Effect of ligand concentration and ultrasonic treatment on inclusion complexes of high amylose corn starch with chia seed oil fatty acids

Chia seed oil is rich in α-linolenic and linoleic fatty acids, which have multiple health benefits but are prone to oxidation due to their high degree of unsaturation. The linear component of starch, amylose, can interact with hydrophobic molecules (ligand) forming amylose inclusion complexes, which may potentially act as delivery systems of polyunsaturated fatty acids. Their physicochemical and functional properties are influenced by the conditions of formation. In the present study, it was investigated the effect of ultrasonic treatment and different ligand/starch ratios (10, 20, and 30% w/w) on the physicochemical properties of inclusion complexes formed between high amylose corn starch and enzymatically hydrolyzed chia seed oil. The increase in ligand/starch ratio, especially from 10 to 20%, yielded complexes with a higher content of α-linolenic acid. The effect of ultrasonic treatment on the acidic composition of complexes depended on the initial ligand concentration. All samples displayed a V-type X-ray diffraction pattern, indicating an effective complexation. Ultrasonically treated complexes showed a higher crystallinity than the untreated ones, suggesting that sonication promoted the fatty acid complexation. All samples displayed the same thermal behavior (Tp > 90 °C, ΔH = 7 J/g) and similar structural properties at the microscopic level. Thermogravimetric analysis showed that the untreated complexes formed with a 10% ligand/starch ratio effectively protected hydrolyzed chia seed oil from oxidative deterioration, suggesting an appropriate behavior as potential carrier agents of fatty acids from chia seed oil in food.