Thermal Stability Study of the Grape Seeds Extracts in the Aqueous Solutions
Abstract
This study was carried out to evaluate the effect of parameters the extraction process of grape seeds extracts on the bioactive compounds. The aqueous extracts were screened for total polyphenol content and total flavonoid content wich were determined spectrophotometrically using a modified Folin-Ciocalteu method, respectively a chromogenic system of NaNO2–Al (NO3)3–NaOH based method. The antioxidant activity was determined using DPPH method while their polyphenolic composition by means of HPLC-DAD- MS/ ESI(+) analysis. Total phenols content and flavonoid content varied between 37.835 and 31.830 mg GAE/g, 23.420 and 17.645 mg QE/g respectively in Fetească Neagră seeds; between 24.265 and 27.065 mg GAE/g, 17.970 and 15.205 mg QE/g respectively in Fetească Regală seeds. All extracts showed remarkable DPPH radical-scavenging activity ranging from 94.110 to 95.515%. The study revealed 14 phenolic compounds belonging to the following groups: flavan-3-ol monomers, proanthocyanidins, hydroxycinnamic acid and hydroxybenzoic acid derivatives. Quantitative differences among the varieties and the level of temperature applied of the extraction process were observed. The results suggested that the heat treatment of grape seeds liberated phenolic compounds having a significant effect in increasing the amounts of active when a 90°C extraction temperature was used.
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