The alterations of phenolic compounds and antioxidant capacity of sour grape juice were investigated during the concentration process stages. Phenolics and antioxidant properties of the samples changed more at the vacuum evaporation stage than that of the other stages. After evaporation, the antioxidant capacity of the samples decreased approximately between 14.2 and 17.0 % for DPPH and ABTS methods, respectively. Besides, phenolic contents also decreased approximately as 14.8%. HPLC data on phenolics of sour grape juice during concentrate processing gave 12 polyphenols, including gallic acid, (+)-catechin, (-)-epigallocatechin, vanillic acid, (-)-epigallocatechin gallate, (-)-epicatechin, caftaric acid, caffeic acid and p-coumaric acid, which were determined as 1.05-1.83 mg/100 g, 5.40-7.83 mg/100 g, 6.35-9.21 mg/100 g, 3.01-5.18 mg/100 g, 0- 1.95 mg/100 g, 2.33-3.54 mg/100 g, 12.40-37.60 mg/100 g, 1.44-2.26 mg/100 g and 0.27-0.44 mg/100 g, respectively. Ferulic, sinapic acids and quercetin were only detected at concentrate step of the sour grape juice processing and were found as 0.18 mg/100 g, 0.28 mg/100 g and 0.76 mg/100 g, respectively. As alterações dos compostos fenólicos e da capacidade antioxidante do sumo de uvas não amadurecidas foram investigadas durante as etapas do processo de concentração. Os compostos fenólicos e as propriedades antioxidantes das amostras sofreram maior alteração na fase de evaporação sob vácuo do que nas restantes fases. Após a evaporação, a capacidade antioxidante das amostras diminuiu aproximadamente entre 14.2 e 17.0% nas determinações efetuadas pelos métodos DPPH e ABTS, respetivamente. Por outro lado, os teores de compostos fenólicos também diminuiram aproximadamente 14.8%. Os resultados obtidos por HPLC revelaram a presença de 12 polifenóis, incluindo ácido gálhico, (+)-catequina, (-)- epigalhocatequina, ácido vanílico, (-)-epigalhocatequina galhato, (-)-epicatequina, ácido caftárico, ácido cafeico e ácido p-cumárico, com teores de 1.05-1.83 mg/100 g, 5.40-7.83 mg/100 g, 6.35-9.21 mg/100 g, 3.01-5.18 mg/100 g, 0-1.95 mg/100 g, 2.33-3.54 mg/100 g, 12.40-37.60 mg/100 g, 1.44-2.26 mg/100 g e 0.27-0.44 mg/100 g, respetivamente. Os ácidos ferúlico e sinápico e a quercetina foram detetados somente na etapa de concentração do sumo de uvas não amadurecidas, com teores de 0.18 mg/100 g, 0.28 mg/100 g e 0.76 mg/100 g, respetivamente.

Beverages are an important part of the food sector their storage is also one of the most critical issues. This study investigated the effects of different storage temperatures and times on physicochemical properties, flavonoid and organic acid contents of soda, sherbet and ice tea produced by adding sour grape concentrate. Changes in the flavan-3-ol content of ice tea were also measured during the storage period. The beverages were stored in three different conditions, cold storage (~4°C), room temperature (~24°C) and controlled storage (20±1°C), for six months and analyzed every two months. Storage temperatures and time affected the total soluble solids and acidities of the beverages (p≤0.05). Tartaric acid decreased during storage, especially during the first two months in sherbets. Ice tea and soda drinks were found more stable than sherbets. The malic acid was found the major organic acid in beverages. Flavonoid content in ice tea was higher than others. The flavonoid concentrations of ice tea stored at 20 and 24°C and of sherbet at 4°C were statistically significant as a function of storage time while these values were not significant for ice tea stored at 4°C and of sherbet at 20 and 24°C (p≤0.05). Concentrations of flavan-3-ols varied with storage conditions. The levels of epicatechin, epigallocatechin and epigallocatechin gallate in ice tea samples decreased between an average of 43.72 and 71.15% at the end of six months of storage. Principal component analysis separated two months storage from other storage periods and perfectly discriminated the studied flavan-3-ols except catechin. Soluble solid and brix-acid ratio also dissociated similarly to flavan-3-ols.

In this work, the amounts of phenolic compounds in the peels of four different pomegranate varieties grown in Özdere-İzmir, Turkey were investigated for the first time. Three different extraction processes namely reflux, ultrasonic bath and mixing, were carried out with dry and fresh pomegranate peels for two different periods of 4 and 12 h. The best results for ellagic acid, hesperidin, and quercetin, except resveratrol, were observed in refluxing extraction in MeOH. It is seen that the amounts of ellagic acid obtained from the dry samples are quite good in shorter extraction time (4-h) as 2778, 3376, 5024 and 3115 µg/g, when compared to fresh samples where reduced amounts were obtained as 973, 2046, 3232 and 1822 µg/g. Similarly, the highest ellagic acid quantities were observed in dry and fresh samples as named of İzmir 8; 2624 µg/g and 8761 µg/g, respectively by using HPLC-DAD for longer extraction time (12-h) which was found to negatively affect the phenolics for fresh samples. In fresh samples, extraction is rapid and long heating causes deterioration. As expected, the amount of ellagic acid was higher in the dry ones. The flavonoids hesperidin and quercetin were detected in quite well amounts for most of the samples, also hesperidin was in high as about 85.5 and 73.3 µg/g in one of the samples. Fifteen different phenolics such as ellagic acid, hesperidin, quercetin, resveratrol, catechin, epicatechin, gallocatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, cyanidin, delphinidin, malvidin, myricetin, caffeic acid, caftaric acid, p-coumaric acid, gallic acid and ferulic acid were investigated. The antioxidant activity and total phenolic content analyses were also conducted in the methanolic supernatant extracts. DPPH inhibitions of all extracts varied from 47.22% to 93.83% at 4-h and from 36.88% to 94.96% at 12-hour extractions. Furthermore, ANOVA analyzes for ellagic acid and some catechin derivatives was conducted.

Seeds are one of the main parts of the grapes, and they contain important constituents such as polyphenols, lipids, proteins and carbohydrates. In this study, oil contents, fatty acid composition, total phenolic content, total flavonoid content, monomeric flavan-3-ols and antioxidant capacities of nine grape seeds from nine cultivars were investigated. The correlations between the analyzed parameters were also examined. The oil contents of seeds ranged from 4.96 to 13.35%. Linoleic acid was the predominant fatty acid in the seeds, and it was followed by oleic acid, palmitic acid, stearic acid, linolenic acid, 11-eicosenoic acid and arachidic acid. Total phenolic and total flavonoid contents were 646.50-1120.78 mg GAE/g and 336.69-589.85 mg CE/g, respectively. ‘Italia’ seeds had the highest antioxidant capacity for DPPH and CUPRAC assays while ‘Cabernet Sauvignon’ seeds had the lowest one. The (-)-epigallocatechin, (+)-catechin, (-)-epigallocatechin gallate, (-)-epicatechin and (-)-epicatechin gallate contents in the seeds varied from 1.23 to 6.53 mg/g, 11.61 to 80.20 mg/g, 0.21 to 0.51 mg/g, 2.78 to 48.26 mg/g and 0.08 to 1.50 mg/g, respectively. The (+)-catechin and (-)-epicatechin were the major flavan-3-ol compounds in the grape seeds. Significant correlations were found between total phenolic content, total flavonoid, RSA (DPPH Radical scavenging activity), CUPRAC (Cupric reducing antioxidant capacity) and flavan-3-ols. Consequently, the current study findings support previous information that grape seeds are an important source of antioxidants as well as unsaturated fatty acids, which have positive effects on human health. As grainhas são uma das principais partes da uva e contêm polifenóis, lípidos, proteínas e hidratos de carbono. Neste estudo, foram avaliados o teor de óleo, a composição em ácidos gordos, os teores de fenólicos totais, teores de flavonóides totais, de 3-flavanóis monoméricos e a atividade antioxidante em grainhas de nove castas. As correlações entre os parâmetros analisados foram também examinadas. O teor de lípidos das grainhas variou de 4,96 a 13,35%. O ácido linoléico foi o ácido gordo predominante nas grainhas, seguido pelo ácido oleico, ácido palmítico, ácido esteárico, ácido linolénico, ácido 11-eicosenoico e ácido eicosanoico. Os teores de compostos fenólicos e flavonóides totais foram de 646,50-1120,78 mg GAE/ge e de 336,69-589,85 mg EC/g, respetivamente. As grainhas da casta ‘Itália’ apresentaram a maior capacidade antioxidante para os ensaios DPPH e CUPRAC, enquanto as grainhas de ‘Cabernet Sauvignon’ apresentaram os valores mais baixos. Os teores de (-)-epigalhocatequina, (+)-catequina, (-)-epigalhocatequina galhato, (-)-epicatequina e (-)-epicatequina galhato nas grainhas variaram de 1,23 a 6,53 mg /g, 11,61 a 80,20 mg/g, 0,21 a 0,51mg/g, 2,78 a 48,26 mg/ge 0,08 a 1,50 mg /g, respetivamente. A (+)-catequina e (-)-epicatequina foram os principais 3-flavanóis nas grainhas. Foram encontradas correlações significativas entre o teor de polifenóis totais totais, flavonóides, RSA, CUPRAC e 3-flavanóis. Consequentemente, os resultados deste estudo corroboram resultados anteriores, evidenciando que as grainhas são uma fonte importante de antioxidantes, bem como de ácidos gordos insaturados, que têm efeitos positivos na saúde humana.

This study investigated the physicochemical properties, sugar and organic acid profiles of 21 grape juice and 3 sour grape juice samples in Turkey. The pH, acidity and soluble solids were ranged from 2.64 to 4.19, 3.58 to 30.75 g L-1 and 5.45 to 25.45 °Bx, respectively. The turbidities varied between 1.59 and 109.50 NTU and the lowest value was in the Sultani Çekirdeksiz sour grape juices. The Denizli Karasi sample had the highest color index. The tartaric and malic acid amounts of the samples ranged from 0.53 to 13.16 g 100-1 g-1 and 0.45 to 30.80 g 100-1 g-1, respectively. The major acid was malic acid in the sour grape juice samples and tartaric acid in the grape juice samples. For all samples, glucose and fructose constituted a great part of total sugars. The glucose, fructose and total sugar contents changed from 28.45 to 48.00 g 100-1 g-1, 15.88 to 48.75 g 100-1 g-1 and 53.67 to 97.27 g 100-1 g-1, respectively. The highest sugar content was observed in Kara Erik and the lowest in Yediveren. As a result; some physicochemical characteristics, sugar and organic acid contents of the examined 24 grape juice samples were revealed by the current work.