Umami

Most people meet umami as an effect rather than a flavor. It makes a soup taste finished and a chip taste more like itself. On its own it is odd: pure MSG in water tastes flat and faintly unpleasant. It needs salt and a savory aroma around it to make sense.

Where the idea came from

In 1908 Kikunae Ikeda, a chemist at Tokyo Imperial University, showed that the savory taste of kombu broth came from glutamate, an amino acid. He named the taste umami, from the Japanese word for delicious, and patented a way to make monosodium glutamate (MSG). It went on sale in 1909 as Ajinomoto.

His student Shintaro Kodama found in 1913 that the savory substance in dried bonito was inosinate (IMP). In 1957 Akira Kuninaka showed that guanylate (GMP), plentiful in dried shiitake, is umami too, and that these nucleotides multiply the effect of glutamate. That is why Japanese dashi uses kombu and bonito together.

Western science took most of the following century to accept umami as a basic taste. The receptor was identified in 2002.

Why two compounds beat one

The main umami receptor is a pair of proteins called T1R1 and T1R3. Glutamate sits deep in a pocket on T1R1 that closes around it like a Venus flytrap. IMP and GMP bind near the mouth of the same pocket and help hold it shut. In human taste tests, an amount of IMP too small to taste on its own made people about 15 times more sensitive to glutamate.¹

This is why commercial seasonings pair MSG with a small amount of "I+G", usually an even mix of disodium inosinate and disodium guanylate. A little goes a long way, and the pair does more than either alone.

Using it to cut salt

MSG is about 12% sodium by weight. Table salt is about 39%. So gram for gram, MSG brings savory impact with roughly a third of the sodium.

It does not taste salty, though. What it does is stop a lower-salt product tasting empty, so you can take more salt out before people notice. That makes it the best-known flavor enhancer and a standard tool in soups, sauces and snack seasonings. The logic is the same as in sugar reduction: you are replacing what the ingredient did, not only its taste.

There is no fixed swap ratio. Published salt reductions vary a lot by product, and much of that research is funded by MSG makers. Test in your own product. And do not overshoot. Past a point, more MSG makes food taste brothy and flat, not stronger. It also cannot fix a flavor that is wrong. It makes a right one read louder.

MSG, yeast extract and the US label

FDA treats added MSG as GRAS, but it has to be declared by name as "monosodium glutamate". It cannot hide inside "spices" or "flavoring".

Yeast extract, autolyzed yeast, hydrolyzed vegetable protein and soy extracts all contain free glutamate. You list them by name, and you do not have to say they contain glutamate. But FDA's position is that a product containing them cannot claim "No MSG" or "No added MSG".² Plenty of clean-label briefs trip over this.

Yeast extract is popular because it reads better on a label. It is not a neutral swap. It brings its own brothy, slightly yeasty or meaty character, and at higher doses you will taste it. In a delicate product that can be the bigger problem.