Effects Of Trellis System And Crop Load On Flavour Compounds In Winegrapes And Wines

Trellis system and crop load have great effect on the chemical constituents, especially the aroma of grape and wine. But little research has been engaged in this field in China. The changes of volatile compounds in Muscat Hamburg (Vitis vinifera L.) for pergola and vertical trellis systems were examined during maturation by GC/MS, and the aroma compounds were determined in wines at late ripening by SPME-GC/MS in this research. Furthermore, the effect of crop load under cultivated conditions on vine growth and quality of Cabernet Sauvignon (Vitis vinifera L.) berries and wines was examined. The indexes of optimal crop load were determined by statistical analysis. The effect of cluster thinning on berries and wine constituents was also studied. The main results are as follows: 1. No obvious correlativity was found between the contents of sugar and trellis systems at the same culture management and load. However the contents of total titratable acids (TA) in pergola system was much higher than that in verticle trellis system. 2. The main volatile aroma constituents of Muscat Hamburg were composed by terpenes, esters, aldehydes, and ketones. There were 84 kinds of volatile aromas detected in pergola system, including 49 terpenes, 10 esters, and 25 aldehydes and ketones; while only 65 kinds of them detected in vertical trellis system, including 38 terpenes, 10 esters, and 17 aldehydes and ketones. 3. The volatile compound contents of Muscat Hamburg varied with harvesting time, the content of terpenes, aldehydes and ketones decreased, respectively, and that of the esters increased. The relative content of total and main terpenes in pergola system, which was higher at later maturation (10/8), was much lower than that of in vertical trellis system at earlier maturation (9/16). The relative contents of total aldehydes and keyones and two main components, 2-hexenal and hexanal, were not found different significantly between the two trellis systems at earlier maturation, and higher levels of these components in pergola system were detected at later maturation. When it came to total esters and main esters, dibutyl phthalate and 1,2-benzenedicarboxylic acid bis(2-methylpropyl)ester, the contents of which were higher in pergola system than that in vertical trellis system at earlier maturation, and lower at later maturation, i.e., changes of volatile compounds in pergola system were less obvious than that in vertical trellis system. In order to produce fruitful wine, the berries of Muscat Hamburg should be harvested at the beginning of full maturation, with the changes of characteristic aroma identified as biochemical index. 4. Main aroma components of wine made from Muacat Hamburg seemed to be terpenes, esters and alcohols, while terpenes and several esters are sensible. The wine made from pergola system grapes had more kinds of esters than that from vertical trellis system grapes. The contents of ethyl lactate and ethyl acetate in wine made from pergola system grapes were much lower than that from vertical system grapes, while other esters in the former were equal to or much higher than that in the latter. Linalool content of wine from pergola system was obviously lower than that from vertical trellis system, while the contents of β-citronellol, terpinene, limonene, myrcene, camphene, ρ-cymene, phellandrene, and α-terpinolene in the former were higher than that in the latter. The contents of furfural and phenylacetaldehyde in wine from pergola system were higher than that from vertical trellis system, too. 5. Shoots per meter had great impact on soluble solid (SS) of berries and color density of wine in Cabernet Sauvignon with vertical trellis system. The SS was higher and more stable when shoot density was between 12 and 16.5 shoots/m, with stable color density and moderate shoot vigor. The SS and wine color density began to decrease, TA increased and shoot growth decreased when the shoot density exceeded 19 shoots/m. The berries had lower soluble solid (SS), higher wine color density and more vigor shoot growth in shoot density of below 7 shoots/m. The shoot density of 16 shoots/m was recommended for moderately vigorous Cabernet Sauvignon vine to achieve economically acceptable yields and higher wine quality, according to regression analysis and multiple objective programming. 6. Under the condition of 15 shoots per meter, cluster thinning at anthesis induced higher growth vigor than that at veraison, while the latter suppressed the net assimilation rate at a higher degree than the former. At the same time, no difference was found between the distal cluster thinning and the basal cluster thinning. Cluster thinning at different stage of maturation had different effect on berry contituents in Cabernet Sauvignon. At the beginningof maturation (7/9), for the cluster thinning at anthesis, the sugar content in berries was lower than that of each treatment at veraison, while TA content was a little higher. No difference was found between the cluster thinning and the control, so as to the distal cluster thinning and the basal cluster thinning at veraison. At full maturation (7/28), whether cluster thinning or cluster thinning at different stage did not affect the sugar and TA contents in the berries, whereas the distal cluster thinning led to a lower level for TA content compared with the basal cluster thinning. At the beginning stage of maturation, the catechin content reached its highest level with the distal cluster thinning at anthesis, followed by that of the basal cluster thinning at veraison, the basal cluster thinning at anthesis, the distal cluster thinning at veraison, and the control in sequence. The highest content of epicatechin was also achieved with the distal cluster thinning at anthesis, and then the basal cluster thinning at anthesis, the basal cluster thinning at veraison, the control, and the distal cluster thinning at veraison in sequence. The highest content level of epigallocatechin was also appeared in the distal cluster thinning at anthesis, followed by the control, the basal cluster thinning at veraison, the basal cluster thinning at anthesis, and the distal cluster thinning at veraison in sequence. As to full maturation stage, the catechin content reached the highest level in basal cluster thinning at veraison, followed by the distal cluster thinning at anthesis, the basal cluster thinning at anthesis, the control, and the distal cluster thinning at veraison in sequence. The highest content level of epicatechin appeared in the basal cluster thinning at veraison, followed by the distal cluster thinning at anthesis, the basal cluster thinning at anthesis, the control, and the distal cluster thinning at veraison in sequence. The content of epigallocatechin reached its highest level in the distal cluster thinning at anthesis, followed by the basal cluster thinning at veraison, the basal cluster thinning at anthesis, the control, and the distal cluster thinning at veraison in sequence. The obvious decrease of all the three catechins contents was a typical physiological change in berry development from the beginning to full stage of maturation. The cluster thinning increased the decrease extent of catechins contents and accelerated the berry development, especially in the distal cluster thinning treatment at anthesis. 7. The full-matured berries of Cabernet Sauvignon in all treatments were made into wines,...