similar mechanical and acoustical properties to those provided by the shortening fats, leading to biscuits with similar texture properties in the mouth.