But there has been debate about whether it is worthwhile ageing pork, which tenderises much faster than beef, with a high proportion of the tenderisation achieved at three days after slaughter, when fresh pork can be retailed. However, several studies have shown that longer ageing, for up to 10 days, is beneficial.
The ageing effect is caused by the breakdown of the filamentous protein structures in muscle by enzymes termed calpains. The weakened structure reduces the force required to cut through the muscle which is how toughness/tenderness is objectively measured. The degradation of some key structures inside muscle also creates more space for water within the muscle structure and greater water retention improves tenderness.
A number of studies have shown that the rate of tenderisation is less in pork that is inherently tender than in pork that starts out at a lower tenderness level. For example, in Duroc-cross pigs in a Danish study and in pelvic-suspended and electrically stimulated carcases in work conducted at Bristol, ageing for 12 days or more increased tenderness, but much less than in more standard material. In beef, dry ageing 'on the bone' is sometimes used and some (but not all) studies show advantages over 'wet ageing' in vacuum packs.
There has been little research on dry ageing in pork which might lead to changes in flavour because of the more unsaturated fatty acid composition of pork. The loss of water by evaporation might also be detrimental to eating quality, thus ageing in pork has all the advantages for eating quality that beef does, although, like all other 'enhancement' procedures, that ageing has to be tailored to the raw material available. Jeff Wood, professor of food animal science, Bristol University