Characterization of the dent and flint corn fractions with different particle sizes and evaluation on the quality expanded extrudes / Caracterização das frações com diferentes granulometrias de milho dentado e duro e avaliação na qualidade de extrusados expandidos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The endosperm of a corn grain is made up of a vitreous region and a farinaceous region, which present different chemical and physical composition. Corn fractions obtained by dry milling, presenting different particle sizes distributions and variations in chemical composition, are used in the production of expanded extrudates (snacks). The objective of the present research was to evaluate the influence of milling fractions from dent and flint corn varieties, with different particle sizes and chemical compositions, on the quality of expanded extrudates. Three fractions from each variety were used, corresponding to the fine flour, coarse flour and fine grits. The raw material was characterized with respect to its chemical (crude protein, ether extract, ash, carbohydrates and amylose), physical (granulometry, hardness and color) and rheological (water absorption and solubility indices and viscoamylographic properties) compositions. For the production of the expanded extrudates, a central composite rotational design was used with two independent variables (x1 = conditioning moisture content, between 14 and 22%, and x2 = die temperature, between 120 and 170°C for dent corn and 130 and 170°C for flint corn), 4 factorial trials, 4 axial trials and 3 repetitions at the central point, giving a total of 11 trials for each fraction was used. The results were analyzed using the Response Surface Methodology and showed that the particle sizes of the different fractions had an influence on the extrusion process and on the quality of the expanded extruded products. Of the independent variables, the conditioning moisture content showed the greatest effect on the quality of the extruded products. In addition, the effect of reducing the particle size of the fine grits fraction to a coarse flour in the production of the extrudates was evaluated. The responses evaluated were the expansion index, the compression force (texture), the water absorption and solubility indices and the viscoamylographic properties, such as the cold and hot viscosities, loss in viscosity and retrogradation tendency. It was shown that the corn fractions had physicochemical and rheological significant different compositions, but the extracted starch for dent and flint corn didn?t present significant diference in the viscoamylographic properties. The best responses were obtained using the intermediate fraction of dent corn (92.72% of particles sizes between 0.500 and 0.177mm) and the smallest fraction of flint corn (91.67% of particles sizes between 0.250 and 0.177mm), the best results were obtained using the intermediate fraction of dent corn. The reduction in particle size of larger fraction, such as fine grits with a predominant particle size between 0.840 and 0.500mm, to smaller sizes (majority <0.250mm), resulted in improvements of great technological importance in the quality of the expanded extrudates, especially for expanxion index and compression force, and was shown to be effectively viable mainly for flint corn. Linear and negative correlation indices were obtained between the expansion index and the compression force (between -0,7617 and -0,9230), and positive between the water absorption and water solubility indices (between 0,5760 and 0,9589). It was concluded that the fractions with different particle sizes presented different effects on the expanded extrudates production and that the greater the fraction of vitreous endosperm with smaller particle sizes, the better the results obtained. M200 fraction presented the best results for dent corn and P100 fraction for flint corn and for each fractions, the best results was obtained whit 14% for conditioning moisture content and 130°C for the die temperature. In addition, fine grits particle sizes reduction showed viability for expanded extrudates production, mainly the flint corn

ASSUNTO(S)

corn frações de moagem extrusão milho milling fractions extrusion particle size materiais granulados

ACESSO AO ARTIGO

Documentos Relacionados