Behaviour of lactoferrin nanohydrogels incorporating curcumin as model compound into food simulants

• Author(s): Araújo, João Miguel Fernandes
• Date: 2018
• Persistent ID: https://hdl.handle.net/1822/65078
• Origin: RepositóriUM - Universidade do Minho
• Document Type: Master thesis
• Language: English
• Contributor(s): Universidade do Minho; Ramos, Óscar Leandro Silva; Coutinho, Paulo J. G.

Description

Food-grade nanostructures can be used as vehicles for the incorporation of nutraceutical agents (e.g., antioxidants or vitamins) aiming at the development of functional foods. These nanostructures provide higher protection, stability and controlled release to such nutraceutical agents. Fundamental knowledge regarding nanostructures behaviour when associated with nutraceuticals and their interactions with real food matrices is essential. In this study, a lactoferrin (LF) nanohydrogel was developed to encapsulate curcumin (nutraceutical model) aiming at its behaviour evaluation. The release kinetics of curcumin from LF nanohydrogels were also assessed by using food simulants (i.e., hydrophilic medium (ethanol 10 %) and lipophilic medium (ethanol 50 %), according to the commission Regulation (EU) No 10/2011). LF nanohydrogel isolated and loaded with curcumin was comprehensively characterized resorting to several techniques such as dynamic light scattering (DLS), fluorometry, circular dichroism (CD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and native electrophoresis. These LF-curcumin nanohydrogels were studied at a spectroscopic level when incorporated into gelatine (food model matrix). This system was able to associate curcumin at 80 μg/mL with a remarkable efficiency of ca. 90 % and loading capacity of ca. 3 %. Within fluorometric characterization, it was suggested that LF and curcumin molecules bind through hydrophobic interactions and FRET (Fluorescence resonance energy transfer) occurrence allowed the determination of r distance between curcumin chromophores and the nearest LF hydrophobic residues at the binding site. Under refrigerated conditions (4 °C), this system is stable up to 35 days, while at room temperature (25 °C) it has shown to be stable up to 14 days of storage. LF nanohydrogel presented higher release rates of curcumin in a lipophilic food simulant (after ca. 7 h) in comparison with a hydrophilic one (after ca. 4 h). LF nanohydrogels were successfully incorporated in a gelatine matrix and the respective characterization indicated that LF and curcumin molecules did not show any degradation in this process. The physicochemical characterization of LF-curcumin nanohydrogels gave rise to valuable information in what binding, interactions and stability concerns. Finally, the behaviour of this system as well as curcumin release kinetics in food simulants endows LF nanohydrogel as an interesting system to associate with lipophilic nutraceuticals and to incorporate in refrigerated food products with hydrophilic character.