ウイスキー貯蔵樽材中におけるモルトウイスキー (原酒) の浸透と抽出成分の分布

Abstract

熟成したモルトウイスキーの香味は, 樽材の性質, とくに, その組織や抽出物に負うことろが大きいと言われている。本報告では, モルトウイスキーの樽材中での分布を明らかにし, 樽材の組織とモルトウイスキーの浸透性を検討した。また樽材中のアルコール抽出物の分布も調べた。その結果, モルトウイスキーの樽材中での含有量は内表面側から外表面側に向かって低下するが, その全体の量は大変大きなものであり, モルトの総欠減量の半量にも達することが明らかとなった。樽材中のアルコール抽出物の割合は内表面側で低く, 中ほどで高い分布を持ち, 内表面側のそれはモルトウイスキー中に溶解されたことを示している。モルトウイスキーの浸透深さと年輪幅あるいは追柾角度との間に, 一定の関係は見られなかった。

Aging of malt whisky in wood casks is an indispensable process to bring excellent flavor, taste and color on the whisky. The role of cask woods which has been supposed to be very important in the aging was examined in relation with malt penetration into cask woods, distribution of alcohol extractives in the woods, and wood structures. Three types of casks (Fig. 1) , which had been made by the traditional method, filled with new malt whisky and aged as shown in Table 1, were offered to the present experiment. Woods were collected from three-sides of casks (Fig. 2) and sub-divided from the inner to the outer, after marking of malt-soaked area by a pencile (Fig. 3). Distributions of malt and alcohol were estimated after the distillation of these wood chips (Figs. 5, 6). Inner part of cask woods were full of malt whisky, while even middle and outer parts contained a considerable volume of whisky (Fig. 5). When the total volume of malt whisky contained in whole cask woods was calculated from the result and compared with the actual loss, it was shown the 'drinking volume' of malt whisky into the woods was occupying a major part of the actual loss (Table 2). Similar wood chips were extracted with 60% ethanol and the ammount of extractives is diagrammed as shown in Fig. 9. The malt-soaked areas were traced all over the stave woods (Fig. 4) and penetration depth was evaluated in relation with annual ring widths of the stave woods (Fig. 7) and also angles fluctuated from the radial direction (Fig. 8). The penetration of malt whisky, however, was not affected by these structural factors of woos.