Insight into the Regulatory Mechanism of the Microstructure of Myofibrillar Protein-Konjac Glucomannan Gel Systems on Their Textural Properties

In the present study, model gel systems of myofibrillar protein (MP) and various concentrations of konjac glucomannan (KG) were evaluated for textural properties, spatial distribution and MP gel networks using a texture analyzer, the paraffin section method and scanning electronic microscopy (SEM), respectively. The regulatory mechanism of the microstructure of MP-KG gel systems on their textural properties was elucidated in order to provide a theoretical basis for the application of KG as a fat replacer in low-fat sausages. The textural analysis results showed that the fracture stress and fracture strain exhibited a parabolic trend with KG concentration, but they reached their maximum at different KG concentrations. The results of low-field nuclear magnetic resonance (NMR) showed that the shortest relaxation time (274 ms) and highest percentage (92.79%) were observed for immobile water in composite gels with 1% KG, suggesting that KG could promote cross-linking of MP and consequently enhance MP binding to water molecules. Paraffin section showed that the spatial distribution of MP-KG gels was transformed from the “trapped structure” to the “penetrated structure” with increasing KG concentration. The SEM micrographs showed that the MP gel networks in the control group were filled with crisscrossed moisture channels and consequently were loose. Addition of a small amount of KG reduced the cross-linked moisture channels, and promoted the formation of compact and well-aggregated MP gel networks. On the other hand, excess addition of KG resulted in the formation of a continuous phase, damaging the MP gel networks. In conclusion, KG could improve the gel strength through stabilizing the water phase and deteriorate the texture of composite gels through the penetrated structure.