EXTRACTS OF SUNFLOWER HULLS: THEIR ANTIOXIDANT ACTIVITY ON LIPIDS OF COOKED MACKEREL FISH

Sunflower (Helianthus annus L) hulls that have been investigated in the present work include the
hulls from variety Giza 1. and hulls from hybrid Vedoc and white seeds. Methanol (M), ethanol (E), acetone
(A) and ethyl acetate (EA) have been investigated as extracting solvents for the phenolic compounds
present in the hulls. Solvent(S): hull (H) ratio (v/w) examined were 5:1, 7:1, and 10:1. Methanol, ethanol,
acetone and ethyl acetate at a S: H ratio 7:1 extracted the highest quantities of phenolic compounds from
Vedoc hulls, extracting 337.9, 367.6, 312.3 and 272.9 mg /l. extract, respectively. The highest extraction
for Giza 1 and white hulls was achieved at S:H ratio 7:1 with ethanol. Vedoc and Giza 1 hull extracts
were examined for their antioxidant activity using the β-carotene / linoleate system. All extracts exhibited
antioxidant activity. Antioxidative power for both hulls were in the following descending order ME ≥ EE
>AE > EAE. Compared to BHT, ethanolic extract of Vedoc hulls possessed 88.5% and 90.5% of the antioxidant
power of BHT-200 and BHT-50, respectively. For further confirmation, the ethanolic extract of
Vedoc hulls (EEV) was investigated on a fish meat model system. Mackerel fish was chosen for this purpose.
Different concentrations of EEV and BHT were added to minced mackerel meat along with a control
and cooked at 75±2°C for 30 min. After cooling to room temperature, the cooked samples were
stored under refrigerated conditions at 4°C for 7 days. The thiobarbituric acid (TBA) values proved that
ethanol extract of Vedoc sunflower hulls (EEV)-100 had a power of inhibiting lipid oxidation comparable
to BHT-200, while EEV-500 and EEV-1000 proved to exhibit antioxidant activity superior to BHT-200
in the mackerel meat model system. The highest % inhibition of TBA formation was achieved with EEV-
1000 at day 5 (75.05%). Surface colour was measured by Hunter Lab. Values of L* and b* increased
while a* values decreased during the storage period, but addition of EEV resulted in meat samples with
less L* and b* values and higher a* values than the control.