What is the proper way to use corn starch to thicken sauces?
How do you mix corn starch slurry and how do you use it?
- Do you add the corn starch to the water, or do you add water to the corn starch?
- Generally what proportions do you need, what is the ratio of water to cornstarch?
- Do you need to use more slurry to thicken more liquid; if so, what is the quantity per volume?
One word of advice: whatever you do, once you add the slurry don't cook for too long or get too hot (do not boil). With enough heat, the starches will break down and the sauce will likely become runny again, except this time it will be runny with added corn starch flavor!
My long experience of using corn starch (or corn flour as we say in the UK) contradicts what stephennmcdonald says. You have to boil the liquid (sauce/custard/fondue) to get the starch to reach its full thickening power, and once it has, continuing to boil certainly won't make it more runny. stephennmcdonald must have accidentally curdled something (not the starch, which does not curdle).
When making the slurry, stir cornstarch into cold water until it has the consistency of cream. This can be set aside until it's needed, but be sure to stir it briefly before you pour it into the sauce to redistribute the starch granules in the water. You should pour it into your sauce toward the end of its preparation.
According to McGee you should use roughly 2/3 as much starch as you would flour. If you aren't using a recipe, add your slurry a bit at time until it's a thick as you like it. Also remember that the sauce will thicken a bit as it cools, so it should be a little bit thinner on the stove than you intend to serve it.
What volume do you use per serve? I use .25 to .5 tsp per serve, with about four times that in COLD water to make slurry