Formation and characterisation of food protein–polysaccharide thermal complex particles: effects of pH, temperature and polysaccharide type

Summary The objective of this study was to prepare and characterise the thermal complex particles (TCPs) based on heating food grade protein–polysaccharide electrostatic complexes. The soybean protein isolate (SPI), cationic polysaccharide (chitosan, CS) and anionic polysaccharide (carboxymethyl cellulose, CMC) were used. Turbidity, particle size, ζ‐potential and morphology of TCPs were measured. The results showed that SPI‐CS and SPI‐CMC soluble complexes were obtained at specific pHs and kept at high electrostatic repulsive force. The particle size and polydispersity index of stable SPI‐CS (pH 4.55/80 °C) and SPI‐CMC (pH 6.15/95 °C) TCPs were 286.6 nm/0.282 and 171.5 nm/0.298, respectively. We inferred that the re‐assembly of SPI after thermal denaturation resulted in the formation of TCPs. The pH and ionic strength sensitivity tests indicated that the TCPs with different properties can be controlled by pH, temperature and polysaccharide type during heating. These TCPs could be used to encapsulate food functional components which were thermal insensitive.