Volume 18, Issue 119 (january 2021)
Abstract
In the present study, the effect of chemical refining process on the oxidative stability of Bene kernel oil during 32 hours of thermal process at 170 ° C was investigated. Examination of fatty acid structure showed that the amount of trans fatty acid was very small after the thermal process. The trend of changes in tocopherol and polyphenolic compounds during the heating process was different from other studies. The rate of tocopherol changes increased at the end of the thermal process in crude, degummed and neutralized oils and decreased in bleached and deodorized oils. The reason for the increase in tocopherols was related to their regeneration process. Also, the amount of polyphenolic compounds after the thermal process compared to the zero moment was largely in line with tocopherol changes. The reason for the increase in phenolic compounds was related to the breakdown of these compounds and their becoming simpler compounds. Examination of oxidation stability tests (conjugated diene vlue and p-anisidine value) also showed that crude kernel oil was the most stable sample, followed by degummed, neutralized, deodorized and bleached oils, respectively. The reason that the decolorization step caused the lowest oxidative stability in Bene kernel oil can be attributed to the greatest reduction in the amount of tocopherol compounds in this oil sample compared to the zero moment. Also, the trend of changes in antioxidant activity was largely consistent with changes in antioxidant compounds.
S. Jalili, A. Tabatabee Naini, M. Ashrafi, M. Aminlari,
Volume 22, Issue 1 (1-2020)
Abstract
The pomegranate Punicagranatum fruit pericarp, contain polyphenolic compounds including alpha and beta punicalagins and ellagic acid, which exhibit remarkable antioxidant activities. The aim of this study was to purify and quantify the phenolic components from different varieties of Pomegranate Pericarp Extracts (PPEs) and determine their antioxidant properties. Methanolic and aqueous extracts of four pomegranate cultivars (Shahvar, Siahsorfeh, Torshsabz and Abdorahimkhany, from Shiraz, Iran) were prepared and total phenolic content of PPEs was determined. PPE components were further purified by XAD-16 column chromatography followed by LH-20 gel filtration. The eluted components were subjected to HPLC analysis to differentiate and quantify polyphenolic compounds. Antioxidant activity was measured using DPPH assay. The result revealed significant difference in total phenolic contents and phenolic components in four cultivars. Total phenolic content in methanolic PPE was significantly (P< 0.05) higher than aqueous extracts. Shahvar cultivar had the highest total phenols (11.72±0.01 mg mL-1 in water, 17.7±0.12 mg mL-1 in methanol) and exhibited the most antioxidant property among cultivars. Analysis of components of Shahvar PPE by HPLC showed that proportions of different phenolic components were alpha punicalagin (28.34±2.12%), beta punicalagin (39.75±2.14%) and ellagic acid (3.49±0.93%). Antioxidant activity of alpha punicalagin, beta punicalagin, punicalagin (sum of alpha+beta) and ellagic acid was 50.8, 60.5, 56, and 27%, respectively. Taken together, these results indicate that PPE of Shahvar cultivar is an excellent source of natural antioxidants and can potentially replace the current synthetic antioxidants in food and pharmaceutical industries.
