A mirepoix is a combination of aromatic vegetables, diced and then subjected to heat to release their flavor and aroma. In french culture, this is the base for many preparations and dishes, stocks, etc. The quantities of onion, celery and carrot vary depending on the use, but the most common one would look something like this:
2 parts onion – 1 part celery – 1 part carrots
But why mirepoix? it sure contains yummy ingredients but why use them, why did the French settled for this trio. Nothing smells better than a mirepoix being sweated at medium heat in some butter, that’s for sure. So that kinda partially answers the question. Looking at it closer, specially at sugar content and ph level of each of the 3 components a few interesting things come to light:
Ph level of the three is above/around 7, barely acidic or slightly alkaline
Food, specially yummy food is usually on the slightly acidic end of the spectrum, who doesn’t like pickles! OK, that’s the extreme of yummy acidity (and usually only works well cold) Mirepoix is balanced more neutrally, favoring onions which is the most acidic out of the three. Acidic is preferred seems to be the case.
By knowing this and the acidity levels of ingredients in a dish, things can be adjusted for a desired acidity level on the finished product. Let’s look at sugar content per ingredient in a mirepoix:
Onions 4g Celery 2g Carrtos 5g of sugar per every 100 grams of each.
The final mirepoix would be barely acidic and somewhat sweet. I don’t know what any of this means, but at least now I know more about what I’m adding in the pot every time I’m preparing some dish using onions, celery and carrots as the base.