Temperature. Conduction. Convection. And why we might want to simmer our chicken and vegetables.
Why do so many recipes ask that you simmer your soups, sauces, vegetables and meat instead of boiling them? After all, when we simmer, it is at around 93°C, whereas boiling is at 100°C. Surely it is not such a big difference?
It is a big difference as it will determine whether you overcook your food, and thus what your buddies think of your cooking. It all boils – pun intend – down to conduction and convection (read all about the science of heat transfer in the 1-Minute NomNom “Pleased to heat you!“).
When hot water moves past any food, heat is conducted from the water to the food. It thus matters how much hot water is circulating around the food.
This is where convection comes in. Hot water and steam rise from the bottom and cold water is sucked in to replace it. This in turn becomes hot and rises, and draws in more cold water to be heated. When we boil water, the convection currents can be pretty violent (just look at how big the bubbles are and how quickly they pop), almost like the stormy waves of a tempestuous sea.
This causes a lot of water to move past the food. Heat is thus conducted to the food much more rapidly. That is why we use boiling when we want to cook something fast like pasta, vegetables and noodles. We do however have to watch out as we might overcook our food.
We avoid this over-cooking risk when we simmer our food. Even though it is just a few degrees cooler, the water around the food is relatively still. Heat transfer is significantly less, and our food cooked in a simmer will cook more slowly and taste better. Thus we use simmering when we are cooking foods such as poached eggs, or a soup where we want to extract the flavors from the ingredients.
We can use a thermometer to get the temperature just right for simmering. If you don’t have a thermometer, you can gauge it by the size of the bubbles in the water (see video below from the Jamie Oliver channel). Boiling water has large, violent bubbles; water perfect for a simmer has small bubbles moving gently upwards from the bottom of the pot.
Like this? Be cooler in simmer and like me to discover more. All you need is a minute a day to explore the world’s marvels through the phenomenon of food!
photos: istockphoto/SilviaJansen; depositphotos/angelp; Ha4ipiri; kovalvs; macrovector; lenyvavsha