•Research progress since melatonin was first reported in grapes in 2006 is reviewed.•Melatonin is found in most wine grapes, as well as in grape-related foodstuffs.•Melatonin contents in grapes vary with many factors, including analysis technique.•Melatonin in wine may originate from grapes or from the yeast fermentation process.•Further research is needed to clarify the mechanisms of melatonin biosynthesis.A decade has passed since melatonin was first reported in grapes in 2006. During this time, melatonin has not only been found in the berries of most wine grape (Vitis vinifera L.) cultivars, but also in most grape-related foodstuffs, e.g. wine, grape juice and grape vinegar. In this review, we discuss the melatonin content in grapes and grape-related foodstuffs (especially wine) from previous studies, the physiological function of melatonin in grapes, and the factors contributing to the production of melatonin in grapes and wines. In addition, we identify future research needed to clarify the mechanisms of grape melatonin biosynthesis and regulation, and establish more accurate analysis methods for melatonin in grapes and wines.

Several environmental stimulants and hormones can affect phenolic accumulation in grape berries, but the effects of ethylene and light and their interaction have not been completely deciphered. We measured the accumulation of anthocyanins (ATs) and proanthocyanidins (PAs) in berries of a red-wine grape, Vitis vinifera cv. Cabernet Sauvignon, in four treatments: light exposure with and without ethephon, a commercial growth regulator that quickly converts to ethylene, and box-shading with and without ethephon. Ethephon did not significantly increase the weight and diameter of the berries but altered maturity parameters at 49 days after treatment. Ethephon and light increased the fresh and dry weights of the berry skins, induced the accumulation of total phenolics, total flavonoids, and PAs and up-regulated the transcription of VvLAR1, VvLAR2, VvANR, and VvMYBPA1. Light promoted the accumulation of ATs and the expression of AT biosynthetic genes more effectively than did ethephon. Ethephon and light had interactive effects on grape ripening and the contents of PAs and ATs by the way that light interfered with the effect of exogenous ethephon on endogenous ethylene biosynthesis and the downstream ethylene regulatory pathway. These findings provide new information about the physiological and molecular function of ethylene during berry development and the impact of the interaction between ethylene and light in Vitis vinifera.

•The effect of exogenous melatonin on grape berries and its wines was evaluated.•Melatonin treatments of pre-veraison grape increased the weight of the berries.•Melatonin treatments increased the synchronicity of the grape berries.•Melatonin treatments of pre-veraison grape berries altered wine aroma components.A comprehensive investigation was carried out to determine the effect of exogenous melatonin treatment of pre-veraison grapes on grape berries and its wines. Two melatonin treatments of pre-veraison grape berries increased the weight of the berries by approximately 6.6%. Meanwhile, this melatonin treatment could be beneficial in the reduction of underripe and overripe fruits and in enhancing the synchronicity of the berries. In addition, there were significant differences in the volatile compound composition between the wine produced from the melatonin-treated berries and the wines made from untreated berries. The wine from melatonin-treated pre-veraison grape berries had stronger fruity, spicy, and sweet sensory properties, compared to the wines made from untreated berries. Prolonging the treatment through repeated applications can enhance these effects and under different seasonal conditions, more pronounced effects on the grape quality and wine properties can be observed.

Phenolic compounds from red wines exert a strong influence on wine quality. Abscisic acid (ABA) is essential for the physiological and biochemical function of plants, but few investigators have thoroughly researched its effects on phenolic compounds in dyer grape varieties. The effects of exogenous ABA treatment on the phenolic composition and individual anthocyanin and non-anthocyanin phenolic contents of Yan 73 and Cabernet Sauvignon wines from the ABA-treated grapes, including anthocyanins, flavan-3-ols, flavonols, phenolic acids, and stilbenes were compared. The phenolic compounds in the Yan 73 wine were different from those in the Cabernet Sauvignon wine. The phenolic content (anthocyanins and non-anthocyanins) of the Yan 73 wine was significantly higher than that of the Cabernet Sauvignon wine. The concentrations of the individual phenolic compounds were enhanced by the ABA treatment for the two different wine varieties. The effects on the compositions varied, a similar trend was observed for the ratios of Cy-derivative and Dp-derivative pigments from the two wine varieties, and all non-acylated pigments were enhanced. The stilbene content was enhanced, the ratios of flavan-3-ol dimers and dimer-glucosides were reduced, and the effects on the composition of other compounds varied between the two grape varieties.

The objective of this study was to investigate the influence of exogenous 24-epibrassinolide (EBR) on the substances involved in antioxidation and osmoregulation responses of young grape plants under chilling stress. The grapevine leaves were sprayed with 0 (control), 0.05, 0.10 or 0.15 mg/L of 24-epibrassinolide and then exposed to 4 and 0 °C for 24 h, respectively. The EBR treatment significantly enhanced the activities of antioxidative enzymes such as catalase, superoxide dismutase, peroxidase and ascorbate peroxidase in the plant leaves compared with the control. The contents of ascorbic acid and reduced glutathione increased after the EBR treatment, while reactive oxygen species (ROS) and lipid peroxidation were inhibited. In addition, the EBR treatment also greatly increased the contents of free proline, soluble protein, and soluble sugar. These results indicated that exogenous EBR treatment could enhance the antioxidation defense system and reduce oxidative damage caused by ROS and lipid oxidation in the young grapevine leaves. Meanwhile, it was found that the treatment could also increase the osmoregulation substance content in the grapevine leaves and improve their resistance against chilling stress.

Spine grape (Vitis davidii Foex) is an important wild plant species in South China. To provide sufficient experimental evidence for the strong antioxidant activity of spine grapes, four cultivars from Chongyi County, China, including three red varieties (Junzi #1, Junzi #2, and Liantang) and one white variety (Baiyu) were evaluated. The Junzi #1 had the highest phenolic content (total phenolic, flavonoids, flavanols, and anthocyanins) and the strongest antioxidant capacity (DPPH radical-scavenging capacity, cupric-reducing capacity and hydroxyl radical-scavenging activity) among the four varieties. HPLC analysis of spine grapes revealed that the (+)-catechin was the most abundant phenolics and the hydroxycinnamic acids were the major phenolic acids in the four varieties. Hierarchical cluster analysis showed that the Junzi #1 belongs to the group with high phenolic content and strong antioxidant power. The results suggest the Junzi #1 has the best health promoting properties, and the higher utilization value and potential for development.Highlights► Spine grape is an important wild plant species in South China. ► Baiyu, a very rare white spine grape variety, was examined in this study. ► The phenolic content and antioxidant activity of spine grapes were evaluated. ► Junzi #1 had the highest phenolic content and the strongest antioxidant activity. ► Baiyu had higher phenolic content and antioxidant activity than some wine grapes.

•Hutai-8 is a new selected grape variety of China.•Aroma of Hutai-8 wine was evaluated by comparing with Merlot and Cabernet Sauvignon wines.•Hutai-8 wines own significantly lower total volatiles concentrations.•Esters and fatty acids are the predominant volatiles in Hutai-8 wines.•The highlighted characteristic aromas of Hutai-8 wines are fruity and floral.Hutai-8 is a new selected grape variety that has been widely cultivated in several provinces of China. Recent years, it has been utilized for the production of wine and ice wine on a small scale. The chemical and sensory characteristics of the Hutai-8 (HT) wine aroma were evaluated by comparing with the varietal wines of Merlot (ML) and Cabernet Sauvignon (CS) in successive years, 2013 and 2014. Solid-phase microextraction with gas chromatography–mass spectrometry (SPME–GC/MS) was used for qualitative and quantitative analysis of aroma compounds. A total of 51 compounds were identified and quantified, among which 33 and 27 compounds were detected in HT wines of 2013 and 2014, respectively. The new HT wine owns less volatile compounds than that of ML and CS wines, while the one-year aged HT owns more than ML and CS wines. And the total volatiles concentrations in HT wines were significantly lower than the other two wines. Besides, the predominant volatiles in HT wines were esters and fatty acids, which took much more percentages of the total than that in ML and CS wines. The principal component analysis (PCA) well differentiated the HT wines from the others. Additionally, less odor active volatiles are detected in the HT wines and the result coincided with the less complexity of aroma sensory profiles. Furthermore, the highlighted characteristic aromas of HT wines were fruity and floral.