In Part 1, we looked at the history of pasteurization, and in Part 2, we explained the method. As mentioned earlier, by inactivating the yeast and enzymes in this process, it prevents deterioration in the quality of the sake, stabilizes the flavor, and enables long-term storage. In Part 3, we will talk about the bacteria that are killed.

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This person will explain

Toji shop owner/producer Eri Nakano

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In 1995, he opened the Japanese sake bar "Janapese Refined Sake Bar Tojiya" in Tenjinbashisuji, Osaka. He is active in various fields as a sake critic, seminar lecturer, and lyricist.

●Hiochi bacteria - Hiochi bacteria love sake!

The unique putrefaction phenomenon of sake, known as Hiochi, has been considered a major disaster in the brewing world.
In 14, Robert William Atkinson, a chemist who taught at Kaisei School in Tokyo, discovered that Hiochi was caused by a type of bacteria.

Later, Dr. Takahashi Teizo, a doctor of agriculture, proved that this bacterium is a type of lactic acid bacterium of the Lactobacillus genus that has extremely strong alcohol tolerance and can only grow in sake. Fermentation methods are divided into the following categories:

Homozygous fermentation bacteria

It breaks down sugar to produce only lactic acid (the lactic acid bacteria used in yogurt production, Lactobacillus bulgaricus, Lactobacillus gasseri, and Lactobacillus thermophilus, use this fermentation method).

Heterozygous fermentation bacteria

It breaks down sugar and produces not only lactic acid, but also ethanol, acids with strong antifungal properties (acetic acid and propionic acid), and carbon dioxide (the bifidobacteria present in the human intestine use this type of fermentation).

●True Hiochi bacteria and Hiochi lactic acid bacteria

Those that require mevalonic acid derived from koji mold for growth are classified as true hiochi bacteria, while those that do not are classified as hiochi-resistant lactic acid bacteria. The most alcohol-tolerant are the homo-type true hiochi bacteria, which can grow even in alcohol concentrations of over 25%, followed by the hetero-type true hiochi bacteria. In contrast, it has been observed that the number of hiochi-resistant lactic acid bacteria, both homo- and hetero-type, decreases at alcohol concentrations of 21% to 22%.

Although true hiochi bacteria can survive in high alcohol environments, the optimal growth environment is thought to be around 7% alcohol. This means that true hiochi bacteria will rapidly grow if they eat their favorite food, mevalonic acid, in a room with an alcohol content of around XNUMX%.

● Fire-off acid = mevalonic acid ~ It's a nuisance for alcohol, but...

Hiochic acid was named in 31 by Tokyo University professor Gakuzo Tamura, who discovered that koji mold was the causative agent of hiochic acid. In the same year, researchers at the American pharmaceutical company Merck & Co. discovered a substance similar to hiochic acid in whiskey distillery wastewater, which they named "mevalonic acid." In 1956, it was confirmed that the two are the same thing.

Mevalonic acid is an optically active substance that rotates the plane of polarization of light. It appears on the way to the target compound and is an intermediate in the biosynthesis of several substances. Surprisingly, mevalonic acid is effective in moisturizing skin and combating high cholesterol, making it a highly useful organic compound that is the subject of research in a variety of fields, including pharmaceuticals, cosmetics, pesticides, and liquid crystal materials. While it may be a nuisance for sake, it is a valuable substance for humans.

White, sour, and smelly

When hiochi bacteria multiply, sake becomes cloudy and may have a sour taste or unpleasant odor.

This time, we talked about lactic acid bacteria, which are troublesome for sake.

Previous article: [Tell me what you can't ask now!? Series 18]Pasteurization Part 2 ~Method~