Science: The Magic of Meringue—Why Timing Matters When Whipping Egg Whites and Sugar скачать в хорошем качестве

Science: The Magic of Meringue—Why Timing Matters When Whipping Egg Whites and Sugar

Cook's Science, pre-order now! http://amzn.to/212U0nC The Science of Good Cooking: http://amzn.to/1O8oGw7 Subscribe to our new Cook's Science YouTube channel!    / cooksscience   Meringue cookies depend on whipped egg whites for both leavening and structure. The sugar that’s added to the whites contributes not only sweetness but also stability. But does it matter when you add the sugar? Watch more Science! How to Buy the Best Parmesan Cheese    • Science: How to Buy the Best Parmesan Cheese   Wild vs Farmed: How to Cook Salmon to the Right Temperature    • Science: How Wild Salmon Differs from Farm...   Meringue cookies and all types of sponge cake, including angel food and chiffon, depend on whipped egg whites for both leavening and structure. The sugar that’s added to the whites contributes not only sweetness but also stability. But does it matter when you add the sugar? EXPERIMENT To find out, we made three batches each of meringue cookies, angel food cake, and chiffon cake, adding the sugar to the whites before whipping, after a minute of whipping, or at the very end, once the foam had reached the “soft peaks” stage. We baked them and compared the results. RESULTS In all three recipes, the timing made a difference. Adding the sugar after a minute of whipping was clearly best across the board. In both types of cake, the crumb structure was compromised when the sugar was added at the very end: The chiffon was dense and flat, while the angel food was coarse and almost crumbly. Adding sugar before whipping was also not ideal, leading to cakes that baked up a bit too dry. In the case of the meringues, adding the sugar at the start of mixing produced a cookie that was dull on the exterior, with a too-fine crumb within. The cookies made when the sugar was added at the very end had an overly airy texture (tasters compared it to Styrofoam) and a grainy consistency. To top it off, they took on an unappealing brown color. EXPLANATION When egg whites are whipped, the eggs’ proteins unfold and then cross-link to form a network that stabilizes the air bubbles. At the same time, the sugar dissolves in the water from the eggs to form a viscous liquid that helps stabilize the structure. If the sugar is added too early, the sugar granules interfere with the proteins’ ability to unfold, resulting in a weaker network that can only support small air bubbles (this is why these cakes and meringues had a finer interior texture). If the sugar is added too late, either the sugar, which is hygroscopic, draws water out of the foam and causes the structure to weaken (as in the dense, crumbly cakes), or the sugar doesn’t fully dissolve (as in the meringue cookies that were grainy and brown from undissolved sugar caramelizing). Adding the sugar after a brief amount of whipping gives the protein network time to form while leaving enough time for the sugar to dissolve. TAKEAWAY: For ideal volume and stability, add the sugar to whipped egg whites after the eggs have started to get foamy but well before they have started to form peaks. If you like us, follow us:   / cooksillustrated     / testkitchen     / cooksillustrated     / cooksillustrate