Gelation of β-lactoglobulin and its fibrils in the presence of transglutaminase

The gelation of β-lactoglobulin (BLG) and its fibrils was investigated in the presence of dithiothreitol (DTT) and transglutaminase (TGase). BLG fibrils were prepared by heating BLG at 80 °C and pH 2 for 10 h and then adjusting to pH 7. The structure of fibrils was observed by atomic force microscopy. The small and large amplitude oscillatory measurements were done to examine the gelation process and to get more insight into gel properties. It was shown that TGase alone could induce gelation for fibrillar BLG although it could not for non-fibrillar BLG. TGase could cross-link BLG fibrils to form a gel at very low protein concentration in comparison with other protein gels, and enhance the network formation of both non-fibrillar and fibrillar BLG in the presence of DTT. The scanning electron microscopic observation revealed that TGase increased the network density for non-fibrillar gels while it made network strands thicker for fibrillar gels.