No abstract

A comprehensive investigation was conducted to determine the effects of exogenous melatonin treatment of pre-veraison grapes on phenolic components and antioxidants of grape berries and wine. The results showed an increase in the concentration of cyanin-3-O-glucoside, peonidin derivatives, and two flavanols [namely (+)-catechins and (−)-epicatechins] of grapes, as well as flavonols in both grapes and wine due to the application of melatonin. These compounds are derivatives of the catalysate of flavonoid 3'-hydroxylase (F3'H) in the flavonoid synthesis pathway of plants. Ot can be inferred that melatonin increased the activity of F3'H or expression of VvF3'H during grape berry maturation. On addition, two melatonin treatments of pre-veraison grape berries reduced the DPPH radical-scavenging ability and copper ion-reducing power of grapes and wine, whereas one melatonin treatment just reduced those in wine. This study will provide a practical strategy to change the phenolic composition of grapes and wine.Keywords: melatonin; grape; wine; phenolics; antioxidant activity.Practical Application: This study will facilitate the production of quality wine using melatonin.

No abstract

Rain-shelter cultivation has been proven an important cultivation method for grape-plantings in continental monsoon climate zones, of which white plastic films are the most common shelter material. However, while this method and material reduces the occurrence of the disease, it can also decrease the grape berry quality. Five colours (including red, yellow, blue, purple, and white) of plastic films were covered above Cabernet Sauvignon (Vitis vinifera L.) grapevine rows before veraison. Rain-shelter cultivation reduced air temperature, wind speed, and total solar radiation and enhanced relative humidity in the fruit sphere of grapevines. For each particular colour plastic film, the irradiance of its corresponding spectrum band in the canopy of vines was higher than with other colour plastic films. Meanwhile, the blue plastic film treatment significantly promoted the accumulation of total phenolics, anthocyanins, flavonoids, tannins, and phenolic acids more than the other colours of plastic films. Blue plastic films are more beneficial for berry quality promotion of wine grapes, especially Cabernet Sauvignon, under rain-shelter cultivation in continental monsoon climate zones.