Geochemical, stable isotope, and numerical modeling studies of sake and groundwater for identification of the location of sake production: A case study from Hakusan City, Japan

Understanding the source and chemical characteristics of groundwater used for sake production is an important strategy for the quality management of sake brewing. Oxygen isotope ratios (δ¹⁸O) of 96 sake samples from 19 provinces in Japan were analyzed. A good correlation was found between the sake δ¹⁸O values and groundwater δ¹⁸O values taken from previously published data, where the δ¹⁸O of sake is similar to that of the groundwater used in the sake breweries. Detailed sampling of 19 sake and groundwater samples was conducted near a sake brewery in the Hokuriku district, central northern Japan (Ishikawa and Toyama Prefectures). The δ¹⁸O of sake and groundwater in the area also showed a good correlation. Our findings indicate that the δ¹⁸O of sake can be used to identify the locality of sake production. This has the potential to help prevent fraudulent representation of the area of production. Water chemistry, hydrogen (δD) and oxygen (δ¹⁸O) isotopes of two groundwater and eighteen river water samples in Hakusan City, Ishikawa Prefecture, were analyzed to determine their origin and water flow patterns. The groundwater is of a Ca–HCO₃ type similar to river water. The results show that the groundwater used to produce the “Hakusan” brand of sake originates from river water at an altitude of 360 to 450 m. This is supported by groundwater flow modeling, which also indicates that the water was sourced 2–3 km away from the sake brewery. The combined geochemical and numerical modeling approach provides a good tool for determining the source of groundwater used in sake production.