Abstract: This study was conducted in order to investigate the mechanism of the effect of adding different concentrations of L-lysine (L-Lys) on the gelling properties of porcine myofibrillar protein (MP) damaged by repeated freeze-thaw cycles. The changes in the conformation, solubility and gelling properties were analyzed by means of circular dichroism (CD) spectroscopy, intrinsic tryptophan fluorescence spectroscopy, a rheometer, a texture analyzer and a scanning electron microscope. The results showed that the addition of L-Lys caused an increase in the α-helix content and intrinsic tryptophan fluorescence intensity of freezing-damaged MP. The solubility of freezing-damaged MP gradually increased with increasing L-Lys concentrations, the storage modulus (G’), gel strength, cooking loss and gel whiteness gradually decreased, and the gel microstructure became gradually more uniform. On the whole, the addition of L-Lys significantly reduced the gel strength and cooking loss of repeatedly frozen-thawed MP gel by changing the conformation, and could thus improve the water-holding capacity and tenderness of freezing-damaged meat.

Key words: L-lysine; freezing-damaged protein; structural changes; rheological properties; gelling properties