Cooking in high-altitude Xizang brings unique pressures

Lhamo Tsering, a resident in Lhasa, Xizang autonomous region, said her neighbors like to use pressure cookers made in the region, as they make food preparation easier and safer.

"Last year, people could buy these pressure cookers for only 100 or 200 yuan ($14 to $28) because they receive a subsidy from the government. The regular price at a store is more than 800 yuan," she said.

With an average altitude of 4,000 meters, Xizang is known as the "roof of the world". But the high altitude means there's less atmospheric pressure than at lower elevations, so water boils at a cooler temperature. Water at sea level boils at 100 C, but in Xizang the boiling point is only around 85-90 C, which is not efficient for cooking. Also, it may not be hot enough to kill food-borne bacteria. Foods such as meat, for example, should be heated to around 116 C, experts say.

Pressure cookers — special pots with airtight lids — are used to contain heated air and steam, and the added pressure raises water's boiling temperature. Basically, the interior of such a pot simulates higher air pressures at lower altitudes, so they are often relied upon for faster and more convenient cooking.