The Complete Book of Pressure Cooking. L.D. Michaels
a while the cooker will be silent; then you should hear the escaping steam again. Some cookers have a special indicator, or the valve starts to murmur or rotate. This means that the internal pressure is now up to full pressure. You should then reduce the heat to keep the process just ticking over.
Applying more heat is not just wasteful. It doesn’t speed the process up any further and only results in the more rapid boiling away of the water. If you are pressure steaming, you could run the risk of boiling dry, and if you are pressure boiling, you could leave your pieces of food without any stock around them and risk burning.
THE TIMING OF ALL RECIPES STARTS FROM WHEN THE COOKER IS FULLY UNDER PRESSURE. PRESSURE-COOKING TIMES ONLY ARE GIVEN AT THE HEAD OF EACH RECIPE.
In general, you should always put as little liquid as possible in the appliance. Firstly, if you overfill the pressure cooker, the water takes longer to boil and thus the cooker takes longer to come under pressure. Secondly, if you are going to use the fluid at the end of the process, say to make a sauce or a stock, then the more water there was to begin with, the more dilute will be the nutrients that have dissolved in it.
The calculation of the amount of water to be used is always very simple. Provided you keep the appliance just ticking over and are not overheating, then at full pressure or normal operating conditions, 140ml (¼pt) liquid is expelled as steam for every 15 minutes of cooking time*.
*If you use US cup measurements (1 cup = 8 fl oz/236ml), you would work on ½ cup per 12-minute period.
Most manufacturers recommend that the minimum amount of liquid you put into your appliance should be 140ml plus 140ml, i.e. 280ml or ½pt. You then add a further 140ml for each additional 15-minute segment. Thus for an hour’s pressure cooking you would need: 4 x 140ml + 140ml = 700ml (1¼pts) fluid. By contrast, if you were to leave the valve off and keep the heat high, 120ml (4 fl oz or 1/5pt) water would be driven off as steam in 5 minutes.
Remember that the timing always starts once the cooker is under pressure. As a very rough guide, once the cooker is under pressure, the cooking time is only one-fifth of conventional times, though an actual recipe will often involve more than just cooking at full pressure.
One thing that will affect the length of cooking time is the degree of freedom that the pressurized steam has to circulate. Food cooked on top of the trivet or in the perforated separator will cook more rapidly than food in a solid separator or in some other vessel like a boil-proof bowl or one of heatproof glass. The recipes will tell you how to adjust.
At the end of the cooking time, you must reduce pressure to bring the contents of the pan down to the same pressure as the atmosphere. There are two ways:
1 Rapid cooling, which involves placing the pan in cold water or, if necessary, under cold running water.
2 Slow cooling, which merely means taking the pan away from its source of heat.
The pressure cooker will be able to withstand the violent changes in temperature arising from the first method. In the interest of speed, the rapid method is usually the better and should only be avoided if the contents are very fragile like vegetables, soft fruits, rice, etc. What normally happens when pressure is reduced rapidly is that there is a turbulence inside the cooker. Delicate foods and large quantities of liquids may be upset, but most solid foods will be unharmed.
Don’t try to remove the lid before pressure is reduced. In most cases it will be impossible anyway.
COOKING SEVERAL ITEMS SIMULTANEOUSLY
Since cooking by pressure steaming means that particles of food need not be touching or have their juices conveyed to each other by liquid, you can easily cook several items together. If they have different cooking times, put in the longest-cooking item first, cook for a short while, reduce pressure, add the next ingredient, raise pressure again and begin timing. Thus if you are cooking whole new potatoes, cauliflowers in quarters and spinach, you would:
1 Load up with potatoes (cooking time 8 minutes) and pressure cook for 4 minutes.
2 Depressurize, load up with cauliflower (cooking time 4 minutes) and pressure cook for 3 minutes.
3 Depressurize, load up with spinach (cooking time 1 minute) and pressure cook for 1 minute.
4 Depressurize and serve.
In fact, this is as complicated as it’s ever likely to be!
WHAT TYPES OF HEAT SOURCE CAN BE USED?
Almost any.
1 GAS. The flame should be as high as possible while bringing to pressure and should then be lowered until the cooker is just muttering over.
2 ELECTRICITY. For a solid hot plate, switch the plate to high to bring to pressure and, if cooking time is less than 15 minutes, switch off and place the cooker on the edge of the plate as it cools down naturally. When the plate has cooled down a little, the cooker can be moved back to cover the plate completely. For a radiant plate, start high in order to bring to pressure and then reduce to a simmer when pressure has been reached.
3 INDUCTION. Stainless steel pressure cookers will work on an induction hob, though you need to check that the base is of “magnetic” grade. Aluminium models will not work. You can buy induction hob cooking converters that are either made of cast iron or two layers of magnetic steel sandwiching a layer of aluminium that is used for heat distribution. The converter heats up and you can then place an aluminium pressure cooker on to it.
4 SOLID FUEL. Follow the instructions given for solid hot plates above.
5 BUTANE (CALOR) STOVES. These don’t normally generate as much heat as a mains gas cooker, so bringing to pressure will take a little longer. You should be able to reduce the flame once pressure has been reached.
6 OPEN FIRES. These need watching carefully, as they vary a great deal in their heat output. A fresh damp log will temporarily lower the heat of a camp fire or barbecue. In general, start on a high heat and, once pressure is achieved, keep the appliance muttering. Watch your fire carefully so that the cooker neither starts boiling too rapidly nor depressurizes when you don’t want it to.
WHEN DO YOU ADD AND ADJUST SEASONING?
Before and after cooking time. Since pressure cooking uses far less liquid than ordinary cookery, any seasoning you use will be less diluted by the end of the cooking time, so you use quite a bit less. In pressure steaming, using the trivet, you can add seasonings (salt, pepper and spices) and herbs before cooking starts. Remember that dried herbs are far more concentrated than fresh ones, but that they need rubbing in order to activate them.
In pressure simmering, when you are cooking without the trivet and placing the food in a liquid such as stock, it is best to season first but to leave the herbs until after. Herbs can’t tolerate prolonged high temperatures – the aromatic oils that provide the flavour simply get dispersed or chemically broken down.
For cooking periods in excess of 10–15 minutes, I usually prefer to take the pressure off a little before the correct cooking time is up, open up the pan and then add herbs and check the seasoning by tasting, using a spoon. I then finish off with ordinary cooking in the open pan so that I have perfect control. This method takes only a little longer.
If you are cooking with some of the more aromatic additives used in vegetarian cooking like garam masala, miso and other soya derivatives or sesame oil, then these should be added at the very last moment when the dish is actually cooling down.
WHAT ADJUSTMENTS DO YOU MAKE FOR COOKING AT HIGH ALTITUDE?
Once you are 600 metres (2,000 feet) above sea level,