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 correlates with beef tenderness. Thus, the study aimed 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 sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE), and μ-calpain activity was determined using casein zymography. Proteins involved in proteolysis were analysed by liquid chromatography-tandem mass spectrometry. 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 Biceps femoris and Diaphragm muscles, a similar 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. Conclusion: The ageing times significantly affect the ratio of type I and III collagen, coinciding with μ-calpain autolysis rates 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.