Water-soluble ions and nitrogen and oxygen stable isotope ratios in nitrate in sake in Akita, Japan

Abstract

Sake is a traditional alcoholic beverage in Japan, and demand for it has increased overseas in recent years. In this study, we analyzed oxygen and nitrogen of stable isotope ratios in nitrate (δ18O–NO3– and δ15N–NO3–) in beverages by using the denitrifying bacteria for the first time. We measured the concentrations of five water-soluble ions and the δ18O–NO3– and δ15N–NO3– values of 49 commercial sakes (11 sake breweries) made in Akita Prefecture, Japan. The similarity of the concentrations of NO3− in sake and groundwater suggested that these ions were derived from brewing water. The δ18O–NO3– value of the 49 sake samples ranged from 2.2 to 12.3‰ (mean, 4.7 ± 2.3‰). The δ15N–NO3– value in the sake ranged from 1.8 to 8.7‰ (mean, 6.1 ± 1.8‰). The δ15N–NO3– value of sake could be used to identify breweries because the δ15N–NO3– value was similar for different sake types in the same brewery. Principal component analysis revealed that the first four principal components could account for 85.2% of the variance of the experimental data. The factor loading plots was found to be similar for different sake types in the same brewery.