Abstract
Bambara groundnut (BGN) is a novel plant protein source, which has not received much attention in terms of the structure-function relation of its proteins in foaming and emulsifying properties. In this study, these functional properties were evaluated for two BGN protein concentrates that have been extracted using different extraction methods. The first method is based on conventional “extensive” purification, which includes pre-processing (dehulling, defatting and milling), two centrifugation steps and isoelectric point precipitation. The second method is a more sustainable “mild” purification, which does not require pre-processing and uses only one centrifugation step. The three major protein fractions in BGN (vicilin, legumin and albumins) were also purified and included in this study. Both extensively and mildly purified protein concentrates showed comparable emulsion stabilising properties, with emulsions stable against coalescence, flocculation and creaming, for at least seven days. A more pronounced difference was found in the foaming properties, with the mildly purified protein concentrate forming up to 9x more foam, with much higher stability (about 8x higher), compared to the extensively purified protein concentrate. This was attributed to the albumins, which were only present in the mildly purified protein concentrate. These albumins had the ability to form stiff viscoelastic solid-like air-water interfaces, with high dilatational moduli up to 90 mN/m; close to that of whey protein-stabilised interfaces. These strong interfaces largely contributed to the excellent foaming properties of the mildly purified protein extract. We conclude that BGN proteins have promising functional properties, and that mild purification further enhances their potential.
Highlights
Plant-based foods are rapidly emerging in the global food market, and for that reason, there is a growing interest in exploiting novel plant sources to obtain plant-based ingredients
The defatted Bambara groundnut (BGN) flour was used in the conventional extensive purification method, and yielded an extensive purified BGN protein concentrate (EP-BGC)
We have investigated the interfacial, foaming and emulsifying properties of Bambara groundnut protein extracts, obtained using either an extensive or mild purification method, which yielded protein concentrates containing vicilin and legumin proteins
Summary
Plant-based foods are rapidly emerging in the global food market, and for that reason, there is a growing interest in exploiting novel plant sources to obtain plant-based ingredients. An emerging source is the pulse crop Bambara groundnut (BGN) (Vigna subterranea (L.) Verdc.), which is extensively cultivated in Africa and widely grown in some areas in Asia, Northern Australia, and South America (Diedericks, de Koning, Jideani, Venema, & van der Linden, 2019). The BGN proteins possess promising struc tural functionalities such as the formation of gels, which have been studied extensively (Adeleke, Adiamo, & Fawale, 2018; Diedericks et al, 2019; Diedericks, Shek, Jideani, & Venema, 2020; Diedericks, Venema, Mubaiwa, Jideani, & van der Linden, 2020; Mubaiwa, Fogliano, Chi dewe, & Linnemann, 2018). Fewer studies exist on other functional properties such as foam and emulsion stabilisation (Arise et al, 2017; Mubaiwa et al, 2018), with a lack of extensive characterisation of the interface-stabilising properties. This work largely focussed on the interface, foam and emulsion stabilising properties of BGN protein extracts
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