Effect Of Thermal Treatments And γ-Irradiation On The Volatile, Phenolic acids, , and Antioxidant Activity of Egyptian Fennel Essential Oil.

Document Type : Original Article


1 Chemistry of Flavour & Aroma Dept National research center .NRC, Dokki, Giza 12622, Egypt.

2 Department of Chemistry, Faculty of Education, Ain Shams University,Roxy, Cairo 11757, Egypt


The effect of various thermal treatments (electric oven, microwave) and γ-irradiation at three doses, (6,8 and 10 KGy) on the
composition of volatile and nonvolatile of Fennel (Feniculum vulgare mill) essential oil and also their antioxidant properties were
considered. The hydrodistilled oil (HD) of control and treated samples were subjected to gas chromatography—mass spectrometry
(GC/MS) analysis. The volatile profile of raw HD oil of fennel consisted mainly of estragole (65.67%) followed by carbon (9.6%),
limonene (6.77%), fenchone (6.71%), and trans-anethole (5.92%). Roasting caused a drastic increase in the total yield of
phenylpropanoid (major compounds) in all treated samples by thermal or by y-irradiation ranging from (82.12%) in the electric oven
roasted sample to (89.63%) in 10 KGy irradiated sample compared to (72.67%) in control one. This is due to the very high increase
in estragole percentage in all treated samples, ranging between (79.7%) in the electric oven sample to (87.75%) in the 10 KGy
irradiated sample compared to (65.67%) in the control one. Roasting caused a decrease in the total yield of monoterpenes in all
treated samples except the electric oven-roasted sample, which gained a slight increase compared to the control sample. At the same
time, roasting caused a drastic decrease in oxygenated terpenoids in all treated fennel samples in comparison to the row sample. i.e.
Roasting cause a drastic decrease in all components of HD oil of all treated samples of fennel except estragole which increased to
reach about 90% in 10 KGy irradiated sample. This compound is considered a flavouring agent and, by the European pharmacopeia
limit, does not exceed 6.0% in essential oils. it has a negative effect on animal health and was deleted from the list of flavour and
food stuffs. This indicated in antioxidant activity of HD fennel essential oil; the strongest effect for reduction of DPPH radical was
by microwave heated sample, which exhibited (58.65%±0.36) followed by 1OKGy irradiated sample, which exhibited
(49.27%±0.32) compared to BHT (98%) at the same concentration 30 mg/m