Stability of anthocyanins as pre-extrusion colouring of rice extrudates

The suitability of anthocyanin as a pre-extrusion colour nutraceutical of rice flour was evaluated as a function of extrusion parameters viz. moisture content, screw speed and temperature of extrusion. The retention of anthocyanin increased with an increase in the moisture content of feed material and screw speed, but decreased with an increase in the die temperature. The effect of citric acid and sodium bicarbonate on colour stability of extrudates during processing, and that of light and packaging materials during storage at ambient conditions (30 ± 2 °C) were evaluated. Addition of 1% citric acid increased the retention of anthocyanin up to 18.2% which could reduce the requirement of pre-extrusion colouring by almost 25%. Metallized polyethylene was found to be a better packaging material than low density polyethylene and protected the extrudates from light as well as losses during storage.

Research highlights► Retention of anthocyanins as preextrusion colouring depended on extrusion parameters. ► 1% Citric acid improved the retention of anthocyanin in the extrudates. ► This reduced the colour requirement by 25%. ► Sodium carbonate reduced the retention of anthocyanin in the rice extrudates. ► Metallized polyester was suitable for packaging of the coloured extrudates.