Effect of Processing Conditions and Optimization of Gluten Free Lentil-Corn Blend Extrudates
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Date
2014-02
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Addis Ababa University
Abstract
An expanded food product was obtained from lentil -corn flour mixtures by extrusion cooking.
Effects of cooking temperature; blend ratio and moisture contents of the feed mixture were
investigated. Effects of these functional properties on expansion ratio, WAI, WSI, WHC, sensory
properties and bulk density were assessed. Specific blends of Lentil and corn were subjected to
twin screw extrusion process with the objective of enriching the protein and mineral content of
corn and produce a range of extruded products. The proportions of lentil and corn were selected
using a unique 15-run, three-factor, and three-level using Response Surface Methodology
(RSM). The lentil flour addition was maintained at 10%, 30% and 50% to test the effect of
protein addition to the cereal or (corn) maintained at 50%, 70% and 90% on the physical
properties of the extruded products. Extruded products were obtained using a co-rotating twin
screw extruder under operating conditions optimized in a previous study.
In general, proportion of ingredients induced significant changes in the product quality
attributes evaluated. Blends with higher proportion of lentil and lower proportions of corn
showed a significantly (p < 0.01) lower specific length value. It was demonstrated that lentil has
good potential for making good extruded products with rich in protein and fiber. 47.8% lentil
flour, 52.2% corn flour (db) processed at 15.82% moisture content and 181.97°C temperature
was selected as the best formulation to yield a protein rich extruded product with desirable
physical and functional attributes. The product was fully expanded and well cooked with almost
uniform in sizes and shapes at these optimum conditions.
The extruded snacks were evaluated and determined for its quality attributes such as chemical
composition, physical and functional properties, sensory qualities and textural properties.
Values of physical properties of extrudates obtained: expansion ratio were in the range of 1.08-
1.43 and bulk density were 0.36-0.54 gm/cm3 and specific length 1.09-3.90 cm/gm and of
functional properties obtained:WAI were 4.11-8.23%, WSI were 6.41-11.74% and WHC were
2.64-8.83%. Over all acceptability is in the range of 4.7-8.24.The textural data were evaluated
by breaking strength test with the help of cylindrical probe TA-XT whose values indicates
between 0.4 to 0.80 N/mm2. The sensory scores of the extruded products had a mean value
greater than 5, and rated acceptable by sensory panels.
Keywords: Extrusion physical properties, Optimization, Response Surface Methodology, lentil,
corn.
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Keywords
Extrusion physical properties, Optimization, Response Surface Methodology, lentil, Corn