Hydrolysis and loss of extractability of proteins during ripening of iberian ham.

To elucidate the extent of the hydrolysis and loss of extractability of protein during the traditional ripening of Iberian ham, the evolution during processing of non-protein nitrogen (NPN) and protein fractions soluble in 0·03 m pH 7·1 phosphate and 1·1 KI + 0·1 m phosphate pH 7·4 buffers and 6 m urea was followed from Semimembranosus and Biceps femoris muscles. The NPN steadily increased during processing, showing maximum intensity at salting and drying. Electrophoretic study of the proteins extracted, and microscopical examination of the pellet obtained after consecutive extractions with the above buffers, revealed that hydrolysis and insolubilization are more intense in myofibrillar than in sarcoplasmic proteins. Protein aggregation involves mainly the myofibrillar fraction, and occurs during the first stage of processing.