Gels and gelled emulsions prepared by acid-induced gelation of mixtures of faba bean (Vicia faba) protein concentrate and λ-carrageenan

Abstract

In this study, gels were successfully prepared at room temperature from mixtures of dry fractionated faba bean protein concentrate (FPC) and λ-carrageenan (λ-CGN), through acidification with glucono-δ-lactone (GDL). At neutral pH, the mixtures were shear thinning liquids, although the shear viscosity increased dramatically with λ-CGN addition. After adding GDL, the gelling kinetics were followed through small amplitude oscillatory rheology for 19 hours, at which point all gels had reached a gel modulus plateau. Elastic moduli for the prepared gels were in the range of 1500 – 4500 Pa, dependent on FPC:λ-CGN ratio and concentrations, and final pH (3.5 – 4). Rheological data further indicated the gels had properties typical of aggregated particle gels, e.g., low yield strains (∼1%). All gels showed some syneresis upon centrifugation (2000g), with the least amount of syneresis (15 – 20%) at the highest λ-CGN concentrations (1.5 – 2%). FPC is a good emulsifier, and gelled emulsions were successfully prepared. Inclusion of emulsion droplets had significant impact on the gel network, with ∼40% and ∼60% increased gel storage modulus at 20% and 30% oil, respectively. Preparing similar formulations using a more extensively processed commercial faba bean protein isolate was also attempted, but this resulted in poor gels with very high syneresis. This indicates that dry fractionation methods may be beneficial to preserve native protein functionality.