Effect of Extraction Techniques and Low-Temperature Fractionation on the Fatty Acid Composition, Bioactive, and...

In the present study, black and white chia seed oils were extracted using different novel (supercritical fluid extraction & SFE) and assisted green extraction techniques (ultrasound-assisted solvent extraction & UASE, conventional solvent extraction & CSE), followed by fractionation applying low-temperature crystallization. The oils were fractionated at temperatures ranging from -15°C to -30°C to obtain olein and stearin fractions. The effect of extraction methods and subsequent winterisation on the physicochemical properties, fatty acid profile, antioxidant content, and oxidative stability of the oil fractions was evaluated. Among the tested temperatures, -25°C produced the higher olein yield and iodine value (IV) for both the seed types. Winterisation significantly modified the composition of the olein fraction, increased the refractive index (1.481), iodine value (219.73 g I₂/100 g), and the polyunsaturated fatty acids, particularly α-linolenic acid (71.12%), linoleic acid (19.83%), and oleic acid (5.95%) in black chia seed oil. The olein fraction also showed higher concentrations of antioxidants, including total phenolics (43.85 mg GAE/100 g), total tocopherol (63.99 mg/100 g), and total carotenoid (57.76 mg/kg), than the corresponding stearin fraction. Despite a decrease in the induction time of the olein fraction (0.97-0.75 h) corresponding to raw oils, the increased degree of unsaturation outweighed the protective effect of the retained endogenous antioxidants under accelerated oxidation conditions. In conclusion, winterisation effectively concentrated omega-3-rich and antioxidant compounds in the olein fraction, which preferably enhanced its nutritional value and functionality for potential food, cosmetic, and nutraceutical applications.