Because fat can be made much hotter than water the cook usually glutenizes the flour in butter and then adds the water or etc. This combination of fat + flour is called a roux; it’s described further on pages ref1 and ref2.
SUGAR
Sugar caramelizes when heated. It turns a golden yellow, then light brown and, according to the amount of heat you apply, eventually black and burned.
VEGETABLES
Vegetables soften when heated by the cook. They don’t contain protein so you can boil them furiously if you want to. Frying is hotter than boiling and so when you fry vegetables you will see the sugar in them caramelize. Fried onions will, with a little heat, lose their capacity for making your eyes water, then they will soften and after that go a golden colour, then brown. Now they have taken on quite a different flavour. The cook sometimes uses this caramelization of onions etc. to add flavour and/or colour to a stew.
EGG
Egg is protein. All protein hardens above boiling point. Although egg is often given a blast of fierce heat we usually eat them only partly cooked. Omelettes, scrambled eggs, poached eggs, boiled eggs are given just enough heat to make them firm. Cook them longer and you’ll find yourself in the plastics industry.
High temperature releases hydrogen sulphide (from the sulphur in the egg-white) and makes an egg taste stale. This same sulphur combines with iron in the yolk to make that grey ring round the yolk of a hard-boiled egg that has been made too hot. So you see that a real boiled egg is unattractive, indigestible and tastes disgusting.
Although a ‘boiled egg’ goes into boiling water, do not bring it back to boiling point. Keep the water well below boiling temperature so that the surface just moves (the French say frémir which means to shiver and perfectly describes it). The water is now at about 185ºF.
The most satisfactory way to cook the egg in its shell is the old-fashioned method of ‘coddling’. Bring a pint of water to maximum boil. This rolling confusion of water, changing to steam, is nearly at 212ºF. Put one egg into the water, put a lid on the saucepan and turn off the heat. After approximately six minutes, eat it. I say approximately because the freshness of the egg influences the cooking time, and you might need to modify your cooking times to find the right one for your eggs, and your taste. Measure the amount of water you use, and provide one pint of water per egg. And from now onwards, remember how to estimate water temperature.
The egg is also a liaison, used, as flour is, to bind liquids into a sauce. But while flour is tough enough to withstand boiling, the protein of the egg curdles at 167ºF., and your sauce collapses. So when there is egg in your sauce be cautious. Heat it gently, and if possible cook it in a double-boiler (a basin over a saucepan of water will do). But there is a way of cheating – add a trace of flour to the egg and the sauce will withstand boiling, if you bring it to the boil slowly.
ALCOHOL
When wine or spirits are used in cooking they must be subjected to considerable heat or they will be very indigestible. Unless alcohol is set on fire, or has over one hour’s cooking at any temperature, it should be boiled until half its bulk has evaporated.
WATER
Water is perhaps the most important of all things subjected to the heat of cooking because all foods contain water. About 60 per cent of the weight of meat is water. Fish is 65–80 per cent water and vegetables and fruit 85–95 per cent water. (Foods that don’t contain water, e.g. dried fish, dried peas and beans, rice, etc., won’t go bad, because the bacteria in water cause that, but they will need water added to them again before being cooked.)
When water is added to food mixtures – especially those containing flour – the amount of water is very important. Any sort of pastry must have only enough water added to make the mixture manageable. Batter mixtures should be like cream. Cake mixtures are somewhere between the two. The difficulty for people writing recipes is that flour varies in its absorbency. And because flour absorbs water, batter mixtures left to stand will thicken.
Thirdly, water is used as a cooking medium. As well as being cheap, it won’t heat beyond 212ºF. What’s more, when it gets near that temperature it will bubble and steam, so the cook has a constant visual check on the temperature.
AIR
Air expands when it’s heated. Cooks use this fact in many cooking processes in order to get a texture of holes through the food. Pastry would be a concrete slab and steamed puddings solid rubber if it wasn’t for the tiny particles of air that expand to raise the texture. Remember this when handling various types of mixture. Everything must be cold when handling pastry – some cooks chill the dough – so that the cold air will expand more. Pastry must not be carelessly handled, or the air particles will be lost. When stiffly beaten egg-whites are folded into a mixture the word ‘fold’ is used to emphasize the gentle way the bubbles must be handled. Wet mixtures for cakes are beaten like mad to get air into them. Batter mixtures are best if beaten just before cooking.
Self-raising flour has bicarbonate of soda – a raising agent – added to it to produce bubbles. Beating such mixtures can reduce the effectiveness of the raising agent. Yeast does exactly the same (although, because oven heat halts the action of the yeast, the raising takes place in a warm kitchen before the actual cooking).
METHODS OF COOKING
Having dealt with the types of foodstuffs available, let’s turn on the heat.
DRY RADIANT HEAT
Dry radiant heat of open fire, barbecue fire, domestic grill, or broiler. This is the most basic sort of cooking heat there is. It uses open radiant heat (as against the enclosed moister heat of an oven). Although this is a favourite way of cooking meat it is something of an abuse. Only first quality cuts, that will be tender under any circumstances, can be cooked this way. The object is to keep as much moisture and flavour in the meat as possible and to avoid drying the meat right through. For that reason the best things to grill are the things that you like to eat with an undercooked centre, e.g. steak, beef hamburgers, and toasted bread. Things that must be cooked right through, e.g. pork chops, fish, and veal, have to be moved a little farther away from the heat source or they’ll be burned outside before they are completely cooked.
There is an old French saying that a chef is made but a grillardin is born. Grilling requires constant attention because half a minute too long means disaster when the heat is so great. The meat or fish is usually painted with a trace of oil; grilling is especially suited to foods that already contain a lot of fat, e.g. streaky bacon or any oily type of fish.
Since fat shrinks at a faster rate than lean meat it is usual to slash the fat around a piece of steak (see