Modeling of Functional Wheat-Based Extrusion Process Conditions
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Date
2018
Authors
Mulugeta, Teamir
Journal Title
Journal ISSN
Volume Title
Publisher
AAU
Abstract
Extruded expanded products are becoming an essential part of the food in the today’s fast-paced
life. However, due to the presence of high amounts of starch, high gluten and low amounts of
beneficial nutrients in most extruded products, frequent consumption of these products can result
in health issues. Limited information are available on the addition of tef flour, sesame protein
concentrate and tomato powder in combined form to the wheat based extrusion cooking system.
Furthermore, knowledge on the effect of extrusion processing on wheat-based product quality is
scarce. Therefore, the aim of this research was to evaluate the prospect of addition of tef flour,
sesame protein concentrate and tomato powder to wheat flour in order to produce functional,
protein-dense and reduced gluten extruded products.
Varying the compositions of the blends and processing conditions showed that feed components
and processing conditions had significant (P ≤ 0.05) effects on physicochemical, functional and
rheological properties. Tef flour and tomato powder significantly improved the antioxidant activity
level of the extruded products to 119.61 µmol TE/100 g, db compared to all wheat extruded
product (60.9 µmol TE/100 g, db). Sesame protein concentrate significantly raised the protein
content and simultaneously lowered the carbohydrate content of the extruded products from 74.15
g/100 g to 61.35 g/100 g. In a formulation containing highest levels of protein content (up to 33
g/100g), product qualities were at the acceptable range.
The wheat-based extruded products had more elastic behavior than viscous ones. Storage modulus
and loss modulus of the extruded products increased with increment of frequency from 0.1 to 100
rad/s. Higher storage modulus than loss modulus over a range of frequency has been found in all
extruded products that testify the extruded products had an elastic behavior than viscous. During
extrusion cooking at higher temperature and lower moisture content, acrylamide was formed but
within the acceptable range (59.33 - 260.01 µg/kg) Antioxidant activities and other product
qualities of wheat-based extruded products were significantly (P ≤ 0.05) affected by the process
conditions.
Increasing screw speed, moisture content and feed rate resulted in a shorter mean residence time
level (less than 63 s) and a decrease in the spread. The flow in the extruder approached plug flow
as the feed rate increased and approaching mixed flow with an increase in the screw speed. Exit age and cummulative fiunction distributions were responsive to process variables and well
predicted.
Relationships of processing conditions and components with extruded product qualities were
investigated using artificial neural network model. The weights and biases for regression
estimation were optimized. Artificial neural network proved to be a powerful tool in modeling of
the interactions of factors and responses. Neural network efficiently predicted with all R-squared
values above 0.89 and very low root mean square error. These models performed better than the
statistical models.
The findings from the present study show that it is possible to produce sensorially acceptable
functional and nutrient-dense wheat-based extruded products. The results obtained add knowledge
on the usefulness of artificial neural networks for modeling of extrusion cooking
Description
Keywords
Wheat-Based Extrusion Process, processing