Sustainability and “Sake Kasu”, a By-Product of Sake – Part 1

Saki Kimura

December 3, 2022

Last October, American food professionals visited fermented food producers to deepen their knowledge of Japanese fermentation culture during the “Hakko Tourism in Japan” tour campaign. As part of the tour, organizers held a tasting session where guests gave candid advice from the perspective of the American market to food product manufacturers looking to enter the United States market.

Surely you could imagine that sake, a drink with a history of 2,000 years, would be made in accordance with a sustainable system. However, in reality it poses some big challenges concerning its role on the environment. One of those challenges is the issue of wasting sake kasu, a by-product of sake production.

1. The problem with wasting sake kasu

Since mainly rice is used as a raw ingredient of sake, it becomes a white pulpy substance when it is fermented into alcohol. In the brewing process of sake, the liquid substance that resembles a mash called “moromi” is pressed to separate the clear sake and white lees. The leftover residue of lees is called “sake kasu.” Although sake kasu flavor depends upon differences in its ingredients and how it is made, the distinctive aromas and flavors of sake remain, as well as the alcoholic content. Sake kasu can be used in cooking to bring back these flavors. Besides mixing it with vegetables to make pickles, or marinating fish or meat, there is also a trend of eating it in a soup called “kasujiru” in the Kansai region; an area that has prospered from sake brewing since long ago. However, none of these particular foods would be considered commonplace, and in accordance with the times, their rate of consumption is decreasing.
Bowl of Arajiru with chopsticks

Arajiru made from sake kasu

Big brewing companies sell sake kasu to specialty manufacturers, who then process it to make sake-lee powder for confectionary, sushi vinegar, or cosmetics. Unfortunately, small and medium-scale local breweries don’t get to sell off their sake kasu in such a way. The CEO of Ethical Spirits & Co., Mr. Yuya Yamamoto, points out this particular problem. “Small sake breweries are able to give out sake kasu for free at the entrance of their storehouse, or provide it to livestock farmers as animal feed. However a considerable amount of sake kasu is produced, so it cannot be said that they are making good use of it all.” The actual amount of sake kasu produced hasn’t been made public, but by calculating the production amount of sake that uses designated sake rice as an ingredient, it is found that 30,000 tons of sake kasu is produced per year. Recently, various efforts have been initiated in order to lower this sake kasu waste. *It was estimated that the production volume of sake rice in 2019 was 97,000 tons. From that, 70% is assumed to have been turned into sake while the remaining 30% would have become sake kasu.

2. A treasure trove of nutrients

In order to stop wasting sake kasu, it’s important to not overlook its highly nutritional merits. First, sake kasu contains B vitamins which keep your skin and mucus membranes healthy. It also includes an ample amount of beauty ingredients. According to joint research conducted by the Kanazawa Institute of Technology and a sake brewery, Shata Shuzo, both located in Ishikawa Prefecture, sake kasu contains the ingredient α-EG (Ethyl α-d-glucoside) which has the effect of increasing collagen in the cortical layer of the skin. Moreover, it also contains other ingredients, such as: kojic acid which suppresses the creation of melanin, the cause of skin discoloration; and ferulic acid, which suppresses aging of the skin. Movements have been increasing in which cosmetic manufacturers and sake breweries cooperate to make use of the beauty ingredients of sake kasu for cosmetic products. The sake brewery Fukumitsuya in Kanazawa, Ishikawa has noticed the beauty effects of sake production since the 1980s. In 2003, they launched a cosmetic venture which uses extracts of fermented rice at its core, and established a skin-care brand that also includes sake kasu as an ingredient. In 2022, the limited liability company YOU of Osaka Prefecture started the cosmetic brand “INAHO Sake Lees” using sake kasu brewed from the “Tedorigawa” system of Yoshida Shuzo Ten of Ishikawa Prefecture.
Two bottles of INAHOSakeLees products placed by the window

The reason that the sake kasu of Yoshida Shuzo Ten was selected was that the company is reducing the environmental impact of its sake production. It uses only renewable energy in the brewery, collaborates with local farmers in rice production, spurs revival of agricultural land, and aims to protect the region’s natural offerings.

As a food product, sake kasu is also very healthy with ample amounts of proteins, dietary fibers, and amino acids. Research done at Gekkeikan, an old sake brewery in Kyoto, proves that the peptides in sake kasu originate from plants, and can be expected to improve one’s health by working to prevent rises in blood pressure.

In addition, it also has active nutritional ingredients too numerous to count, including: adenosine which is said to induce vasodilation, and relieve stiff shoulders and headaches; and plasminogen which breaks up blood clots, which are the cause of stroke and arteriosclerosis.

In line with modern market trends of recent years, sustainable businesses have been increasing thanks to the expected health and beauty effects of sake kasu. In Part 2, I will introduce some of their efforts.

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Saki Kimura is an accomplished journalist specializing in sake. With a journalism certificate from UCLA, she's reported on sake consumption worldwide. Currently the director of SAKETIMES International, she writes, translates, and promotes sake, focusing on overseas distribution and international breweries. Her expertise has made her a respected figure in the industry.