Sakekasu (sake lees) is the solid white substance that remains after pressing the main fermenting mash used to make Japanese sake (rice wine)
When sake is brewed, 25% of the sakekasu is removed and, according to the Standard Tables of Food Composition in Japan, this consists of 51% water, 23% carbohydrate, 13% protein, lipids and ash in addition to peptides, amino acids, vitamins and yeast; meaning that has come to be reevaluated as a health food.
Because of the decline in sake production after 1975 as well as the adoption of high-temperature saccharification mainly by major sake manufacturers, there was a downward trend in the amount of sakekasu by-product distributed.
The amount produced between July 2006 and June 2007 was just below 46,000 tons. The estimated amount produced between July 2007 and June 2008 is 45,000 tons (from Food News).
Mirinkasu taken from the main fermenting mash of mirin has a different flavor because it includes glutinous rice, and shochukasu taken from unrefined shochu (Japanese distilled spirit) has a sour taste because it contains a large amount of citric acid.
It is also called 'sakahone' (sake bones), taking its meaning from the bones that remain after meat has been removed from fish.
Itakazu (board-shaped sakekasu)
Sakekasu separated from refined sake before being pressed and carefully peeled and cut by hand. In some regions, all white sakekasu is referred to as itakasu.
Sakekasu which could not be made into a board shape. Some sakekasu cannot be made into a board shape due to time constraints, manpower shortages, because types such as sakekasu from daiginjo (top-quality sake brewed at low temperatures from rice grains milled to 50 percent of weight or less) and ginjo-sake (high-quality sake brewed at low temperatures from rice grains milled to 60 percent of weight or less) are too crumbly to be made into a board shape because the rice grains are often not completely dissolved due to low-temperature fermentation, or because some types are just too soft because they still contain a large amount of sake. In some regions, this is called kogasu.
Sakekasu kneaded into a paste.
Made by stepping on barakasu or itakasu in a tank, forcing out air, and allowing it to mature (ferment) for four to six months. Because the sugar content of the sakekasu is transformed into amino acids, it increases in flavor and gains umami. Many varieties are brown or gold in color.
In some regions, it is called 'oshikasu,' 'morohakukasu,' or 'nerikasu.'
It is often used as an ingredient for vinegar and tsukemono (Japanese pickles).
Barakasu that has been kneaded and squeezed into a cylinder before being used to form itakasu.
Some manufacturers call it 'new itakasu.'
In recent years, mechanization by sake brewers and a lack of workers has meant that itakusu is not as commonly removed and a shortage of itakasu has resulted in the word taking on a strong meaning of a manufactured substitute product. It is easy to use because it has been kneaded, but lacks flavor because rice-malt is crushed during the kneading process and oxidation takes place.
In addition to preexisting products such as those used for making tsukemono, numerous products, including those for sweet sake, adapted for use in various dishes have been developed in recent years.
Simple amazake ingredients made from sakekasu.
Made by acetic acid fermentation. Vinegar made from matured sakekasu is called as akasu (red vinegar) due its red color. It is mainly used as sushi vinegar.
Shochu made from sakekasu. The alcohol of sakekasu is distilled.
Kasujiru (soup of sakekasu)
Made using only sakekasu or sakekasu mixed with miso (fermented soy bean paste).
A local specialty of Tochigi Prefecture.
Sakekasu can be eaten as it is, but the flavor is brought out when it is grilled over an open flame, and it can be made to appeal to women and children by sprinkling sugar on it (its flavor can be brought out by simply heating it gently in a microwave). Yeast mash left in sakekasu can also be used to ferment bread (it is called sakadane).
Precautions for Handling Sakekasu
According to the Standard Tables of Food Composition in Japan, sakekasu still contains on average 8% alcohol, which can vary depending on conditions of the sakekasu, so should not be consumed in excess by those intending to drive a vehicle or operate machinery, by those who are not able to drink much alcohol, or by children. Average people should also be careful when eating uncooked sakekasu since it contains yeast mash which could make them drunk.
One example of this is a teacher from Kobe City who drove home after eating two bowls of kasujiru (sake-lees soup) on September 15, 2006 and, when pulled over, was found to have exhaled 0.15ml of alcohol in 1l of breath, following which charges were filed on suspicion of driving under the influence of alcohol in March 2007.
Since sakekasu is a by-product of manufacturing refined sake, it sometimes contains the rice germ. In addition, since traditional sake-brewing tools such as wooden tubs are used to brew sake, it may happen that some wood chips come off a tub and get mixed in sakekasu.
As sakekasu contains alcohol, it does not decay easily.
However, the yeast contained within sakekasu carries out fermentation and the Maillard reaction between sugar and amino acids leads to its color changing from white to yellow then pink followed by brown, dark brown and black depending on temperature and time. It is common to use sakekasu which has been matured for between four months and one year for making tsukemono, and to use sakekasu which has been matured for between one and seven years for making of vinegar.
In order to restrict maturation speed, most sakekasu products on the market carry a best before period of 120 days and an indication to store it below 10℃. If it is kept at below -18℃, the quality will not change greatly even if it is kept for more than 3 years.
In addition, white dots of crystallized tyrosine, an amino acid, sometimes appear on the surface during the maturation process.