The review discussed the fundamental characteristics of grape phenolic compounds, focusing on their chemical properties and significance in winemaking. Given the higher phenolic content in red wines, particular attention is devoted to attributes such as pigmentation, co-pigmentation, bitterness, and interactions with proteins—key contributors to the perception of astringency. Phenolic compounds undergo substantial qualitative and quantitative transformations during grape ripening, which affect both their inherent properties and their extractability from solid components such as grape skins and seeds. The review also examined extractability dynamics and provides a concise overview of the analytical methods used to assess phenolic compounds in grapes and wine.

The review discussed the fundamental characteristics of grape phenolic compounds, focusing on their chemical properties and significance in winemaking. Given the high-er phenolic content in red wines, particular attention is devoted to attributes such as pigmentation, co-pigmentation, bitterness, and interactions with proteins—key con-tributors to the perception of astringency. Phenolic compounds undergo substantial qualitative and quantitative transformations during grape ripening, which affect both their inherent properties and their extractability from solid components such as grape skins and seeds. The review also examined extractability dynamics and provides a concise overview of the analytical methods used to assess phenolic compounds in grapes and wine.

The chemical composition, the antioxidant activity and the organoleptic profile of Bulgarian wines from the hybrid varieties Misket Kaylashki, Rubin, Kaylashki Rubin and Trapezitsa was studied. The properties of the red wines were compared to those of Cabernet Sauvignon wine. The varieties were grown in the region of Pleven, Central Northern Bulgaria. The results had shown that the wine composition was mainly determined by the variety and its peculiarities. Misket Kaylashki white wine had the lowest rate of sugar-free extract and total acidity. From the red wines, Rubin contained the highest sugar-free extract and glycerol, Kaylashki Rubin had the lowest concentration of glycerol and the highest total acidity, Trapezitsa had the lowest sugar-free extract. In the red wines, the rate of total phenolic compounds and anthocyanins was highest in Rubin and the lowest in Trapezitsa. Misket Kaylashki, as a typical muscat wine, had the highest rates of esters. From the red wines Rubin contained the highest rate of total esters and aldehydes and the lowest higher alcohols. According to the ABTS and MRAP methods, Misket Kaylashki had the lowest antioxidant capacity, while from the red samples Rubin was reported to have the highest and Kaylashki Rubin the lowest.

A study of the chemical composition, the antioxidant capacity and the sensory characteristics of three Bulgarian wines (vintage 2015) from the native cultivars Misket Vrachanski (white), Pamid (red) and Gamza (red), grown in the region of Pleven, Central Northern Bulgaria was carried out. The results showed that the wine composition was mainly determined by the cultivar and its peculiarities. Misket Vrachanski white wine had the lowest rate of sugar-free extract, glycerol, total phenolic compounds and the highest acid content. From the red wine samples, Pamid had lower rates for the above parameters compared to Gamza. The experimental wines were analyzed for total content of esters, aldehydes and higher alcohols. A correlation was found between the rates of the studied volatile components in the wines and their aromatic sensory characteristics. At the wine tasting, Misket Vrachanski that contained the most of esters and aldehydes, was the best evaluated, followed by Gamza and Pamid. There was no correlation between the amount of total phenolic compounds in the experimental samples and their antioxidant capacity, which according to ABTS and MRAP methods increased in the order of Pamid < Misket Vrachanski < Gamza.

Study on the phenolic composition and antioxidant activity of white and red wines obtained from introduced (Chardonnay, Cabernet Sauvignon), local (Dimyat, Gamza) and hybrid (Druzhba, Rubin) varieties was performed. The wines had optimal chemical parameters. Almost identical total phenolic compounds (TPC) content (700.00 ± 0.0.000 mg/dm³ and 703.33 ± 5.773 mg/dm³) in the white wines of the introduced Chardonnay variety and the local Dimyat was found. The wine of the introduced Cabernet Sauvignon showed the highest quantitative presence of TPC (1666.66 ± 5.773 mg/dm³) from the red wines group. Chardonnay wine showed the highest content of flavonoid phenolic compounds (FPC) (769.84 ± 1.833 mg/dm³), and for the red wines FPC content dominated quantitatively in Rubin (2532.40 ± 49.938 mg/dm³). The wine of the introduced Chardonnay also showed the highest content of non-flavonoid phenolic compounds (NPC) (115.78 ± 0.325 mg/dm³), and in the red wines Gamza (235.63 ± 0.498 mg/dm³) was distinguished by this indicator. The quantitative presence of anthocyanins in the studied red wines followed the order wine - introduced variety > wine - hybrid variety > wine - local variety. The highest antioxidant activity (AA) in white wines was found in Chardonnay. Gamza and Cabernet Sauvignon red wines showed a close percentage of radical scavenging activity, but it was slightly higher in the wine of the local Gamza variety. There was a correlation between the antioxidant activity of red wines and the content of NPC in them, respectively: NPC (AA) Gamza > NPC (AA) Cabernet Sauvignon > NPC (AA) Rubin. The white and red wines from introduced, local and hybrid grapevine varieties from the region of Pleven, Central Northern Bulgaria showed good and balanced phenolic accumulation capacity, resulted in optimal ability for in vitro elimination of free DPPH radicals.

The development of viticulture and winemaking, including the preservation and cultivation of old local grape varieties, is an opportunity to preserve traditions and diversity of vine genetic resources in Bulgaria. This research was a part of the DIONYSOS project, investigated the biological diversity of local varieties grown in different regions of Southern Bulgaria. The subject of the current study were 10 grapes samples from 3 white (Dimyat, Red Misket, Tamyanka) and 3 red (Pamid, Mavrud, Gamza) autochthonous to Bulgaria wine grape cultivars grown in the region of Haskovo district. The aim was to determine the chemical composition and organoleptic profile of the experimental wines obtained after spontaneous alcoholic fermentation. After crushing, the fermentation of the grape pomace was run under the impact of wine yeast from the natural microflora of the grapes. The dynamics of the process was monitored by daily measurement of dry matter by refractometer. The yeasts showed different fermentation activity. The process onset was between the 48th and 72nd hours and proceeded dynamically and efficiently. The spontaneous fermentation was complete and ensured a high ratio of sugar conversion into alcohol. An exception was observed in both samples of the cv. Tamyanka. The content of residual sugars, alcohol, titratable acids, volatile acids, pH in the experimental wines were analyzed by generally accepted in winemaking practice methods. No deviations were found in the values of the studied indicators and metabolites formed were within acceptable limits for white and red wines. The organoleptic features of the samples were evaluated by a tasting panel of 7 oenologists. The sensory qualities of the variants were represented by radial diagrams using the method of principal characteristics. All samples had specific sensory profile, with a positive rating of the organoleptic criteria, according to the variety and the created experimental conditions for their making.