JOURNAL OF THE INSTITUTE OF
ENOLOGY AND VITICULTURE
Copper salt micromethod for the determination of peptides in juices and wines.
横塚 弘毅・相原 俊秀・櫛田 忠衛
KOKI YOKOTSUKA, TOSIHIDE AIHARA, and TADAE KUSHIDA
果汁,野菜ジュースあるいはワイン中のペプチドをDowex 50-X2 (活性炭)処理,銅キレート化及びイオン交換クロマトグラフィーを含む方法によって定量した。
Dowex 50-X2(活性炭)の小カラムを用いて前処理した試料を, pH8.0で過剰の塩基性炭酸銅を加えて反応させ,生じたアミノ酸銅塩とペプチド銅塩をDEAE Sephadex A-25 クロマトグラフィーで分離した。ペプチド銅塩を含む溶出液をpH6.5にした後,250nmの吸光度を測定し,Gly-Leu銅塩の検量線からペプチド量を求めた。
Peptides in fruit juices, vegetable juices, and wines were determined by a method including treatment with Dowex 50-X2 (charcoal), Cu2⁺ chelation, and ion-exchange chromatography. After removal of polyphenols and organic acids by treatment with Dowex 50-X2 (charcoal), the sample was shaken at pH 8.0 with CuCO₃. Cu(OH)₂. The copper salts formed were separated into an amino acid fraction and a peptide fraction by DEAE Sephadex A-25 chromatography. The peptide fraction was collected and adjusted to. pH6.5. The absorbancy of the fraction was measured at 250nm.
the determination was not affected by various juice or wine components including glucose, polyphenols, organic acids, metal salts, and ethanol. Sometimes, this method, however, could not be applied to the samples containing a large amount of acidic amino acids and very basic or aromatic peptides.
Quality characteristics of Koshu white wine tested by chromatographic profile analysis.
CHIEKO YONEYAMA and TADAE KUSHIDA
In order to find the quality characteristics of Koshu white wine the procedure of chromatographic profile analysis was examined.
The best resolution of the UV absorption profile of the white wine was obtained by the Sephadex G-10 column chromatography, and 8 varieties of white wines were tested by this method.
From the profiles the characteristics of Koshu white wine were found as follows :
1. The first peak (protein-tannin complexes and peptides) was the smallest among all samples and protein content was the least.
2. The peaks 2, 3, and 4 (nucleic acid related compounds) were smaller than those of Europian and American wines and nearly equal to those of varieties crossed with the Koshu variety.
3 . The peak 7 (cinnamate derivatives) was the largest among all samples, and either p-coumaroyl-tartaric acid and caffeoyl-tartarie acid was contained over the threshold value of bitterness and astringency.
The control of browning of white table wine by ultrafiltration.
YOSHIFUMI AMANO, KAZUO NAKAMURA, TOSHITERU KOMURO, SHINJI KIRIBAYASHI and MOTOO KAGAMI
1. ワインの褐変に対する安定性を全ポリフェノール含量だけから判定することは出来ないが, Capacity法を用いて褐変安定度を数値で表わせば, 成分や製造年度の異なるワインであっても相互の褐変安定度の比較が容易に行えることを示した。
2. 限外液過処理したワインの褐変安定性をBC法により評価したところ,褐変速度,OD, スペクルパターンから判断して、処理酒はコントロールインと比較し,褐変安定性が非常に増していることがわかった。
It was confirmed that ultrafiltration increased the resistance to browing of white table wine. The following points were clarified.
1. A wine's resistance to oxidative browning could not be determined merely by the total polyphenol content of the wine. The measurement of “browning capacity” by a modified Singleton method proved to be useful in comparing wines capacity to brown even if the components or vintage years of tested wines were different from each other. By this method, it was significantly increased, judging from the browning rate, absorbance at 420nm, and spectrum pattern of the wine.
2. By ultrafiltration, the oxygen uptake rate of a wine was reduced to 57% to 66% of the control. Polyphenols and nitrogenous compounds were also partially removed from the wine by ultrafiltration.
3. Wine's buffering capacity for the change in the redox potential was reduced by ultrafiltration.
4. The flow rate of ultrafiltration was changed by adjusting the applied pressure. When the high pressure (3kg/cm²) was applied, the flow rate was high initially but reduced rapidly during the ultrafiltration. A significant increase in the flow rate occurred when the ultrafiltering temperature was elevated.
Correlation between the contents of various constituents and the grade in quality assessment of wine.
野村隆弘・橋本 佳三・志賀 勝徳・田中健太郎
TAKAHIRO NOMURA, YOSHIMI HASHIMOTO, KATSUNORI SHIGA, and KENTARO TANAKA
(Depart. of Fermentation Technology, Faculty of Engineering, Yamanashi University)
The contents of minerals (Na, K, Ca, Mg), heavy metals (Cu, Zn, Mn, Fe), total nitrogen, and six organic acids were compared among different table wines which had been graded by tasting in the Wine contest. The correlation coefficients between the analytical results (some data were taken from “Report of the Institute for Wine and Food Technology, Yamanashi Prefecture” by courtesy of the institute) and the grade by sensory evaluation in the contests were computed.
In the dry white wines (WOD, WND), a significant positive correlation was found between the grade in the contest and the content of K, Zn, Mn, and total nitrogen as well as the color of the wine (OD530, OD430). However, a negative correlation was found between the tartaric acid content and the grade of wine, except in the case of old red wines / ; those wines containing higher levels of tartaric acid (WOD, WND, WNS, RN) received higher grades. Also a somewhat common pattern in the contents of citric, tartaric, malic, lactic, and acetic acids was found among the quality wines.
Changes in the Wild Yeast Flora of Suflited Grape Musts
|Progressive changes in the wild yeast flora at the initial stage of incubation of grape musts added with various concentrations of SO₂ were studied qualitatively and quantitatively. Initial total counts of yeasts in the original grape must were 6.5X 10⁵cells/ml and increased rapidly within a short period of time, and after 32 hours fermentation was observed. As early as 4 hours after incubation, total counts of yeasts and the proportion of the five yeast groups (Apiculate, Saccharomyces, Torulopsis, Film, and Others) were affected by the initial levels of free-SO₂ added. Total counts of yeasts in the must containing 46.7 ppm of free-SO₂ decreased gradually and reach ed a minimum after 48 hours. After this period, however, total counts of yeasts increased gradually, and this was due to the increase in Saccharomyces group. Total counts in the musts containing 97.5 and 228ppm of SO₂ decreased rapidly to less than 10cells/ml after 24 and 48 hours. Apiculate yeast group and part of film and other yeast groups decreased rapidly in the initial stage of incubation of sulfited grape musts, whereas Saccharomyces and Torulopsis yeast groups decreased gradually. Yeasts remainded in the sulfited musts were resistant to SO₂.|
The Institute of Enology and Viticulture, University of Yamanashi