Carrot pomace enhances the expansion and nutritional quality of corn starch extrudates

• Carrot pomace enhanced the expansion quality when included at 5% level.
• Surface of extrudates with 5% carrot pomace showed reduction in surface shrinkage.
• Carrot pomace retained some β-carotene through extrusion thus increasing nutrition.
• Results indicate active interaction between insoluble fiber and starch polymers.

Corn starch was extruded with the inclusion of carrot pomace at levels of 5, 10, and 15 g/100 g at three different feed moisture levels of 15, 22.5 and 30 g/100 g. Corn starch without any added pomace was extruded as a control treatment. A thorough evaluation of the extrudate properties (expansion ratio, unit density, water solubility index, water absorption index, microstructure, and β-carotene content) was conducted to understand the role of the insoluble fiber in the carrot pomace on the extrusion process, specifically relating to expansion. The best expansion was observed in the extrudates with 5 g/100 g carrot pomace inclusion, and at 15 g/100 g feed moisture. The surface of this extrudate also improved, compared to the control and extrudates with higher levels of pomace inclusion. The extrudates with higher levels of carrot pomace showed a significant decrease in expansion. Overall, the results showed that the level of carrot pomace inclusion had significant impact on the extrudate quality.