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Associative phase separation of potato protein and anionic polysaccharides

Stounbjerg, Lykke, Vestergaard, Christian, Andreasen, Birgitte, Ipsen, Richard
Colloids and surfaces 2019 v.566 pp. 104-112
acidification, alginates, beverage industry, binding capacity, biopolymers, calorimetry, carboxymethylcellulose, colloids, electrophoresis, electrostatic interactions, enthalpy, gum arabic, heat, light scattering, mixing, mixing ratio, pH, potato protein, separation, titration, turbidimetry, turbidity
Plant proteins are receiving growing interest from the food and beverage industry. However, the properties of these proteins are still insufficiently characterised. The present study investigated the associative phase separation between potato protein (PP) isolate and anionic polysaccharides (PS), namely alginate (ALG), carboxymethylcellulose (CMC), and gum arabic (GA) to further the understanding of interactions between PP and commonly used PS with potential applications in the food industry. Through biopolymer titration and acidification, the effect of PP–PS mixing ratio (0.1-5:1, at 0.1 wt%) and pH (9-3) was investigated. The complexation process was characterised on micro- and macroscale by turbidimetry, electrophoretic light scattering, isothermal calorimetry, and precipitate composition was analysed. Turbidity measurements showed that ALG, CMC, and GA were saturated with PP at ratios of 5:1, 3:1, and 2:1, respectively. Isothermal calorimetry measurements confirmed that there was no additional binding at higher mixing ratios. Turbidimetry also indicated that PP and PS formed soluble complexes above pI, at highly alkaline pH. ALG, possessing the highest electrostatic charge density, yielded the most pronounced enthalpy change upon addition of PP, indicating more heat was released by the electrostatic complexation compared to GA and CMC. This could explain the resultant highest PP binding capacity and a precipitate that did not dissociate at low pH. At certain mixing ratios, PP and GA formed micro-dispersions, while complexing with ALG or CMC predominantly resulted in soluble complexes or insoluble precipitate. During acidification, the charges of the complexes followed the trend of PS instead of PP, suggesting the PP was internalised in the complexes.