Science & Food

A Primer on Sake

Neither a beer nor a wine, sake is like their often-forgotten cousin, an alcoholic drink made from fermented rice. Typically paired with sushi and lighter Japanese fare, sake can be described as being fruity, flowery, and astoundingly complex.

Photo credit: Flickr user Tokyo.natural

The origins of sake are largely unknown, but some historians guess that like many fermented foods, its origins arose spontaneously. One such theory suggests that cooked rice was left out in the open, and spaces between the grains harbored hungry molds that fed on the starches. Over time, this leftover rice became alcoholic, and thus sake was born (1).

A brief overview of sake production:

  1. Rice is polished in a process known as seimaibuai (2). The protein and rice are removed from the bran of the rice, leaving behind a starchy core.
  2. The polished rice is steamed, then inoculated with Aspergillus oryzae, a mold that converts rice starch into fermentable sugars.  This inoculated rice forms what becomes known as koji (1).
  3. Next, the koji is converted into a yeast starter, known as moto. Lactic acid bacteria (Lactobacillus sake) and a pure yeast culture are mixed in with the koji and left to sour (2).
  4. In a large brewing tank, water, rice, koji, and yeast starter are combined. Additional portions of rice and water are added in batches, and this mixture is left to mature for up to a month at relatively low temperatures. (1). Lower temperatures are believed to draw out more optimal flavors from the yeast (2).
  5. With time, the yeasts convert this mix of sugars and starches into an alcoholic beverage that can have up to 20% alcohol concentration (1).
  6. Once brewing is deemed complete, the mixture is pressed and filtered to release the liquid sake, leaving behind a solid rice mass.
  7. The sake is then pasteurized to promote shelf stability; pasteurization prevents any additional fermentation or enzyme activity, which can potentially lead to off-flavors(3).

The flavor of sake is impacted by a range of factors from the type of rice used to the length of fermentation. Sake is versatile; it can be served at a range of temperatures, and can present a multitude of flavor profiles, ranging from sweet and fragrant to savory and robust. It’s pretty amazing for something made from moldy grains!

References cited:
1. Harold McGee, On Food and Cooking: The Science and Lore of the Kitchen. New York: Simon & Schuster, 1997.
2.  Samuels, Monica. “Sake School: Koji, The Miracle Mold.” Serious Eats.
3. Sullivan, Timothy. Sake Production Process. Urban Sake.


Mai NguyenAbout the author: Mai Nguyen is an aspiring food scientist who received her B.S. in biochemistry from the University of Virginia. She hopes to soon escape the bench in pursuit of a more creative and fulfilling career.

Read more by Mai Nguyen

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