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Cooking at altitude
While this may seem a stage item when relevant to the British Isles, for those contemplating a self-catering skiing holiday, the information is useful to record - and have at hand.
Lower air pressure complicates nearly all the processes of the kitchen. It slows down boiling and speeds up deep-frying, making chips almost impossible to be crisp. It throws sugar cookery out of kilter, and makes the baking of bread and cakes an unpredictable affair.
Effects become marked above 2,500 feet, and cuisine threatening above 5,000 - not high by Alpine resort standards. For while water boils at 100ºC/212ºF at sea level, at 2,500 feet this is reduced to 97ºC/206ºF, and at 5,000 feet to 94ºC/202.6ºF. at 10,000 (admittedly an unusual height for Europeans to be cooking at, but easily possible elsewhere), the hottest it will get is ?ºC/194ºF - making the cooking of dried pulses correctly impossible, without the aid of a pressure cooker; even these need 450g/1lb of extra pressure for every 2,000 feet, and an increase in cooking times of 5% for every 1,000 feet of elevation.
Altitude also effects our taste-buds, adding to the complaints on airline food.
At 12,000 feet, it takes 6 minutes to produce a "3 minute" boiled egg.
The thinner air even at 2,500 feet means the lift from baking powder and beaten eggs is greatly effected - leading to flat, heavy cakes. The gas omitted from baking powder in particular, has too little pressure to work against, so rises too quickly, escaping before the cake is cooked - the end result then collapses.
For baking powder the guidelines are to reduce the baking powder quantities given in a normal recipe by ¼ teaspoon per 1,000 feet you rise above sea level. Sugar should also be reduced by ½ teaspoon per 1,000 feet, and the shortening again by ½ a teaspoon. A little extra flour, and liquid is also recommended above 2,500 feet.
When deep frying you have to reduce oil temperatures. Even at 2,500 feet chips should fried at 180ºC/350ºF, rather than the normal 190ºC/375ºF, because the boiling point of the internal water in the potatoes is lower. Without lowering the temperature you will have chips that are externally brown well before the inside is cooked. A McDonalds at altitude would have major problems!
If you enjoy cooking take a minute to look at ‘Simon Scrutton French Cookery Classes’ on Google – and learn how to make top class bistro-style dishes. Suitable for beginners upwards. Small classes.