Yeast – Home Brew Sake

Sake Yeasts

Discusses yeast, sake yeast and what yeast need to do a good job fermenting.

Yeast: a single cell fungus whose activities have been known to man for far longer than we have known about yeast itself. We have evidence of yeast being used as far back as four thousand years ago in Egypt. They used yeast for both baking and brewing. Wine was also present in this period.

In 1857 Louis Pasteur proved that fermentation was the results of living yeast rather than a chemical reaction. In this work, Pasteur showed that as oxygen is added the growth of the cell count increases and fermentation slows. Not only did this show the significant of yeast but also its two distinct modes of operation: the aerobic and the anaerobic. In the aerobic mode, yeast reproduce by budding, a process of a child cell being created and split off from the parent cell. The anaerobic mode proceeds with little to no growth in the number of cells but with increased alcohol and CO₂ production. Alcohol and CO₂ are produced in equal amounts based on the following formula:

C₆H₁₂O₆ -> 2 C₂H₅OH + 2 CO_{2 Continue reading “Sake Yeasts”}

SakéOne Brewer’s Tour, last week

I describe a tour the lead brewer at SakeOne gave to a group of brewer from the Oregon brew crew.

This last weekend I joined a group of brewers for a brewer’s tour of the SakéOne Kura. Greg Lorenz, SakéOne’s Sakémaster gave the tour to a group of brewers from the Oregon Brew Crew.

As we gathered in the tasting room, we sampled the current nama on tap, a junmai ginjo genshu namazake; wow, very nice. What a way to start the tour. Once everyone had gathered we topped off our glasses and headed out with Greg in the lead.

Stopping in front of a picture of Mr Murai, Greg explains how Mr Murai was a man ahead of his time and how he thought that it was time to establish a Kura in the US. How he had pushed this idea for some time without success, until one day on a flight when he sat next to Grif Frost.

Continue reading “SakéOne Brewer’s Tour, last week”

Sake Yeast Mash – The Moto

This article looks at the three types of Sake yeast mashes, also known as moto and shubo. The differences between these three moto are examined.

Moto (元), Shubo (酒母), Yeast mash are all names for the Sake yeast starter. In this article I will only use the term “moto” but the three can be used interchangeably. Moto is where the number of yeast cells is increased to the needed level. The moto is used to inoculate the main sake fermentation, the Moromi (諸味). To build the moto we start with rice (米), koji (麹) and yeast (酵母). These three ingredients along with water were the only ones used for moto originally. The method to produce this original moto is known as Kimoto. It features a vigorous mixing, taking many hours, to produce a puree of the ingredients. It was thought this vigorous mixing, called Yama-Oroshi, was needed for the ingredients to properly work together.

In 1909 a modification to the Kimoto method was developed. The modification was to drop the vigorous mixing. As it turned out, the mixing was not really needed. The modified process was called Yama-Oroshi haishi moto or Yamahai moto for short. Continue reading “Sake Yeast Mash – The Moto”

Sake basic ingredients

Sake has four basic ingredients: rice, koji, yeast and water. Each play an important part in producing the taste, aroma and appearance. Each are discussed and how they come together to form the sake we love.

Sake is made with four ingredients: rice, koji, yeast and water. All, except the koji, are familiar to most people. Koji is a mold culture grown on rice in the case of Sake. The mold is Aspergillus oryzae. It forms a white fluffy coating over the rice and excretes alpha-amylase which converts the rice starch into sugar. This is the primary function of koji in brewing sake; to provide enough alpha-amylase to convert most of the starch provided by the rice to sugar. Other compounds produced by the koji contribute to the final taste.

Once the koji converts the starches from the rice to sugar, yeast converts the sugars to alcohol. Beyond this major contribution the yeast also produces other compounds that contribute to the final taste and aroma of the sake. These two processes, conversion of starch to sugar and conversion of sugar to alcohol, proceed at the same time which allows the yeast to produce higher levels of alcohol than is the case in beer and wine. This is not to say that beers and wines can not ferment to the high levels that sake does but that special processes, outside the norm are needed to obtain the same high level normally reached with sake. Continue reading “Sake basic ingredients”