Genki Kainuma, Tohru Okuda,* Fumie Watanabe-Saito and Masashi Hisamoto
*University of Yamanashi, 1 13 1 Kitashin, Kofu Yamanashi, 400-0005, Japan 
(okuda@yamanashi.ac.jp)

Sugars from oak barrels were quantified by extracting oak chips toasted under various conditions in model wine. When 6.0 g of untoasted chips were extracted in 1 L of model wine for 21 days, 73 mg/L of neutral sugars were quantified. Chips toasted at 180 °C to 240 °C for 10 min had similar or slightly higher levels of neutral sugars extracted than untoasted chips; the difference did not reach statistical significance. Toasting at 240 °C resulted in the maximum level of 74 mg/L. On the other hand, toasting at 260 °C and 280 °C for 10 min resulted in extremely low levels of neutral sugars extracted. Two acidic sugars and seven neutral sugars were detected by high-performance liquid chromatography after hydrolysis. Glucose, arabinose, and xylose were also detected, suggesting that sugars derived from wood polysaccharides such as cellulose and hemicellulose were likely to be extracted from oak chips. Furthermore, differences in toasting temperature affected the composition of the extracted sugars. Therefore, it is possible that different toasting temperatures may result in different extents of cellulose and hemicellulose pyrolysis inside the wood and significantly affect the amount and composition of sugars extracted. In addition, gel permeation chromatography was performed to estimate the molecular weight of the extracted sugars. The detected peaks corresponded to monosaccharides and oligosaccharides, and peaks that appeared to correspond to polysaccharides in some samples were also observed. These results indicated that different toasting temperatures of the barrel wood also affect the molecular weight of the extracted sugars.

Funding Support: This work was supported by JSPS KAKENHI Grant Number 21K05467 and JST, the establishment of University fellowships toward the creation of science technology innovation Grant Number JPMJFS2117.