Calorimetric and rheological behavior of cowpea protein plus starch (cowpea and corn) gels

Thermal transition and gel formation in dispersions (10% solids) of cowpea protein, and in mixtures of the protein and corn starch and cowpea starch, were examined using a differential scanning calorimeter (DSC) and dynamic rheometry, respectively. In mixtures of the protein and corn starch, two DSC peaks due to starch gelatinization and protein denaturation were observed. A single peak observed during the heating of the proteinlcowpea starch mixtures appeared to be an overlap of the starch and protein endotherm peaks. With an increase in the proteinl starch ratio (R), the starch gelatinization onset and peak temperatures shifted to higher values, while endotherm enthalpy decreased proportionally. G of the protein/starch gels increased with aging time at 20°C and attained plateau levels that decreased with increase in proteinl starch ratio (R). For proteinl cowpea starch gels, G growth with time was adequately described by a first-order kinetic model. In the early stages of structure development, a faster increase in G for the proteinl cowpea starch mixture ensured higher levels of G after 1 h of aging compared with that for starch gel at the same starch concentration. In comparison to corn starch gels, there was no significant increase in G of gels of protein/corn starch.