Study on the process of single-screw extrusion-cooking of mixtures with a content
of pea hulls
More details
Hide details
1
Engineering and Cereals Technology Department, University of Agriculture, Skromna 8, 20-704 Lublin, Poland
Int. Agrophys. 2006, 20(4): 327-336
KEYWORDS
ABSTRACT
A study was conducted on the possibility of
application of pea hulls as a valuable source of dietary fibre and of
biologically active compounds for the production of cereal
extrudates. The research was performed using a single-screw
extrusion-cooker with a compression ratio of 3:1 and L:D=12:1,
using the following cereal materials: commercially available corn
grits, pea hulls of cv. Opal, and oats bran. The aim of the study was
to examine the effect of the leguminous material and of the process
parameters (profile of barrel temperature distribution and raw
material moisture) on the possibility of stabilization of extrusion
conditions, physical properties of the extrudates, and on the
sensory features of the product. The study showed that the technology
of single-screw extrusion-cooking can be applied to process
mixtures containing maximum 15% of pea hulls; higher levels of
the pea hulls content caused a disturbance of the stability of the
process and so-called 'material slippage'. Increase of the pea hulls
content in the mixture above 10% caused a decrease in radial
expansion and an increase in specific density even up to 140 kgm-3.
Moderate introduction of pea hulls did not result in any deterioration
in the texture of the extrudates. The physical properties of the
extrudates were significantly affected by the temperature of extrusion
and by the raw material moisture content. Increased process
temperature resulted in a decrease in radial expansion with simultaneous
decrease in specific density of products, increase in crispness
and decrease in the WAI of the extrudates. Increase in the moisture
of the processed material, on the other hand, resulted in lower radial
expansion, increased specific density, and increased water
absorption index (WAI) of grinded extrudates. Admixture of pea
hulls in amounts up to 7.5% did not cause any deterioration in the
sensory features of the extrudate.