The effect of extrusion conditions on mechanical-sound and sensory evaluation of rye expanded snack Original Research Article

Rye-based extrudates were produced according to different conditions of barrel temperature (150 °C and 190 °C) and feed moisture content (12% and 16%) using a 22 factorial design. A combined mechanical and acoustic method was employed using a texture analyzer (TA-XT Plus, Stable Micro Systems) in combination with the acoustic envelope detector (AED), to describe the influence of extrusion parameters on the properties of extrudates. The results showed with increasing extrusion cooking temperature increasing number of force and number of sound peaks but decreasing maximum forces. Moreover the thickness of the cell wall decreased with increasing extrusion cooking temperature. All these trends were reversed with increasing feed moisture content. The results show further significant interactions, which means that the effect of barrel temperature depends on the feed moisture content and vice versa. Additionally, the quantitative descriptive analysis (QDA) was applied to examine the products in terms of sensory properties. The data were analyzed by principle component analysis (PCA) in order to investigate the relationship between sensory attributes and the instrumental data. The PCA showed a positive correlation between the sensory parameters hardness and sound intensity of crunchiness and the instrumental parameters force area, mean force, maximum force, and negative correlations between the number of sound peaks, mean sound peak, number of force peaks and crunchiness.