Effect of extrusion temperature and pre-extrusion particle size on starch digestion kinetics in barley and sorghum grain extrudates

AL-Rabadi, Ghaid J., Torley, Peter J., Williams, Barbara A., Bryden, Wayne L. and Gidley, Michael J. (2011) Effect of extrusion temperature and pre-extrusion particle size on starch digestion kinetics in barley and sorghum grain extrudates. Animal Feed Science and Technology, 168 3-4: 267-279.


Author AL-Rabadi, Ghaid J.
Torley, Peter J.
Williams, Barbara A.
Bryden, Wayne L.
Gidley, Michael J.
Title Effect of extrusion temperature and pre-extrusion particle size on starch digestion kinetics in barley and sorghum grain extrudates
Journal name Animal Feed Science and Technology  (ERA 2012 Listed)    (ERA 2010 Rank A)   Check publisher's open access policy
Publication date 2011-09-22
Sub-type Article
DOI 10.1016/j.anifeedsci.2011.04.097
Volume number 168
Issue number 3-4
ISSN 0377-8401; 1873-2216
Start page 267
End page 279
Total pages 13
Place of publication Amsterdam, Netherlands
Publisher Elsevier BV
Collection year 2012
Language eng
Formatted abstract Barley and sorghum milled grains were separated into three size fractions (fine, <0.5 mm; medium, 0.5–1.0 mm; coarse, >1.0 mm) and extruded at two temperature levels (maximum of 100 °C or 140 °C), to determine the effect of pre-extrusion fraction size on starch digestibility. Following extrusion, in vitro enzymatic starch digestibility was markedly enhanced with a first order rate, typically ten times greater than before extrusion, but following the same trend i.e. faster digestion for finer pre-extrusion grain sizes. For sorghum, the projected maximum digestibility was also reduced with pre-extrusion grain size. There were only minor differences in digestibility following extrusion at 100 °C compared with 140 °C. Grains were not pre-conditioned, so moisture uptake during extrusion may have been limited, resulting in extrudates containing residual ungelatinized starch granules. It is proposed that the main effect of extrusion processing was to open up the grain endosperm structure, thereby reducing the diffusion path lengths for amylase to digest starch. The results indicate that an efficient use of extrusion processing could be to target separated larger particles from milled grains for re-combination with finer ground grains for improved energy utilization in monogastric feeds.
Keyword Barley
Sorghum
Extrusion
In vitro digestion
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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