It's the first line in many recipes:"Preheat the oven to 350 degrees."Some peoplequibble with the language—is "preheat" really all that different from "heat"? Others, expressing admirable environmental sensitivities—isn't this sort of a waste of energy?—wonder about the concept itself. The oven,as we discussed earlier this year, uses a pretty substantial amount of energy. Do you really need it to be going full-blast when there's nothing in it?
The answer is...it depends. And the reasons why it depends are as numerous as the things you might want to cook in the oven.
Take bread, for instance: What the heat of the oven does here is provide the last little push the yeast needs to raise the dough to the loftiest heights possible before the flour structure sets; starting from a cold oven would produce a flat, dry, chewy product. A similar principle holds true for doughs or batters that have been leavened with baking soda and/or baking powder—like those for cakes and cookies—which also need a certain level of heat, applied quickly, in order to do their thing.
Take this notion and apply it to any food with a delicate architecture that might be prone to collapse:soufflés,meringues,génoises. Apply it topie dough, in which the flour structure needs heat to set itself before all the butter melts. In short, does it have flour and/or eggs? Preheat the oven.
This might be difficult advice for those of us who prefer a looser approach in the kitchen. But fear not, for we've gotcasseroleson our side.Roasts. Lasagnas. Entire classes of savory foods that don't need to get any sort of lift, that just need to sit in the heat for a while until they're cooked through—recipes that are on the wet side, with ingredients that need to sit and marinate in each other for a long time, low-and-slow recipes. Makemacaroni and cheesethis way. Stick it in the oven, turn it on, come back later. Toasting nuts? No need to wait for a hot oven—just throw 'em in and roast them till they're done. We're going off-road here, into territory that the recipe may not cover, but the best course is to fall back on your eyes and nose. Does it smell good, is it golden? Bam, it's done. And without a minute wasted waiting for the oven to preheat.
