Tomato Oil Encapsulation by ?-, ?-, and ?-Cyclodextrins: A Comparative Study on the Formation of Supramolecular Structures, Antioxidant Activity, and Carotenoid Stability

Cyclodextrins (CDs) are oligosaccharides, comprising 6 (), 7 (), or 8 () glucose residues,used to prepare oil-in-water emulsions and improve oil stability towards degradation. In thisresearch, the aptitude of -, -, and -CDs to form complexes with a supercritical CO2 extractedlycopene-rich tomato oil (TO) was comparatively assessed. TO/CD emulsions and the resultingfreeze-dried powders were characterized by microscopy, Fourier transform infrared-attenuated totalreflection (FTIR-ATR), and dierential scanning calorimetry (DSC), as well as for their antioxidantactivity. Furthermore, carotenoid stability was monitored for 90 days at 25 and 4 C. Confocal andSEM microscopy revealed morphological dierences among samples. - and -CDs spontaneouslyassociated into microcrystals assembling in thin spherical shells (cyclodextrinosomes, Ø 27 m)at the oil/water interface. Much smaller (Ø 9 m) aggregates were occasionally observed with-CDs, but most TO droplets appeared "naked". FTIR and DSC spectra indicated that most CDs didnot participate in TO complex formation, nevertheless structurally dierent interfacial complexeswere formed. The trolox equivalent antioxidant capacity (TEAC) activity of emulsions and powdershighlighted better performances of - and -CDs as hydrophobic antioxidants-dispersing agentsacross aqueous media. Regardless of CDs type, low temperature slowed down carotenoid degradationin all samples, except all-[E]-lycopene, which does not appear eciently protected by any CD type inthe long storage period.