Effect of different oil extraction methods on bioactive compounds, antioxidant capacity and phytochemical profiles of raw flaxseeds (Linum usitatissimum) and after roasting at different temperatures

BACKGROUND

Factors such as variety, genetics, soil structure and plant diseases affect the oil amount and properties of flaxseed. By applying heat and various extraction treatments to flaxseed, the storage ability of the seed is increased by the removal of moisture, and the stability of phytochemicals in the seed against heat can be determined.

RESULTS

Total carotenoid and phenol of flaxseeds changed from 0.13 (control) and 0.61 mg g-1 (120 °C) to 202.64 (control and 90 °C) and 225.69 mg 100 g-1 (120 °C), respectively. While total flavonoid of flaxseed roasted at different temperatures varied between 636.0 (90 °C) and 786.00 mg 100 g-1 (120 °C), antioxidant activity values for raw and roasted flaxseeds between 59.32% (control) and 68.64% (120 °C) were recorded. Oil content of seeds changed between 34.07 and 42.57% (P < 0.05). Viscosity of flaxseed oil extracted using different systems was between 31.95 (cold-pressed; control) and 36.00 mPa s (ultrasonic; 120 °C). The dominant phenolics of flaxseeds were identified as isorhamnetin, resveratrol, quercetin, catechin, apigenin-7-glucoside and campherol. The oils of flaxseeds contained 55.27-58.23 linolenic, 17.40-18.91 oleic, 14.03-14.84 linoleic and 4.97-5.37 palmitic acids, depending on extraction method and roasting temperature.

CONCLUSION

Roasting and oil extraction methods did not have a significant effect on free acidity, but was found to affect peroxide value. The predominant phenolic constituents of flaxseed samples were isorhamnetin, resveratrol, quercetin, catechin, apigenin-7-glucoside and campherol, respectively. The major fatty acids of flaxseed oil were determined as linolenic, oleic, linoleic and palmitic. © 2023 Society of Chemical Industry.

Effect of Rosemary Extracts on Stabilitiy of Sunflower Oil Used in Frying

The oxidative stability of sunflower oil containing rosemary essential oil and extracts in the oil during frying were followed by measuring peroxide value. Variation in the values of L* of the frying oil containing extract was less than that of frying oil containing essential oil. a*-Value of the fried oil containing extract highly significant decreased. Increase in the value of b* of 1. and 2. frying oil with 0.5 % rosemary essential oil was less. b* Value of the frying oils containing rosemary extract increased compared to b* values of frying oils containing essential oil. b* Value of the frying oil that the essential oil of rosemary added showed less increase than b* value of the frying oil that extract of rosemary. The viscosity values of frying oils containing rosemary extract changed between 30.3 mPas (1. frying oil containing 0.5% extract) and 35.5 mPas (2. frying oil containing 0.5% extract). In addition, free fatty acidity values of frying oils containing essential oil at 0.1, 0.3 and 0.5% levels ranged from 0.160% (1. frying oil containing 0.5% essential oil) to 0.320% (1. frying oil containing 0.3% essential oil). Peroxide values of frying oils containing rosemary extracts were determined between 12.84 meq O₂/kg (1. frying oil containing 0.1% extract) and 28.98 meq O₂/kg (2. frying oil containing 0.1% extract). Peroxide value of frying made with 0.3 % the rosemary essential oil increased less than that of made with the raw sunflower oil (control) (p < 0.05). Whenever rosemary essential oil and rosemary extract compare, the essential oil seems to be more effective on the peroxide value of the frying oil. The essential oil of rosemary have been effected more from the extracts of rosemary on the oxidative stability of sunflower oil.