On-line monitoring during extrusion cooking of an expanded cereal snack

Abstract

On-line monitoring devices are fast and precise tools that enable characterization of materials during processing. Raman spectroscopy and non-destructive ultrasound techniques were utilized on-line during extrusion cooking of a cereal snack in this study. The objectives were to determine the effects of extrusion variables on final properties, determine the type of chemical bonds present during extrusion, and to establish a relationship between on-line monitoring tools and textural properties of an extrudate. The results showed that temperature and formulation have significant effects on color values as well as hardness, crispness, and brittleness of the product. Common Raman bands found during extrusion were indicators of bonding in starch, protein, and lipids; many of these chemical bonds withstood high levels of shear but not temperatures above 90C. The data displayed that attenuation from non-destructive ultrasound is a good predictor for the texture variables hardness and brittleness (P < 0.05).