LOCAVORE Robert Butterworth
Silver skin is the connective tissue found in the muscles of animals. It is generally white and shiny: hence the name. Silver skin is made up of a protein called collagen which acts as the scaffolding of the body. In humans, collagen is the most abundant protein and makes up about one third of the body by mass. I imagine it is about the same percentage in deer. Most of this mass comprises skin, intestines and bones but all muscles contain collagen.
Collagen takes various forms in muscle meat: thin tubes which enclose muscle fibres, sheaths which surround individual muscles, and larger sheaths that enclose whole muscle groups. Strong muscle tissue contains about six per cent collagen. At the ends of muscle groups collagen forms thick ropes in the form of tendons. In bones, collagen is strengthened by mineralisation with calcium phosphate.
Older, stronger animals such as bucks and stags develop thick silver skin to better support their muscles. This physical change largely explains why older animals are deemed to be tough.
All this is a bit boring for the average deer hunter, butcher and home cook, except for the fact that collagen density and distribution is a key factor in deciding how to cut up the deer and cook it so that it is most palatable. The traditional butchery cuts of sheep and cattle were largely developed as an optimum way of dealing with collagen in meat and this is why deer butchers use them as a guide.
Collagen and muscle fibres react to cooking in very different ways and the interaction determines whether your steak is tender and juicy or tough and dry. In cooking you can’t defeat the ingredient and must go with the flow.
Collagen is readily digested once swallowed, but in raw or semi-cooked form it is virtually tooth-proof. This detracts markedly from the eating experience.
When heat is applied to a piece of meat the collagen initially contracts and becomes even tougher. But with sustained temperatures above 60-70˚C, collagen slowly softens and converts to gelatine. It is gelatine that gives stews and soups that unctuous texture and surface sheen. But that conversion comes at a cost because the initial shrinking of the collagen squeezes moisture (and flavour) out of the muscle and into the matrix of the stew, leaving the meat dry and fibrous. Slow and at low temperatures is the best approach to cooking collagen-rich cuts.
Ideally, we would remove the collagen from the cuts we intend to cook quickly and slow cook the cuts where this is impractical. And in traditional butchery this is what we do.
We slow cook the shanks, neck and shoulder whole or in blocks because removal of the silver skin would take too long. And if we did succeed, we would be left with tiny pieces. We choose the backstrap, top side and rump for steaks and cut them across the grain to shorten the silver skin sections and/or limit it to one side of the cut so it can’t squeeze the muscle as it shrinks.
Some otherwise tender muscles can be trimmed to remove the silver skin from their surface and ends. Examples include the tenderloins, salmon cut (girello), knuckle or thick flank, backstrap and rib eye. All these cuts can be improved for quick frying or grilling with a little knife work to remove the thicker silver skin and cutting across the grain. Butchering pedants (like me) also remove the silver skin from the flatiron and the flank steak with excellent results, but it is tedious.
The technique for silver skin removal is to use a fine, sharp-pointed, flexible knife blade. Poke the point of the blade a short way into the meat under the silver skin and push the knife away and towards the silver skin (up or down) while holding the muscle with your other hand behind the knife. Try to slide the knife the length of the muscle or until the thicker silver skin peters out. Repeat until you have removed as much as you care to. For the flatiron and flank steak, several passes are required because the silver skin stretches from one end to the other and there is an internal seam of it.
The traditional slow cooking cuts are a lost cause for silver skin removal. These are best cut into thick discs such as neck chops or cooked whole. The larger pieces will take longer to cook but the meat will be shielded by the outer coating of silver skin and remain juicy as the collagen dissolves in cooking. If these muscles are cut into small pieces, or cooked too quickly, they will tend to dry out despite being in a wet medium.
Leaving the silver skin on joints for slow cooking also holds them together through the cooking process.
Mincing is a popular method for dealing with trimmings and lesser cuts. Mincing will break up silver skin and when cooked, the mince will have a little more texture from the small pieces of silver skin that went through the holes in the mincer screen. However, silver skin will clog up the cutter and build up on the axle between the blade and plate, causing unhelpful heat and delay. It pays to spend a little time removing the larger/thicker pieces of silver skin before you mince.
Silver skin removal is essential if you are going to make jerky. If you do not remove it your jerky will taste fine but you will be left with a mouthful of white string.
One heavily sheathed muscle that is worth attention is the silverside. This muscle has a very heavy collagen sheath, but it is easily removed to reveal a long thick grained muscle. Cut across the grain into thin steaks and pounded flat silverside makes excellent minute steak and schnitzels, or jerky.
The silver skin in and around bones is the reason they make good stock. Authorities such as Hank Shaw recommend that you save your trimmed silver skin and add it to the stock pot. The modern enthusiasm for bone broth is largely based on the claimed nutritional value of collagen. But this is debateable since collagen breaks down into standard amino acids when digested. I am more interested in its flavour profile than health benefits, but I keep the bones from deer carcasses for conversion into stock for soups and gravy. This is not popular with the Labradors, but they get to lick the gravy from the plates after dinner as a consolation.