Assessment of color development due to twin-screw extrusion of rice–glucose–lysine blend using image analysis

Abstract

An image analysis method was developed to determine the color change of rice–glucose–lysine blend during extrusion. The color of extrudates was analysed and compared by using different extrusion conditions. Extrusion process variables included moisture content, screw speed, barrel temperature, and screw geometry. The influence of specific mechanical energy input (SME) and product temperature on the color of extrudates was significant. The color parameters were related to product temperature and SME by a 4th degree polynomial. Product temperature and color were modeled and tested using rice–glucose–lysine blend at various screw configurations and extrusion conditions with reasonable accuracy. Validations of product temperature and color models were done using different screw geometries and other processing variables with reasonable accuracy. Extrusion tests indicated that the developed predictive models can be of use for extrusion processing. The results also showed that the image analysis method developed provides an objective and efficient approach for assessing the color development of extrudates.