Abstract
The applications of plant proteins in the food and beverage industry have been hampered by their precipitation in acidic solution. In this study, pea protein isolate (PPI) with poor dispersibility in acidic solution was used to form complexes with soybean soluble polysaccharide (SSPS), and the effects of PPI aggregates on the structure and stability of PPI/SSPS complex emulsions were investigated. Under acidic conditions, high pressure homogenization disrupts the PPI aggregates and the electrostatic attraction between PPI and SSPS facilitates the formation of dispersible PPI/SSPS complexes. The PPI/SSPS complex emulsions prepared from the PPI containing aggregates prove to possess similar droplet structure and similar stability compared with the PPI/SSPS emulsions produced from the PPI in which the aggregates have been previously removed by centrifugation. The oil droplets are protected by PPI/SSPS complex interfacial films and SSPS surfaces. The emulsions show long-term stability against pH and NaCl concentration changes. This study demonstrates that PPI aggregates can also be used to produce stable complex emulsions, which may promote the applications of plant proteins in the food and beverage industry.
Highlights
IntroductionOil in water emulsions have attracted much attention in the fields of pharmaceutics, cosmetics, food, and beverage for encapsulation and protection of lipophilic bioactive components in aqueous phases [1,2,3]
Oil in water emulsions have attracted much attention in the fields of pharmaceutics, cosmetics, food, and beverage for encapsulation and protection of lipophilic bioactive components in aqueous phases [1,2,3]and for increasing their oral bioavailability [4,5]
Compared with the emulsions produced from proteins, the emulsions produced from these polysaccharides have better stability against unfavorable environmental conditions because the carbohydrate part tends to stretch into the aqueous phase, preventing the droplets from aggregation and coalescence
Summary
Oil in water emulsions have attracted much attention in the fields of pharmaceutics, cosmetics, food, and beverage for encapsulation and protection of lipophilic bioactive components in aqueous phases [1,2,3]. For the formation of plant protein/polysaccharide electrostatic complexes, the challenge is that such pH range is usually narrow and close to the isoelectric point (pI) of the plant protein, where both the solubility and emulsifying ability of the protein are poor [19,20,21] To address this challenge, one approach is by first mixing the protein solution with a polysaccharide solution at higher pH, where the protein is soluble and carries negative charges, and adjusting the mixture to an acidic pH to produce the complex. At a 2:1 PPI/GA ratio, soluble and insoluble complexes, formed at pH 4.23 and 3.77, respectively, could produce more stable emulsions compared with PPI alone [19] Another approach is by respectively adjusting the protein and polysaccharide solutions to the pH where they carry opposite changes and mixing them together. This study demonstrates that PPI aggregates can be utilized to produce stable PPI/SSPS complex emulsion
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