Museum of Sake Journal Summer 2016 - Page 34

WHAT IS GINJO-KA AND WHERE DOES IT COME FROM? FERMENTATION TEMPERATURE In the early days of sake, almost every sake tended to smell grainy as the main material came from the rice itself. Subsequently there was a period of time when sake aroma was primarily woody, because all vessels for sake production were made from Japanese cedar. However nowadays there is a wide choice of materials for sake vessels ranging from enamel, stainless steel tanks or traditional Japanese cedar tanks. Therefore sake aromas are no longer limited by the vessel and breweries can have more control in achieving the sake aroma they desire - whether rice-based and grainy as in traditional sake, or with amazing fruity or floral aromas. During the fermentation process, sake yeast will happily do its job at around 20 degrees Celsius to create alcohol. Below 6 degrees or above 35 degrees yeast will stop working. When the temperature is higher than the optimum, fermentation will speed up. Sake made in this quick-fermentation style tends to have cereal aromas and a fuller body. However, when the fermentation temperature is lowered, enzyme activity also slows down and less ‘food’, ie. sugar is produced for the yeast to consume. The interesting thing is that although the yeast doesn’t like these uncomfortably low temperatures, the stress of low temperature and shortage of food stimulates the yeast cells to create weak acids to protect themselves from the cold and starvation. These weak acids don’t have much effect on the acidity of the sake, but they do combine with ethanol to create amazing aromas such as melon, apple and banana- know as ginjo aroma. Over one hundred kinds of aroma have been discovered, but well-known ginjo aromas are isoamyl acetate which creates banana fragrances and ethyl caproate which creates aromas of green apple and melon. 15° FERMENTATION SPEEDS UP CO 2 CO AT AL 2 CO YEAST YEAST 12-18° GENERAL SAKE HE AT AL <6° OR >35° YEAST STOPS WORKING HE CO HO L HO L Fruity and floral aromas can be created by sake yeast, but only under certain conditions. Determining factors include a low fermentation temperature of around 6 to 12 degrees Celsius, reduced effects from nutrients and the potential of the yeast type to create a specific type of aroma. 6-12° FERMENTATION SLOWS DOWN CEREAL AROMA & FULLER BODY CREATED CREATES WEAK ACID EFFECT WITH ETHANOL GINJO AROMA LIGHTER BODY TEMPERATURE EFFECT MUSEUM OF SAKE JOURNAL 34 ‘STRESSED OUT’ BY LOW TEMPERATURE