Spatial distribution and time-course of polyphenol accumulation in grape berry (Vitis labruscana cv. ‘Kyoho’)

Impacts of Selenium-Chitosan Treatment on Color of "Red Globe" Grapes during Low-Temperature Storage

Maintaining the vibrant color of fruit is a longstanding challenge in fruit and vegetable preservation. Chitosan and selenium, known for their protective and antioxidant properties, have been applied to preserve these produce. This study aimed to investigate the influence of selenium-chitosan treatment (comprising 25 mg L-1 selenium and 1.0% chitosan) on the color of "Red Globe" grapes and to analyze the relative expression of genes associated with anthocyanin synthesis enzymes (VvCHS, VvCHI, VvF3H, VvF3'H, VvF3'5'H, VvDFR, VvLDOX, VvUFGT, VvOMT, Vv5GT, and VvGST) using RT-qPCR. Our goal was to uncover the regulatory mechanisms governing grape color. Comparing various treatments, we observed that selenium-chitosan treatment had a significant effect in reducing decay, maintaining the soluble solids content of grape flesh, and preserving the vivid color of grape. This research indicated that selenium-chitosan treatment slowed down browning and prevented the reduction in total phenolic, flavonoids, and anthocyanin in the grape. Moreover, gene expression analysis revealed that selenium-chitosan treatment increased the expression of VvCHS, VvF3H, VvF'3'H, VvLDOX, and Vv5GT, while also stabilized the expression of VvCHI, VvF3'H, and VvDFR in grape skins. These findings shed light on the potential mechanism by which selenium-chitosan impacts grape color. This study established a theoretical foundation for investigating the molecular mechanisms behind selenium-chitosan's ability to slow down grape browning and provides a novel approach to enhancing fruit and vegetable preservation techniques.

Potential role of exogenous melatonin involved in postharvest quality maintenance of Vitis labrusca × vinifera 'Kyoho'

BACKGROUND

Melatonin is an endogenous free radical scavenger with antioxidant activity that preserves the commercial value of postharvest fruits and delays fruit senescence. To explore the effect of exogenous melatonin on antioxidants and aroma volatile compounds of grapes (Vitis labrusca × vinifera 'Kyoho'), the grapes were treated with distilled water (control), 50 μmol L-1 of melatonin (M50), and 100 μmol L-1 of melatonin (M100) for 30 min and were then stored at 4 °C for 25 days.

RESULTS

Exogenous melatonin decreased the rachis browning index, the decay development, the weight loss rate, the berry abscission rate, and the respiration rate, promoted the accumulation of total phenolics and total flavonoids, and delayed the reduction of anthocyanins and total soluble solids. In volatile compounds, the accumulation of esters, aldehydes, and alcohols in grapes was promoted, and the terpenes content was reduced by exogenous melatonin.

CONCLUSION

Exogenous melatonin had potentially positive effects on the postharvest life and quality maintenance of grapes. These findings provide theoretical support for the application of melatonin in grape storage and preservation. © 2023 Society of Chemical Industry.

Italian Grape Ale Beers Obtained with Malvasia di Candia Aromatica Grape Variety: Evolution of Phenolic Compounds during Fermentation

Italian grape ale (IGA) beers have been categorized by the Beer Judge Certification Program as a sub-category of fruit beers in which grape, or grape must, is added during the brewing process to provide additional characteristics to the final beer. In the present work, IGA beers have been produced with must and pomace of the Malvasia di Candia Aromatica (MaCA) grape variety, which were added before fermentation at two different percentages (10% and 20%). The (poly)phenolic profile of IGA beers have been characterized with HPLC-MS/MS and compared to a golden ale control beer (produced in the same conditions without the addition of grape-derived ingredients). A series of sub-samples have been collected to monitor the (poly)phenol profile at time 0 and during the different phases of the fermentation process (1, 3, 5, 7 30, 65 days). Results demonstrated how the addition of pomace allowed to significantly enrich (p < 0.05) final beers in total (poly)phenols detected by MS, while must addition did not influence that amount if compared to the control sample. However, a PCA cluster analysis identified strong similarities among IGA beers and differentiated them to control beer samples. This study underlined how the addition of must and pomace from the MaCA grape variety improved the (poly)phenolic profile of beer from both a qualitative and quantitative point of view.

Assessment of Selected Parameters for Determining the Internal Quality of White Grape Cultivars Grown in Cold Climates

Viticulture in a cool climate is more challenging than in traditional wine regions. Due to the weather conditions, the berries may not achieve their full maturation composition. Therefore, suitable grape cultivars should be selected for cultivation in cool climate regions. The aim of this research was to compare selected grape cultivars grown under the same climatic conditions in terms of their antioxidant activity, chemical composition, and macronutrient contents. Their dry matter content, total soluble solids, pH, total acidity, and vitamin C were also analyzed. This research confirmed the existence of differences between the cultivars regarding their antioxidant activity, total soluble solids and polyphenols, and content of vitamin C and macronutrients.