No More Green Eggs and Ham: Flavor Development in Dry-Cured Spanish Jamón

In Spain, ham is a way of life. Not only does jamón feature prominently on most traditional Spanish tables, but its unique flavor profile also occupies the time and resources of many Spanish scientists. And all for good reason – Spanish dry-cured hams are some of the most delectable in the world, and who wouldn’t like to know the reason for that? In the current issue of the American Chemical Society’s Journal of Agricultural and Food Chemistry (JAFC), a group of scientists from Britain and Spain report their latest findings on the biochemical changes that occur during the curing process and contribute to the characteristic flavor and texture of jamón (the abstract can be found here). Others have previously determined that the lengthy curing process (which can last anywhere from nine months to more than two years and involves at least five steps – refrigeration, salting, resting, drying, and ripening) facilitates the degradation of muscle proteins into their constituent parts, known as amino acids. These amino acids can be thought of as the alphabet from which all proteins “words” are formed, contributing to the enormous diversity of proteins in existence. Free amino acids are known to impart a variety of flavors in both animal- and plant-based foods, and one, glutamic acid, is responsible for the distinctive “fifth taste” of umami.

In the JAFC article, Mora et al. investigate the degradation of creatine kinase (CK), a particular protein found in muscle cells. Physiologically, CK is involved in cell metabolism (breakdown of chemical substances into the cell’s primary unit of energy – adenosine triphosphate, or ATP), but it also plays a role in converting muscle to meat, and its degradation seems to be related to meat quality. Using samples from traditionally cured hams, the scientists were able to distinguish 58 different peptide sequences (a peptide is a chain of amino acids too short and simple to be considered a protein), which are the fragments of CK resulting from degradation by enzymes (proteins with the ability to catalyze biochemical reactions - in this case, cleavage between two particular amino acids). The scientists used a technique known as MALDI-TOF mass spectrometry to distinguish the peptides, separating them by mass, thus allowing the researchers to determine the sequence of each peptide. By comparing the peptide sequences both with each other and with the complete protein sequence, Mora et al. were able to determine which types of enzymes are likely to be responsible for the protein degradation that occurs during dry-curing, as the enzymes are known to cleave at specific locations in peptide sequences. They found that two major classes of enzymes are involved, exopeptidases (exo- meaning outer, -ase being the suffix denoting an enzyme – thus an enzyme which cleaves an particular amino acid from the end of a peptide chain) and endopeptidases (endo- meaning inner – so an enzyme responsible for cleaving a peptide chain anywhere other than the ends). Many such enzymes have been found in hams after 12-15 months of curing, and seem to be the major facilitators of free amino acid production in dry-cured ham.

The JAFC paper provides further evidence of protein degradation in dry-cured Spanish hams, with the characterization of nearly sixty peptide fragments of the CK protein. Moreover, the existence of these fragments suggests the action of exo- and endopeptidases in the liberation of free amino acids from muscle proteins during curing. Understanding of these processes provides insight into the generation of the unparalleled flavor and texture of Spanish jamón. A more robust understanding of this flavor profile could allow us to modify the curing procedure to further enhance desirable flavors, or may even allow us to appropriate combinations of flavor molecules unique to jamón and creatively apply them to other food products.

Mora, L.; Sentandreu, M.A.; Fraser, P.D.; Toldra, F.; Bramley, P.M. Oligopeptides Arising from the Degradation of Creatine Kinase in Spanish Dry-Cured Ham. J. Agric. Food Chem. [Online] 2009, 57, 19, 8982-8988. http://pubs.acs.org/doi/abs/10.1021/jf901573t (accessed October 15, 2009).