Influences of Physicochemical Characteristics of Rice Flour and Cassava Starch on the Gelation of Calcium-Induced Egg Albumen-Flour Composite

Abstract

Mechanical properties of calcium-induced composite gel made of egg albumen (EA) containing 15% protein (w/v) and 30% of rice flour (RF), cassava starch (CS) or a mixture of RF and CS at the ratio of 1:1, added with 0-70 mM calcium lactate and 1% of i-carrageenan were characterized. The twophase exponential decay model suggests that the calcium lactate concentration did not have significant effect on the stress decay mechanism of the flour-protein composite gel (p≥0.05). However, the type of flour filler regulated the stress decay behavior (p<0.05). This was due to the high content of flour to protein ratio in the composite. Such protein to starch ratio led to the close-packing composite structure, where the swollen starch granules packed densely within the continuous EA protein matrix. The EA-CS composite gel relaxed faster and to a much higher extent than the EA-RF gel. This was likely to be due to the high capacity of CS to absorb water, which weakened the strength of the granule after the composite
structure was heated during structure-forming process. In addition to the lower water absorption ability of RF compared with CS (p<0.05), light micrograph revealed that the reinforcement mechanisms of RF could be due to the higher number of granular particles per unit volume of the RF in the composite gel and the aggregation of the swollen and deformed amylose-rich fraction of the RF after heat-treatment. The aggregation of CS granules and remnants was not evident in the heated EA-CS composites.