Antioxidant efficacy of amino acids on vitamin A palmitate encapsulated in OSA-starch electrosprayed core-shell microcapsules

The encapsulation and the oxidative stability of vitamin retinyl palmitate (AP), a vitamin A derivative, within coaxial electrosprayed (AP) core – octenyl succinic anhydride (OSA-modified starch) shell microcapsules were investigated. The antioxidant efficiency of amino acids (AAs) (namely histidine, leucine, valine, tryptophan, tyrosine, cysteine and lysine) added to the core, on the oxidative stability of AP was evaluated using differential scanning calorimetry at the isothermal temperature of 140 °C. Confocal microscopy confirmed the location of the AP within the core with AAs microcapsules, surrounded by the shell layer of OSA starch. Scanning electron microscopy revealed that the microcapsules are uniform in size with an average diameter ranging from 2.06 ± 1.05 to 2.41 ± 1.42 μm. The AAs contributed substantially to enhance the oxidative stability of AP, with histidine being the most efficient with an improvement in oxidative stability of about 214 times, while lysine showed the lowest protection (about 3.9 times), compared to non-encapsulated AP. For the encapsulated AP, the presence of histidine or lysine enhanced the oxidative stability of the vitamin by about 70.6 or 1.3 times, respectively. The enhancement of the oxidative stability was mainly due to both the hydrophobic interactions formed between AP and AAs, and the adsorption of AP on the surface of AAs crystals (except lysine), assisted by the suspension of the AAs in ethanol antisolvent, as confirmed with attenuated total reflection–Fourier transform infrared (ATR–FTIR) and X-ray diffraction (XRD) analyses.