Abstract
We investigated the complementary roles of napins and cruciferins present in a rapeseed protein mixture (RPM) in structuring emulsion-filled gels (EFGs). Napins are small molecular weight albumins with high interfacial activity, while cruciferins are high molecular weight globulins that form gels upon heat-induced gelation. The role of napins is to stabilize the emulsion droplets, while cruciferins, which were previously found to interact with the adsorbed napin interfacial layer, can build the protein gel network around the droplets. The effects of oil concentration (0–30 wt%) and pH (5 and 7) on the rheological and microstructural properties of EFGs were investigated. In the absence of oil, at pH 5, due to low protein solubility, RPM formed a heterogeneous network built of protein aggregates. At pH 7, RPM was more soluble and formed a homogeneous network built of strand-like protein structures with higher gel firmness. In the presence of emulsion droplets, the gel firmness increased, with a more pronounced reinforcement at pH 5 compared to pH 7. The type of gel network did not change by the presence of emulsion droplets neither at pH 5 nor at pH 7, as suggested from confocal microscopy and the unchanged response to large deformation. This implies that oil did not really change the protein network structure. The emulsion droplets, being stiffer than the protein matrix, and being integrated in the structural matrix, increased the gel firmness. This research shows that the presence of two different proteins with complementary roles in a less purified protein extract, provides a single protein ingredient suitable for structuring food emulsion-filled gels.
Highlights
Plant protein extraction processes focus on high pro tein purity and yield (Berghout, Pelgrom, Schutyser, Boom, & Van Der Goot, 2015), often there is a trade-off between purity and yield (Loveday, 2020; Tamayo Tenorio, Kyriakopoulou, Suarez-Garcia, van den Berg, & van der Goot, 2018)
The resulting rapeseed protein mixture (RPM) had an average pro tein content of 39.4 ± 0.4 wt%, and consisted of napins and cruciferins in a mass ratio of 1:1
We showed that when napins and cruciferins are both present in a less purified rapeseed protein mixture, they can have complementary roles in structuring emulsion-filled gels (EFGs), with napins stabilizing the emulsion droplets and cruciferins building the protein network
Summary
Plant protein extraction processes focus on high pro tein purity and yield (Berghout, Pelgrom, Schutyser, Boom, & Van Der Goot, 2015), often there is a trade-off between purity and yield (Loveday, 2020; Tamayo Tenorio, Kyriakopoulou, Suarez-Garcia, van den Berg, & van der Goot, 2018). It has been reported that less purified plant protein extracts yield equal or better foaming, emulsi fying, and gelling properties compared to highly purified plant protein extracts for a variety of plant sources Examples of such plant sources include soy (Peng, Kersten, Kyriakopoulou, & van der Goot, 2020), peas (Sridharan, Meinders, Bitter, & Nikiforidis, 2020; Fuhrmeister & Meuser, 2003; Kornet et al, 2021), chickpeas (Papalamprou, Dox astakis, Biliaderis, & Kiosseoglou, 2009), sunflower seeds (Karefyllakis, Octaviana, van der Goot, & Nikiforidis, 2019) and rapeseeds (Yang et al, 2021). In previous work we showed that using an alternative extraction method, where no defatting is applied, and an aqueous extraction is followed, the physicochemical and functional properties of the proteins can be preserved (Ntone, Bitter, & Nikiforidis, 2020; Ntone et al, 2021) This paves the path to explore the function ality potential of rapeseed proteins that could initiate their use in foods
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