Abstract:The activities of cathepsins B, D, H and L have been assayed at various stages in the slow processing (15 months) of dry-cured ham. Cathepsins B, H and L showed low recovered activity (5-10 % of the initial activity) at the end of the process. However, cathepsin D almost disappeared after 5-10 months. Watersoluble protein extractability decreased throughout the process while myofibrillar protein extractability was constant. There was a progressive disappearance of myosin heavy chain, myosin light chains 1 and 2, and troponins I and C, a marked increase of three breakdown products with molecular weights of about 150,95 and 16 kDa and some minor products in the ranges 5&100 kDa and [2][3][4][5] kDa. Cathepsins B and L could be particularly active in the observed proteolysis which had a special relevance when the drying started. Actin, actinin, troponin T and tropomyosin did not seem to change.

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Free amino acids have been analyzed in biceps femoris muscle and adipose tissue from raw and dry-cured ham. A high increase was observed for all amino acids except glutamine and taurine. Major increases were in glutamic acid, arginine, alanine, valine, leucine, and lysine. A survey of five aminopeptidase activities of muscle and adipose tissue from raw and dry-cured ham was performed by using 7-amino-4-methylcoumarin derivatives of five amino acids (Leu, Arg, Ala, Tyr and pGlu) as substrates. Optimum activity was found at neutral DH and around 37°C. exceut the leucvl hvdrolvzine activitv which was 45°C. High recoveries of activity (is-75%) &ere"obtaineh in the dry-cured ham. These enzymes might be responsible for free amino acids increasing during dry-curing.

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The effect of curing agents (nitrate, glucose, ascorbic acid and chloride) and physical parameters (temperature, water activity and pressure) on porcine muscle cathepsin D has been studied. Chloride (in the assayed range 0 to 75 g Cl-/L) showed a strong inhibitory effect. Nitrate (in the assayed range 0 to 800 mg/L) and high concentrations of ascorbic acid (4 to 8 g/L) slightly inhibited cathepsin D. However, its activity increased when glucose was added up to 4 g/L. Cathepsin D activity was maximal when incubated at 33 to 53 degrees C, was affected by a decrease in water activity and unaffected by pressure.