About The Fat Cap, And Busting The Myth That Melting Fat Penetrates Meat
"Are you gonna eat your fat?" Spaulding in the classic 1980 movie, Caddyshack
No aspect of food is more misunderstood than fat. All mammals have it, and many vegetables do too. It is essential to human life. Cut it out of your diet and you die. Eat too much and you die.
There are many different kinds of fat: Saturated, monounsaturated, polyunsaturated, trans fat, vegetable oils, fish oils, nut oils, olive oils, omega 3, 6, 9, hike. This article will focus on solid animal fat on the surface of meat, and what it does from a culinary standpoint, and try to settle the argument once and for all: On or off?
As far as the health apects, suffice it for me to say: I have digested authoritative research and learned that there is a huge amount of conflicting data, so much so that one might conclude that the only ones who really know the answers with any certainty are the food fascists who want you to adopt their pet diet. There is even a growing body of research that shows that the dangers of cholesterol in our systems from animal fats is vastly overrated. I am not qualified to form a conclusion other than to say that fat is probably like everything else in our diets, moderate amounts as part of a balanced diet can't hurt you and it probably can help you. What I can tell you with authority is that fat many foods taste better and what to do with fat that you find in and on meat.
Melting surface fat does not penetrate muscle
Now it is important to differentiate between subcutaneous fat, the thick hard fat layer right under the skin of many animals, intermuscular fat, the fat that lays in thick layers on top of muscles as well as between muscle groups, and intramuscular fat, the thin whisps of fat that thread their way between fibers within the muscle also called marbling, and intercostal fat that is found between ribs.
Marbling is vital to the juiciness of meat and its flavor. But the subcutaneous fat, the fat cap as it is often called, is another story altogether.
So let's say that you have a hungry crowd of rowdies to feed and this big ole honkin' pork shoulder, beef brisket, leg of lamb, or prime rib. It has a thick layer of fat on top. The question is, leave it on or trim it off? Most books, TV cooks, and websites say that you should leave it on because it will melt and percolate down into the meat making it juicier.
This is the fat layer that animals have between the skin and muscle to keep them warm. It is usually white, fairly hard, and can be as much as an inch thick. Meat scientist, Dr. Tony Mata, the AmazingRibs.com beef consultant, explains "Fat will not migrate into the muscle as it is cooked. First of all, the molecules are too large to squeeze in. Second, fat is mostly oil. The red stuff in meat is made from muscle and it is mostly water. Oil and water don't mix. Protein in muscle is also immiscible in fat because of its chemical configuration. Third, in most cases there is an anatomical barrier between muscle and fat cap, namely, a layer of connective tissue holding muscle groups together. It too is water based." The AmazingRibs.com science advisor Dr. Greg Blonder adds a fourth reason: "Meat is like a protein sponge. It is fully saturated with water. There's no room for the fat to go in. As the meat cooks, water-based juices are being expelled from the interior. No way fat can swim upstream."
Consider this myth busted.
So when you cook meat with the fat cap on it softens, some of it browns, some melts and lightly coats exposed muscle groups below, and some of it drips off into the fire where it is vaporized and can settle on the meat adding flavor. Some of the fat will drip off and can be collected for use in making gravy or stored for use in frying later. If you leave on a thick fat cap, most people are going to trim it off at the dinner table, along with all your spices and the wonderful browning flavors created by the Maillard reaction and caramelization. On the other hand, in Brazil they treasure a cut called coulotte which is a smallish section of sirloin with about 1/4" of fat left on. This particular fat is especially tasty.
If you coated the meat with a wonderful spice rub, it will remain on the fat and not get onto or into the meat. But much of that flavor will drip off and if you have a drip pan, make great gravy. Alas, the flavor will not be on or in your meat surface.
Worse, smoke cannot penetrate fat. Most of the flavor from smoke comes from microscopic particles and gases, and they cannot get through to the meat and flavor it or make a smoke ring.
But fat is full of flavor, often tastier than the meat itself, and the best tasting meats are those with small fat deposits strewn throught the muscles, marbling.
So a better strategy is to remove all but a thin layer, 1/8" or less, as on the top of the slice of brisket at right. Much of it will melt away, but if you leave a little people can eat mostly muscle and still get a taste of flavorful fat, as well as the spices and herbs you lovingly blended and rubbed all over.
When to leave a fat cap on
There are some good arguments for leaving on a fat cap.
If your cooker has the meat sitting directly above the heat, putting the fat cap down creates a heat shield protecting the meat surface from drying heat.
On the other hand, if you like a crunchy crust, a thin layer of fat coated with salt, spices, and herbs, can combine to create something that barbecue lovers lust for on pork butt for pulled pork, a jerky-like dried surface packed with flavor called bark.
On the other hand, the fat layer will trap evaporating moisture and produce juicier meat, but not a hard bark. I recommend removing all the fat except 1/4" to 1/8". Most of that will melt off and drop away leaving 1/8" to 1/16", and people will see that the spices are on that cap and most will eat it, significantly enhancing the dining experience.
And what about the fat dripping into the fire and being resurrected as flavorful droplets mixed in with smoke? I save the fat cap and put it on the grate over the fire and let it drip away.
Mata points out one case where the fat cap is essential. In Brazil and Argentina, they relish a cut called picanha. In the US it is called coulotte or sirloin cap steak. "There is a way of grilling this cut by impaling wedges of this muscle on a large skewer. A specific amount of fat cap is left attached on purpose. The skewers are placed against coals from wood. When served, the wedges are sliced onto the plate directly from the skewers. The fat is consumed, not trimmed off. It is fantastic."
You may have seen this presentation in Brazilian themed restaurants presented tableside with a fluorish on sword-sized skewers. The photo here is from the website of the Brazilian steakhouse chain, Fogo de Chão. Next time you go Brazilian, eat the fatcap.
This page was revised 2/2/2013
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