Extruded snacks from pigmented rice: Phenolic profile and physical properties

This study arose from the need to meet the request of consumers for healthy, ready-to-eat foods. The behavior of pigmented rice was investigated during extrusion in terms of nutritional (i.e., phenolic acids, anthocyanins and antioxidant capacity (AC)) and physical (i.e., starch pasting properties, texture, porosity and biometric indices) properties. Snacks were produced from brown, red, and black rice, by means of a co-rotating twin-screw extruder, and their features were compared with those of snacks from white rice. Although the soluble and cell-wall bound phenolic acid contents of pigmented and brown rice did not differ, the red and black rice both resulted in a higher AC after extrusion. Black rice showed the highest anthocyanin and AC contents, even after extrusion. Furthermore, the high phenolic compound content of black rice affected the starch pasting properties, and led to a lower viscosity and higher snack porosity than those of brown rice. Nevertheless, considering both the biometric and textural properties, the best results were obtained from red rice. Optimizing the extrusion conditions will help reduce the loss of anthocyanins in snacks made of pigmented rice, increase the nutritional value and improve the physical properties of the product.