I’ve often wondered what miso is made of and how it’s made. I went back to a fun book, The Story of Sushi: An unlikely Saga of Raw Fish and Rice, by Trevor Corson. It covers the history, culture, and other fun nuggets of information regarding sushi. There are also the experiences of students and chefs attending California Sushi Academy . One of the chapters is all about miso, and the field trip that a group of students took to a miso factory. I was able to find a few miso factories in california, including the Japanese giant Marukome, that just opened it’s first American factory in Irvine just a year ago.
Mold is probably the last thing on your mind when you think about what you want in a tasty dish. However, this is essential for miso. Mold is considered such an important product, that there are shops in Japan that just manage and sell mold (known in Japanese as koji). There are caves and vaults that hold back ups of mold filled jars. In form of a green powder, a small amount is poured into a giant machine of cooked rice. The mold spores in the jar are dormant until they have something to feed on. Once they are introduced to the rice, they go to town and are given time to engulf each grain of rice. The story in the book mentions that in an incubator filled with 6,600 pounds of rice, 500 pounds of rice will simply disappear by the end of the waiting period.
The infected rice is then churned with cooked soybeans, followed by the addition of sea salt, bacteria, and yeast. After all the ingredients are mixed up, it is poured into huge tubs where they are then sealed up and then stored away for some months. In these sealed containers, the mold runs out of air and dies. However, it leaves behind its digestive enzymes, which does not need air to survive.
These enzymes from the mold break down the protein of the rice and soybeans and produce amino acids. Most of the protein in soybeans is a type called glycinin. The enzymes tear apart that glycinin and leave behind an amino acid called glutamate. Glutamate tastes great to humans! It contains a lot of flavor that is enjoyed by the human taste buds. In fact, when a Japanese chemist realized that it was glutamate that contributes to a delicious flavor in certain foods, he figured out how to manufacture it. The product was monosodium glutamate (MSG). Glutamate is also important for human functioning. “It’s a fast excitatory neurotransmitter in our brains and spinal cords; it is believed to be important for thought and memory.”
These enzymes also break down the carbohydrates into glucose and other sugars, which also contributes to a pleasing flavor. The good bacteria that was added has its own enzymes, these ones feed on the sugars. The result of that sugar feast is lactic acid and acetic acid. These are the acids that give yogurt its tartness. It’s also these acids that keep these foods from spoiling.
Last but not least, the yeast helps out by also consuming the sugars and producing alcohol. Now, the alcohol reacts with the acids made by the bacteria. From this union, esters are born! Esters are the compounds that provide those fruity aromas, same ones found in wine. At this point, the miso has achieved all its attributes for its delicious flavor.
After a few months, it is ready to be taken out of storage and prepped for packaging. Along with the miso in the containers, there is also a brown liquid that can be found seeping out of the edges. This liquid contains all the same attributes of the miso, including the glutamate taste. Since decades ago, this liquid has been known to be drizzled over food for additional miso tasting goodness. It is said that soy sauce had to have originated as a by-product of making miso.
Something interesting that the author mentions, are the other foods that are high in glutamate, such as ham, parmesan cheese, and tomatoes. He writes that a serving of sushi with soy sauce has the same taste elements as a plate of pasta smothered in tomato sauce, anchovies, and Parmesan cheese. So enjoy your miso and think of the wonderful combination of saltiness, sugary, tart flavor that also has your good bacteria and glutamate that just makes eating it all the more delicious!