For the sake of saké: combating beverage fraud in Japan

The traditional alcoholic beverage of Japan called saké is made using rice, rice koji (a type of fungus) and water. As demand for saké increases globally, so does the potential for related beverage fraud. To address this issue, researchers from Japan identified a novel method to authenticate saké.

The research duo — Professor Hiroto Kawashima and Momoka Suto — devised a novel strategy using denitrifying bacteria to identify the origin of saké and distinguish between products from different breweries. They examined the proportional presence of isotopes, ie, variations of a chemical element differing in neutron count, while retaining the same proton count of oxygen (O) and nitrogen (N) within nitrate molecules across various saké samples.

“Recently, many parts of the world are home to saké production, and studies such as ours can help prevent the falsification of saké breweries. We believe that our research will be important for saké breweries,” said Kawashima who is from the Shibaura Institute of Technology.

The researchers found an N isotope signature across various types of saké within a single brewery, which could be used as a marker to identify or authenticate saké from specific breweries.

“The denitrification method can analyse the stable isotope ratios of N and O in nitrate with high precision. Since our laboratory was able to perform these analyses, we proceeded with the idea that these analyses could find use in foods and beverages,” Kawashima said.

To perform the study, the researchers measured the concentrations of five water-soluble ions and the stable isotope ratios of nitrate, including δ¹⁵N–NO₃⁻ (read as “delta fifteen N, nitrate”), in 49 commercial saké samples from 11 breweries in Akita Prefecture, Japan, stable isotopes being those that do not undergo radioactive decay over time.

The study showed that the nitrate concentrations in saké were similar to those in groundwater, indicating that these ions originated from the brewing water. Specifically, as revealed by the principal component analysis technique, the δ¹⁵N–NO₃^– values could distinguish between different breweries, as the values were consistent within saké types from the same brewery.

The denitrifying method combined with the solid-phase extraction method, a technique used to isolate and concentrate specific compounds from the saké, was claimed to be applied for the first time, indicating the novelty of the approach taken in the study to analyse the composition of saké.

“We have analysed the isotope ratios of N and O in nitrate in beverages for the first time in the world. Notably, these ratios differed from brewery to brewery,” Kawashima said.

The study has contributed to our understanding of the factors influencing the composition and quality of saké and its potential applications in quality control in traditional food and beverage products.

The research findings have been published in Food Science and Technology.

Image credit: iStock.com/Claudiac8