This relationship was also observed through the Pearson correlation coefficient between the expansion ratio and density (r = −0.952, p < 0.001), thus indicating a strong negative correlation between these two dependent variables. Density is a parameter that can also be used to assess the degree of expansion of the extrudates. While the expansion ratio considers only the cross-section of the material, density Ku-0059436 cell line considers expansion in all directions. Low density is desirable for extruded products ( Meng, Threinem, Hansen, & Driedger, 2010). The same temperature effect on extrudate density was observed by Yuliani et al. (2009) in relation to extrusion of corn starch with d-limonene and by Saeleaw

et al. (2012) in relation to extrusion of rye flour. The cutting force of the extrudates ranged from 20.98 to 51.60 N, which was close to the range of values found by Conti-Silva et al. (2012) for the cutting force of flavored corn grit extrudates, which was 23.7–34.2. The best fit for the cutting force of extrudates was also observed for the linear model, and only the extrusion temperature was significant (Table 2). It was observed that increasing the extrusion temperature not only decreased the density but also decreased

the cutting force of the extrudates, also verified by the negative sign of the coefficient of the linear RO4929097 term of temperature (Table 2). Since temperature increases reduce the viscosity of the dough and promote growth of air bubbles, the thickness of cell walls in the extrudates decrease (Yuliani et al. 2006a), thus reducing the cutting force. The cutting force of the extrudates was negatively correlated with the expansion ratio (r = −0.628, p = 0.007) and positively Monoiodotyrosine correlated with the density (r = 0.726, p = 0.001), given that extrudates presenting greater expansion or lower density may be structurally more fragile or have lower mechanical strength ( Yuliani et al., 2009). Volatile compounds retention ranged from not-detected (ND) to 0.49 mg/g of extrudate for isovaleraldehyde, from 0.05 to 0.62 mg/g of extrudate for ethyl butyrate

and from ND to 36.10 mg/g of extrudate for butyric acid. The bigger retention was found to the butyric acid, followed by ethyl butyrate and isovaleraldehyde, as found by Conti-Silva et al. (2012). This behavior is due to vapor pressure and boiling temperature of the volatile compounds. Isovaleraldehyde, the compound less retained in all extrusion conditions, has the biggest vapor pressure (4009 Pa) and lowest boiling temperature (92.5 °C), as opposed to butyric acid that was more retained because of the lowest vapor pressure (57 Pa) and biggest boiling temperature (163.7 °C) (Lide, 1997). The low volatility promotes a higher diffusivity of the compound through the matrix of the extrudate, resulting in a bigger encapsulation and, consequently, higher retention.