On food and cooking the science and lore of the kitchen ( PDFDrive ) 1497

evaporate moisture continuously Cooks take advantage of it when they bake delicate preparations like custards gently by partly immersing the containers in an open water bath, or oven-roast meats slowly at low temperatures, or simmer stock in an open pot In each case, evaporation removes energy from the food or its surroundings and causes it to cook more gently Steam Releases a Lot of Heat When It Condenses into Water Conversely, when water vapor hits a cool surface and condenses into liquid water, it gives up that same high heat of vaporization This is why steam is such an effective and quick way of cooking foods compared with plain air — also a gas — at the same temperature We can put a hand into an oven at 212ºF/100ºC and hold it there for some time before it gets uncomfortably warm; but a steaming pot will scald us in a second or two In bread baking, an initial blast of steam increases the dough’s expansion, or oven spring, and produces a lighter loaf Water and Acidity: The pH Scale Acids and Bases Despite the fact that the molecular formula for water is H2O, even absolutely pure water contains other combinations of oxygen and hydrogen Chemical bonds are continually being formed and broken in matter, and water is no exception It tends to “dissociate” to a slight extent, with a hydrogen occasionally breaking off from one molecule and rebonding to a nearby intact water molecule This leaves one negatively charged OH combination, and a positively charged H3O Under normal conditions, a very small number of molecules exist in the dissociated state, something on the order of two ten-millionths of a percent This is a small number but a significant one, because the presence of relatively mobile ... even absolutely pure water contains other combinations of oxygen and hydrogen Chemical bonds are continually being formed and broken in matter, and water is no exception It tends to “dissociate”... extent, with a hydrogen occasionally breaking off from one molecule and rebonding to a nearby intact water molecule This leaves one negatively charged OH combination, and a positively charged H3O Under normal conditions, a very small number of molecules... conditions, a very small number of molecules exist in the dissociated state, something on the order of two ten-millionths of a percent This is a small number but a significant one, because the presence of relatively