Sensory Dynamics in Emulsion Products Differing in Fat Content
Doctoral thesis, 2001
Flavour, taste and texture are important qualities when purchasing food and the richness and smoothness of fat are desired properties for many individuals. However, fat is the major nutrition concern of many consumers. It is therefore important to be able to produce attractive products containing low amounts of fat. This thesis focuses on the sensory dynamics in emulsion products differing in fat content. Two main aspects were studied. One aspect was the influence of ingredients and production parameters on sensory properties, mainly the dynamic influence of fat. The other aspect was the dynamic nature of the perception of sensory properties and took into account how the information in dynamic sensory measurements could be analysed. Sourmilk, mayonnaise, cream cheese and salad dressing were produced according to factorial designs. Fat content was the main design / production parameter and was varied in all the products. The other design parameters varied between the products and were for example type of aroma compound and content, thickener type and content, homogenisation pressure, salt content and emulsifier content. The products were then analysed by sensory (quantitative descriptive analysis and time intensity analysis) and instrumental (rheology and microstructure) methods. Sensory and instrumental data correlated well to each other, as well as data from the two types of sensory analysis.
Fat content was the main influencing parameter on perceived texture and mouthfeel attributes in all the analysed products. Its influence on taste and flavour was less than expected in these products. An increased fat content increased perceived thickness and fattiness. Thickeners and emulsifiers as well as homogenisation pressure were significantly influencing the sensory properties, mainly the texture attributes. Addition of thickeners gave products which were perceived as thicker and fattier. Addition of emulsifiers in salad dressing increased the perceived thickness and fattiness mainly in samples containing low amounts of fat and thickener. An increased homogenisation of mayonnaise and cream cheese gave increased whiteness and decreased perception of fattiness.
Perceived texture attributes and instrumentally measured structure correlated highly. In salad dressing the Pearson correlation coefficient was 0.96 between rheologically measured viscosity and sensorily measured thickness. The sensory methods, quantitative descriptive analysis and time intensity, also related well to each other in the fattiness attribute. The correlation coefficients were 0.99 for the salad dressing and 0.87 for the cream cheese.
Two mathematical methods, one based on polynomials and one on ordinary differential equations (ODEs), were developed in this thesis in order to analyse dynamic sensory data. The polynomial method fitted a polynomial to TI-data. The polynomials were derivated and integrated so that new polynomials were calculated. These polynomials could then be used to plot curves of intensities, velocities, accelerations and area under the curves versus time. The polynomial model could also be used to characterize products. In the ODE-model the eigenvalues characterized the solutions and could be used for characterization of products. The ODE-model also related perceived intensity to experimental factors such as recipe and process parameters in one equation. The ODE-model could then be used to simulate and predict the perception of an attribute at intermediate recipe and process conditions.
ordinary differential equation