Concentrated pea protein – apple pectin mixtures as food glue: Influence of biopolymer concentration and pH on stickiness

Abstract

Many of the currently used binding agents such as methylcellulose are not clean label. A key property of binding agents or so-called “food glues” is their stickiness, a property that is governed by a balance between adhesion, i.e. the ability to stay attached to other structures or surfaces, and cohesion, i.e. the internal strength of a material to resist rupture. The aim of this study was to investigate stickiness of concentrated pea protein – apple pectin mixtures (mixing ratio r = 6:1) at different biopolymer concentrations (17.5–50.0% w/w) and pH values (3.50, 4.75, 6.00). At a biopolymer content of 17.5–22.5% (w/w), the pea protein – apple pectin mixtures showed poor stickiness due to a low cohesion of the biopolymer matrix, resulting in cohesive failure. On the other hand, the pea protein – apple pectin mixtures at 25–30% (w/w) with the right balance of adhesion and cohesion showed the highest stickiness as also indicated by their viscoelastic character (G’ ≈ G″). At 40.0–50.0% (w/w), the biopolymer mixtures had a low stickiness that was attributed to high cohesion and firmness of the matrices, resulting in adhesive failure. The applied pH also played a major role in stickiness at intermediate biopolymer concentrations (25–30% w/w), where the pea protein – apple pectin mixtures at pH 6 were the stickiest. This was due to an increased hydration and swelling behavior of the pea proteins at this pH that led to more entanglement and cohesion. Overall, this study demonstrated that both the biopolymer concentration and pH can be used to tailor adhesion and cohesion and thereby desired sticking properties in biopolymer blends for the application as clean-label binding agent in foods to increase consumer acceptance particularly in novel plant-based products. • Pea protein – apple pectin mixtures at 17.5–50.0% were investigated for stickiness. • Biopolymer mixtures at 17.5–22.5% were adhesive and yielded cohesive failure. • Biopolymer mixtures at 25–30% were viscoelastic and sticky. • Biopolymer mixtures at 40–50% were cohesive and yielded adhesive failure. • Biopolymer mixtures at pH 6.00 had the highest stickiness compared to pH 3.50 and 4.75