Why You Should Be Salt-Curing Egg Yolks

Umami has grown into more than just a trend. It's been used with unrelenting frequency since being added to the list of core flavor profiles in 2002 (via Ajinomoto). However, umami is an important concept to understand because, per Vox, it is found in a lot of natural foods that contain glutamate and cannot be made up of other flavors. According to Ajinomoto, the three principles of umami include how the taste spreads across the tongue, how long the flavor lasts, and how much saliva is produced. You could just call umami savory, but you'd be diminishing the flavor complexity that is found in many foods, like egg yolks (via MSG Facts).

Mayonnaise is another umami-rich delicacy. Specifically, the Japanese brand Kewpie is renowned for its rich flavor and can elevate even a simple grilled cheese to Momofuku-chef levels of flavor. This mayo's richness comes from its use of only egg yolks, instead of the whole egg like other brands, which is one of the reasons that Kewpie mayo is so different in flavor. 

According to Umami-Info, egg yolks contain a balance of amino acids and vitamins that the body needs to absorb protein, but only the yolks contain glutamic acid — which is the source of their umami flavor. However, even with their already remarkable richness, you can concentrate the umami flavors of egg yolks further by salt curing them.

Salt-curing your egg yolks is a surefire way to intensify their umami flavor, as well as change the texture of the yolks, according to MasterClass. Curing the yolks is a simple process of separating the yolks from the whites and preserving them in salt. The salt draws out the moisture of the yolks, hardening their texture and concentrating their flavor.

The hardened yolks are packed full of salty umami flavor and can be used as a substitute across a wide variety of dishes. They can replace hard-boiled eggs in fresh salads or be grated into mayonnaise-based mixtures — like tuna salad — to add extra richness (via MasterClass). You can even use cured yolks as a substitute for hard cheeses like parmesan in pasta dishes and soups, or as a sea salt replacement. The cured yolks can even be smoked over oak for a subtle, smoky flavor. 

Another way to increase the umami flavor of egg yolks is the Japanese method of pickling them in soy sauce, rice vinegar, and sugar. The finished product is called a shoyuzuke egg yolk; it has a dark color and absorbs much of the umami flavor from the pickling brine (via Umami Days). However, shoyuzuke yolks are still raw egg yolks and should be eaten with caution.