Abstract: The effects of adding different amounts (0.1%–0.5%) of arabic gum (AG) or guar gum (GG), natural polysaccharides with similar molecular mass but different viscosity, on the emulsifying properties of myofibrillar protein (MP) were investigated. The results showed that both AG and GG could significantly improve the emulsifying properties of MP, and AG was more effective in improving the emulsifying activity, while GG was more conducive to the emulsion stability. Both emulsifying activity index (EAI) and emulsion stability index (ESI) initially increased and then decreased with increasing the amount of added polysaccharides, reaching maximum values when 0.3% AG or 0.2% GG was added. Both polysaccharides, especially GG, resulted in a marked reduction of the interfacial protein content. The droplet size of emulsions gradually decreased with increasing the amount of added polysaccharides, and the droplet size distribution became more uniform. When more than 0.3% GG was added, slight flocculation occurred in the emulsions. At the same concentration, GG reduced the droplet size of the emulsions compared to AG. Rheological analysis confirmed that all emulsions were pseudoplastic fluids, exhibiting weak gel properties. AG at low levels (≤ 0.3%) caused a decrease in the viscosity of the emulsions while remarkably increasing the storage modulus. In contrast, the addition of GG significantly increased the apparent viscosity and storage modulus of the emulsions. Compared with AG, the emulsion prepared with GG, with higher viscosity, exhibited greater apparent viscosity and storage modulus, which was more favorable to the emulsion stability.

Key words: myofibrillar protein; arabic gum; guar gum; emulsion; interfacial protein; rheological properties