Water boils at a lower temperature at lower altitudes because atmospheric pressure decreases as altitude increases. At lower pressure, the boiling point of water decreases.
Water boils when its vapor pressure (the pressure exerted by evaporating molecules) reaches the ambient atmospheric pressure. At sea level, this atmospheric pressure is about 1013 hPa, which corresponds to a boiling temperature of 100°C. If we decrease the atmospheric pressure, for example when ascending to high altitudes, water no longer requires as much energy to boil, so it boils at a lower temperature. Conversely, if this pressure is increased, you will need to heat your water above 100°C for it to boil. This is why some people use a pressure cooker: the pressure inside is higher, so water can heat more before evaporating, reducing cooking time.
The air around us exerts a pressure because it is pulled towards the Earth by gravity. The higher you go, the fewer air molecules there are above your head pushing down, so atmospheric pressure decreases. At sea level, the average pressure is around 1013 hPa (hectopascals). At 2000 meters, it drops to about 800 hPa, and it decreases further the higher you climb. That's why in the mountains, you can quickly feel out of breath: there is simply less air to breathe, and especially much less pressure to push that oxygen into your lungs.
Since water boils faster due to the lower pressure at altitude, one might think this would speed up cooking. But it's just the opposite! At altitude, water boils at a lower temperature: about 90-95°C instead of 100°C at sea level. As a result, certain foods take longer to cook because the available heat is less intense. This significantly extends the necessary cooking time, especially when trying to cook pasta, potatoes, or rice. The thing is, at these lower temperatures, we need to extend the cooking time, which can be confusing for those who are not used to it.
At the summit of Everest, water boils at around 69°C only, far from the usual 100°C at sea level. In the city of La Paz, located at about 3,600 meters above sea level, water boils at around 88°C, which significantly extends cooking times. Hikers often notice this phenomenon in the mountains: no matter how long they wait, their pasta always remains a bit too crunchy after the usual cooking time. The same goes for rice at high altitude; it becomes more challenging to achieve even cooking without adjusting recipes or methods. High-altitude residents, in cities like Cusco in Peru or the villages in the Himalayas, are well aware of these tricks and automatically adapt their culinary practices.
At high altitude, to properly cook your food, you will likely need to increase the cooking time. If you are preparing pasta or rice, expect it to take a few extra minutes. In terms of baking, the lower atmospheric pressure may affect cake rising, so it’s a good idea to slightly adjust the amount of yeast by reducing it a bit. Also, at high altitude, liquids evaporate faster: plan for moister preparations by adding a bit of water, broth, or milk to your usual recipes. When it comes to hard-boiled or soft-boiled eggs, you will need to significantly extend the cooking time since the water boils at a lower temperature, making the process take longer. Finally, consider using a pressure cooker or an instant pot, as it helps speed up cooking by increasing the pressure inside.
Hard-boiled eggs require a longer cooking time at high altitude due to the reduced boiling temperature, forcing climbers to adjust their cooking method accordingly.
A pressure cooker (also known as a stovetop pressure cooker) allows for artificially increasing the internal pressure and thus the boiling point of water, making it easier to cook at high altitudes.
Some cities located at high altitudes, such as Mexico City at over 2,200 meters, have their traditional culinary recipes modified to adapt to the lower boiling temperatures.
Cooking pasta at high altitude often requires more water and a longer cooking time, as pasta cooks at a lower temperature than the usual 100°C.
Adding salt to water slightly raises the boiling temperature, but this effect is limited and generally does not suffice to offset the significant decrease observed at high altitudes. Using a pressure cooker is a much more effective method to compensate for this drop.
At the summit of Mont Blanc (approximately 4,810 meters above sea level), water boils at around 85°C, compared to 100°C at sea level. This decrease in temperature is explained by the low atmospheric pressure at this high altitude.
At high altitudes, it is advisable to slightly increase the cooking time of dishes or to use a pressure cooker to compensate for the lower boiling temperature. Some preparations also require adjustments to the amount of water and the cooking temperature.
Yes, at high altitudes, the reduced atmospheric pressure also affects baking. It may be necessary to slightly increase the oven temperature, shorten cooking times, and sometimes adjust the quantity of certain ingredients such as yeast to achieve proper baking.
Packaging sometimes provides specific instructions because the decrease in boiling temperature and the reduction in atmospheric pressure disrupt the optimal cooking times originally intended for a lower altitude. Following these guidelines ensures that food is cooked at the right temperature and under optimal conditions for hygiene and taste.
At high altitudes, water boils at a lower temperature, but that doesn't necessarily mean it boils faster. Although boiling will start more quickly, cooking food actually takes longer, as it requires more time to reach the desired doneness due to the reduced temperature.
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