The Erzincan plain is one of the richest regions in Turkey in terms of plant biodiversity. In this region, the famous grape cultivar ‘Karaerik’ has always dominated grape production due to its berry characteristics. The cultivar shows great morphological variation at clonal level. In this study, the total phenolic content and antioxidant activity of peel, pulp and seed extracts of nine ‘Karaerik’ clones sampled from same location were investigated. The Folin–Ciocalteu method was used to determine the total phenolic content of peel, pulp and seed extracts of nine clones. To determine antioxidant activity, three well known assays such as DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), FRAP (Ferric Reducing Antioxidant Power) and TEAC (Trolox Equivalent Antioxidant Capacity) were used. In addition, the correlation between total phenol content and DPPH, FRAP and TEAC was determined. Results showed that among the tissues, seed samples in berries of all clones had the highest total phenol content and antioxidant activity determined by three assays. Seed samples were followed by peel and pulp for total phenolic content and antioxidant activity. Among the nine ‘Karaerik’ clones, Clone 8 had the highest total phenolic content (149 mg GAE/100 g FW) while Clone 3 had the lowest (111 mg GAE/100 g FW). Peel, pulp and seed samples of nine ‘Karaerik’ clones showed strong antioxidant activity in DPPH, FRAP and TEAC assays. In particular, grape seeds were found rich for better in phenolic compounds including gallic acid, quercetin, catechin, chlorogenic acid, caffeic acid and p-coumaric acid. Clones such as 7, 8 and 9 higher antioxidant activity may present great potential for grape breeders and the food industry as well as health-conscious consumers.

In this study, nutraceutical properties of fruit juice and seeds, which are important for human health, of green (Kabarcik, Cavus), red (red Globe) and black (Honusu, Yildiz, Yediveren and Helvani) skin colored grape cultivars grown in same ecological conditions were investigated. Harvest period, number of seeds, cluster form, cluster weight, berry weight, berry color and usage area were determined as morphological parameters. The Folin-Ciocalteu method was used for total phenol content analysis. The total antioxidant status of juices and seeds of grape cultivars have been determined by 2,2–diphenyl−1–picryl-hydrazyl–hydrate (DPPH), ferric reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays. Seeds of all grape cultivars exhibited higher nutraceuticals than fruit juices. Total phenolic content of seed samples was found to be quite variable in range of 1.90 mg GAE/g (cv. Yildiz)–3.46 mg GAE/g (cv. Honusu) fresh weight base (FW), indicating 2 folds of differences between green and black grape cultivars. Green and black cultivars also showed the lowest and the highest total phenolic content in juices between 1.69 (cv. Yediveren) and 2.45 (cv. Honusu mg GAE/g FW). Seeds and fruit juices of all cultivars analyzed showed high antioxidant capacity and total phenol content. Of all different colored cultivars, black peel-colored cultivars had the highest values and combined better morphological and nutraceutical traits with an excellent berry qualitative profile for cv. Honusu and Helvani.

Grape production has a long history in the Elazig province and surrounding vicinity and produced grapes have been used for table consumption and also processed into traditional beverages, Şıra (special non-alcoholic grape juice) and wine. In the Elazig province, the main grape cultivars are ‘Ağın Beyazı’, ‘Öküzgözü’, ‘Boğazkere’, ‘Şilfoni’, ‘Tahannebi’, and ‘Köhnü’. Among them, ‘Köhnü’ cultivar is highly preferred by consumers due to its black color and perfect berry characteristics. The cultivar has grown for centuries in different parts of Elazig and shows a great variability for most of its morphological and biochemical characteristics. In the present study, we aimed to determine morphological and biochemical traits in six ‘Köhnü’ clones sampled from Elazığ. The cluster weight of six clones was found between 334–394 g. The highest total phenolic content was observed in seeds followed by peel and pulp samples. The seed extract of Clone 2 had the highest total phenolic content at 254 mg gallic acid equivalent/100 g fresh weight. The results also showed that peel, pulp, and seed samples of ‘Köhnü’ grape clones had considerable amounts of antioxidant components determined by DPPH (1,1-Diphenyl-2-picryl-hydrazyl), FRAP (ferric reducing antioxidant power), and TEAC assays and might be rich sources of natural antioxidants. Among the six ‘Köhnü’ clones, Clone 3, and Clone 6 differed from the others in respect to the highest cluster weight, the highest concentrations of total phenolic content, and antioxidant activity. The results also implied that all clones could be used potentially as a readily accessible source of natural antioxidants and as a possible pharmaceutical supplement.

The grape is one of the most produced and processed horticultural crops. This study evaluated the grape genetic resource belonging to the Vitis labrusca species. The diversity was assessed according to morphometric, antioxidant, physicochemical, and colorimetric characteristics. The diversity was evaluated using a variation index and multivariate analyses. The bunch weight of the vines exhibited a range from 21.05 g to 162.46 g, with a coefficient of variation (CV) of 38.97%. The average bunch weight was 64.74 g. In terms of the berry properties, the highest CV was observed for the berry weight (21.95%). The peel thickness displayed a CV of 36.40%, and an average of 0.23 mm. The CVs for the juice characteristics in the berries of the studied vines were 7.11%, 16.61%, 19.41%, and 28.10% for the pH, TSS, must yield, and TA, respectively. The TPC of the accessions exhibited a notably low variation (CV = 4.63%). The color properties of the accessions displayed an immense variation, except for the L* values. The hierarchical clustering analysis divided the accessions into two main clusters, which both had two subclusters. The multivariate approaches separated individuals into different groups, and they were considered useful tools for utilization in the genetic diversity assessments. Further studies on the cultivation technique and crossbreeding with Vitis vinifera will provide more insights into the population, and this study will be a source for upcoming studies on V. labrusca in the region.

Raisins are a significant grape product with an annual trade volume of approximately USD 2 billion. There are various methods employed for drying grapes into raisins. This study aimed to investigate the effects of different drying methods on raisins, specifically, without pretreatment (SD), treatment with potassium carbonate (5%) containing 2% olive oil (POT), and treatment with ashy water with 2.5% olive oil (AOW). The study examined the changes in raisin weight, physicochemical characteristics, total phenolics, antioxidant and anthocyanin contents, color properties, and protein content in three grape varieties: Deyvani, Haseni, and Reşek. The results indicated that POT treatment resulted in the lightest raisins in Deyvani (0.48 g) and Reşek (0.58 g), while Haseni exhibited the heaviest raisins (0.64 g) under the same treatment. The variations in physicochemical characteristics were relatively limited compared to the changes observed in phenolic and antioxidant properties. Nontreated raisins had the lowest anthocyanin content across all varieties. Protein content was significantly affected by the POT treatment, while the effects of the AOW and SD treatments were comparatively minor. SD drying resulted in slightly brighter raisins, but lower phenolic content and significantly lower color properties. The findings of this study highlight the differential effects of drying methods on different grape varieties, emphasizing the importance of considering a variety-specific approach when selecting the drying method.