Properties of extruded snacks containing tomato and garlic
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Tomato and garlic may provide health benefits due to their bioactive compounds and fibers. The main objective of this study was to investigate the effects of tomato (0, 4, 8%), screw speed (200, 275, 350 rpm), and feed moisture content (19, 20.5, 22%) on extruder responses and product properties using a three-level full factorial design with two replications. Spray-dried tomato and dehydrated garlic powder were blended with white corn flour and extruded using a corotating twin-screw extruder. Feed rate and barrel temperature at the metering section were set at 36 kg/h and 121.1oC, respectively. A four blade cutter rotating at 350 rpm was used to cut the extrudates once they leaved the die opening. The samples were stored in sealed plastic bags and were kept at room temperature (25oC). All extruder responses studied (product temperature, die temperature, die pressure, torque, and specific mechanical energy) were significantly affected by tomato, screw speed, and feed moisture content. Increases in tomato level and feed moisture content generally resulted in decreases in extruder responses. Higher screw speeds were associated with lower die pressure and torque, higher temperature and specific mechanical energy. Increasing tomato level resulted in extruded snacks with a lower radial expansion, lower lightness and redder color. While screw speed effect on hardness was dominant, tomato had no significant effect on hardness although an increasing trend in hardness was noticed as the tomato level was increased. However, the effect of tomato on the hardness was significantly different at a feed moisture content of 22%, where a decreasing trend occured. A higher feed moisture content generally resulted in extruded snacks with a lower specific volume, higher lightness and yellowness.
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