, 2006a, Yuliani et al., 2006b, Yuliani et al., 2009 and Conti-Silva et al., 2012). Thus, further work to develop better understanding of the effect of extrusion conditions on the structure and retention of flavor in pre-flavored extrudates is required. Therefore, the aim of this study was to investigate the effects of the moisture content of

the raw material, extrusion temperature and screw speed on the structural parameters, volatile compounds retention and sensory acceptability selleck chemicals llc of corn grit extrudates flavored using response surface methodology. The corn grits (7.7 g/100 g protein, 1.1 g/100 g fat, 0.3 g/100 g ash and 90.0 g/100 g total carbohydrates, on a dry basis) were purchased from a local market

and were not subjected to any process before extrusion. For flavoring, a mixture of three volatile liquid compounds was used: isovaleraldehyde, ethyl butyrate and butyric acid (Sigma–Aldrich, Milwaukee, USA). The corn grits composition was determined in accordance with the AOAC (1997) for ash and proteins, and in accordance with the AOCS (2009) specifications for lipid content, and the total carbohydrates content was estimated by difference. The corn grits were ground in a knife mill (model 340, Marconi, Piracicaba, Brazil) and Akt inhibitor ic50 the analyses were performed in triplicate. The response surface methodology was applied using a rotational central composite design for three independent variables (Barros-Neto, Scarminio, & Bruns, 2010), namely: the moisture content of the raw material (dry basis), the extrusion temperature (temperature in third barrel zone) and the screw speed. The dependent variables used were the expansion ratio, density, cutting force and volatile retention for each compound individually and in total for all the compounds. Seventeen tests were performed: eight tests of factorial points (23) (three levels for each factor), six axial points (two for each variable) and three repetitions of the central point (Table 1). The results from the dependent

variables were subjected to multiple regression analysis using the Statistica 7.0 software (StatSoft Inc., Oklahoma, EUA) and coefficients with p values below 0.05 were considered significant. The regression was evaluated by means of analysis P-type ATPase of variance: the regression was considered to be significant when p ≤ 0.05, but no lack of fit at p > 0.05. Linear and quadratic models were tested to explain the influence of independent variables on the response variables, because in Response Surface Methodology, the relationship between these variables is unknown and, therefore, it is necessary to find an adequate approximation to the true relationship between the response and the independent variables ( Montgomery & Runger, 2006). Samples of 400 g of grits were prepared to achieve moisture contents of 10, 12, 15, 18 and 20 g/100 g on a dry basis.