Cold shortening is caused by the release of stored calcium ions from the sarcoplasmic reticulum of muscle fibres in response to the cold stimulus. The calcium ions trigger powerful muscle contraction aided by ATP molecules. In large abattoirs especially those supplying large amounts of meat to supermarkets, in order to prevent cold shortening, a process known as high voltage electrical stimulation is carried out, especially in beef carcasses, immediately after slaughter and skinning. In this process, the carcass is stimulated with an alternating current, causing it to contract and relax, which depletes the ATP reserve from the carcass and prevents cold shortening.

When rigor mortis has finally passed and the muscles relax again, it is important to hang the meat in a large cold store room with plenty of ventilation at around the 3°C mark until it is required. In industry the time between slaughter and purchase can be as quick as 24 hours on to the supermarket shelf following the high voltage electrical stimulation process. In the good old days with knowledgeable butchers in every town and village, beef was hung to the point where it developed a ‘bloom’, which took anything up to eight weeks. Now, for industry, in general, the longest time a piece of meat is ‘matured’ for is approximately 21 days and for beef, that normally means ‘primal cuts’ matured in vacuum bags until it is required to be cut, packed and distributed.

At Percy’s, the lamb is hung for 3 – 6 weeks depending on sex, age, size, breed, time of year and weather. This may be a little longer than most but it works for us. As the meat hangs, enzymatic action on the cell structure ‘tenderizes’ the meat and the liquid within the cells (containing myoglobin, salts, protein) evaporates thereby concentrating and retaining the flavour together with the nutrients. If subsequently frozen, this meat will thaw with little weight loss and will not exude much liquid as it thaws. This means less shrinkage coupled with a better texture to the meat and a much tastier flavour. The size of meat therefore is closer to the cooked weight than a supermarket joint would be for example, so you don’t need to buy as much uncooked meat for the same yield. The amount of ‘weeping’ from a standard piece of meat can represent in excess of 5% and is generally greater if the freezing was done slowly.