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For years I’d been making a family recipe for brown bean soup with a packet of dried oxtail soup, not thinking much about it. The soup always turned out great, with a lot of flavor. Never did I think twice about it using oxtail. That is, until I visited a local butcher and noticed they sold oxtails. I became intrigued, could I use the actual oxtails to make the soup?
Turns out, the continuous sweeping of the tail while the animal is still alive, makes oxtails great for long-simmering foods such as soups. The strong muscles, with plenty of support tissue, fall apart after several hours of cooking. It gives a luscious, tasteful end result. Of course, powered stock takes only seconds to dissolve, whereas the oxtail takes a few additional hours, but it’s worth it, even if you’d only do it just to see what happens to the tail during cooking.
A Hard-Working Oxtail
Have you ever seen a cow that isn’t moving its tail, swapping away fleas? That simple observation is your first piece of evidence that oxtail is perfectly suited for soups.
Animals have a lot of different muscles, each with their own function in the body. Some of these, such as the muscle that forms a piece of tenderloin, are barely used. Since they don’t have to work as hard, they are made up of mostly just muscle cells. These are long fibers, grouped together in bundles, made to contract and elongate. The piece of meat from these parts of the animal tend to be almost completely red and soft (with the exception of maybe some fat marbled throughout). If you want to cook these pieces, all they need is a short blast of heat and they’re good to it. Some you can even eat raw, while still melting on your tongue.
Other muscles in the animal, e.g. those in the neck, the legs, and the tail, are used a lot during its lifetime. Whether it’s to move around or just to support the weight of the animal. To strengthen and help these muscles do their job, they contain a lot of connective tissue. This tissue is white and tough. It’s pretty much inedible because of this toughness.
In the piece of oxtail below you can actually see this quite clearly. The dark red meat is the muscle. Each cylinder of muscle is surrounded by fat and connective tissue, which are whitish. That bone in the middle is also crucial to how an oxtail cooks. Bones contain a lot of flavors and molecules that break down during cooking, enriching the final stock.
Collagen in Oxtail
Cause of this toughness: collagen. Collagen is a protein that makes up most of the connective tissue. It doesn’t dissolve in water though and is quite a branched protein, giving it the ability to form strong tough textures. When you cook pieces of meat that contain a lot of collagen, such as oxtail, the key to getting delicious edible meat is to break down that collagen.
Breaking down collagen
By heating up collagen in a moist environment (this doesn’t work well in a hot dry environment) the protein will start to break down. Chemical reactions called hydrolysis cut the protein into smaller pieces. These smaller pieces dissolve in water (whereas collagen doesn’t) and as such leave the meat. You’re probably familiar with these smaller proteins: it’s gelatin. Gelatin forms by partially breaking down collagen.
Gelatin adds a smoothness to the liquid. When a broth with a lot of gelatin sets, you might notice it sets into a gel, a clear sign that gelatin has been released from the meat!
This process doesn’t happen very quickly though. Depending on how much collagen needs to be broken down to make the meat edible and how big the piece of meat is, it generally takes at least an hour but can easily take several hours!
How to Prepare Oxtail
Oxtail contains a lot of connective tissue, but also bones and fat. All of these benefit from a long cooking time in a moist environment. Bones contain a lot of flavor (it’s why you often use bones from fish and meat to make stock) as well as gelatin, that slowly gets out while cooking in enough moisture. The collagen needs that heat for a long period of time to break down and the fat will melt and dissipate throughout the dish.
As such, there are a lot of different ways to prepare oxtail but just about all of them have time and moisture and their core ingredients. You can roast oxtail in the oven for hours, or use it in soups or stocks which simmer away for hours (similar to meat stews).
Pulling away the meat
Oxtail contains a lot of bones. But don’t even try to pull away the meat from the bone before cooking. It’s just about impossible to remove it. Instead, focus on cutting the tail into smaller pieces or cut at least through the bone (see photo above).
Once you’ve cooked the meat for long enough, after the collagen has broken down, the meat will literally fall off the bone. It shouldn’t take any effort at all to take the meat of. As such, this is the clear indication that your oxtail is cooked enough. If the meat doesn’t come off easily, just continue cooking, don’t waste your time trying to get the meat off the bone.
Jeff Potter, The Science of Collagen—and How to Make Mean Duck Confit—from Cooking For Geeks, Sep, 23, 2010, link