Assessing functional properties of rapeseed protein concentrate versus isolate for food applications

Abstract

Rapeseed protein concentrate (RPC) and isolate (RPI) were fractionated from rapeseed meal and their techno-functional properties were characterized. RPC prepared by aqueous ethanolic washing process yielded less refined and insoluble fractions with largely denatured protein. Hydrated insoluble RPC particles held 6.7 g water without swelling. RPI fractionated from aqueous extraction and ultrafiltration still contained certain phenolic compounds but protein nativity was preserved including a high protein solubility of 78%. RPC dispersion with 40 w/w % showed the highest apparent complex modulus G* among all rapeseed materials. In contrast, the G* for RPI dispersion increased upon heating, suggesting a thermal induced denaturation and gelation capacity of the proteins. Thus, a largely denatured RPC free of phenolic compounds or a native but phenolic containing RPI were obtained by the applied processing conditions, which differ in their techno-functional properties and thus have different promising application potential in food applications. The growing demand for plant as opposed to animal protein has sparked the interest of exploring currently underutilized plant protein sources in food industry. Rapeseed by-products obtained after oil extraction are promising but the presence of anti-nutritional components in rapeseed meal presents a barrier for its usage in food products. Aqueous ethanolic washing or aqueous extraction combined with membrane filtration were applied to remove the antinutritional factors from rapeseed meal to yield rapeseed protein concentrates and even more refined isolates. In this work, the functional properties of the fractionated rapeseed materials were characterized for its relevance in food applications. The similarities of the rheological properties between rapeseed protein concentrates and soy materials, as well as presence of native proteins in RPI might suggest their potential for diverse in food industry applications.