Extrusion, structure and mechanical properties of complex starchy foams

Cellular architecture and its relationship with mechanical properties in expanded extrudates containing apple pomace

“…Ellipsoid shape cells are predominant with greater elongation in the direction perpendicular (y/z) to extrusion and the shorter axis of the ellipsoids in the extrusion flow direction (x). Robin et al (2010) observed similar anisotropic expansion in wheat flour extrudates. The primary reason for such anisotropy is the elastic recovery forces at work at the discharge end of the extrusion die (Moraru & Kokini, 2003;Pai et al, 2009).…”

“…Within a narrow D cell band of 0.3-0.4 mm, F cr varied from 54.4 to 121.4 N. There was a clear separation of data with respect to in-barrel moisture content in this band, with 25% MC treatments having the highest F cr (89.6-121.4 N), followed by 20% MC (68.5-91.3 N) and 17.5% MC (54.4-67.6 N). As discussed increase in t wall with MC was the primary reason, but reduced degree of starch depolymerization could also have contributed by further strengthening the cell walls (Barrett & Peleg, 1992;Carvalho & Mitchell, 2000;Robin et al, 2010). F cr versus D cell data also indicated reinforcement of the solid matrix (or increase in E s ) by apple pomace.…”

“…XMT provides a non-invasive means of accessing features such as cell size and cell wall thickness, along with their distributions, which is impossible with 2D imaging (Trater, Alavi, & Rizvi, 2005). XMT has been successfully used to analyze the internal structure of extruded samples comprising of starch only Babin et al, 2007;Cheng, Alavi, Pearson, & Agbisit, 2007), starch with proteins Cho & Rizvi, 2009;Trater et al, 2005), wheat flour (Robin et al, 2010) and flours with guar gum (Parada, Aguilera, & Brennan, 2011). To the best of our knowledge, this technique has not yet been used to study the impact of fruit fibers on the cellular architecture of extrudates.…”

Nondestructive Imaging of Cellular Solid Foods

“…The sample extruded at 163 Wh/kg SME had thicker cell walls with a maximum at 0.04 mm. Robin et al (2010;2011a, b, c;2012a, b) made an extensive study on structural and textural effects of wheat bran supplemented extruded solid foams. The authors used 1172 desktop µCT for scanning and CTAn software for data processing (Skyscan, Kontich, Belgium).…”

“…XMT imaging was done with 1172 MCT system (Brüker MicroCT, Kontich, Belgium). Image processing was done using same approaches of Robin et al (2010). A linear increase of porosity vs. average cell size was reported for both whole wheat-and corn-based extrudates (Chanvrier et al 2014).…”