Designing food structures to enhance sensory responses

<strong>Background and Aim</strong> The current overconsumption of sugar, salt and fat has been linked to the incidence of health problems. For this reason, it is necessary to decrease the intake of these food components. In the context of reducing the contents of sugar, salt and fat in food products while maintaining sensorial quality, the aim of this thesis was to identify and understand the factors that affect the perception of taste and fat-related sensory attributes in semi-solid foods. To achieve this aim, the relationship between the spatial distribution of sucrose, the mechanical properties of semi-solid gels and the perception of taste was investigated in detail. In addition, the relationship between the spatial distribution of fat and the perception of fat-related sensory attributes was investigated. <strong>Methods</strong> Model systems composed of layers of mixed agar-gelatin gels were used to control the spatial distribution of sucrose and fat. Layers varying in concentration of sucrose or oil-in-water emulsion droplets (i.e. fat) were combined to prepare gels with homogeneous and inhomogeneous distributions of sucrose and fat. A series of experiments were carried out using 2-Alternative Forced Choice (2-AFC) tests, line scale ratings and time-intensity analysis to investigate the effects of modulation of the spatial distribution of sucrose and modulation of the mechanical properties of gels on sweetness intensity. The relationship between the spatial distribution of tastants and consumer preference was investigated in different types of foods (e.g. semi-solid gels, breads and sausages). Furthermore, a Quantitative Descriptive Analysis (QDA) panel was carried out to investigate the effect of modulation of the spatial distribution of fat on the perception of fat-related sensory attributes. <strong>Results</strong> An inhomogeneous distribution of sucrose at large sucrose concentration differences enhanced sweetness intensity. The frequency of high-intensity discontinuous stimulation of taste receptors, which is related to the presence of tastant concentration differences in the mouth during oral processing, was identified as the driving factor for taste enhancement. The oral breakdown of semi-solid gels, which is affected mainly by fracture strain, and the mixing behavior of gel fragments formed upon breakdownwere shown to influence the frequency of receptor stimulation and, consequently, taste enhancement. Furthermore, the optimum frequency of high-intensity discontinuous stimulation required to maximize taste enhancement was shown to depend on the textural properties of the gel. These findings suggest that the spatial distribution of tastants and the mechanical properties (especially fracture strain) can be modulatedto maximize taste enhancement. Additionally, consumer preference was found to be maintained or increased in products containing tastants heterogeneously distributed in the food matrix. Fat-related mouthfeel attributes, such as spreadable and melting, were enhanced by an inhomogeneous distribution of fat at large fat concentration differences. The presence of high-fat zones on the surface of the model system was shown to maximize the enhancement of attributes related to fat. Therefore, the enhancement of fat-related attributes seems to be driven by the presence of high-fat zones preferably on the surface of the product rather than by the presence of fat concentration differences within the product. <strong>Conclusions</strong> The combined effects of modulation of the spatial distribution of tastants and fat and modulation of the mechanical properties can be applied in the development of low-sugar, low-salt and low-fat food products with improved taste quality. &nbsp