Effect of Combined Microwave-grilled Drying on antioxidant properties of Russian Olive (Elaeagnus augustifolia L.,) Berries

Authors:
Soussene Boudraa

Volume 26, Issue 3;
Pages: 175-190; 2020
ISSN: 2069-0053 (print) (former ISSN: 1453-1399), Agroprint;
ISSN (online): 2068-9551
Abstract:
The aim of this study is to investigate the effect of microwave-grill drying (MWGD) at three power levels (300, 450 and 600 Watts) on kinetics and antioxidant properties of berry Russian olive extracts were qualitatively and quantitatively determined by using HPLC analysis and antioxidant activity through different in vitro tests (Diphenylpicrylhydrazyl Assay (DPPH), the ferric reducing antioxidant power (FRAP) and the oxygen radical absorbance capacity (ORAC) of E.angustifolia L. were determined. The total polyphenols of fresh fruit Russian olive (420.57mg GAE.100 g-1) are higher compared to the fruits dried (137.5mg GAE.100 g-1) in the microwave-grill with a power at 300 W. The presence of vanillic acid, procyanidin, p-coumaric, and quercetin was responsible for high bioactivity of MWGD at 450W in Russian olive fruit dried .At high powers superior to 450 W, drying negatively influences the polyphenols of Russian olive. Microwave-grill dried at 300 W Russian olive had a higher content of ascorbic acid, and β-carotene. Results of the present study confirmed that microwave-grill drying at 450 Watts is the best method of retention of antioxidant properties of fresh fruit of E.angustifolia L. It was found that the Russian olive fruit contains relatively high amounts of antioxidant.However; thermal- and oxidation-induced degradation of thermolabile polyphenols was responsible for the loss of antioxidant activity. This work demonstrates that Russian olive (indigenous cultivars) can be a good source of different nutrients for the local population and showed that E. angustifolia developed from microwave-grill-drying fruit able to preserve the polyphenols and hence contribute to excellent antioxidant capacity. Incorporation of unfermented E. angustifolia in the diet can be a good source of natural antioxidant.
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