Physical and chemical properties of tomato, green tea, and ginseng-supplemented corn extrudates produced by conventional extrusion and CO2 injection process

Abstract

In this study, extrudates were produced from corn flour supplemented with tomato, green tea, and ginseng powder by conventional extrusion and CO2 injection methods. In conventional extrusion process, the die exit temperatures were adjusted to 80, 110, 130 °C and CO2 injection method was carried out at 80 °C. In both extrusion methods, the feed moisture, screw speed, and die diameter were kept constant at 20 %, 250 rpm, and 3 mm, respectively. Corn flour was supplemented with tomato powder at three different levels (4, 8, and 12 %), but ginseng and green tea were added only at 8 % level. The bulk density results generally had an inverse relationship with the expansion index values. Higher tomato powder supplementation levels resulted in higher total phenolic compound levels and antioxidant activities. These increases were around 11-fold as compared to control samples in 12 % tomato powder supplementation level at 130 °C extrusion temperature. The results indicated that antioxidant activity increased with increasing extrusion temperature. This increase might be due to higher amount of Maillard reaction products, with antioxidant activity, formed at higher extrusion temperatures. The color (L*, a*, b*) and hydroxymethylfurfural results proved that the rate of Maillard reaction increased at higher extrusion temperatures during the extrusion process. Green tea supplementation resulted in higher total phenolic compounds and antioxidant activity values as compared to tomato and ginseng supplementation under the same extrusion conditions.