Utilization of albumin-rich soluble fractions from faba bean (Vicia faba) obtained by mild fractionation in the development of beverage emulsions

Abstract: Proteins from faba bean can be extracted by a mild-fractionation method which can be utilized efficiently to prepare beverage emulsions. However, to enhance their performance as an emulsifier, the proteins must be isolated by a process that could preserve their native functional attributes. The aim of the present research was to extract native faba bean proteins from the flour using a mild aqueous fractionation, characterize the protein-rich soluble fraction and utilize it directly to prepare beverage emulsions. The protein-rich soluble fraction was obtained by subjecting 10wt% faba bean flour dispersion to centrifugation at different speeds (4000 and 3000 rpm) for 1.5-4.0 mins. The interfacial tension of the soluble fractions decreased from 6.9 mN/m to 4.8 mN/m with an increase in the duration of centrifugation; however, it was not affected by the centrifugation speed. The soluble fractions had prominent bands on SDS PAGE that mainly correspond to albumins (10-14 kDa). The soluble fractions (containing 0.5 wt% protein) with interfacial tension < 6.5 mN/m were used directly to make 1 wt% oil-in-water emulsions at pH 7. Lower average droplet size (400-440 nm) was observed for the emulsions prepared at 4000 rpm compared to 3000 rpm ( >450 nm). The emulsion prepared with the soluble fraction at 4000 rpm for 2.5 mins had the lowest creaming velocity (631 µm/min) at accelerated gravitation (2100g). Extensive creaming was observed in all the emulsions prepared with the soluble fractions at 3000 rpm. The results indicate that the emulsions prepared with soluble fractions obtained at 4000 rpm for 2.5 mins-3.5 mins were more stable with smaller droplet sizes compared to those with soluble fractions at 3000 rpm for 3 mins and above. Hence, by controlling the centrifugation process, suitable albumin-rich pulse protein fractions can be obtained, which can be utilized in the development of stable beverage emulsions.