MSG is made through bacterial fermentation, a process surprisingly similar to how beer, yogurt, and vinegar are produced. Factories feed sugar to specialized bacteria, which convert it into glutamic acid. That acid is then neutralized with sodium to create the white crystalline powder you find on store shelves. The whole process starts with common crops like sugarcane, corn, or cassava.
The Raw Materials
MSG production begins with whatever starch or sugar source is cheapest and most available in a given region. In Southeast Asia, that’s typically sugarcane molasses or cassava starch. In North America and Europe, corn starch is more common. These crops aren’t chosen for any special property. They’re simply rich in the sugars that bacteria need as fuel.
The sugar is extracted from the raw crop and dissolved in water to create a nutrient broth. Producers add nitrogen sources (like ammonium salts) and trace minerals to the mix, giving the bacteria everything they need to grow and do their work.
Fermentation: Where the Magic Happens
The key player in MSG production is a bacterium called Corynebacterium glutamicum, first discovered in Japan in the late 1950s. This microorganism has an unusual talent: when placed in the right conditions, it consumes sugar and excretes large quantities of glutamic acid as a byproduct.
Here’s how it works at a basic level. The bacteria break down glucose through their normal metabolic pathways, producing energy and building blocks for growth. But scientists have learned to manipulate the conditions inside the fermentation tank so that the bacteria’s metabolism gets rerouted. Instead of using all their intermediate compounds for growth, the bacteria funnel a disproportionate amount toward producing glutamic acid, which they then push out of their cells through specialized channel proteins in their membranes.
Industrial fermentation tanks hold tens of thousands of liters. The process runs for roughly 30 to 40 hours at carefully controlled temperatures, with oxygen pumped in continuously since these bacteria need it to thrive. By the time fermentation wraps up, the broth is rich in dissolved glutamic acid.
From Broth to Crystal
Once fermentation is complete, the bacteria and other solids are filtered out of the liquid. What remains is a solution of glutamic acid in water. To turn this into MSG, producers add sodium hydroxide (a common food-grade base), which neutralizes the acid. The glutamic acid picks up a sodium atom and becomes monosodium glutamate.
The solution is then concentrated by evaporation, which triggers crystallization. MSG crystals form naturally as the liquid becomes more saturated, much like sugar crystals forming in a cooling syrup. The crystals are separated, washed, and dried. The final product is a white, odorless powder with a purity typically above 99%.
How This Compares to Older Methods
MSG wasn’t always made by fermentation. When Japanese chemist Kikunae Ikeda first isolated glutamic acid from seaweed broth in 1908, he used a chemical extraction process. For decades, commercial MSG was produced by breaking down wheat gluten or soybean protein with hydrochloric acid, a harsher and less efficient method. The shift to bacterial fermentation in the 1960s made production cheaper, more scalable, and more sustainable. Today, virtually all of the world’s MSG (estimated at over 3 million metric tons per year) comes from fermentation.
It’s the Same Compound Found in Food
The glutamic acid produced by fermentation is chemically identical to the free glutamate that occurs naturally in many foods. Tomatoes, aged cheeses like parmesan, soy sauce, fish sauce, and mushrooms are all rich in free glutamate. Even watermelon and ketchup contain meaningful amounts. When you taste the savory depth in a slow-cooked tomato sauce or a piece of aged cheese, you’re tasting the same molecule that ends up in a packet of MSG.
Your body doesn’t distinguish between glutamate from a tomato and glutamate from a fermentation tank. Both bind to the same taste receptors on your tongue, triggering the sensation known as umami.
Sodium Content and Safety
One practical detail worth knowing: MSG contains about 14% sodium by weight, compared to roughly 40% in table salt. This means you can use MSG to enhance flavor while adding significantly less sodium to a dish. A typical serving of food with added MSG contains less than half a gram of the seasoning.
The FDA classifies MSG as “generally recognized as safe,” the same category that covers salt, sugar, and baking soda. A comprehensive review by the Federation of American Societies for Experimental Biology concluded that MSG is safe for the general population. The review did note that some sensitive individuals may experience short-term symptoms like headache or flushing after consuming 3 grams or more on an empty stomach, but that’s roughly six times the amount found in a typical serving of food and an uncommon way to encounter it.