Influence of flour type on mechanical properties of calcium-induced egg albumen-flour composite gel

Abstract

The mechanical properties of composite network of hen egg albumen (EA) and flours; i.e., rice flour (RF) and/or cassava starch (CS) formed at 80 degree C using a salt-induced two-step gelation process were investigated. This structure-forming process induced gelation of pre-heated EA suspension in the presence of calcium ion and subsequent gelatinization of starch during the second heating regime. Increasing calcium lactate concentration up to 50 mM increased the aggregation of EA suspension and the Young's modulus of EA gel. Above 50 mM, both aggregation of EA suspension and Young's modulus of EA gel decreased. Addition of flour fillers to the EA suspension increased Young's modulus, stress at fracture, initial stress at 20% deformation and residual stress after 20% deformation for 5 min. Raising the calcium lactate concentration influenced the mechanical characteristics of only EA-RF and EA-RF-CS but had no effect on those of EA-CS gel. The composite gels containing RF were more rigid than the ones containing CS. The EA-CS composite gel relaxed faster and to a much greater extent than the EA-RF gel. This was likely due to the high capacity of CS to absorb water, which weakened the strength of the granule after the composite structure was heated during the structure-forming process. Overall, results suggest that different flour fillers create composite gels with different mechanical properties due to the different pasting characteristics of flour constituents. Copyright ©2006 The Berkeley Electronic Press. All rights reserved.