Fabrication of millet starch nanocapsules loaded with beta carotene using acid hydrolysis and ultrasonication: Characterisation, release behaviour and bioactivity retention

The acid hydrolysis process was used to create novel millet starch-based nanoparticles from three different sources: sorghum, foxtail millet and pearl millet. An environment-friendly, risk-free ultrasonication technique was used for encapsulating beta carotene in starch nanoparticles to create nanocapsules that will shield the bioactivity of beta carotene in gastrointestinal conditions and increase its accessibility after consumption. Formulated nanocapsules were examined for zeta potential, particle size and encapsulation efficiency. The particle dimensions of beta carotene-loaded sorghum (SSB), foxtail millet (FSB), and pearl millet (PSB) starch nanoparticles were 416, 399 and 587 nm with zeta potential of −17.98, −19.03 and –22.31 mV respectively. Encapsulation efficiencies of nanocapsules were found to be 85.83, 89.65 and 78.32 % for SSB, FSB and PSB respectively. Scanning electron microscopy (SEM) was also harnessed as a confirmatory tests towards the presence of beta carotene in nanocapsules. Beta carotene encapsulation in starch nanoparticles was also demonstrated using ATR-FTIR which revealed broad characteristic peaks at 3000, 1086 and 885 cm⁻¹ that occur without any discernible interaction. Intestinal juice with higher beta carotene content ensured controlled release in the intestine. Encapsulated beta carotene showed more bioactive properties in terms of antioxidant activity as compared to free beta carotene form.