Fermentation of Thai rice wine

Fermentation of Sato (Thai rice wine)
- Hands on activity for anaerobic respiration in Grade 10 Biology -

Health & Safety: Wear eye protection and gloves!
Material: The ingredients for Sato (Thai rice wine) are simple: 1) sticky rice; 2) a starter culture (look-pang; Thai: ลูกแป้ง) with several species of yeasts and molds; 3) brewers’ yeast (Saccharomyces cerevisiae); and 4) water. 5) A primary fermenter (basically a large can with a snap on lid) and 6) a secondary fermenter; large plastic bottle (1.5 – 5 liters) with an air lock (anaerobic fermentation).
The biochemical reactions follow the flowchart below.

Procedure:
1 Step: Sticky rice is mixed with ‘look pang’, rich in mould and yeast, and kept in a simple fermentation tank for three to four days as the starch in the rice changes to glucose. You can add a little water to make rice and starter culture mix well.    
2. Step:  Transfer the mixture to the large bottles. Add clean water and yeast to a tank. Make sure the bottles are sealed and the CO2 can escape safely without letting air in the container. The second fermentation takes about 7 days. Keep in a dark place at room temperature.

3. Step:  Strain out rice, filter the liquid and bottle the finished Sato.Homemade Sato contains about 8-10% ethanol.
Note:  Traditionally, a starter culture known as look pan, a small ball of starch rich in various microbes, is used to assist in breaking down of the starch into sugar. Since the exact composition of the microbes is unknown the fermentation process can be unstable and unpredictable, resulting in liquor of differing quality and, often, a short shelf life.

Distillation
Additionally we can distill the product into a spirit with higher alcohol content. We collect the fraction between 80–85 °C. (Ethanol boils at 78 °C.) Next to typical alcohol odor we can test the product by burning. The fraction should burn easily with bluish flames  compared with the non-flammable original solution (i.e. Sato). When distillated at the right temperatures we should get a product with about 45% ethanol content.

Sources and further readings:

Limtong, S., Sintara, S., Suwanarit, P. and Lotong, N. 2002. Yeast diversity in Thai traditional alcoholic starter. Kasetsart Journal (Nat. Sci.). 36 : 149-158.

Limtong, S., Sintara, S., Suwanarit, P. and Lotong, N. 2005. Species diversity of molds in Thai traditional fermentation starters (Loog-Pang). Kasetsart J. (Nat. Sci.). 39 : 511-518.

Thitisararak, N., Plumcharoen, S. and Rungsardthong, V. (2003) The Use of  Dry Starter Cultures for the Fermentation of Sato, a Traditional Thai Rice Wine. The 1st International Symposium and workshop  on “Insight into the world of Indigenous Fermented Foods for Technology Development and Food Safety” 13-15 August, 2003. Kasetsart University, Bangkok, Thailand. Proceeding paper.

Phongmanee, S., and Kukietkul, T., (2004) “Identification of Microorganism from Look-pang for Sato fermentation” (P5-04) Page 103-104, The 6th Agro-Industrial Conference, May 28-29,2004, IMPACT, Bangkok, Thailand.

http://en.wikipedia.org/wiki/Sato_(rice_wine)

Pratt, C. W., Voet, D. & Voet J. G.(2003) Fundamentals of Biochemistry: Life at the Molecular Level. New York, Wiley.