Comparison of rheological properties of different protein/gum arabic complex coacervates

This study mainly focused on the comparison of rheological properties of soy proteins (SP)/gum arabic (GA) complex coacervates and gelatin (G)/gum arabic (GA) complex coacervates. Frequency sweeping (0.1–100 Hz) results at 25°C showed that SP/GA coacervates storage modulus and loss modulus were crossed at a frequency of 30 Hz. According to the Doi‐Onuki model, it was confirmed that SP/GA complex coacervates were structured with a characteristic length scale (L) of 40 nm, which was much larger than others. It meant that the structure of SP/GA complex coacervates was less tight. Temperature sweeping (40–10°C) results illustrated that L of G/GA complex coacervates were decreased from 600 to 10 nm during the cooling process due to the formation of hydrogen bonds, while L of SP/GA complex coacervates were not changed greatly. Light microscopy observations revealed that the G/GA complex coacervates were more regular after cooling to 10°C. All the results indicated that protein types greatly influenced the structures of the complex coacervates. The results in this article will be useful for clarifying the reasons why different complex coacervates showed different morphologies and will provide theoretical support for rational use of protein/polysaccharide complex coacervates in food industry. PRACTICAL APPLICATIONS: Complex coacervation between proteins and polysaccharides is a common phenomenon in the food processing. Understanding the interactions of proteins and polysaccharides is of importance not only in making cost‐efficient use of functional ingredients, but also in designing novel foods, controlling and improving structures of food ingredients and textural properties of fabricated foods. This study mainly focused on the rheological properties of soy proteins/gum arabic (SP/GA) complex coacervates and gelatin/gum arabic (G/GA) complex coacervates. The results indicated that protein types greatly influenced the structures of the complex coacervates. Structures of SP/GA coacervates were less tight than others. Characteristic length scales of G/GA coacervate significantly decreased during cooling process. The results in this paper will provide theoretical support for rational use of protein/polysaccharide complex coacervates in food industry.