Where Does Sake's Fruity Aroma Come From?
．Elements of Aroma
There have 3 elements of Sake’s aroma: At first, the original aroma influenced by its ingredients; At second, the aroma generated in the process of fermentation (the essential elements of Ginjo aroma); and the last one is the aroma by aging. Let us introduce each one of them here.
① The original aroma of ingredients.
Most of sake have the rich aroma influenced by rice. Sometimes, natural aroma is described as daily products or mushrooms and so forth. Sake produced with less polished rice tends to have this kind of rich aroma.
② The aroma generated in the process of fermentation (Ginjo Aroma)
This aroma is produced during the transformation of sugar into the alcohol by sake yeast. Mainly 2 types of aroma are generated in this process, each of them is called “isoamyl acetate” and “ethyl hexoate”. Isoamyl acetate is the source of fruity aroma, such as bananas or melons; and ethyl hexoate is also the source of fruity aroma like apples, pears, and pineapples.
I guess you have tried fruity type of sake beofore. The aroma of Ginjo grade tends to be fruity and flamboyant. The most important element of producing Ginjo aroma is the selection of yeast. Sake of Ginjo grade is basically produced with highly polished rice, the amount of protein in the rice is relatively lower, so that yeast can’t absorb much nutrients, plus the fermentation in low temperature puts stress on the yeast. In this severe environment, yeast abnormalises its metabolism and generate very unique Ginjo aroma.
③ Matured aroma
As same as wine, it’s possible to mature sake for long. Aging makes its aroma sweeter like honey. It also has rich-layered aroma such as dried fruit and spices etc. We call that “Matured aroma”.
・Differences between the matured aroma and the spoiled aroma
By leaving in the high temperature for long time, its aroma tends to be a bit pungent and burnt. Spoiled aroma comes from the degradation by heating.
In addition, SAKEMARU also found an article in Journal of Bioscience and Bioengineerin that they did a scientific experiment of the two kinds of aroma. The data shows the of Dimethyl trisulfide (DMTS), which is the source of onion smell, in the spoiled aroma is higher than it in the matured aroma. It’s worth to research this topic more deeply.
・Types of the aromas
After understanding the components of aromas, let us introduce the types of sake’s aromas. They are classified into 4 types:
The aroma produced in the process of fermentation has the aroma like flowers, tropical fruits, citrus fruits, and the aromatic herbs. Those are the “glamorous aroma” and the “refresh aroma”, and Daiginjo and Ginjo grade usually have them. The original aroma influenced by rice tends to be like cereals and daily products, these are classified in “gentle aroma” and “mild aroma”. Junmai and Kimoto sake tends to have this kind of aroma.
Don’t forget to appreciate the aromas of sake in the next time. You will definitely have an unexpected impressive experience. Let’s expolore the brand new world of sake!
References磯谷 敦子, 「清酒の老香成分ジメチルトリスルフィド（DMTS）の生成に関する」,生物工学会誌 第93巻 第3号 116–121．2015