Yes to Yeast: November 1, 2009

Yes to Yeast was organized by the VMS as part of their 30th anniversary events and programs.  Over the course of the day a small group of us attended a tour of the Granville Brewery and the Artisan Sake Maker, Masa Shiroki.  The making (and tasting) of Sake was the most exciting part of the day for me.  Sake is primarily made from rice which is fermented using a microorganism called koji and yeast.  Shiroki orders his koji from Japan.  It is sent in a vial and can be used for sake making for a period of time and then more freshly cultured koji needs to be ordered.

Koji is steamed rice that has koji mould spores cultivated onto it.  The latin name for the mould is Aspergillus Oryzae an asexual ascomycetous fungus that has been used for centuries in the production of soy sauce, miso and sake.  The mould produces enzymes that break down the starch in the rice into sugar that can be fermented by the yeast cells, which in turn give off carbon dioxide and alcohol.  Koji is critical to the taste and quality of the sake.

Shiroki’s workshop is well set up for producing sake in a small space.  He has a small lab for testing the level of alcohol and acidity throughout the fermentation process.  He invited each of us to look into the fermentation tank  and smell the rice mash.  It was amazingly sweet smelling- like apples or pears.  Eventually the sake is distilled by cooling it.  The sediment falls to the bottom of the cooling tank.  The sake is not filtered though.  Instead different type of sake are produced, some with more sediment, than others.