جستجوی مقالات مرتبط با کلیدواژه « oxidative stability » در نشریات گروه « مکانیزاسیون کشاورزی »

The aim of this study is to determine the total phenol and flavonoid content and antioxidant activity of hydroalcoholic extracts from different parts of pumpkin (skin, seed and flesh). The maximum extract production was obtained for flesh (27.83 g extract/100 g powder) while the lowest yield obtained from the seed extract (6.30 g extract/100 g powder). For seed extract, the highest amount of total phenol (25.80 ± 0.69 mg (GAE)/g extract) and flavonoid content (7.24 ± 0.28 mg(QE)/g extract) obtained respectively through the assay of Folin Ciocalteu and aluminum calorimetric and the best antioxidant activity was gained through antioxidant  assays of DPPH (IC50=794.32µg/ml) and β-carotene bleaching (at a dose of 2000 µg/ml it was equivalent to synthetic antioxidant BHA in the concentration of 200 µg/ml). Based on the results of oxidative stability index (OSI) for extracts, the skin extract showed the highest stability (8.58 ± 0.55 h) and no significant difference was observed between the seed and fruit extracts (7.13 ± 0.168 h and 7.33 ± 0.08 h, respectively). The results suggested that hydroalcoholic extracts of various parts of the pumpkin’s fruit, especially its seeds, may serve as a potential source of natural antioxidant for food and pharmaceutical products.

In the present study, oxidative stability of gallic acid, methyl gallate, and syringic acid at four concentration (200, 400, 800, and 1600 ppm) and three temprature (110, 120, and 130 °C) levels in soybean oil was studied using rancimat. The results showed that the fatty acid profile of this oil, mainly consist of linoleic acid (51.01 %), oleic acid (24.50 %), palmitic acid (12.20 %), and linolenic acid (7.10 %). Among various tempretures, the induction period of gallic acid, methyl gallate, and syringic acid (200-1600 ppm) was at the range of 2.90 to 17.49, 2.38 to 16.94, 1.27 to 5.41 h, respectively. With increasing the conceration of gallic acid, methyl gallate, and syringic acid or decreasing temperature, the oxidative stability was increased, thus oxidation rate was decreaed. Antioxidant activity of gallic acid and methyl gallate in soybean oil were not difference at different temperatures, but syringic acid showed lower power in oxidative stability of soybean oil, as compered with control sample. Generally, gallic acid and especially methyl gallate have high potential in increasing oxidative stability of edible oils, specially soybean oil.