Mixed legume systems of pea protein and unrefined lentil fraction: Textural properties and microstructure

Mathias Johansson,Epameinondas Xanthakis,Maud Langton,Carolin Menzel,Francisco Vilaplana,Daniel P Johansson,Patricia Lopez-Sanchez

doi:10.1016/j.lwt.2021.111212

Abstract

Within the context of circular economy, there is an increasing interest to utilise agrifood by-products. However, extensive extraction and purification steps make the valorisation of side streams not always cost effective. Therefore, an increased knowledge of the functionality of unrefined side streams could increase their utilisation in food products. We investigated the thermal gelation of mixed legume systems containing a commercial pea protein isolate (Pisum sativum) and the unrefined fraction remaining after protein extraction from lentils (Lens culinaris). The unrefined lentil fraction contained mainly starch (~45 g/100 g) and insoluble cell wall polysaccharides (~50 g/100 g) with minor amounts of soluble protein (4 g/100 g) and polyphenols (<1 mg GAE/g). The addition of the unrefined lentil fraction increased the strength and Young's modulus of pea protein gels in the pH range 3–4.2, and also increased the gels’ elastic modulus G'. The microstructure could be described as a mixed network of swollen protein particles of different sizes (5–50 μm), gelatinised starch and cell wall fragments. The results demonstrate that unrefined side streams from lentils could be used for textural modification of plant protein gels, with implications for the design of novel plant-based foods.

Highlights

Strategies to reduce the environmental impact of agrifood industry include replacing the consumption of animal proteins by plant alterna tives and to valorise agrifood by-products (Ripple et al, 2017, Poore & Nemecek, 2018; Willett et al, 2019)
The starch content represented 42–48 g/100 g of the unrefined fraction (Table 1), which is in agreement with previous reports on starch content in lentils (Brummer, Kaviani, & Tosh, 2015; Dalgetty & Baik, 2003; García-Alonso, Goni, & Saura-Calixto, 1998)
In our study insoluble cell wall polysaccharides are present as cell struc tures of different size (Fig. 1), and the starch and the insoluble cell wall polysaccharides were not separated, the results showed that presence of the latter is not detrimental for the functionality and rein forcement of the gels, and it could even have a nutritional benefit as they are considered dietary fibre which are related to health benefits

Summary

Introduction

Strategies to reduce the environmental impact of agrifood industry include replacing the consumption of animal proteins by plant alterna tives and to valorise agrifood by-products (Ripple et al, 2017, Poore & Nemecek, 2018; Willett et al, 2019). The general process of heat-induced gelation of globular proteins includes partial denaturation, aggregation due to newly exposed residues and agglomeration of the aggregates to form a spatial network (Clark, Kavanagh, & Ross-Murphy, 2001). Studies on heat-induced pea protein gelation have mainly focused on the effect of salt, pH, concentration and extraction methods in single-component systems (Munialo, van der Linden, Ako, & de Jongh, 2015; Munialo, van der Linden, & de Jongh, 2014; Sun & Arntfield, 2011). The pH during gel formation has been found to largely affect the structure of the formed pea protein network (Ako, Nicolai, Durand, & Brotons, 2009; Munialo et al, 2015) as well as the viscoelastic properties (Munialo et al, 2015)

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