The reason spaghetti takes longer to cook in the mountains (about 14 minutes) compared to sea level (about 9 minutes) is due to the lower boiling point of water at higher altitudes.
Boiling Point and Atmospheric Pressure
At sea level, atmospheric pressure is higher, which allows water to boil at 100°C (212°F). At higher altitudes, the atmospheric pressure decreases, causing water to boil at lower temperatures—sometimes significantly below 100°C. For example, at 8,000 feet elevation, water boils at about 92°C (198°F). Because the water temperature is lower, the spaghetti cooks at a lower temperature, which slows down the cooking process and thus increases the cooking time.
Implications on Cooking Time
Since boiling water can't get hotter than its boiling point, the maximum temperature at which food cooks is lower at high altitudes. This means the pasta is exposed to a lower cooking temperature for an extended period, resulting in the longer time needed to reach the desired tenderness of pasta.
Summary
- Lower air pressure at higher altitude
- Lower boiling temperature of water
- Lower cooking temperature for boiling foods
- Requires longer cooking times to achieve the same level of doneness
Therefore, the longer cooking time for spaghetti in the mountains is primarily due to the reduced boiling point of water caused by lower atmospheric pressure at high altitudes.