Effect of sugar on the extrusion of maize grits and wheat flour

Abstract

The influence of added sucrose on the degree of expansion and extent of starch conversion on extrusion processing of wheat flour and maize grits has been reported.Very different behaviour was found for the two cereal systems. In agreement with previous work, replacement of maize by sucrose at constant water content reduced the specific mechanical energy and as a consequence, reduced the degree of starch conversion and sectional expansion. In contrast, replacing wheat flour by sucrose even at levels as high as 20% of the flour weight had little effect. Possible causes discussed were less efficient plasticization of wheat flour by sucrose compared with maize grits at low water contents, a specific role for gluten and the larger particle size of maize grits compared with wheat flour.

Effect of some extrusion variables on fermented maize-soybean blend

“…Bulk density and SEI are inversely related and they help to explain the phenomenon of expansion as the extrudate exits the die. A high bulk density is associated with a low SEI (Fan et al 1996a;Carvalho and Mitchell 2000) because a more compact material is obtained after milling a less expanded product. The milled flour occupies less space and therefore more material is required to fill a unit volume than that obtained by milling a less compact extrudate.…”

Stability and Functionality of Grape Pomace Used as a Nutritive Additive During Extrusion Process

“…Other possibilities could be that sugar in addition to fiber in GP might have more specific effects. Sugar crystals act as filler at lower feed moisture and enhances expansion of the extrudates [41]. Fiber in GP might have acted as a nucleating agent allowing cornstarch to trap more air cells by surrounding them firmly, while sugars in GP at low feed moisture might have enhanced the film forming effect by allowing bubble walls to be stabilized, resulting in larger porous structure.…”

Effect of sugar and water contents on non-expanded cassava flour extrudates

“…Sucrose has been found to affect significantly the structure and texture of extrudates and the magnitude of sucrose effect may vary according to the cereal source. Carvalho and Mitchell (2000) found that the sectional expansion of wheat flour extrudates was less affected by sucrose than by corn grit extrudates, which was attributed to the starch molecular integrity of wheat being lower than corn starch under severe shear condition. Structural changes have also been attributed to competition for water (HSIEH;PENG;HUFF, 1990) and inhibition of starch gelatinization (JANG et al, 2001).…”

“…In the present work, however, antiplasticizing effects were not seen when sucrose content was increased (Figure 3) probably due to the limited water content in the extrusion process available for starch conversion. Another explanation is particularly related to cassava starch granular structure, which seems to be converted easier under similar thermal shearing conditions imposed during extrusion than cereals, as observed in the work of Carvalho and Mitchell (2000).…”

“…particularly sucrose, on the functional properties of extruded cereal flours has been investigated by a number of researchers who have used different techniques to evaluate degrees of gelatinization, retrogradation, expansion, water solubility, thermal and other properties of extrudates (BARRETT et al, 1995;MITCHELL, 2000MITCHELL, , 2001FARHAT et al, 2000;MOUSIA;MITCHELL, 2003;HSIEH et al, 1993;SOPADE;LE GRYS, 1991). Sucrose has been found to affect significantly the structure and texture of extrudates and the magnitude of sucrose effect may vary according to the cereal source.…”