Pumpkin-based carotenoids complexed with dairy and plant proteins: Stability of complexes and characteristics of their spray-dried powders

While pumpkin can be used as raw material for production of natural yellow colorant, pumpkin-based carotenoids (PBC) exhibit practical limitations due to their instability and water insolubility. The present study proposes to alleviate such limitations by complexing PBC with different proteins, i.e., casein and soy protein. Complexes formation was investigated via fluorescence spectroscopy and further analyzed via molecular docking simulation. Characteristics of different complexes were determined. Spray drying of both complexes and properties determination of the resulting powders were also conducted. Only one binding site was found to be available on each protein, suggesting that suitable ratio of PBC to each protein should be 1:1. Hydrophobic and van der Waals interactions dominate within PBC-soy protein and PBC-casein complexes, respectively, enhancing stability of PBC. Yellow hue of both complexes remained stable upon heating; PBC-soy protein complex nevertheless exhibited higher stability under accelerated storage condition. Spray-dried powders of different complexes exhibited different colors, while their reconstituted solutions exhibited similar hues. Both complexes well dispersed in water, although PBC-casein complex powder required longer reconstitution time due to its larger particles with smoother surface. In reconstituted complexes solutions, carotenoids retention was 60 %, compared to only 45 % in reconstituted pumpkin flour.