Prediction method for determining the carbon stable isotopic composition of berry sugars in the original must of Chardonnay wines

The carbon stable isotopic composition, as indicated by the delta C-13 value, of wine ethanol is inherited from berry sugars, but little is known about the variation in sugar delta C-13 values of Japanese grapes relative to overseas grapes. This study found a large variation in sugar delta C-13 values of Chardonnay grapes grown in Japan (-27.2 +/- 0.9 parts per thousand, mean +/- standard deviation, n = 33), with sugar delta C-13 values depending on the delta C-13 values and content of monosaccharides. After complete fermentation, the carbon isotope discrimination between berry sugars and wine ethanol was 1.5 +/- 0.1 parts per thousand. Ethanol delta C-13 values and carbon isotope discrimination enabled prediction of sugar delta C-13 values in the original must. Imported wines had higher sugar delta C-13 values than those of wines made from Japanese grapes, suggesting drier overseas viticulture conditions. The determination of sugar delta C-13 values in grape berries provides valuable information for viticulture and wine authentication.

Automated summary

This study found a large variation in sugar δC-13 values of Chardonnay grapes grown in Japan, depending on the δC-13 values and content of monosaccharides. Carbon isotope discrimination can be used to predict sugar δC-13 values in the original must.