Back Fat

Back fat is the subcutaneous fat lying along the spine, above the loin, and it is the standard fat of sausage making because of one property: it is hard. Kept cold it dices into clean cubes that stay as cubes through mixing and stuffing, giving the crisp white mosaic of a good salame. It melts slowly enough to survive a fermentation and a long dry without weeping. Worked warm it smears like any fat, but it tolerates handling far better than the softer fats do.

The firmness is not a given, and this is the part most people learn the hard way. Fat hardness depends on the ratio of saturated to unsaturated fatty acids in it, and that ratio comes substantially from what the animal ate. A pig fed on cereals lays down firm fat. A pig fed on acorns, nuts or high-oil residues lays down softer, more unsaturated fat with a lower melting point. This is why Iberian pigs finished on acorns produce the famously soft, almost liquid fat of a good jamón ibérico, wonderful on a slice of ham and difficult in a salami dice. Fat that will not hold its edge is not necessarily bad fat; it is fat suited to a different product.

There is a gradient along the back too. The fat over the shoulder end is firmest and thickest, and it softens progressively towards the loin and the tail. Where a formula wants the cleanest dice, the shoulder end is the piece to ask for. The layer also has structure: the outer layer nearest the skin is firmer than the inner layer nearest the muscle, and lardo, which is the whole slab cured in its own right, is best from a thick even back.

Handling follows from all of this. Chill or partially freeze the fat before cutting, work quickly, and use a sharp plate or a knife rather than a blunt grinder that crushes and smears. Where a mosaic is the point, hand-diced fat beats ground fat every time. Fat that has been frozen and thawed carelessly, or stored warm, oxidises: it yellows, it smells of old cooking oil, and it will carry that rancidity into the finished product no matter how good the meat is. Back fat should be bought fresh, used soon, and frozen properly if it is to be kept.

Back fat is distinct from leaf fat, the soft crumbly fat around the kidneys that is the preferred material for rendering into lard, and from belly and jowl fat, which are softer and used where softness is wanted. A recipe that names back fat specifically is asking for the hard fat and its behaviour, not simply for fat.