Abstract
The corridor area of Gansu Province is one of the most important wine grape growing regions in China, and this strip of land results in a significant difference in terms of terroir between its regions. Chemical composition and antioxidant capacity of the main wine grape varieties (Vitis vinifera L.) cultivated in the corridor area of Gansu Province in northwest China were compared. Three regions (Zhangye, Wuwei, and Jiayuguan) were selected to explain the influence of soil and climate conditions on the quality of wine grapes. This study aims to investigate the effect of different regions on berry composition and antioxidant capacity, providing a general evaluation of red and white wine grapes quality in the corridor area of China. The results showed that ‘Merlot’ grapes grown in Zhangye had the best quality among the different varieties in the three regions of Gansu evaluated. The moderate temperature and nitrogen deficiency were associated with improved fruit quality. It was identified that the most suitable grape variety from Zhangye is ‘Merlot’, and that ‘Cabernet Sauvignon’ and ‘Italian Resling’ are the most suitable varieties from Wuwei and Jiayuguan, respectively.
grape varieties; corridor area; berry composition; antioxidant capacity
1 Introduction
Grape and wine quality are often influenced by the soil and climatic conditions,
cultural practices, and training system; all of which interact with the concept of
terroir and grape variety (Deloire et al.,
2005Deloire, A., Vaudour, E., Carey, V., Bonnardot, V., & Van
Leeuwen, C. (2005). Grapevine responses to terroir, a global approach. Journal
International des Sciences de la Vigne et du Vin, 39(4),
149-162.). In general, soil and climate, or the interaction between them, are
considered to be the simplest methods used for the determination of terroir (Spayd et al., 2002Spayd, S. E., Tarara, J. M., Mee, D. L., & Ferguson, J. C.
(2002). Separation of sunlight and temperature effects on the composition of cv.
Merlot berries. Vitis ViniferaAmerican Journal of Enology and
Viticulture, 53(3), 171-182.). European vignerons
(winemakers) have found that planting grapevines in a suitable soil can make a
difference between a great wine and a poor wine. In addition, a previous research
shows that the localization of the vineyards have more influence on the
characteristics of wine than the maceration type (Daudt & Fogaça, 2013Daudt, C. E., & Fogaça, A. O. (2013). Phenolic compounds in
Merlot wines from two wine regions of Rio Grande do Sul, Brazil. Food Science
and Technology (Campinas.), 33(2), 355-361.
http://dx.doi.org/10.1590/S0101-20612013005000045.
http://dx.doi.org/10.1590/S0101-20612013...
). However, another study shows that the vintage
effect on grape metabolic profiles prevailed over the soil effect in a place where
climatic traits, such as the seasonal sum of temperatures and water balance, were
the main factors (Pereira et al., 2006Pereira, G. E., Gaudillere, J.-P., Leeuwen, C., Hilbert, G.,
Maucourt, M., Deborde, C., Moing, A., & Rolin, D. (2006). H-1 NMR metabolite
fingerprints of grape berry: comparison of vintage and soil effects in Bordeaux
grapevine growing areas. Analytica Chimica Acta, 563(1-2), 346-352.
http://dx.doi.org/10.1016/j.aca.2005.11.007.
http://dx.doi.org/10.1016/j.aca.2005.11....
).
Phenolic compounds are one of the major quality factors in wine grapes and in the
resulting wines. In addition, phenolic compounds have a direct effect on some
important organoleptic characteristics of wines, such as color, flavor, bitterness,
and astringency (Garrido & Borges,
2011Garrido, J., & Borges, F. (2011). Wine and grape polyphenols––A
chemical perspective. Food Research International, 44(10), 3134-3148.
http://dx.doi.org/10.1016/j.foodres.2011.11.001.
http://dx.doi.org/10.1016/j.foodres.2011...
). Although phenolic compounds found in wines can also originate from
microbial and oak sources, the majority of the phenolic compounds are grape-derived
(Kennedy, 2008Kennedy, J. A. (2008). Grape and wine phenolics: Observations and
recent findings. Ciencia e Investigación Agrari, 35(2),
107-120.). Grapes contain two
groups of phenolics: flavonoids and non-flavonoids. Phenolic compounds include
non-flavonoid compounds, such as hydroxycinnamic acid esters and stilbenes, and
flavonoid compounds, such as anthocyanins, flavonols, and proanthocyanidins (PAs).
The anthocyanins are the principal source of color in red grape skins and wines, and
there are many interactions occurring among the three flavonoid compounds in wine
resulting in new pigments (Brouillard et al.,
2003Brouillard, R., Chassaing, S., & Fougerousse, A. (2003). Why are
grape/fresh wine anthocyanins so simple and why is it that red wine color lasts
so long? Phytochemistry, 64(7), 1179-1186.
http://dx.doi.org/10.1016/S0031-9422(03)00518-1. PMid:14599515
http://dx.doi.org/10.1016/S0031-9422(03)...
; Jackson, 2008Jackson, R. S. (2008). Wine science: principle and applications (3rd
ed., pp. 287-295). Oxford: Elsevier-Academic Press.; Wrolstad et al., 2005Wrolstad, R. E., Durst, R. W., & Lee, J. (2005). Tracking color
and pigment changes in anthocyanin products. Trends in Food Science &
Technology, 16(9), 423-428.
http://dx.doi.org/10.1016/j.tifs.2005.03.019.
http://dx.doi.org/10.1016/j.tifs.2005.03...
). Proanthocyanidins
(PAs) or condensed tannins are composed of flavan-3-ol subunits and are primarily
responsible for the astringency of wine and contribute to its bitterness (Vidal et al., 2003Vidal, S., Francis, L., Guyot, S., Marnet, N., Kwiatkowski, M.,
Gawel, R., Cheynier, V., & Waters, E. J. (2003). The mouth-feel properties
of grape and apple proanthocyanidins in a wine-like medium. Journal of the
Science of Food and Agriculture, 83(6), 564-573.
http://dx.doi.org/10.1002/jsfa.1394.
http://dx.doi.org/10.1002/jsfa.1394...
). In addition, many
phenolics have antioxidative, anticarcinogenic, and antimicrobial activities (Eberhardt et al., 2000Eberhardt, M. V., Lee, C. Y., & Liu, R. H. (2000). Antioxidant
activity of fresh apples. Nature, 405(6789), 903-904.
PMid:10879522.; Kawaii et al., 1999Kawaii, S., Tomono, Y., Katase, E., Ogawa, K., & Yano, M.
(1999). Antiproliferative effects of the readily extractable fractions prepared
from various citrus juices on several cancer cell lines. Journal of Agricultural
and Food Chemistry, 47(7), 2509-2512. http://dx.doi.org/10.1021/jf9812228.
PMid:10552518
http://dx.doi.org/10.1021/jf9812228...
; Kim et
al., 2000Kim, M. Y., Choi, S. W., & Chung, S. K. (2000). Antioxidative
flavonoids from the garlic ( L.) shoot. Allium sativumFood
Science and Biotechnology, 9, 199-203.). Some phenolics, including flavonoids in fruits and
vegetables, may reduce the risk of cardiovascular disease (Cook & Samman, 1996Cook, N. C., & Samman, S. (1996). Flavonoids-chemistry,
metabolism, cardioprotective effects, and dietary sources. The Journal of
Nutritional Biochemistry, 7(2), 66-76.
http://dx.doi.org/10.1016/0955-2863(95)00168-9.
http://dx.doi.org/10.1016/0955-2863(95)0...
).
The corridor area is located in China’s Gansu province. The climate in the corridor area is described as hot and arid with a high biologically effective day degrees, sufficient sunlight, and low rainfall. The soils are gravelly sandy and have high content of salt. In recent years, the grape and wine industry has showed fast development in China, and many wineries have been established. In the corridor area, there are three representative wine grape growing regions for their different climatic conditions and soil properties, Zhangye, Wuwei, and Jiayuguan. However, there have been little experimental studies on the influence of terroir on wine grape composition and antioxidant capacity in China. In the present study, grape composition and antioxidant capacity of main wine grape varieties cultivated in the corridor area were investigated and compared. The purpose was to determine the effect of different regions on berry composition and antioxidative activity, providing a general evaluation of red and white wine grape quality in the corridor area of China and determine the suitable grape variety for different regions.
2 Materials and methods
2.1 Meteorological survey
The meteorological data of three different regions were obtained from the local meteorological administration. Sunlight duration (hour), temperature (°C) and rainfall (mm) were recorded daily.
2.2 Soil sampling and analysis
The chosen soils belonged to three regions with three different depths: 0-20 cm, 20-40 cm, and 40-60 cm. The 10 soil sampling points selected were in a Z-shape, and 500 g of soil were collected from each depth and point, maintaining a distance of 100 cm away from the trunk. All soils from the same depth were mixed, and 1 kg was retained for every sample based on ‘quartering’. A Mastersizer 2000E laser particle size analyzer was used to determine the physical properties of the soil samples from the three regions. The soil texture sorting method followed the criteria of the Soil Survey Manual (Soil Survey Division Staff, 1993Soil Survey Division Staff. (1993). Soil survey manual (United States Department of Agriculture Handbook, No. 18). Washington: United States Department of Agriculture.). Organic matter and the pH of the soil samples were measured by potassium dichromate volumetry and potentiometry, respectively. The nutrient elements present in the soils were identified using a plasma spectrometer (Vista-AX, Varian, USA) after extraction and digestion.
2.3 Grape samples
Four Vitis vinifera grape cultivars were investigated in this study, which included four red-skinned cultivars (Merlot, Cabernet Gernischet, Cabernet Sauvignon, and Pinot Noir), and two white-skinned cultivars (Italian Riesling and Vidal). The grapes were grown in Zhangye, Wuwei, and Jiayuguan, regions of Gansu province in northwest China, and were managed equally in terms of fertilizer application, soil management, disease control, and pruning. More information of experimental sites and plant materials are shown in Table 1. Canopy management is generally performed to maintain growing shoots and their fruit in an optimal microclimate for grape quality.
Data of experimental sites and plant materials from three different wine grape growing-regions in Gansu province of China.
Grapes were manually harvested when the soluble solids in the berries reached the
maximum value (approximately 150-180 g/L). The white-skinned grapes were
harvested in the middle of September in 2012, and the three red-skinned
cultivars were harvested in early October in 2012. In order to have a
representative grape sample, 900 berry samples (300 per replicate) were
collected from at least seven 30-cluster selections at similar positions in 100
vines at maturity stage. Sampling was performed at a fixed time: from 9:00 to
10:00 in the morning. The fresh samples were kept in refrigerated bags and taken
to the laboratory within a few hours. Then, 300 berry samples (100 per
replication) were crushed in a hand press through 2 layers of cheesecloth.
Titratable acidity and the content of sugar, total phenolics, and anthocyanidins
were quantified according to the National Standard of the People’s Republic of
China (China National Standardization
Administration, 2006China National Standardization
Administration2006GB/T15038-2006Ampeliology analytical methods of wine and fruit
wine(pp223Beijing, ChinaChina Standards Press). The pH of the juice was measured using a
Mettler-Toledo LE438 pH meter. The tannin levels were determined in 300 berry
samples (100 per replication) by methyl cellulose precipitation (Sarneckis et al., 2006Sarneckis, C. J., Dambergs, R. G., Jones, P., Mercurio, M.,
Herderich, M. J., & Smith, P. A. (2006). Quantification of condensed tannins
by precipitation with methyl cellulose: development and validation of an
optimised tool for grape and wine analysis. Australian Journal of Grape and Wine
Research, 12(1), 39-49.
http://dx.doi.org/10.1111/j.1755-0238.2006.tb00042.x.
http://dx.doi.org/10.1111/j.1755-0238.20...
). Additionally, the
berry skins were separated from the rest of the 300 berry samples (100 per
replication) and were immediately frozen in liquid nitrogen and then ground to a
fine powder, freeze-dried, and stored at –40 °C until analysis.
2.4 Measurement of antioxidant capacity
A total amount of 1.0 g of grape skin powder was immersed in 20 mL methanol, which contained 60% methanol and 0.1% hydrochloric acid. Grape skin extraction was performed using ultrasound-assisted extraction at dark at 25 °C for 30 min. The homogenate was then centrifuged at 10,000 ×g for 10 min, and the supernatant was collected. The residues were re-extracted four times, and all the supernatants were mixed and used as an antioxidant solution to measure the parameters describe below.
Determination of total flavonoids:total flavonoids were measured by a
colorimetric assay developed by Zhishen et al.
(1999)Zhishen, J., Mengcheng, T., & Jianming, W. (1999). The
determination of flavonoid contents in mulberry and their scavenging effects on
superoxide radicals. Food Chemistry, 64(4), 555-559.
http://dx.doi.org/10.1016/S0308-8146(98)00102-2.
http://dx.doi.org/10.1016/S0308-8146(98)...
. An aliquot of 1 mL of the antioxidant solution of
appropriately diluted sample or standard solutions of catechin (20, 40, 60, 80,
and 100 mg/L) was added to a 10 mL volumetric flask containing 4 mL
ddH2O. At zero time, 0.3 mL 5% NaNO2 was added to the
flask. After 5 min, 0.3 mL 10% AlCl3 was added. At 6 min, 2 mL 1 M
NaOH was added to the mixture. Immediately, the reaction flask was diluted to
volume with the addition of 2.4 mL of ddH2O and thoroughly mixed. The
absorbance of the mixture, pink in color, was determined at 510 nm against
prepared water blank. The results were calculated from a calibration curve using
catechin as a standard.
Determination of total flavanols:the antioxidant solution (0.1mL) was added to
3.0 mL of a 6 × 10–5 mol/L p-DMAC solution, left at
room temperature for 20 min, and the absorbance was read at 643 nm. The results
were calculated from a calibration curve using catechin as a standard (Li et al., 1996Li, Y. G., Tanner, G., & Larkin, P. (1996). The DMACA–HCl
protocol and the threshold proanthocyanidin content for bloat safety in forage
legumes. Journal of the Science of Food and Agriculture, 70(1), 89-101.
http://dx.doi.org/10.1002/(SICI)1097-0010(199601)70:1<89::AID-JSFA470>3.0.CO;2-N.
http://dx.doi.org/10.1002/(SICI)1097-001...
).
Antiradical activities of potent antioxidants by DPPH:the antioxidant solution
(0.1mL) was added to 3.9 mL of a 6 × 10–5 mol/L methanol DPPH
solution. The decrease in absorbance was determined at 515 nm at 0 min, 1 min,
and every 15 min until the reaction reached a plateau. The exact initial DPPH*
concentration (CDPPH) in the reaction medium was calculated from a Trolox
calibration curve (Brand-Williams et al.,
1995Brand-Williams, W., Cuvelier, M., & Berset, C. (1995). Use of a
free radical method to evaluate antioxidant activity. LWT-Food Science and
Technology, 28(1), 25-30.
http://dx.doi.org/10.1016/S0023-6438(95)80008-5.
http://dx.doi.org/10.1016/S0023-6438(95)...
).
The reducing power of Cu measurement: To a test tube 1 mL of Cu (II), Nc, and
NH4Ac buffer solutions was added. The antioxidant sample (or standard) solution
(x mL) and H2O [(1.1 - x) mL]
were added to the initial mixture so as to make the final volume 4.1 mL. The
tubes were stoppered, and after 1 h, the absorbance at 450 nm
(A450) was recorded against a reagent blank. The results
were calculated from a Trolox calibration curve (Apak et al., 2004Apak, R., Güçlü, K., Ozyürek, M., & Karademir, S. E. (2004).
Novel total antioxidant capacity index for dietary polyphenols and vitamins C
and E, using their cupric ion reducing capability in the presence of
neocuproine: CUPRAC method. Journal of Agricultural and Food Chemistry, 52(26),
7970-7981. http://dx.doi.org/10.1021/jf048741x. PMid:15612784
http://dx.doi.org/10.1021/jf048741x...
).
2.5 Statistical analysis
Means and standard deviation were obtained from at least 3 repetitions. One-way ANOVA and Tukey’s Range Test were used to evaluate the differences among the three regions for each grape cultivar. Significance analysis was performed using SPSS (SPSS Inc., Chicago, IL) for Windows, version 20.0. Principal component analysis (PCA) was used to determine the discrimination index of the different regions and cultivars. Prior to the PCA, the evaluation factors must be standardized because of different dimension of assessment indexes. Both the positive indexes (reducing sugar, pH, total phenols, tannin, and total anthocyanidins) and negative indexes (total acidity) were standardized using the following formulas:
-
1
the positive indexes: yij=(xij-min xij)/(max xij-min xij);
-
2
the negative indexes: yij=(max xij- xij)/(max xij-min xij)
The number of principal components was determined by the cumulative variance of traits. Then, the function of the main ingredients was listed according to the eigenvectors of the correlation matrix. Lastly, the comprehensive quality ratings of the wine grapes were determined by the comprehensive principal component values. PCA was performed with the SAS factor procedure.
3 Results and discussion
3.1 Analysis of grape quality of the main wine grape varieties cultivated in the corridor area
Table 2 shows different performances of the main grape varieties quality in different regions. the reducing sugar of the‘Merlot’ grapes of Wuwei was lower than that of the other two regions; Total acidity, total phenols, tannins, and total anthocyanidins were the highest in Zhangye, while there were no significant differences of total acidity, tannins, and total anthocyanidins between Wuwei and Jiayuguan; The order of pH value in the different regions was as follows: Jiayuguan>Zhangye>Wuwei. Reducing sugar of the ‘Cabernet Grnischet’ grapes form Zhangye, was lower than that of the other two regions; However, the total acidity, total phenols, tannins, and total anthocyanidins of the grapes from Zhangye had the highest values among the regions; In addition, there was no significant difference in the pH values among the three regions. The reducing sugar, pH, tannins, and total anthocyanidins of the ‘Cabernet sauvignon’ grapes from Wuwei were the highest, but the total acidity and total phenols were significantly higher in the grapes from Zhangye. The total acidity and tannins of the ‘Italian Resling’ grapes from Zhangye were significantly higher, and the total phenols of the grapes from Wuwei were the highest among the three regions; Grapes from Jiayuguan had the highest values of reducing sugar and pH.
3.2 Climatic conditions
The climate was described as hot and arid with a high biologically effective day degrees and low rainfall in all the experimental regions. The meteorological data of 2012 were obtained from the local meteorological administration. With respect to annual mean temperature, average maximum temperature, and GDD (growing degree days, calculated from daily mean temperatures, base temperature of 10°C), Wuwei was significantly warmer than the other two regions (Table 3). With regard to the average minimum temperature, Jiayuguan was the coldest among the three regions. These results are expected according to the latitude-longitude of three regions in Gansu. However, the sunlight duration in Jiayuguan was longer than that in Wuwei and Zhangye during the growing season (April-October), the ripening period (August-September), and during the whole year. The shortest sunlight duration and the highest rainfall were observed in Wuwei; Jiayuguan had the lowest rainfall during the period of time evaluated.
Main climate parameters for the growing season (April–October) and the ripening period (August–September) in the studied regions.
The wine grape-growing regions of China have unique ecological conditions either
from south to north or from east to west. The regions in the study, located in
Gansu of China, have semi-arid climate with a significant temperature difference
between daytime and nighttime. They have abundant sunshine and an annual
rainfall of 100-150 mm, just like the conditions of Ningxia wine grape-growing
region, which are very different from those of Hebei, semi-humid climate and
annual rainfall of 700 mm (Jiang et al.,
2013Jiang, B., Xi, Z. M., Luo, M., & Zhang, Z. W. (2013). Comparison
on aroma compounds in Cabernet Sauvignon and Merlot wines from four wine
grape-growing regions in China. Food Research International, 51(2), 482-489.
http://dx.doi.org/10.1016/j.foodres.2013.01.001.
http://dx.doi.org/10.1016/j.foodres.2013...
). Thus, the same variety may show different features in
different regions of Gansu.
Climate has the greatest influence on the grapevine growing and wine production
(Hidalgo, 1999Hidalgo, L. (1999). Tratado de viticultura general (pp. 1172).
Madrid: Mundi-Prensa.). Although low
temperatures (14/9°C day/night) are not conducive to high concentrations of
anthocyanin (Coombe, 1987Coombe, B. G. (1987). Influence of temperature on composition and
quality of grapes. In ISHS Acta Horticulturae 206: Symposium on Grapevine Canopy
and Vigor Management, XXII IHC (pp. 23-35). Davis, USA.), temperatures
of 30°C or higher lead to lower anthocyanin synthesis (Spayd et al., 2002Spayd, S. E., Tarara, J. M., Mee, D. L., & Ferguson, J. C.
(2002). Separation of sunlight and temperature effects on the composition of cv.
Merlot berries. Vitis ViniferaAmerican Journal of Enology and
Viticulture, 53(3), 171-182.; Tarara et al., 2008Tarara, J. M., Lee, J., Spayd, S. E., & Scagel, C. F. (2008).
Berry temperature and solar radiation alter acylation, proportion, and
concentration of anthocyanin in merlot grapes. American Journal of Enology and
Viticulture, 59(3), 235-247.). The anthocyanin accumulation is inhibited in
regions where the temperature is higher, and the controlled high temperature
decreases their contents (Kliewer, 1970Kliewer, W. (1970). Effect of day temperature and light intensity on
coloration of . Vitis vinifera L. grapesJournal of the America
Society Horticultural Science, 95(6), 693-697.;
Mori et al., 2007Mori, K., Goto-Yamamoto, N., Kitayama, M., & Hashizume, K.
(2007). Loss of anthocyanins in red-wine grape under high temperature. Journal
of Experimental Botany, 58(8), 1935-1945. http://dx.doi.org/10.1093/jxb/erm055.
PMid:17452755
http://dx.doi.org/10.1093/jxb/erm055...
; Winkler et al., 1962Winkler, A. J., Cook, J. A., Kliewer, W. M., & Lider, L. A.
(1962). Development and composition of grapes. In A. J. Winkler, General
viticulture (pp. 138-196). Berkeley: University of California
Press.). Several studies
have demonstrated a positive association between temperature and seed number or
total proanthocyanidin concentrations per berry at harvest (Del Rio & Kennedy, 2006Del Rio, J. L. P., & Kennedy, J. A. (2006). Development of ins
in Vitis vinifera L. cv. Pinot noir grapes and extraction into wine.
proanthocyanidAmerican Journal of Enology and Viticulture,
57(2), 125-132.; Ewart & Kliewer, 1977Ewart, A., & Kliewer, W. M. (1977). Effects of controlled day
and night temperatures and nitrogen on fruit-set, ovule fertility, and fruit
composition of several wine grape cultivars. American Journal of Enology and
Viticulture, 28(2), 88-95.). The influence
of temperature on total acidity has been widely discussed (Koundouras et al., 2006Koundouras, S., Marinos, V., Gkoulioti, A., Kotseridis, Y., &
van Leeuwen, C. (2006). Influence of vineyard location and vine water status on
fruit maturation of nonirrigated cv. Agiorgitiko (Vitis vinifera L.). Effects on
wine phenolic and aroma components. Journal of Agricultural and Food Chemistry,
54(14), 5077-5086. http://dx.doi.org/10.1021/jf0605446.
PMid:16819919
http://dx.doi.org/10.1021/jf0605446...
) and higher concentrations have
been reported in grapes grown in cool regions than that of grapes from warm
regions (Lakso & Kliewer, 1975Lakso, A. N., & Kliewer, W. M. (1975). The influence of
temperature on malic Acid metabolism in grape berries: I. Enzyme responses.
Plant Physiology, 56(3), 370-372. http://dx.doi.org/10.1104/pp.56.3.370.
PMid:16659305
http://dx.doi.org/10.1104/pp.56.3.370...
). In
the present study, the temperature of Zhangye was moderate when compared with
that of Wuwei and Jiayuguan, and the low temperatures and GDD of Jiayuguan might
have resulted in the low concentrations of phenols (Table 3).
3.3 Analysis of chemical and physical properties of the soil
The selected soils from three regions had different physical and chemical properties (Table 4). The soils from Wuwei and Jiayuguan were classified as ‘clay’ according to the texture classes in the soil survey manual. However, the soil from Zhangye was classified as ‘sand’, because the soil from Zhangye was richer than that of Wuwei and Jiayuguan. Specifically, the sand percentage was 85.59% in Zhangye, and only 44.92% and 40.28% in Wuwei and Jiayuguan, respectively (Table 4).
Physical and chemical properties of the selected soils from three different wine grape growing regions in Gansu province of China.
Higher organic material may result in less compact soils. In the present study, the concentrations of organic matter and total N, P, and K of the soil samples were higher in Wuwei than in the other two regions (Table 4). This suggests that there are different physical and chemical properties of the soils in different regions of Gansu.
The pH of soils in the three regions ranged from 8.0-9.0 (alkaline). At pH values
from 5.0 to 5.5, grapevine performance should not be seriously impeded (Conradie, 1983Conradie, W. J. (1983). Liming and choice of rootstocks as cultural
techniques for vines in acid soils. South African Journal for Enology and
Viticulture, 4(2), 39-44.), and none of the soils
showed any signs of sodicity in the experimental regions. Among the physical and
chemical indicators, those most used by winegrowers are soil bulk density, pH,
availability of major nutrients (N, P, K, Ca, Mg), and organic matter content,
which is known to increase soil water holding capacity to promote soil
aggregation and constitute a pool of available nutrients (Haynes, 1999Haynes, R. J. (1999). Labile organic matter fractions and aggregate
stability under short-term, grass-based leys. Soil Biology & Biochemistry,
31(13), 1821-1830.
http://dx.doi.org/10.1016/S0038-0717(99)00102-9.
http://dx.doi.org/10.1016/S0038-0717(99)...
; Morlat
& Chaussod, 2008Morlat, R., & Chaussod, R. (2008). Long-term additions of
organic amendments in a Loire valley vineyard. I. Effects on properties of a
calcareous sandy soil. American Journal of Enology and Viticulture, 59(4),
353-363.; Teixeira et
al., 2011Teixeira, R. F. M., Domingos, T., Costa, A., Oliveira, R., Farropas,
L., Calouro, F., Barradas, A. M., & Carneiro, J. (2011). Soil organic matter
dynamics in portuguese natural and sown rainfed grasslands. Ecological
Modelling, 222(4), 993-1001.
http://dx.doi.org/10.1016/j.ecolmodel.2010.11.013.
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). The soil properties have great influence on grape and
wine quality (Esteban et al., 2001Esteban, M., Villanueva, M. J., & Lissarrague, J. R. (2001).
Effect of irrigation on changes in the anthocyanin composition of the skin of
cv. Tempranillo ( L.) grape berries during ripening. Vitis
viniferaJournal of the Science of Food and Agriculture, 81(4),
409-420.
http://dx.doi.org/10.1002/1097-0010(200103)81:4<409::AID-JSFA830>3.0.CO;2-H.
http://dx.doi.org/10.1002/1097-0010(2001...
;
Gurovich & Páez, 2004Gurovich, L. A., & Páez, C. I. (2004). Influencia del riego
deficitario controlado sobre el desarrollo de las bayas y la composición química
de los mostos y vinos. Ciencia e investigación agraria, 31(3),
175-186.). The
content of nitrogen was associated with grape and wine quality, which when in
excess can affect the contents of sugar and phenolics in grapes (Xoné et al., 2001Xoné, X., Van Leeuwen, C., Chéry, P., & Ribéreau-Gayon, P.
(2001). Terroir influence on water status and nitrogen status of non-irrigated
Cabernet Sauvignon (). Vegetative development, must and wine composition
(Example of a Medoc Top Estate Vineyard, Saint Julien Area, Bordeaux, 1997).
Vitis viniferaSouth African Journal for Enology and
Viticulture, 22(1), 8-15.; Hilbert et al., 2003Hilbert, G., Soyer, J. P., Molot, C., Giraudon, J., Milin, S., &
Gaudillere, J. P. (2003). Effects of nitrogen supply on must quality and
anthocyanin accumulation in berries of cv. Merlot. Vitis, 42(2),
69-76.). Studies on terroir have shown that
moderate nitrogen deficiency has been associated with improved fruit quality
(Xoné et al., 2001Xoné, X., Van Leeuwen, C., Chéry, P., & Ribéreau-Gayon, P.
(2001). Terroir influence on water status and nitrogen status of non-irrigated
Cabernet Sauvignon (). Vegetative development, must and wine composition
(Example of a Medoc Top Estate Vineyard, Saint Julien Area, Bordeaux, 1997).
Vitis viniferaSouth African Journal for Enology and
Viticulture, 22(1), 8-15.). Thus, moderate
temperature and nitrogen deficiency results in better performance of grape
quality. In addition, the influence of environment and soil on grape
compositions should be correlated with characteristics of different
varieties.
3.4 The comprehensive quality ratings of the of red and white wine grapes
All parameters evaluated were standardized using a standardization method. The eigenvalues, the cumulative proportions, and the eigenvectors are shown in Table S1 and Table S2. Using the dimension-reduction technique, Prin1, Prin2, and Prin3 explained respectively 43.86%, 30.93%, and 15.26% of the total variance for red wine grapes; thus, the first three principal components were selected, accounting for 90.05% of the total variance (Table S1). As for the white grapes, Prin1, Prin2, and Prin3 explained respectively 55.36%, 25.50% and 19.14% of the total variance, and the three major components were selected because they accounted for 100.00% of the total variance (Table S1). Then, the predictive models (Q) of the red and white wine grapes were established, respectively, using the principal components and their cumulative proportions. Lastly, the comprehensive quality ratings of the wine grapes were determined based on the Q values. Specifically, the higher the Q value, the better the performance of the grape quality. The general evaluation of the red and white wine grape quality in the corridor area is shown in Table S3. Among the four red wine grapes from the three regions evaluated, ‘Merlot’ grown in Zhangye had the best quality, followed by ‘Cabernet Sauvignon’ grown in Wuwei and ‘Cabernet Gernischet’ grown in Zhangye. On the other hand, ‘Merlot’ was better in Zhangye and Jiayuguan. In Wuwei, ‘Cabernet Sauvignon’ had the best quality than that the other varieties. As for the two white wine grapes from the three regions, ‘Vidal’ grown in Jiayuguan ranked first, followed by ‘Italian Riesling’ grown in Zhangye. In addition, ‘Pinot Noir’ and ‘Italian Riesling’ grown in Wuwe had the lowest scores among the red and white wine grapes, respectively.
3.5 Antioxidant capacity of grapes grown in the Corridor Area
Different methods are used to determine the antioxidant capacity of fruits (Apak et al., 2004Apak, R., Güçlü, K., Ozyürek, M., & Karademir, S. E. (2004).
Novel total antioxidant capacity index for dietary polyphenols and vitamins C
and E, using their cupric ion reducing capability in the presence of
neocuproine: CUPRAC method. Journal of Agricultural and Food Chemistry, 52(26),
7970-7981. http://dx.doi.org/10.1021/jf048741x. PMid:15612784
http://dx.doi.org/10.1021/jf048741x...
; Brand-Williams et al., 1995Brand-Williams, W., Cuvelier, M., & Berset, C. (1995). Use of a
free radical method to evaluate antioxidant activity. LWT-Food Science and
Technology, 28(1), 25-30.
http://dx.doi.org/10.1016/S0023-6438(95)80008-5.
http://dx.doi.org/10.1016/S0023-6438(95)...
; Li et al., 1996Li, Y. G., Tanner, G., & Larkin, P. (1996). The DMACA–HCl
protocol and the threshold proanthocyanidin content for bloat safety in forage
legumes. Journal of the Science of Food and Agriculture, 70(1), 89-101.
http://dx.doi.org/10.1002/(SICI)1097-0010(199601)70:1<89::AID-JSFA470>3.0.CO;2-N.
http://dx.doi.org/10.1002/(SICI)1097-001...
; Zhishen
et al., 1999Zhishen, J., Mengcheng, T., & Jianming, W. (1999). The
determination of flavonoid contents in mulberry and their scavenging effects on
superoxide radicals. Food Chemistry, 64(4), 555-559.
http://dx.doi.org/10.1016/S0308-8146(98)00102-2.
http://dx.doi.org/10.1016/S0308-8146(98)...
). We chose four indexes to evaluate the antioxidant
capacity of grapes grown in different regions of the corridor area based on the
antioxidant concentrations (total flavonoids and flavanols), reducing capacity
(the copper (II) (or cupric) ion reducing ability), and radical-scavenging
activity (DPPH). The concentrations of total flavonoids and flavanols, CUPRAC
and DPPH clearance rate in ‘Merlot’, ‘Cabernet Grnischet’, and ‘Italian Resling’
grapes grown in Zhangye was significantly higher than those of Wuwei and
Jiayuguan although there was no significant difference in DPPH clearance rate
for ‘Italian Resling’ among the three regions (Figure 1). ‘Cabernet Sauvignon’ grown in Wuwei and Jiayuguan showed
no significant difference in the concentrations of total flavonoids (Figure 1A), but ‘Cabernet Sauvignon’ grown
in Jiayuguan had higher concentrations of total flavanols (Figure 1B). ‘Cabernet Sauvignon’ grown in Wuwei had higher
value of CUPRAC than that of Jiayuguan (Figure
1C), but ‘Cabernet Sauvignon’ grown in Wuwei and Jiayuguan had no
significant difference in DPPH clearance rate (Figure 1D).
Comparison of antioxidant capacity of different grape varieties grown in the Corridor area. Each bar is the mean of three values and their standard deviation. Different letters above each bar of the same variety are significantly different at the 0.05 level according to ANOVA by Duncan’s test.
Moreover, the concentrations of total flavonoids and flavanols, CUPRAC, and DPPH clearance rate of the red grapes were higher than those of the white grapes in general (‘Vidal’ had higher values of total flavonoids and flavanols, and CUPRAC, than those of ‘Pinot Noir’). In Zhangye, the concentrations of total flavonoids and flavanols in ‘Merlot’ grapes were 241.1 mg/L and 162.3 mg/L, respectively, which were 25-30% higher than those in ‘Cabernet Gernischet’ grapes. However, the concentrations of total flavonoids and flavanols of ‘Merlot’ grapes were lower than those of ‘Cabernet Grnischet’ and ‘Cabernet Sauvignon’ grapes grown in Wuwei and Jiayuguan. This suggests that the influence of environment on the quality of wine grapes was greater than that of the variety characteristics. ‘Merlot’ grapes grown in Zhangye had the highest values of CUPRAC and DPPH, followed by ‘Cabernet Gernischet’ grapes grown in Zhangye and ‘Cabernet Sauvignon’ grown in Wuwei (Figure 1C and D). ‘Italian Resling’ grapes showed the lowest values of CUPRAC and DPPH in all regions.
There are many studies that have reported that the antioxidant capacity of grapes
and wines is closely related to their content of phenolic compounds (Cimino et al., 2007Cimino, F., Sulfaro, V., Trombetta, D., Saija, A., & Tomaino, A.
(2007). Radicalscavenging capacity of several Italian red wines. Food Chemistry,
103(1), 75-81.
http://dx.doi.org/10.1016/j.foodchem.2006.07.042.
http://dx.doi.org/10.1016/j.foodchem.200...
; Minussi et al., 2003Minussi, R. C., Rossi, M., Bologna, L., Cordi, L., Rotilio, D.,
Pastore, G. M., & Durán, N. (2003). Phenolic compounds and total antioxidant
potential of commercial wines. Food Chemistry, 82(3), 409-416.
http://dx.doi.org/10.1016/S0308-8146(02)00590-3.
http://dx.doi.org/10.1016/S0308-8146(02)...
). Flavonoids, as the most abundant
phenolics, are important for their antioxidant and free radical scavenging
activities; its content can reflect the antioxidant capacity of the fruit (Verzelloni et al., 2007Verzelloni, E., Tagliazucchi, D., & Conte, A. (2007).
Relationship between the antioxidant properties and the phenolic and flavonoid
content in traditional balsamic vinegar. Food Chemistry, 105(2), 564-571.
http://dx.doi.org/10.1016/j.foodchem.2007.04.014.
http://dx.doi.org/10.1016/j.foodchem.200...
). In the present
study, the concentrations of total flavonoids and flavanols were higher in the
red grapes than in the white grapes, in general, and the ‘Merlot’ grapes grown
in Zhangye had the highest concentrations of total flavonoids and flavanols.
These results are in agreement with our findings of the chemical analysis of the
phenolics in the main grape varieties (Figure
1). Moreover, the CUPRAC and DPPH clearance rate also showed
consistency with the chemical analysis results, Figure 1.
4 Conclusions
The chemical analysis and the antioxidant capacity measurements in the grapes of main wine grape varieties cultivated in the corridor area were investigated and compared. Three interesting results were found in the present study: ‘Merlot’ grapes grown in Zhangye had the best quality among the different varieties in the three regions of Gansu; the moderate temperature and nitrogen deficiency were associated with improved fruit quality; and the most suitable grape variety in the region Zhangye is ‘Merlot’, and in the regions Wuwei and Jiayuguan, the most suitable grape varieties are ‘Cabernet Sauvignon’ and ‘Italian Resling’, respectively.
Acknowledgements
The authors acknowledge the grant provided by the China Technology System for Grape Industry (CARS-30). The authors would like to thank the College of Resources and Environment, Northwest A&F University for providing technical support and laboratory facilities during the course of this study.
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Data availability
Publication Dates
-
Publication in this collection
Jan-Mar 2015
History
-
Received
24 July 2014 -
Accepted
23 Nov 2014