Effect of curing agents on m-calpain activity throughout the curing process

Curing of ham involves a number of biochemical reactions, mainly related to lipolytic and proteolytic enzymes that contribute to the development of taste and flavour. Calpains are calcium-dependent enzymes that are known for their proteolytic activity in the first stages of meat tenderisation during postmortem storage. However, their activity in longer processing and in the presence of curing agents remains unclear. This study shows that the curing agents and process parameters have an important effect on m-calpain activity. This enzyme is activated with increasing concentrations of NaCl, obtaining a maximum at 0.34 M NaCl. Activation is also promoted by the addition of sucrose. In contrast, ascorbic acid, phosphates and particularly polyphosphates promote enzyme inhibition. Finally, calpain activity is not affected by nitrates and levels of water activity higher than 97%. Therefore, a careful selection of curing agent concentrations and process parameters is required for these types of processes, since the proteolytic activity is greatly affected and, as a consequence, the resulting tenderness and flavour of the final cured product.