Effect of Extrusion on Essential Amino Acids Profile and Color of Whole-Grain Flours of Quality Protein Maize (qpm) and Normal Maize Cultivars

Abstract

Whole-grain flours of Quality Protein Maize (QPM) and normal maize were extruded under controlled conditions in order to evaluate the effect of extrusion on the essential amino acids profile and color of the raw material used in the production of maize based extrudates. Flours were conditioned to 150g/kg moisture and processed in a single screw extruder at a screw compression ratio of 3:1, screw speed of 80 rpm, and die head temperature of 130 0 C, using two different die nozzle diameters (3 and 5 mm). Extrusion caused a diminishment in the contents of the essential amino acids isoleucine, leucine, lysine, threonine and valine when compared to their original flours (P<0.05). But, the contents of histidine, methionine, phenylalanine and tryptophan were not different for flours and extrudates of the same source (P>0.05). QPM samples, either raw or extruded, were significantly higher in lysine, methionine and tryptophan compared to samples of normal maize (P<0.05). Extrudates produced with yellow QPM flours were lighter than their correspondent raw material (P<0.05), different from that of yellow normal maize. This trend was also observed for redness (a values) in extrudates. On the other hand, white and yellow extrudates presented higher b values (yellowness) than their correspond raw flour. Despite the adverse effect of extrusion in the amino acid retention, the use of QPM flours in replacement of normal maize flours can provide maize extrudates with superior protein quality.

Effect of Extrusion on Physicochemical Properties, Digestibility, and Phenolic Profiles of Grit Fractions Obtained from Dry Milling of Normal and Waxy Corn

“…African tall extrudates showed an increase, whereas HQPM1 and waxy extrudates showed a decrease in a * with rise in ET. This may attributed to the white color of African tall where the nonenzymatic browning caused an increase in redness (Paes and Maga, ). HQPM1 extrudates from each RS showed a significant decrease in b * value with rise in ET which might be attributed to the partial destruction of certain pigments imparting yellow color to HQPM1 (Paes and Maga ).…”

“…This may attributed to the white color of African tall where the nonenzymatic browning caused an increase in redness (Paes and Maga, 2004). HQPM1 extrudates from each RS showed a significant decrease in b * value with rise in ET which might be attributed to the partial destruction of certain pigments imparting yellow color to HQPM1 (Paes and Maga 2004). African tall and waxy extrudates showed a small change in b * with rise in ET.…”

“…The lower L * of extrudates than their grits might be attributed to degradation of starch to sugars during extrusion resulted into enhanced Maillard reaction. Paes and Maga (2004) also reported that extrusion processing adversely affected the L * of corn. HQPM1 and waxy extrudates from each RS showed a significant increase in L * with rise in ET (Table 2), consistent with earlier findings (Dehghan-Shoar and others 2010; Selani and others 2014).…”

Effect of extrusion variables on antioxidant activity, total phenolic content and dietary fibre content of gluten‐free extrudate from germinated Chenopodium (Chenopodium album) flour

“…S2a), it was observed that with increased screw speed, the lightness of extrudates increased significantly, although lightness was increased initially in accordance with increase in barrel temperature but declined slightly at higher temperature. The fading was attributed to the partial destruction of pigments upon processing, resulting in extrudates with higher L‐values (Paes & Maga, ); however, L* value decreased on further increase in temperature as higher temperatures are known to promote nonenzymatic browning. Increase in screw speed resulted in increase in brightness due to low retention time in extruder (Nazir et al ., ).…”

Effect of banana flour, screw speed and temperature on extrusion behaviour of corn extrudates

“…The higher L* value indicated greater lightness of extrudates. As more expanded extrudates had higher surface area that caused light to disperse, giving a lighter appearance to the puffed products (Paes and Maga 2004). The interaction effect of SS and ET on L* value was significant.…”