Green extraction of lycopene from tomato juice with layered double hydroxide nanoparticles

Layered double hydroxides (LDHs) are inorganic compounds with particle size ranging from micrometres to nanometres. On the nanoscale, particles tend to aggregate themselves; therefore, the synthesis of nanoparticles must consider a final step to passivate the surface avoiding aggregation. In this work, zinc/aluminium LDHs particles were synthesised in tomato juice as a reaction medium. This medium promoted the formation of 50 nm particles, which aggregated and simultaneously captured the lycopene in the juice, thus forming a precipitate. The precipitate is a composite material formed by LDH and 11% of organic matter according to an estimation done by thermogravimetric analysis. The organic fraction in the composite presented more thermal stability than that of the tomato flesh. The washing of this composite with ethanol removes lycopene as the main component according to infrared and visible spectroscopy data. As the metal cations in LDH can be selected to comply with food, cosmetic or pharmaceutical applications, the current method to produce lycopene/LDH composites is a promising route to easily obtain antioxidant additives for these industries.