In order to study effect of oak sawdust on the quality of Kyoho wine immersed by fermented Cabernet Sauvignon residual, Kyoho wine aged without oak sawdust (KWO), including KWO1 and KWO2 according to immersed orders by fermented Cabernet Sauvignon residual, was taken as control to compare the effect of oak sawdust on quality of Kyoho wine (KO), including KO1 and KO2 according to aged orders by oak sawdust. During the 15 days of aging, physical and chemical indicators, such as chroma, tonality, and total phenol in wine were determined simultaneously by using a spectrophotometer, including tannin content by KMnO4 titration, once every 3 days. The results showed that the chromaticities of Kyoho wine were 3.21, 3.02, 4.46, and 3.71 for KO1, KO2, KWO1, and KWO2, respectively. Similarly, the hues were in turn 0.73, 0.68, 0.97, and 0.72, respectively. Tannin contents were 1601.5 mg/L, 1517.3 mg/L, 337.2 mg/L, and 115.6 mg/L; total phenol contents were 277.67 mg/L, 222.1 mg/L, 64 mg/L, and 79.8 mg/L. Therefore, the contents of tannin and total phenol from KO1 wine were all the highest values. The chroma and tone of the four types of wine showed an upward trend of “S.” The chromaticity and tone were the lowest for the KO2 wine and the highest for the KWO1 wine with the larger difference between KO2 and KWO1.
Cabernet Sauvignon is a variety of grapes grown widely, originated in Bordeaux, France, with a strong adaptability to environment. Shangri-La is located in valleys among Lantsangesis, Salweense, and the Jinsha River, namely, the core areas of the “three parallel rivers” on the world natural heritage. About 1700–2800 m of elevation and the strong ultraviolet radiation in Shangri-La were beneficial to the accumulation of anthocyanins and flavonoids in Cabernet Sauvignon fruits [
Kyoho grape, introduced from Japan, belongs to a hybrid variety of European and American. It had been planted in large areas and became a popular grape variety between the grower and consumer after being introduced in China in 1959. Thick-skinned and succulent fruit contained essential trace elements, including 16%–18% soluble solid and 6–8 g/L acidity, with fresh aroma of the flower and fruit, which supplied just general condition of wine-making [
Impregnation can be carried out before or after fermentation. Cabernet Sauvignon skin residue after fermentation can improve the utilization of skin residue, enhance the color of Kyoho wine, and enrich the flavor substances of Kyoho wine. Impregnation during aging is an important factor affecting the quality of wine. Oak chips are the leftover waste after making oak barrels and oak blocks, with the larger specific surface area. Phenolic compounds in oak chips could promote the increase of tannin polymer and the degree of polymerization after transferring to wine [
Storing wine in oak keeps the wine up to thousands of years. Oak barrel could improve the quality of wine, which was the key to determine the aging potential of wines. At present, the domestic researches on the selection and effect of oak products on the sensory quality of wine are still in the preliminary stage [
Cerdán et al. [
There are many studies on ageing wine with oak. Li et al. [
Skins, pedicels, and seeds of late-harvested Cabernet Sauvignon in Shangri-La contained high-quality anthocyanins, tannin, and aromatic substances. Fermented Cabernet Sauvignon pomace could enhance the color and taste of Kyoho wine by maceration and also bring about defect including rough feeling; however, oak sawdust could improve the rough feeling of wine. Additionally, the polyphenol and aroma component in fermented Cabernet Sauvignon skin could still be absorbed partly by Kyoho wine through soaking, which, on the one hand, improved the quality of Kyoho wine and on the other hand, realized reduction of waste by reasonable use of Cabernet Sauvignon skins. Phenol and tannin could be increased in Kyoho wine by impregnating Cabernet Sauvignon residue, which contributed a harmonious body, stable color, rich aroma, and complete sensory quality through aging with oak sawdust again in a shorter time. Oak sawdust aging played an important role in improving the quality of wine. Slow oxidation between oak and wine could improve color, aroma, and palate fullness of wine. Therefore, wine aged by oak could be accepted by most people [
The whole idea of this experiment was as follows:
As shown in Figure
Flow diagram of the treatment.
Four hundred kilograms of Kyoho grapes with uniform color and ripeness from the local market were divided into 20 copies of equal weight before being brewed into dry red wines in twenty 25-kilogram glass pots according to the conventional technology, respectively. Wines were then stored in the dark under room temperature until the following treatment on June 25, 2017. The conventional technology was as follows:
It is worth noting that the pressed wine and first automatically separated wine were combined together as raw wine.
Cabernet Sauvignon pomace originated from castoff after soaking and fermenting late-harvested Cabernet Sauvignon in Shangri-La on December 4, 2017. Pectinase, yeast, and sulfite were provided by Shangri-La Wine Industry Co., Ltd Oak chips, moderately baked, were from Seguin Moreau, France
On December 4, 2017, the above Kyoho wine was divided and stored in four 20 liters of glass jars according to the color similarity as the experimental material for impregnation of pomace, which was numbered as Kyoho wines 1, 2, 3, and 4 (KW1, KW2, KW3, and KW4) one by one. KW1 and KW2 as well as KW3 and KW4 were thought of as the same repetitions, respectively. The wine was analyzed in duplicate. Then, the residual of Cabernet Sauvignon in Shangri-La after fermentation was soaked in KW1 and KW2 wines for the first time, all named “KWO1.” After 7 days, the other KW3 and KW4 wines were also soaked with the above drained residue for the same 7 days, all named “KWO2.”
On December 28, 2017, the above KWO1 and KWO2 were stored in four 750 mL bottles labeled first according to the color similarity, respectively. On April 28, 2018, 300 mg oak chips were put into two bottles of KWO1 wine and named as “KO1;” the other two bottles were thought of as control of KO1, labeled as KWO1. Similarly, 300 mg oak chips were also put into two bottles of KWO2 wine successively, marked as KO2, and the other two bottles were thought of as control of KO2, flagged as KWO2.
The physical and chemical indexes of Kyoho wine, within the GB 15037 2016 (Table Reducing sugar: Fehling reagent titration Titrated acid: potentiometric titration Alcohol and dry extract: thermostatic bottle Total SO2 and free SO2: iodometry
Basic physical and chemical indicators of raw wine KWO1 and KWO2.
Reducing sugar (g·L−1, glucose) | Titrable acid (g·L−1, tartaric acid) | Alcohol (%) | Dry extract (g·L−1) | Free SO2 (mg·L−1) | Total SO2 (mg·L−1) | |
---|---|---|---|---|---|---|
KWO1 | 3.5 ± 0.1 | 5.925 ± 0.1 | 12.01 ± 0.3 | 24.2 ± 0.2 | 5.4 ± 0.1 | 23.7 ± 0.3 |
KWO2 | 3.0 ± 0.2 | 6.450 ± 0.2 | 11.78 ± 0.1 | 23.4 ± 0.2 | 4.8 ± 0.2 | 22.0 ± 0.1 |
GB 15037-2006 | ≤4.0 | — | ≥7.0 | ≥18.0 | — | — |
The values of KWO1 in the first, third, and sixth columns are significant at 5% probability level. The values of KWO2 in the first and third columns are significant at 1% probability level and those in the fourth and sixth columns are significant at 5% probability level.
After adding oak chips, the wine was aged for 15 days at room temperature. The following experiments were simultaneously conducted.
Tannin (KMnO4 titration), chroma and hue (spectrophotometry), and total phenol (Folin phenol method) were measured once every three days.
After 15 days of aging under oak clastic, 25 students with the intermediate certificate of SWET wine taster were invited to examine the 4 wines. The sensory characteristics were determined finally by the evaluation and score given.
All analyses were done at least in triplicate, which were then presented as average values along with standard derivations. Data were analyzed using the Excel 2010 software. Statistical comparisons were performed with one way analysis of variance, and
According to the datum in Table
Most of the tannin in wine originated from grape skin, while a few of which were supplied by grape seeds and oak sawdust; poor-quality tannin made young wine bitter and astringent, and high-quality tannin softened wine with maturation and oak aging [
It could be seen from Figure
Effect of oak shavings on tannins. Different letters in each bar indicate significant differences between mean values (≤0.05).
Before adding oak sawdust, the tannin content was 338.2 mg·L−1 in KWO1 wine and 116.4 mg·L−1 in KWO2 one, respectively. After 15 days of soaking with oak sawdust, both the tannin content increased to 1601.5 mg·L−1 and 1517.3 mg·L−1, respectively. While the tannin content of another two Kyoho wines (KO1 and KO2) increased always with the aging time and increased rapidly in the first three days before aging. Further, the tannin content of the KO1 wine increased faster than that of the KO2 wine, rising to 1122.4 mg·L−1 and 623.6 mg·L−1, respectively. In Figure
Tannin in oak sawdust extracted by depolymerization could enter Kyoho wine [
Consumers would normally observe the color of wine first when buying a wine, so the effect of color on the wine was very important. However, color was determined mainly by tannin, phenol, and anthocyanins [
According to Figure
Effect of oak shavings on chroma. Different letters in each bar indicate significant differences between mean values (≤0.05).
In the first nine days of aging, the chromaticity of the two wines showed a gentle declining trend until the lowest value together on the ninth day, mainly because tannin in oak sawdust interacted with anthocyanins to form polymeric anthocyanins, which decreased the pigment content of the wine [
Hue could indicate the maturity of wine. Due to the action of anthocyanins, young dry red wine showed usually purple hue, but purple could disappear gradually when anthocyanins combined with other substances including tannin as the wine matured; meanwhile, the yellow hue would increase and became brick red eventually [
According to Figure
Effect of oak shavings on tone. Different letters in each bar indicate significant differences between mean values (≤0.05).
In Figures
The standard solutions, 0 mg·L−1, 50 mg·L−1, 100 mg·L−1, 150 mg·L−1, 250 mg·L−1, and 400 mg·L−1, were prepared with the standard sample of gallic acid, respectively. The standard curve was drawn by absorbance values measured at 765 nm.
According to Figure
Standard curve of total phenol.
Phenols were important factors determining the structure, taste, and flavor of wine. The abundant phenolic substances would endow wine an advantage in color, aroma, and taste [
As could be seen from Figure
Effect of aging of oak chips on total phenolics. Different letters in each bar indicate significant differences between mean values (≤0.05).
After the 13 days of aging, the total phenol content of the two wines were the same. The main reason was obvious that the total phenolic contents in KWO1 wine and KWO2 wine, with KWO2 wine having more phenolic content than KWO1, were reduced under oak sawdust, respectively, which was similar to results of Zahri et al. and Del Alamo Sanza et al. [
The total phenolic substances in red wine included mainly pigment and tannin [
The color, aroma, and taste were important factors determining the sensory quality of wine. The sensory evaluation was usually divided into three aspects, such as vision, smell, and taste, which were analyzed and evaluated by the color, aroma, and taste of wine, respectively. Through sensory evaluation and verbal description, wine could be given objective and correct evaluation. The average score given by 25 students with Intermediate Certificate of SWET Wine Taster was as follows.
Table
Comments of Kyoho wine.
Comments | |
---|---|
KWO2 | Light brick red, turbid, slightly fruity, sour, oxidizing, hard taste |
KWO1 | Ruby red, clear and transparent, aromatic, high acidity, general structure, long after taste |
KO2 | Brick red, dull, fruity and floral, not full-bodied, rough in body, thin in structure, general typicality |
KO1 | Purplish red, clear and bright, fruity, mellow, acidic, uniform structure, moderate in style |
According to Table
Average scores of Kyoho wine.
Color (20 score) | Fragrance (20 score) | Taste (40 score) | Structure (10 score) | Typicality (10 score) | Total points (100 score) | |
---|---|---|---|---|---|---|
KWO2 | 10.0 ± 0.1 | 12.0 ± 0.2 | 30.0 ± 0.1 | 6.5 ± 0.1 | 4.5 ± 0.3 | 63.0 ± 0.2 |
KWO1 | 16.5 ± 0.2 | 14.0 ± 0.3 | 33.0 ± 0.2 | 7.0 ± 0.1a | 5.0 ± 0.1 | 75.5 ± 0.3 |
KO2 | 15.5 ± 0.1 | 16.5 ± 0.2 | 32.5 ± 0.1 | 7.5 ± 0.3 | 6.5 ± 0.2 | 78.5 ± 0.1 |
KO1 | 18.5 ± 0.2 | 17.5 ± 0.3 | 35.0 ± 0.1 | 8.0 ± 0.2 | 7.0 ± 0.1 | 86.0 ± 0.2 |
Note. The values of KWO2 in the first, third, and sixth columns are significant at 5% probability level. The values of KWO1 in the first, second, and third columns are significant at 1% probability level, and that in the sixth column is significant at 5% probability level. The values of KO2 in the first and sixth columns are significant at 5% probability level. The values of KO1 in the second and third columns are significant at 1% probability level, and those in the fourth and sixth columns are significant at 5% probability level.
Therefore, the physicochemical indexes and sensory characteristics of Kyoho wine aged with oak sawdust had changed to a certain extent compared with those without oak sawdust. Although the change trend of physicochemical indexes was not significant, the different sensory characteristics were quite prominent. Tannin and total phenol were increasing during the aging. Hue showed a downward trend (Figure
The tannin, total phenol, chroma, and hue of KO1 wine were 1601.5 mg·L−1, 277.67 mg·L−1, 3.21, and 0.72, respectively; the control group had 337.2 mg·L−1 tannin, 64 mg·L−1 total phenol, 4.46 chroma, and 0.97 hue, respectively. The KO2 had 1517.3 mg·L−1 tannin, 222.1 mg·L−1 total phenol, 3.02 color, and 0.68 in hue, respectively; the control had tannin 115.6 mg·L−1, total phenol 79.8 mg·L−1, chroma 3.71, and tone 0.72, respectively. Therefore, oak chip aging could increase obviously the tannin, total phenol, chroma, and hue content in Kyoho wine; the influence of KO1 to tannin, total phenol, chromaticity, and color in Kyoho wine was more obvious than the effect of KO2 on them, but the tannin and total phenol in KO2 were higher than those of KWO1 and chromaticity and tone were lower than those of KWO1, which showed that the KO2 was also beneficial to the improvement of the tannin and total phenol. Tannin, chroma, and tonality in the KWO1 were higher than those in the KWO2, whereas total phenol in the KWO1 was lower than that in the KWO2, but these values were much lower than those in the KO1 and KO2. Taking all these factors into account, the impregnation of Cabernet Sauvignon pomace could improve the tannin, total phenol, chroma, and tone content of Kyoho wine, which, however, was negligible compared to effect of oak chip. In other words, the impregnation of oak chip accelerated the accumulation of tannin, total phenol, chroma, and tone. In terms of flavor substances, Kyoho wine aged with oak sawdust was not only brighter in color, fuller and softer in taste but also of much better quality than Kyoho wine aged without oak sawdust. Therefore, the quality of Kyoho wine could be improved by aging with oak sawdust after being soaked with Cabernet Sauvignon residue, which had important value for developing new products and meeting the market demand.
The data used to support the findings of this study are available from the corresponding author and co-corresponding author upon request.
The authors declare no conflicts of interest with respect to the authorship and/or publication of this article.
This study was financially supported by the Engineering Technology Research Center of Grape and Wine for Advanced School in Yunnan, 12th Five-Year Degree Authorized Construction Discipline in Biology of Yunnan Province, University-level Academic Backbone Training Project for Chuxiong Normal College (XJGG1603), Youth Project of Yunnan Applied Basic Research Projects (2016FD088), key major construction projects on “biotechnology” for Chuxiong Normal College, Scientific Research Fund Major Special Projects for Education Department of Yunnan Province (ZD2015016), support plan of scientific and technological innovation team for Research and Development of Characteristic Plant Resources in Colleges and Universities in Yunnan Province (IRTSTYN), and Research on Key Techniques of Production of Characteristic Ice Wine in Yunnan Plateau.