Laura Pazzaglia is the creator of the popular HipPressureCooking.com, dedicated to make pressure cooking hip. She is more than a prodigious cook, writer and educator. Laura has also devised a simple but ingenious benchmark to measure one key aspect of pressure cooker performance. She calls it evaporation measure. In her own words, this is done as:
“Starting with a “cold cooker” (not heated from a previous test) pour exactly 1000g of water into the liner and pressure cook for 10 minutes, with natural release. Then remove the lid and shake vigorously into the base and pour the contents into a zeroed-out bowl on digital scale. Record the weight of remaining water. “
Dividing the missing water amount over the total gives you evaporation rate. It’s a straight forward measure of leakage of a pressure cooker, which works for both electric and stove-top pressure cookers, probably for stock pots too.
Why is evaporation rate important? In “Modernist Cuisine” (so far the most comprehensive and authentic book on the art and science of cooking), Nathan Myhrvold states that sealed cooking pots trap most aromatic volatiles which make stocks more flavourful (Volume II, pages 292). We also blogged about the astonishing discovery by Dave Arnold at the International Culinary Center that leaking steam means leaking flavour. Dave Arnold’s experiments showed that not all pressure cookers are equal in preserving flavour in stocks. Leaky ones do a bad job, sometimes worse than a stock pot.
Hence, the evaporation rate is not just a simple leakage measure but an indicator of the quality of food the pressure cooker prepares.
What did Laura find out?
“Instant Pot only had an average 2% evaporation during ten minutes of pressure cooking (compared to Cuisinart 4% and most stove top pressure cookers 3.5%).”
In comparison, an uncovered pressure cooker at a vigorous boil for the same amount of time and same weight of water and the evaporation rate is 30%. You can read Laura’s meticulous review of the Instant Pot IP-LUX60 here.
Laura has very high standards. Instant Pot didn’t earn a perfect score. She gave IP-LUX60 a “Very Good” rating. We really appreciate Laura straight to-the-point approach and constructive criticism. These give us something to strive to improve upon in our next model.