Cellulose Interferes with the Transformation of Cornstarch during Extrusion Processing

This study investigated the interactions of cornstarch and cellulose during extrusion and their influence on expansion. Mixtures of starch with up to 70% cellulose were extruded, and raw and extruded materials were analyzed using microscopy (scanning electron and confocal microscopy), spectroscopy (Fourier-transform infrared (FTIR) spectroscopy), and other techniques, including X-ray diffraction (XRD) and differential scanning calorimetry. The thermal properties and XRD analysis indicated that cellulose did not undergo molecular or phase changes. The FTIR spectra indicated that the molecular interactions could be through hydrogen bonding. The reduced expansion in starch–cellulose extrudates could be a result of the interference by cellulose for two reasons: (1) the phase separation of cellulose and the starch melt and (2) the aggregation of cellulose under heat and shear in the low moisture system. The contradictory results of the pasting and thermal properties of raw cornstarch–cellulose mixtures suggested that the competition for water needs further investigation.