This research was carried as a part of the basic study, in which the aptitude of the Korean oak varieties as barrels for aging apple fine spirits was investigated, and the following results were obtained.
1. Following was the result of the chemical analysis of the fruits which are now mass-produced and can be used as a substitute for raw materials for wine production. Apple (Malus pumila Miller var. domestics Schneider):
Total sugar. total acid, volatile acid and pectin of Jonathan (Hong-og) were 13.95%, 0.46%, 0.012%, 0.20% respectively.
Total sugar, total acid, volatile acid and pectin of Ralls (Koog-kwang) were 13.35%, 0.43%, 0.011%, 0.45% respectively.
2. Because of low yield of apple juice due to cellulose, pectin, hemicellulose which are present besides sugars, acids in apples, the apple juice were treated with xylanase of Aspergillus niger SUAFM-430, cellulase and pectinase of Aspergillus niger SUAFM-6.
This treatment increased the yield of apple juice. And the apple juice was sterilized by adding potassium metabisulfite (K₂S₂0_5) and Saccharomyces cerevisae var. ellipsoideus Rasse Johannisberg II (SUAFM-1018) as a cultivation yeast, which has a strong fermentation power was used to ferment.
The yield of apple wine based on raw material was 86-87%. The amount of ethanol, extract and methanol obtained from Jonathan and Ralls were 13.5%, 5.4%. 0.04-0.05% respectively.
3. Wines were distilled for two times by the pot still method to make fine spirits. The yield of fine spirits from apple wine mash was 86.6%, and the pH of fine spirits from Jonathan and Ralls were 4.1, 4.2 respectively.
4. The oak chips made of inner part or outer part of 24 Korean oak varieties were used to select the barrel for aging fine spirits. Two oak chips (one oak chip: 1×1×5㎝) of the inner part or of the outer part of each oak variety were dipped into 300 ㎖ of fine spirits, which was bottled in 640㎖ beer bottle, and followed aging. The colors, flavors and tastes of the fine spirits were checked during 6 months.
A. As a criterion for the first screening of oak barrels for aging fine spirits, the rate five of color extraction was determined. The oak chips showed good results in their order as follows and the best 5 varieties were selected. Gal-cham: Quercus aliena Blume (Inner part), Gul-cham: Quercus variabilis Blume (Outer part}, Gal-chain: Quercus aliena Blume (Outer part), Jol-cham: Quercus serrata Thumb (Inner and Outer part). Sin-gal-cham: Quercus mongolica Fisher (Outer and Inner part) Sang-su-ri: Quercus acutissima Carruthers (Outer and Inner part)
B. To find out the influence of aging temperature on aging, apple fine spirits were aged by dipping each oak chip at room temperature (24-25℃) and 45℃. Aging at 45℃ gave the best result followed aging at 30℃ and then at room temperature.
C. Apple fine spirits was aged for six months by dipping oak chips in Erlenmeyer flasks and was irradiated with U.V light. The U.V irradiation enhanced the aging effect by nearly two times, compared with the aging without U.V irradiation.
D. In aging apple fine spirits by dipping two oak chips, it was observed that the extent of the extraction of most components of oak chips were strongly dependent upon the pH of fine spirits.
E. Oak chips of five selected oak varieties and a Limousin white oak from France as a control were used. Each apple fine spitits was dipped by two oak chips, and was aged at room temperature (24-25℃), 30℃, 45℃, and with the U.V irradiation at room temperature shaking every week. After six months of aging, the panel test of these aged fine spirits (Young Brandy) showed the following result.
Young brandy of apples aged at 45℃ by dipping oak chips of Gal-chain was almost as the fine spirits which were aged at room temperature by dipping Limousin white oak chips from France.
Young brandy of with U.V. irradiation at room temperature which were aged by dipping oak chips of Gal-chain was a little worse than that from the fine spirits aged at room temperature by dipping Limousin white oak chips from France. And so, Korean oak varieties are thought to be able to be used for aging every apple fine spirit which was here investigated.
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