Monosodium glutamate

While we are born with receptors for sweet, sour, salty, and bitter, MSG targets a distinct fifth receptor: umami. It is the sodium salt of glutamic acid, an amino acid that signals the presence of protein to the brain. When MSG hits the tongue, it dissociates into free glutamate, tricking the palate into perceiving a deep, meaty richness even in foods that lack protein.

This isn't a "flavor" in the traditional sense, but a flavor enhancer. By lowering the threshold of other taste perceptions, it makes savory notes more intense and lingering. It is so effective at this signaling that it is used globally in processed foods to provide "craveability" at a very low cost.

In 1908, Tokyo Imperial University professor Kikunae Ikeda noticed his wife’s cucumber soup tasted better when made with kombu (kelp) dashi. He set out to isolate the specific molecule responsible for this "deliciousness" (umami). Through a process of evaporation and treatment, he extracted crystalline glutamic acid, eventually stabilizing it with sodium to create the shelf-stable salt we know today.

Ikeda’s discovery wasn't just a culinary win; it was the birth of a global industry. He partnered with businessman Saburosuke Suzuki to form Ajinomoto ("Essence of Taste"). By 1909, they were selling MSG as a tabletop seasoning, effectively commodifying a flavor profile that had been central to East Asian cooking for centuries but lacked a name in the West.

The widespread fear of MSG in the West can be traced back to 1968, when a physician named Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine. He described a "numbness" and "palpitations" after eating at Chinese restaurants and speculated that MSG might be the cause. This anecdotal observation sparked a media firestorm that stigmatized Asian cuisine for decades.

Despite the persistent myth, dozens of double-blind, placebo-controlled studies have failed to find a consistent link between MSG consumption and the symptoms Kwok described. While a tiny subset of the population may have an idiosyncratic sensitivity to very large doses on an empty stomach, for the vast majority, MSG is metabolized no differently than the glutamate found naturally in tomatoes or mushrooms.

One of the great ironies of the "No MSG" movement is that the human body cannot distinguish between the glutamate in a processed snack and the glutamate in a piece of Parmesan cheese. High levels of free glutamate occur naturally in many staples of Western "health" diets, including walnuts, peas, grapes, and even human breast milk.

When you age a steak or ferment soy sauce, you are essentially performing the same chemical process as an MSG factory: breaking down proteins to release free glutamic acid. In fact, a serving of ripe tomatoes contains more glutamate than a typical MSG-seasoned dish, yet the former is viewed as "fresh" while the latter is often viewed as "synthetic."

Though it looks like an industrial chemical, modern MSG is produced through a biological process similar to making vinegar, yogurt, or beer. Large-scale production uses the bacterium Corynebacterium glutamicum, which is fed sugar (from beets, sugarcane, or corn) and "breathes" out glutamic acid as a metabolic byproduct.

This fermentation method replaced earlier, more laborious techniques like extracting the acid from wheat gluten or soy protein. Today, the world produces over 3 million metric tons of MSG annually. This efficiency has allowed it to become a staple in everything from bouillon cubes and ranch dressing to the "hidden" savory profile of global fast-food chains.