Title:Optimization of Single Screw Extrusion Processing Variables and Soy and
Rice Flour Blend Formulations based on Physical Properties of Extrudates
Volume: 3
Issue: 4
Author(s): Pranabendu Mitra*, Srikanth Manohar Pakki, Binu Acharya and Sagar Khanvilkar
Affiliation:
- Department of Kinesiology, Health, Food, and Nutritional Sciences, University of Wisconsin-Stout, Menomonie, WI,
54751, USA
Keywords:
Soy protein-rich extrudates, physical properties, central composite rotatable design, response surface methodology, single screw extruder, RDA, CCRD.
Abstract: Background: Extruded cereals and snacks are mainly carbohydrates. Most adults require
more protein above RDA by restricting carbohydrates for many health benefits. A wide variety of
soy protein-rich extrudates can be produced by blending with rice flour. However, optimum extrusion
processing variables (i.e., screw speed, die temperature, and product formulations) are required
for maximum retention of nutrients with desired product characteristics.
Objective: The objective of this study was to optimize the extrusion operating conditions and soy
flour and rice flour blend formulations for developing protein-rich cereal-like extrudates.
Methods: Twenty formulations using CCRD with the combinations of soy flour content (43-77%),
die temperature (123-157°C), and screw speed (250-350 rpm) were extruded using a single screw
extruder. The physical properties (expansion ratio, density, porosity, hardness, crispness, color, and
water solubility index) of extrudates were determined. The regression models and 3-dimensional
response surface models were developed for each property of extrudates using RSM. Numerical and
graphical optimizations were conducted based on the desirability to determine an optimum condition.
Results: The regression models were able to predict the physical properties of extrudates with an
accuracy of 75-90%, depending on their properties. The 3-dimensional response surface models indicated
that the soy flour content, die temperature, and screw speed affected the physical properties
of extrudates significantly (p < 0.05). Soy flour content (50-55%), die temperature (140-145°C), and
screw speed (290-320 rpm) were very effective for the desired quality of soy flour and rice flour
blend extrudates.
Conclusion: The optimum condition is expected to be very useful for soy protein and rice flour
blend extruded cereal-like product development commercially within the experimental range.
