Why You Don't Need Cornstarch To Thicken Teriyaki Sauce
Traditionally, teriyaki derived its name from the classic Japanese method of grilling meat that's been marinated in the sweet and salty sauce we've all come to know and love. Over time, the flavor of the marinade caught on and is now so popular that the name is ubiquitous for the sweet and slightly addictive dark brown glaze, and not necessarily for the method of cooking.
Teriyaki sauce is a relatively simple sauce that contains only a handful of ingredients. In fact, this Inspired Taste recipe only calls for five ingredients. Teriyaki sauce is quick and easy to make from scratch, but one mistake home cooks usually make is adding a thickening agent. A good rule of thumb when thickening a sauce is to make a basic "slurry" by dissolving cornstarch or flour in water (via recipetips.com). While a slurry is a useful method, it's one that you should avoid when putting together certain sauces at home, including teriyaki sauce.
Don't miss out on the magic of caramelization
Adding cornstarch to teriyaki sauce will result in two things you don't want — an altered look and impaired flavor of the sauce, as noted by No Recipes. Adding cornstarch affects the appearance by clouding the sauce, and although that might not seem like a big deal, it may not look as appetizing as you're used to when it comes time to plate the sauce. When cornstarch is added as a thickening agent it will enhance the sauce's thickness, but you're also sacrificing a lot of flavor.
Teriyaki needs to go through a caramelization process, which is what happens when sugar is introduced to heat, according to Science of Cooking. During caramelization, compounds are released that alter the flavor and color of the sugar. Adding cornstarch doesn't allow the sauce to caramelize and will result in a flat taste. Instead, allow the soy sauce and sugar to caramelize during cooking. As an added bonus, this will naturally thicken the sauce and transform it into a glaze.