Type I and III collagen contents and μ-calpain autolysis as a function of dry ageing time for eight different muscles from Hanwoo cattle.

Objective: Type I and III collagen content exert contrasting influences on meat tenderness. μ-calpain autolysis has shown a correlation with beef tenderness. Thus, the study was designed to determine the changes in these proteins.

Methods: Three hundred twenty-four Hanwoo cattle, including cows and steers, and eight muscles were evaluated for proteolysis during dry ageing period. The ratios of type I and III collagen were determined by densitometric scans of bands resolved by SDS-PAGE, and μ-calpain activity was determined using casein zymography. Proteins involved in proteolysis were analysed by LC-MS/MS.

Results: The ratio of type I and III collagen in every muscle showed a significant difference with increasing ageing times (p < 0.05). In steers, the ratio decreased with increased ageing time, and in cows, except for BF and DP muscles, a similar decreasing trend was observed. Significant differences in the ratio of type I and III collagen were found between different muscles of cows at the same ageing time (p < 0.05), but no significant differences were found in steer muscles at the same ageing time (p > 0.05). Casein zymogram results showed an inverse relationship between pH values and μ-calpain autolysis in every muscle. A significant reduction in μ-calpain activity was observed in all muscles with extended ageing times, while the rate of autolysis differed greatly (p < 0.05) between muscles at the same ageing time. Interestingly, electropherogram analysis showed that cow muscles had a higher μ-calpain activity than steer muscles. Ageing time significantly influenced proteolysis, with 24 proteins showing marked changes and being identified.

Conclusion: The ageing times significantly affect the ratio of type I and III collagen, which coincided with the rate of μ-calpain autolysis in steers. The ratio of type I and III collagen had a significant changes during the ageing period from cows, which may be related to the amount of collagen cross-linking.