Fact: Searing the outside of a steak creates no “seal” or waterproof barrier to prevent juices from escaping from the inside.
Reason: Steaks do not have pores. Pores exist only in the skin (epidermis) of an animal. Searing the outside of a steak does not close any pores or create any seal or waterproof barrier. In fact, rather than sealing in the juices, searing the meat does almost the opposite: it dries out and removes the moisture near the meat's surface, so searing causes a loss of moisture rather than protecting against it.
Note: In fact, there is a valid reason to sear the outside of a steak, but it is not to "seal in" the juices. Instead, the reason to sear the outside of the steak is to caramelize the surface (i.e. use the Maillard or browning reaction) to create an exterior crust. When steaks are grilled in the heat and smoke of a wood fire, the result produces wonderful contrasts: contrasts between the surface crunchiness and the soft, buttery interior; contrasts between the surface dryness and the juicy interior; and contrasts between the surface’s complex grilled flavors and the interior’s beefy flavor. In short, searing intensifies the taste, tenderness and appearance of the exterior while keeping the interior rare and juicy.
Harold McGee, the esteemed author and food scientist, explains, in "On Food and Cooking: The Science and Lore of the Kitchen", p. 112:
SEARING IN JUICENESS AND FLAVOR
There is one misconception about meat cookery that still enjoys great popularity, even though it has long since been discredited. Does the gist of this description of cooking sound familiar?
"Thus as the exterior pores contract, the moisture contained in the object cannot escape any more, but is imprisoned there when the pores close."
This quotation comes not from a blurb for convection ovens, but from Aristotle's treatise on meteorology (Book 4). The theory has changed little except for the terminology -- today we would say that the food's juices are "sealed in" by high temperatures, keeping it moist and tender.
McGee then traces the history of this theory through the 17th, 18th, 19th and 20th Centuries, including the mid-19th Century explanation of the "science" for the "sealed in" theory by the German chemist, Justus von Liebig in his "Researches on the Chemistry of Food. McGee continues:
We know today that most of [Liebig's science] is simply not true. . . . Any crust formed around the surface of the meat is not waterproof. . . . But in its day, Liebig's account answered the unspoken need for some rational, systematic approach to cookery. . . . But even after Liebig's rationale for the early-searing method had been disproven, the method itself lived on under various guises, often rather eccentric. . . . [T]he grounds of the argument have shifted since Liebig's time. The issue is no longer nutritional value or juiciness, but taste. And here we are on firmer ground. We do know for a fact that whether done early or late, searing does not seal, but it does brown: it won't prevent flavor from escaping, but it creates flavor via the complex browning reactions. . . . So there is a good reason to sear meat, but it has nothing to do with nutrition or juiciness. The many recipes and ads that perpetuate Liebig's theory probably do so because the image it evokes is vivid and appealing.
Perhaps it is understandable that laymen and amateurs wax poetic about how high heat "sears in" their steaks' flavor and juiciness. But steakmasters and other experts should dispel this prevalent myth and teach others the basic science of SteakPerfection.
SteakPerfection is a complex process that involves every detail, from pasture to plate.
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