Effect of Freeze-thaw Cycles on Quality Characteristics of Mutton

The effect of freeze-thaw cycles (0, 1, 2, 3, 4 and 5 cycles) on the mutton food quality were investigated by measuring the thawing loss, cooking loss, pH, shear force, TBARS, TVB-N, total number of colonies and moisture condition.The results indicated that with the increase of freeze-thaw cycles, thawing loss, cooking loss, thiobarbituric acid reactive substances (TBARS), total volatile base nitrogen (TVB-N) and total bacterial colony of mutton increased significantly (P<0.05), pH value decreased significantly (P<0.05), and shear force first increased and then decreased. Low-field NMR T₂ relaxation time analysis showed that with the increase of freeze-thaw cycles, the content of uneasily flowing water (T₂₂) increased, the content of free water (T₂₃) decreased, and the content of bound water (T₂₁) remained almost unchanged (P>0.05). Repeated freezing and thawing significantly reduced the quality of mutton, and with the increase of freeze-thaw cycles, the quality damage was more serious.