Effects of green tea contents on the quality and antioxidant properties of textured vegetable protein by extrusion-cooking.

The aim of this study was to evaluate the effects of green tea contents (0, 5, 10, and 15%) on texturization and antioxidant properties of textured vegetable protein (TVP) by using a twin-screw extruder. Extrusion conditions were fixed at 140 °C barrel temperature, 50% moisture content, 100 g/min feed rate, and 200 rpm screw speed. The integrity index, hardness, and cutting strength of TVP significantly (< 0.05) increased with the increase in green tea levels, while cohesiveness, springiness, water holding capacity, and nitrogen solubility index (NSI) significantly (< 0.05) decreased. Increasing the amount of green tea resulted in better DPPH radical scavenging activity, higher total phenolic, total flavonoid, catechins, and caffeine contents. The (-)-epigallocatechin gallate, (-)-epicatechin, (-)-epigallocatechin, and (-)-epicatechin gallate contents of TVP significantly (< 0.05) decreased, compared to that of raw materials. The incorporation of green tea in TVP can negatively affect expansion and NSI while positively affect texturization and antioxidant properties.