Influence of processing conditions on apparent viscosity and system parameters during extrusion of distiller's dried grains-based snacks

Abstract

A combination of different levels of distillers dried grains processed for food application (FDDG), garbanzo flour and corn grits were chosen as a source of high-protein and high-fiber extruded snacks. A four-factor central composite rotatable design was adopted to study the effect of FDDG level, moisture content of blends, extrusion temperature, and screw speed on the apparent viscosity, mass flow rate or MFR, torque, and specific mechanical energy or SME during the extrusion process. With increase in the extrusion temperature from 100 to 140°C, apparent viscosity, specific mechanical energy, and torque value decreased. Increase in FDDG level resulted in increase in apparent viscosity, SME and torque. FDDG had no significant effect (p > .5) on mass flow rate. SME also increased with increase in the screw speed which could be due to the higher shear rates at higher screw speeds. Screw speed and moisture content had significant negative effect (p < .05) on the torque. The apparent viscosity of dough inside the extruder and the system parameters were affected by the processing conditions. This study will be useful for control of extrusion process of blends containing these ingredients for the development of high-protein high-fiber extruded snacks.

In our study, we have combined pulse flour with ethanol industry by-product which is rich in protein and fiber. We studied the effect of extrusion processing on the viscosity, SME, MFR, and torque. The study provides new experimental data of the influence of extrusion processing on system parameters during single screw extrusion of distiller's dried grains-garbanzo flour-corn grits blends. The results obtained will be of great significance for formulation and development of protein and fiber-rich extruded snacks.

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