Articles
Food-grade protein nanocomplexation as a potential functional delivery system of bioactive honeybush polyphenols
Article number
1466_6
Pages
45 – 52
Language
English
Abstract
An extract of Cyclopia subternata (CSE) contains phenolic compounds, which demonstrated immune-regulating potential in a preliminary in vivo animal model.
Commonly used as honeybush tea, Cyclopia subternata is a good choice for a functional product with standardised phenolic content, such as a ready-to-drink iced tea containing CSE. However, this presents a problem because phenolic constituents are unstable during storage and processing.
Protein-phenolic interactions, the basis of protein nanocomplexation, have demonstrated potential to enhance phenolic stability.
Fluorescence spectroscopy was used to investigate the binding of CSE phenolics to whey (WP), soy (SP) and pea (PP) protein isolates at pH 2, 5 and 7. After confirmation of binding and suitability of pH levels and protein sources, nanoparticles were prepared by crosslinking the proteins using transglutaminase and coating with pectin.
The CSE-protein nanoparticles were characterised in terms of loading capacity (LC) and encapsulation efficiency (EE) of CSE phenolics using high-performance liquid chromatography, as well as particle size, polydispersity index (PDI) and zeta potential using dynamic light scattering.
The binding of CSE phenolic compounds to proteins was confirmed by significant suppression of fluorescence emission.
Calculated binding strengths were similar, irrespective of the pH and protein, except for PP at pH 5 and 7. Based on these results and practical considerations, pH 5, the natural pH of CSE, and the pH at which WP exhibited superior dispersibility in water, was chosen for nanoparticle preparation.
A factorial experiment, varying CSE and WP concentrations, showed a substantial effect only on the LC. The final formulation for CSE-WP nanoparticles, prepared using 5 mg mL‑1 CSE and 1 mg mL‑1 whey protein, had an EE, LC, size, PDI and zeta potential of 34%, 26%, 358 nm, 0.24 and -24.9 mV, respectively.
Commonly used as honeybush tea, Cyclopia subternata is a good choice for a functional product with standardised phenolic content, such as a ready-to-drink iced tea containing CSE. However, this presents a problem because phenolic constituents are unstable during storage and processing.
Protein-phenolic interactions, the basis of protein nanocomplexation, have demonstrated potential to enhance phenolic stability.
Fluorescence spectroscopy was used to investigate the binding of CSE phenolics to whey (WP), soy (SP) and pea (PP) protein isolates at pH 2, 5 and 7. After confirmation of binding and suitability of pH levels and protein sources, nanoparticles were prepared by crosslinking the proteins using transglutaminase and coating with pectin.
The CSE-protein nanoparticles were characterised in terms of loading capacity (LC) and encapsulation efficiency (EE) of CSE phenolics using high-performance liquid chromatography, as well as particle size, polydispersity index (PDI) and zeta potential using dynamic light scattering.
The binding of CSE phenolic compounds to proteins was confirmed by significant suppression of fluorescence emission.
Calculated binding strengths were similar, irrespective of the pH and protein, except for PP at pH 5 and 7. Based on these results and practical considerations, pH 5, the natural pH of CSE, and the pH at which WP exhibited superior dispersibility in water, was chosen for nanoparticle preparation.
A factorial experiment, varying CSE and WP concentrations, showed a substantial effect only on the LC. The final formulation for CSE-WP nanoparticles, prepared using 5 mg mL‑1 CSE and 1 mg mL‑1 whey protein, had an EE, LC, size, PDI and zeta potential of 34%, 26%, 358 nm, 0.24 and -24.9 mV, respectively.
Publication
Authors
J. Lotter, C. Human, D. de Beer
Keywords
nanoencapsulation, functional extracts, protein-phenolic binding, honeybush herbal tea
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