Jin, X.

Koa, S. S.

Sopade, P. A.

Zhang, J.

University of Queensland eSpace

Extruder response and properties of extrudates from a model sorghum-
barley blend 
S.S. Koa*, X. Jin*, J. Zhang*,† and P. A. Sopade *,†, ‡  
 
*School of Agriculture & Food Sciences, †Centre for Nutrition & Food Sciences, University of Queensland, St. Lucia, QLD 4072 
‡ Correspondent (E-mail: p.sopade@uq.edu.au; Phone: 07 334 67653; Fax: 07 336 51177)  
Why Sorghum-Barley Blend? 
Cereals are important food and feed materials globally, and in Australia, barley and sorghum are two of the three (wheat, barley and sorghum) most important cereals. 
Barley is recognised for its β-glucan, which is associated with reduced risk of chronic diseases1. As the least digestible of the cereals due to pronounced starch-
protein interactions, resistant starch is high in sorghum, and its phytochemicals and associated nutraceutical properties2, appeal to the health food industry. Mixing 
sorghum and barley can maximise the food benefits of the resulting products, and with extrusion, which is a notable cereal processing technique, the products can be 
diverse and varied. Despite studies on the grains individually or mixed with other ingredients1,3,4, extrusion of sorghum-barley mixtures has not been widely 
reported. The present study reports the relationships between extrusion conditions, extruder response and extrudate properties of a model sorghum-barley blend. 
References 
1. Altan A, McCarthy KL, Maskan, M. 2009. Int. J. Food Sci. Technol. 44: 1263.  
2. Awika JM, Rooney LW. 2004. Phytochemistry 65: 1199.  
3. Baik BK, Powers J, Nguyen LT. 2004. Cereal Chem. 81: 94-9.  
4. Mahasukhonthachat K, Sopade PA, Gidley M. 2010. J. Cereal Sci. 51, 392. 
5. Yong L-Z, Chan CH, Garcia C, Sopade PA. 2011. Carbohyd. Polym. 84: 162. 
6. Altan A, McCarthy KL, Maskan, M. 2008. J. Sci. Food Agric. 88: 1648.ti 
20 25 30 40 150 220 300 2 3 4 5 110 140 160 
Extruder SME (kJ/kg) 575d  465a 340b 137c 278a 318ab 346b 395a 307b 240c 199d 369a 395b 351c 
Pressure (bar) 60d  40a 21b 8c 26a 22b 21b 21a 21a 22a 22a 18a 21b 21b 
Melt temperature (oC) 106c  103a 102a 98b 99a 101a 103a 105a 106b 105a 105a 97a 105b 111c 
Expansion Transverse (m/m) 1.8a  1.8a 1.8a 1.4b 1.5a 1.7b 1.8c 1.9a 1.8a 1.7b 1.7b 1.5a 1.9b 1.9b 
Longitudinal (m/kg) 152c  161a 180b 256c 206a 197b 193b 170a 176ab 188c 183bc 190a 170b 174b 
Density (kg/m3)  692a  624a 570b 628a 688a 589b 547c 536a 542ab 589b 575ab 783a 536b 501b 
Colour ∆E  58.9c  63.5b 64.7a 64.3ab 65.1a 63.2c 64.2b 65.4a 65.7a 62.7a 62.8a 65.3a  65.2a  60.4b  
Browning index 20.5c  13.9a 12.1ab 11.2b 10.3b 14.0a 12.9a 10.7a 9.4b 16.8a 17.4a 10.3a  10.7a  16.2a  
Pasting Initial viscosity (cP) 78c  63a  57a  27b  40c  49b  58a  65ab  79a  45b  41b  44c  65b  94a  
Peak viscosity (cP) 408b  390b  370b  546a  479a  434b  394c  341b  389a  316b  424a  364a  341ab  288b  
Trough viscosity (cP) 333d  277b  196c  392a  353a  278b  235c  162c  227b  209b  283a  255a  162b  139c  
Final viscosity (cP) 687d  494b  366c  938a  762a  558b  479c  290c  392b  412b  599a  494a  290b  242c  
Swelling# WAI  (g/g solids) 3.4a  3.6a  3.6a  2.2b  3.0a  3.2a  3.3a  3.9a  4.2a  3.2a  3.2a  3.1a  3.9a  4.0a  
WSI (g/g solids) 12.7a  10.0b  8.7c  5.9d  6.9c  8.0b  9.7a  10.4a  10.2ab  9.2bc  8.3c  8.5c  10.4b  11.8a  
Textural‡ Hardness (N) nd†  5.0a  3.5b  1.4c  3.0a  3.2a  3.6b  nd  nd  nd  nd  nd  nd  nd  
Crisp-AUC (mN.m) nd  2.4a  1.8b  1.1c  1.6a  1.8a  1.8a  nd  nd  nd  nd  nd  nd  nd  
Crisp-Slope (MNm-1) nd  8.7a  7.2b  2.3c  5.6a  5.7a  6.8b  nd  nd  nd  nd  nd  nd  nd  
Digestibilityƒ D240 (g/100 g DS) 92.9
a  93.3a  89.3a  92.5a  92.0a  94.1a  89.0a  88a  79.2ab  89.4a  76.2b  80.3a  88.0a  75.2a  
Glycemic load (GL) 54.2a  54.7a  54.0a  54.3a  54.4a  54.7a  54.0a  53.8a  51.4ab  53.9a  50.5b  51.4ab  53.8a  50.9b  
Parameter Moisture (%) Screw speed (rpm) Feed rate (kgh-1) Temperature (oC) 
Key Findings 
The main effects of the extrusion conditions are 
summarised in Table 1 with the following deductions: 
• The specific mechanical energy (SME) reduced as either 
the feed rate or moisture was increased because of 
changes to melt viscosity. Increasing the feed rate or 
degree of fill of the extruder barrel demanded a lower 
energy per unit mass. 
• With more superheated water in the melt, increasing the 
barrel temperature increased the pressure to benefit 
directly expanded products. This could explain why a 
dense product would result from reducing the barrel 
temperature or screw speed. 
• Reducing the moisture increased the extent of browning 
in the extrudates from non-enzymatic browning, while 
an increase in the moisture produced softer and less-
crisp extrudates. 
• The extrudates were more digestible than the non-
extruded blend (D240, ≈ 70 g/100 g dry starch; GL = 40). 
Even though the different levels of starch gelatinisation 
and retrogradation in the extrudates produced different 
pasting and swelling properties, the starch digestibility 
was essentially independent of extrusion conditions. 
Extruding the sorghum-barley mixture at a temperature of 
140oC, screw speed of 300 rpm, feed moisture of 30% and 
feed rate of 3 kg/h will optimise the physical and 
digestibility properties of the cereal blend for extruded 
sorghum-based products in the food chain. 
*Values with the same letters are not significantly different (p>0.05). 
#WAI and WSI are respectively water absorption, and solubility indices. 
‡Crisp-AUC and Crisp-Slope are crispness indices respectively measured by the area under the force-distance graph, and the slope of the graph. 
†nd: not determined. 
ƒIn-vitro starch digestion, DS = dry starch, and glycemic load was calculated relative to fresh white bread, and using the area under the starch digestograms. 
Table 1: The main effects of extrusion conditions on extruder response and extrudate properties* 


Extruder response and properties of extrudates from a model sorghum-barley blend

http://espace.library.uq.edu.au/view/UQ:310998/SOPADE_Extruder_Response_Properties_-_Poster.pdf

Extruder response and properties of extrudates from a model sorghum-barley blend

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