A self-sorted gel network formed by heating a mixture of soy and cod proteins

The development of binary protein networks featuring superior nutritional and rheological properties is an intriguing, as well as challenging, aspect in the food industry. In this study, a novel, self-assorted double protein network was constructed, which was achieved by simply heating soy protein (SP) and cod protein (CP) at 100 °C with different SP/CP ratios (5 : 0 to 0 : 5). Atomic force microscopy revealed that the heat-induced protein aggregate size increased with increasing CP ratio from 0 to 100%, which was accompanied by a significant increase in surface hydrophobicity and the content of disulfide bonds. Meanwhile, the ratio of non-network proteins in the gel network decreased significantly from 12.5 to 3.2% with the increase of the CP ratio from 0 to 100%. Concomitantly, the networks formed at a higher CP ratio were found to be less homogeneous and more porous with higher storage modulus. Interestingly, results from far-UV CD, near-UV CD, and fluorescence demonstrated that there were no interactions between SP and CP during thermal treatment, suggesting that the gel formed by mixed proteins was a self-sorted network. The study would advance the utilization of blended fish proteins and plant proteins toward tailor-made double networks that may find many applications in food and relevant areas.