Dry-cured ham is a meat-based product made from salted leg of pork left to age over time to gain aroma and flavour. At the end of the aging process (more than 12 months), dry-cured ham is stable because it has an average humidity percentage of 61% (minimum 57%, maximum 63%), an average ratio between the percentage of sodium chloride and the humidity of 8.9% (minimum 7.8%, maximum 11.2%). Finally, it has an Aw value (Water Activity: water used by spoilage bacteria to grow) markedly lower than 0.90.
The dry-cured ham is sold whole with bone, whole boneless, in vacuum packed slices or sliced and packaged in an oxygen-free Controlled Atmosphere. The packaging prevents the product acquiring humidity from the environment, oxidising quickly on contact with oxygen or being contaminated with pathogenic micro-organisms of human or environmental origin, even though these are not able to grow on the ham.
The consumer, after buying ham in slices or whole boneless or receiving it as a gift, faces the problem of how to preserve it after opening the packaging. Indeed, often while being kept in the fridge, the unpackaged product decays, loses its “freshness” and the “initial aromatic quality” because it goes rancid, darkens or absorbs the odours in the fridge. The choice of preservation technique is problematic since there is no golden rule. Various methods exist that are widely used by families; techniques sometimes recommended by experts in food production. The best system is to repackage the product under vacuum every time part is sliced off. This method, however, is almost impossible to achieve in the home unless the family owns a packaging machine. Some experts recommend wrapping the product in a slightly damp cloth and placing it in the fridge. Others and, in my opinion, they are absolutely right, recommend wrapping the part of the muscle that has been sliced with foil or, even better, plastic film. In this way, excessive surface humidity that could produce a high degree of “blooming” or the appearance of salts and amino acids (tyrosine etc.) is avoided. Furthermore, this simple method prevents the ham’s surface darkening and becoming impregnated with odours from the fridge itself. Finally, the sliced ham can also be kept in the fridge without any packaging. If, however, consumption takes place too slowly, a greasy film may be seen due to a mixture of water, salt and fat. This film must be removed with the first slice and then the rest will be edible and acceptable. It’s then best to place it in a pantry at room temperature (maximum 18°C) in a dry environment. The ham will remain stable: at most, a slight superficial dehydration will be noted; this dehydration will not influence the quality of the product. A dry environment and a maximum temperature of 18 °C will prevent the formation of greasy films connected to the fat and the humidity condensing on the product.
Prof. Giuseppe Comi