Why You Should Never Add Cornstarch To Cooked Grits
Runny grits (as if the name "grits" wasn't inelegant enough) have been insulting the efforts of aspiring home cooks since the advent of the awkwardly dubbed corn-based dish. While there is an advocacy for the idea that there is no such thing as an incorrect consistency for grits, per Southern Spicy Kitchen, others – like Kitchen Harry – hold onto the sentiment that grits should never be runny.
When unintended, soupy grits can be the result of incorrect methods, insufficient knowledge, or lack of experience. According to award-winning cookbook author and chef Virginia Willis, successful grits depend on the correct ratio of dry grits to liquid, which is one to four, respectively. Additionally, you cannot rush the cooking process. Non-instant grits need to cook slowly in order for their starches to create the desired smooth consistency, per Food Network. So, if grits depend on starches for good results, why can we not simply use cornstarch to improve grits that didn't cook to the desired thickness, especially since they are both corn products?
How not to rescue your runny grits
Cornstarch's role in contemporary cooking is mainly as a thickening agent, but it lacks in the taste department. Foods Guy warns that cornstarch's neutral flavor will enhance the blandness of the starches already present in cooked grits without thickening them. One could imagine this overwhelming whatever taste profile you were going for. Another reason cornstarch is not the fix you are looking for is its unique cooking requirements.
Per Bob's Red Mill, raw cornstarch forms lumps when it comes into contact with hot liquids instead of being gradually heated. So, it should first be combined with a cold liquid, stirred into a slurry, and added to a mixture at room temperature. Additionally, while cornstarch thickens quickly, it must be heated to a temperature of at least 203 degrees F before its thickening qualities are unlocked, per Exploratorium. So it would not be ideal for adding to cooked grits.
Side note: Instead of looking to starches as thickening agents for runny grits, Foods Guy suggests alternatives like adding egg protein, recooking the food, or straining the grits.