UNIAXIAL COMPRESSION OF UF-FETA CHEESE RELATED SENSORY TEXTURE ANALYSIS

Rheological characteristics of seven Feta cheeses with different textu res and produced from ultrafiltered milk (UF-Feta cheeses) were evalua ted by uniaxial compression and sensory texture analysis. The effect o f uniaxial deformation rate (50-2500 mm/min) on four rheological param eters: Stress at fracture (sigma(f)), Hencky strain at fracture (epsil on(f)), deformability modulus (E) and work to fracture (W-f) was exami ned. Three Principal Components (PC) described 76, 16 and 4% respectiv ely, of the variation in the uniaxial compression data set (4 paramete rs at 12 deformation rates). Statistically sigma(f), E and W-f describ ed the same type of information in the data set. Six sensory texture a ttributes of the UF-Feta cheeses were evaluated by a sensory texture p anel: nonoral firmness, nonoral brittleness, nonoral spreadability, or al crumbliness, oral firmness and oral stickiness. One PC described 93 % of the variation in the sensory texture data and grouped the sensory variables into two negatively correlated groups: normal firmness nono ral brittleness, oral firmness and oral crumbliness versus nonoral spr eadability and oral stickiness. Correlations and Partial Least Squares regression (PLS) between instrumental and sensory texture variables s howed that nonoral and oral firmness were the nonoral and oral sensory variables best predicted from instrumental measurements. sigma(f), E and W-f were all able to predict nonoral and oral firmness. Of the ins trumental parameters, sigma(f) generally gave the best correlation to nonoral firmness at all deformation rates. Above a deformation rate of 50 mm/min correlations between sigma(f) and normal firmness were almo st independent of deformation rate, and at any deformation rare correl ations between sigma(f) and oral firmness were independent of deformat ion rate, implying that it is not necessary to do compression testing of UF-Feta cheese at the chewing rate to get a good correlation with s ensory evaluation. Using four instrumental variables (sigma(f), epsilo n(f), E and W-f) for prediction increased correlations slightly, compa red to prediction using sigma(f) alone. However, sigma(f) was preferre d as a measure for nonoral firmness because of the simplicity in model ling, and also as a measure for the total variation in the sensory tex ture quality of UF-Feta cheese because of the high correlations among the sensory variables.