The Complete Book of Pressure Cooking. L.D. Michaels
following the instructions carefully and applying a little common sense. Provided you are not too slap-happy (in which case you’ll never be a good cook, whatever method you try), you should have no trouble.
7 PRESSURE COOKING CAN’T BE USED FOR GOURMET RESULTSJust you wait till the end of this book and see!
2 HOW AND WHY PRESSURE COOKING WORKS
I’ve always enjoyed cooking if I’ve understood what was going on. It’s made the actual activity more enjoyable and the results much better. In addition, I now find it a lot easier to invent and adapt my own recipes. You can’t really appreciate how best to use a pressure cooker unless you know a little about cooking techniques in general. If you are at all worried about the healthiness of the food you eat, you should know something about what happens when various ingredients are heated. You can, if you wish, skip most of this chapter and go straight to the recipes and tables, but it would be a pity if you did.
I have tried to avoid too much of the domestic science/catering college/chef school/food science laboratory narrative, but some of the information is of great use to the cook who may think that they work solely on instinct and experience.
The pressure cooker delivers two cooking techniques: pressure steaming and pressure simmering/pressure poaching. Nearly all forms of pressure cooking take place at a temperature of about 121°C (250°F) and at a pressure twice that of the atmosphere we normally breathe (and cook at). It is these unusual conditions that, by a combination of heat and steam penetration, give the rapid results. Heat gets to the heart of a lump of food more easily if moisture (either liquid or steam) helps to conduct it there, and the pressure helps to get it there even more rapidly.
The simplest – and most misleading – description of cooking is the application of heat to food. A cooking encyclopedia could easily identify more than 20 sorts of cooking, and if you thought about it yourself, you’d find you knew and used most of them. Different levels of heat, different combinations of air and water and steam, the presence of fat, both solid and liquid, even the type of cooking vessel and the source of heat – all contribute to the taste of the various sorts of food we eat. A potato can be fried, baked, boiled, steamed, roasted, sautéed, mashed, combined with milk or cheese, sprinkled with herbs and spices … it can even be first boiled, then mashed and seasoned before frying or baking … and in each case the taste will be quite different, while still obviously being a potato.
What we admire in food is its taste, its texture and its appearance. Increasingly, too, we are concerned about its effect on our health. Most of us know by instinct what cooking method to use in each case, but only a few of us can actually explain what is going on. Some of the fear that the pressure cooker arouses comes, I am sure, because instinct doesn’t seem to help and everything goes on inside beneath a firmly sealed lid. In fact, the rules of cooking don’t alter that much.
I was fortunate that, when I was finally free of home and college and was sharing a house in West London, one of my friends had completed a proper cordon bleu course – but in Jamaica. So added to the traditional grande cuisine menu were Caribbean specialities bought in Portobello Market, which we watched him cook with interest. As he operated over the stove, he would murmur to himself what he was doing to the food, how it was changing in colour and taste, how juices were flowing in and out and how each ingredient affected the next. That’s how I really began cooking.
The two variables in cooking are the make-up of the original food and the method of applying heat. We need to heat certain foods in order to be able to digest them in our systems. We need to cook certain foods simply to improve their taste – we eat more if we like what we eat. In some cases heating destroys them, at least partly. You have to make a choice.
Our diet consists of five components: carbohydrates, fats, proteins, minerals and vitamins.
No one eats these pure ingredients by themselves, so any application of heat to a given piece of raw food has a variety of effects. We have to trade off the loss of certain nutrients in return for releasing others and making the entire result more palatable. This is what happens when heat is applied to the various basic components listed above:
Carbohydrates – the sugars, if they are solid, melt very easily and become sweeter to the taste. If they are heated above a certain point, they start to turn yellow and caramelize. Sugar eventually turns a light brown and then becomes black and burnt. You can watch the process happen if you fry carrots or onions (in fact, onions make a good colouring agent for stocks and soups, as well as a flavour, if used in this way – fry an onion clear for a white well-flavoured stock, and fry it dark brown for a dark stock).
The other edible carbohydrate – starch – is inedible unless cooked. The starch in uncooked flour, potato, rice and so on is locked up in a series of packages that resist the stomach juices. Cooking breaks down the packages so that the digestive system can reach the edible starch. Overcooking results in a breakdown of the shape of the food itself, and while that isn’t bad nutritionally, the texture is mushy and that offends us.
Fats – heating fat melts it. Whether one has to heat it at all depends on the type of fat and is really a matter of what you happen to like; most people will cheerfully spread butter on bread, but not lard. If overheating occurs, the fat burns and produces fatty acids. Butter burns at 137°C (278°F), beef suet at 180°C (356°F), lard at 200°C (392°F), vegetable oil at about 260°C (500°F) and olive oil at 290°C (554°F).
Proteins – on heating, protein coagulates and hardens; watch what happens to egg white. We can digest cooked protein rather more easily than uncooked, so raw eggs are not always as health-giving as is sometimes claimed – a raw egg can slip through your digestive system without having very much of its protein absorbed. Protein is located in the fibres of meat, which is why meat can taste tough or stringy if not carefully treated. The only meats that can put up with violent exposure to heat are the very soft-textured ones like steak. Otherwise, they have to be physically cut up (as in hamburgers and meat loaf), marinated in wine or vinegar to soften the fibres chemically or cooked slowly at a low heat. Rare beef is “done” at 65°C (150°F) and fresh pork and poultry at 87°C (190°F), those being the final temperatures of the cooked foods at their centre.
The hardening of the protein fibres also causes shrinking of the meat and a squeezing out of the juices that contain other forms of goodness. Cooking of protein in general – and meat in particular – is quite possible in a pressure cooker, but obviously needs a bit of thought. A lot of people waste meat using perfectly “normal” techniques. Excessive heat breaks down protein.
Minerals – there are no general rules here. The calcium in milk becomes a little less available if it’s heated, but if greens are boiled in hard water (not normally a good idea), then more calcium becomes available to be digested. Iron is normally more easily picked up after cooking (a lot comes from cast-iron cooking pots!), and salt is unaffected by heat. However, a lot of minerals are lost if they are allowed to soak or leach away into cooking fluid (water or gravy) that is then thrown away. For this reason, boiled vegetables are in general not a good idea, unless use is made of the vegetable water. Steaming is far better, as the vegetables retain all their fluids and very little water is involved in the process. Pressure cooking is high-pressure steaming, of course.
Vitamins – vitamins A and D are unaffected by baking and boiling, though vitamin A is destroyed at the high temperatures used for frying. Vitamin B, or rather the various sorts of vitamin B, can be destroyed by high heat but, more importantly, they are soluble in water, which means that losses can take place in the same way as for minerals.
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