Effect of molecular characteristics of Konjac glucomannan on gelling and rheological properties of Tilapia myofibrillar protein

• Type of KGM affects property of Tilapia myofibrillar protein gels.
• KGM behaves as space filler under neutral condition in gels matrix.
• KGM with smaller molecular size improves gel strength of composite gels.
• KGM with larger molecular size breaks the network structure of composite gels.

Konjac glucomannan (KGM) is an important gelling agent in composite gels. This study aimed to investigate the effects of KGM molecular characteristics (molecular weight, size and conformation) on gelling properties of Tilapia myofibrillar protein (TMP). In this work, TMP composite gels were prepared under neutral pH with varying KGM (native KGM, 10 kGy-KGM, 20 kGy-KGM, and 100 kGy-KGM) of different molecular characteristics. Native KGM, 10 kGy-KGM, and 20 kGy-KGM exerted negative effect on gel strength or whiteness of TMP gels. Interestingly 100 kGy-KGM improved gelling properties and whiteness of TMP gels. Such effects presented by varying KGM were attributed the physical filling behaviors and the interaction between KGM and TMP. These behaviors or interactions are resulted from different molecular size and conformation. Smaller molecular size (root-mean square radius, Rz 20.2 nm) and approximated spherical conformation in 100 kGy-KGM enhanced its interaction with TMP and maintained its compact and smooth structure, but the larger molecular size (Rz ≥ 40.2 nm) and random coil conformation in other KGMs inhibited part of actins from gelling and deteriorated the network structure. Our study provided principle knowledge to understand the structure-functions relationships of KGM-TMP composite gels. These results can be used to provide theoretical guidance for surimi gel processing.