SAKE BREWING BASICS

Sake brewing is a natural process of the hydrolysis of starch in rice by Koji and yeast fermentation that takes place simulutaneously in a vessel. Green River Sake adopts a traditional brewing with innovations, snow-aging and QC (quality control) program. The basic science and technology of sake brewing are described below.

1. Ingredients:

Rice	Up to 60% milled or polished to remove rice embryo, endosperm and some starchy endosperm that may give unpleasant flavor like fusel alcohols
Koji	Fungal microbial seeds (Aspergillus niger) to hydrolyze rice starch to fermentable sugars and dextrin
Yeast	Saccharomyces cerevisiae converts fermentable sugar to alcohol, carbon dioxide and flavor compounds
Water	Mineral soft water from our own secured water source

2. Hydrolysis of rice starch:

The polished rice is steamed to gelatinize starch. At Green River Sake, Koji is then added to hydrolyze starch to fermentable sugars. Some sake brewers use commercially available amylase enzymes with bacterial origins. In the practical process, water is added to steamed rice at a certain level of the total solids or sugar content in a brewing vessel.

3. Fermentation:

Yeast is inoculated to ferment at controlled low temperatures for 20 to 30 days depending on products. Fermentation proceeds slowly due to low temperatures and least available nitrogenous/other nutrients. The simultaneous saccharification and fermentation process is unique only for sake.

4. Separation of Liquid Portion:

Clear supernatant is taken out from the fermentation vessel. The sediment at the bottom is filtered to separate liquid from solid.

5. Pasteurization:

Fresh sake is pasteurized by heating up and cooling down rapidly in order to kill harmful microbes and to inactivate remaining enzymes. No sulfite or preservatives are added to our sake for long microbial stability.

6. Aging:

Pasteurized sake in a holding vessel or bottles is aged for up to 6 months under designated aging conditions. Green River Sake developed snow-aging that was originally done in a snow dome but now it is performed in a more controlled environment. During aging, fresh sake becomes smoother, mellower and well-balanced. This is a natural aging process that current science may not be able to explain fully.

7. Finishing Process:

If needed, aged sake can be re-conditioned to adjust alcohol content or total solids, and then re-pasteurized before shipment.

8. Quality Control:

Green River Sake brewery applies a strict QC program to ensure the highest quality from rice milling to the end of the brewing process. The program includes traditional visual observations and tasting evaluation in process and finished products in addition to chemical or physical instrumentations.