Abstract
In this study we evaluate the chemical composition of sunflower oils obtained separately by pressing and subsequent solvent extraction from a new seeds rich in phytosterols (IASP-18) and conventional seeds (HA-89). Results have shown that the total content of oil was much lower in the IASP-18 (18.1%) than in the conventional (37.5%) seeds. The extraction yield obtained by pressing was as low as 3% in the IASP-18 seeds and 37.5% in HA-89, while in the solvent extraction it was of the same order (~18 wt% on seeds extracted by pressing) for the two types of seeds. No significant changes in the fatty acid composition were found between the oils extracted by the two procedures, but the pressed oils presented significantly lower acidity and larger content of the unsaponifiable fraction. Expressed as free sterols, the total sterols were 37–38% more concentrated in the oils extracted with solvent, reaching amounts of 13 700 and 6500 mg/kg in the IASP-18 and HA-89 oils, respectively. No substantial differences were found in the composition of total sterols analysed as free sterols between the oils extracted with the two procedures, but the contents of free sterols and sterol glycosides were much higher in the oils extracted with solvent.
Highlights
Vegetable oils are the richest natural sources of phytosterols, followed by cereal grains and nuts (Piironen et al, 2000)
No substantial differences were found in the composition of total sterols analysed as free sterols between the oils extracted with the two procedures, but the contents of free sterols and sterol glycosides were much higher in the oils extracted with solvent
The extraction yield obtained by pressing was as low as 3% in the IASP-18 seeds and 37.5% in the HA-89 seeds, while the yield in the solvent extraction was of the same order (∼18 wt% on seeds extracted by pressing) for the two types of seeds
Summary
Vegetable oils are the richest natural sources of phytosterols, followed by cereal grains and nuts (Piironen et al, 2000). Phytosterols and the related phytostanols are essential components of plant cell membranes. They are C28 and C29 steroidal alcohols and differ from the C27 sterols such as cholesterol, commonly found in animal cell membranes. Plants do contain cholesterol but only in very small amounts, typically amounting only to 1–2% of the total sterol fraction. Phytosterols are found in plant tissues as free steroids and in a variety of conjugated forms. Through the C3 hydroxyl group the sterols can be found esterified with fatty or phenolic acids, or glycosylated with D-glucose or acyl-glucose (Plumb et al, 2011)
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