Creating functional nanostructures: Encapsulation of caffeine into α-lactalbumin nanotubes

Abstract

This work evaluated the stability and functionality of nanotubes obtained from α-lactalbumin (α-LA). α-LA nanotubes' structure was highly stable during a freeze-drying process but not after grinding. The ability of α-LA nanotubes to encapsulate caffeine, used as a model molecule, was evaluated. α-La nanotubes were highly effective for this purpose as encapsulation efficiency (%EE) was near 100% and loading capacity (%LC) near 10% at 1.5/20 and 2/20 ratios (caffeine/α-LA, w/w). α-LA nanotubes' structure was not affected by the presence of caffeine. Also, in general, refrigeration temperatures and neutral or alkaline conditions, under which the adverse effect of chelating agents was prevented, helped to stabilise α-LA nanotubes' structure and maintain caffeine encapsulated. At 8°C and pH 7.5, in the presence of 75 μg mL −1 of EDTA, N 50% of the caffeine remained encapsulated into α-LA nanotubes. Industrial relevance: Linear and hollow structures could be highly effective to increase the viscosity while encapsulating bioactive compounds to protect them from degradation, provide on-demand release, or mask unpleasant organoleptic properties. However, until now, carbon nanotubes are the most commonly used carriers for the controlled release of bioactive molecules and these are not food-grade materials. Enzymatic partial hydrolysis of α-lactalbumin (α-LA) in the presence of a divalent ion results in the formation of food-grade nanotubes with high potential in the food and cosmetic industry. In this work the functionality of α-LA nanotubes was evaluated considering their applicability in real food.

Protein-Based Nanostructures for Food Applications

“…Depending on the protein:cationic agent ratios different gel networks structures can be obtained. Cold-set protein hydrogels can be obtained by adding cationic agents such as ferrous, calcium or barium salts to solutions of denatured globular proteins [57,58].…”

Use of α-Lactalbumin [α-La] from Whey as a Vehicle for Bioactive Compounds in Food Technology and Pharmaceutics: A Review

“…The presence of this cavity enables the α-La nanotubes to function as vehicles for encapsulating molecules such as vitamins, bioactive compounds, colorants, and enzymes. Fuciños et al [46] encapsulated caffeine at high efficiency using α-La-based nanotubes. Additionally, the growth of nanotubes induces the formation of stiff transparent protein gels due to the well-arranged networks formed by the strands.…”

Does the Future of Food Pass by Using Nanotechnologies?

“…Some of the interesting approaches are the use of pH, temperature or ionic driven methodologies for the creation of new nanostructures in raw materials, and thus controlling organoleptic properties (i.e., texture). The formation of nanofibrils using milk proteins (Fuciños et al, 2017) or nanostructured crystals using waxes or monoglycerides (Martins et al, 2016;Cerqueira et al, 2017a) are some of the examples of structures that can be used to change food characteristics.…”