Effect of pH and mixing ratios on the synergistic enhancement of Bambara groundnut-whey protein gels

Claudine F Diedericks,Vanessa Stolten,Victoria A Jideani,Paul Venema,Erik Van Der Linden

doi:10.1016/j.foodhyd.2021.106702

Claudine F Diedericks, Vanessa Stolten + Show 3 more

Open Access

https://doi.org/10.1016/j.foodhyd.2021.106702

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Abstract

Plant and animal-based protein mixtures are increasingly recognised as a new group of functional ingredients offering novel structuring capabilities. When combining new sources of plant and animal proteins, it is important to gain a mechanistic understanding of such mixtures to enable their use as food ingredients. In this study, we have investigated the synergistic enhancement of Bambara groundnut (Vigna subterranea (L.) Verdc.) protein isolates [BGN-PI] when combined with whey protein isolates [WPI] in heat-induced gelled mixtures. Mixed proteins were characterised for their rheological and structural properties at 12% (w/w) total protein concentrations at three mixing ratios (70:30, 50:50 and 30:70) and three pH values (pH 3, 5 and 7), with comparison to the single protein systems. At acidic pH (pH 3) WPI dominated the gel formation of the mixed gels with BGN-PI having no effect, whilst close to the isoelectric point of both proteins at pH 5, BGN-PI lowered the gel strength of the mixtures. Synergistic enhancement was observed at pH 7, where independent of the BGN-PI concentration in the mixtures, the mixed gels were characterised with similar high gel strengths comparable to that of the single BGN-PI. Hence, BGN-PI dominated the elasticity of the mixed gel networks at neutral pH.

Highlights

In recent years, plant proteins have become of increasing interest from a nutritional perspective, and as a means of creating a more sustainable and secure food supply (Day, 2013; Nadathur, Wana sundara, & Scanlin, 2017)
The turbidity and crumbly nature of these gels could be attrib uted to the presence of larger aggregates/irregularly-shaped particles in the Bambara groundnut protein isolate (BGN-PI) gel networks (Jose et al, 2016; Renkema, Lakemond, De Jongh, Gruppen, & Van Vliet, 2000), which as shown for lupine protein isolates are typically induced by freeze drying (Berghout, Venema, Boom, & van der Goot, 2015)
The mixed protein gels at pH 3 and pH 7 were visually characteristic of both single protein systems, whereas at pH 5 at all mixing ratios the gels were visually comparable to the single BGN-PI gel

Summary

Introduction

Plant proteins have become of increasing interest from a nutritional perspective, and as a means of creating a more sustainable and secure food supply (Day, 2013; Nadathur, Wana sundara, & Scanlin, 2017). The addition of soy to whey protein systems at different ratios resulted in gels with similar gel strengths, but with visibly different microstructures (McCann, Guyon, Fischer, & Day, 2018). Jose et al (2016) have shown that both soy and whey proteins contributed to the formation of a gel network when mixed at different ratios, noting the decrease in gel strength upon increasing concentrations of soy proteins in the mixed protein gels. In comparison to soy proteins, research on other plant proteins and pulse proteins in admixture with whey proteins and their effect on gelation functionality, is limited (Ainis et al, 2018, 2019; Wong et al, 2013). Considering again the shift towards sustainable and “climate-smart crops” (Calles et al, 2019; Nadathur et al, 2017), it becomes increasingly important to diversify our

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