Chromatography Combats Sake Fraud

Sake - a traditional Japanese wine - is like many foods and drinks open to adulteration. Adulteration usually refers to the addition of foreign or inferior ingredients with the aim of mimicking high-quality products at a much lower production cost - thus increasing profit. A recent paper - Compound Specific Carbon Isotope Analysis in Sake by LC/IRMS and Brewers’ Alcohol Proportion - published online in the journal Scientific Reports discusses how Sake is open to fraudulent activity and how chromatography can combat sake fraud.

For the sake of Sake

Sake is also known as Japanese rice wine and is made from rice polished to remove the outer layers. It is an alcoholic drink, but the alcohol is produced using methods closer to beer brewing than wine making. In wine, the alcohol is produced from fermenting the sugar in grapes. In sake, the starch in rice is converted into sugar and alcohol.

A similar process to beer, but in beer the starch to sugar and sugar to alcohol reactions occur in two distinct steps. In sake, the conversions happen simultaneously. Rich starch is a long polymer of sugar molecules, and yeast cannot convert it into alcohol. So, the starch is broken down using koji mold (saccharification) before saki yeast converts the sugars to alcohol (fermentation).

Sake usually has a stronger alcohol content that beer and wine too. Whilst beer contain 3-9% ABV and wine contains 9-16% ABV - sake contains 18-20% ABV, although this is often diluted to 15% with water before bottling.

Junmai and Ginjo - big business in Japan

It has been estimated that there are over 1400 sake breweries in Japan brewing over 530 million litres of sake per year. The two main categories of saki are Jummai and Ginjo. Junmai is made from water, rice and koji and is the premium product. There are many different grades of Junmai that depend on the ratio of polished rice in the mix. The more the rice is polished the greater the quality of saki that can be made and hence a higher price can be charged. Polishing removes the outer husks of the rice - these contain more fats and proteins that could taint the flavour of sake leaving a core which has a much higher starch content. Ginjo saki is similar to Junmai but has brewers’ alcohol added to the liquor.

Chromatography gets the measure of saki

There have been recent cases where brewers’ alcohol has been added fraudulently to saki that has been labelled as Junmai saki. In the work referenced above, team of researchers developed a method for determining if brewers’ alcohol had been added to saki using liquid chromatography coupled with isotope ratio mass spectrometry. The advances in analytical methods using MS is a topic discussed in the article, Recent Advances to Conquer Analytical Challenges with High-Resolution, Accurate Mass Spectrometry.