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pH-driven encapsulation of curcumin in casein nanoparticles enhances dispersibility.

Phytochemicals have excellent anti-oxidation properties and potential bioactivity against various diseases. However, the poor water solubility and in vivo bioactivity of lipophilic phytochemicals are barriers against their application in functional foods.

This dilemma may be solved if appropriate delivery systems can be fabricated. Scientists at the University of Tennessee developed a low-cost, low-energy and organic solvent-free encapsulation technology. They harnessed the pH-dependent solubility properties of curcumin, a phytochemical, and the self-assembly properties of sodium caseinate. Their encapsulation technique holds promise as a delivery system for the food and pharmaceutical industries.

First, the researchers deprotonated and dissolved curcumin, while sodium caseinate was dissociated at pH 12 at room temperature after about 30 minutes. The subsequent neutralization made it possible to encapsulate 0.2 to 1.0 mg per mL of curcumin in 2% self-assembled casein nanoparticles, yielding an encapsulation efficiency of more than 90%.

Very little degradation occurred to curcumin under encapsulation conditions, based on an analysis by the scientists using visible light spectroscopy and nuclear magnetic resonance spectroscopy.

The dissociation of sodium caseinate at pH 12 and its re-association after neutralization were studied using the dynamic light scattering and analytical ultracentrifugation techniques. At pH 12, sodium caseinate particles dissociated into smaller particles which had loose structures that enabled the interaction with deprotonated curcumin.

After neutralization occurred, caseins re-associated to smaller and denser particles than they did at pH 12. Next, the scientists studied the molecular binding between curcumin and sodium caseinate at pH 12, using fluorescence spectroscopy, which, based on the analysis using the Stern-Volmer equation, suggested a complex formation had occurred between the two molecules.

The curcumin encapsulated in the casein nanoparticles exhibited significantly improved anti-proliferation activity against human colorectal HCT-116 and pancreatic BxPC3 cancer cells.

The researchers compared the anti-oxidation activity, using the DDPH and ABTS free radical scavenging methods, for pristine curcumin, which had been extracted from the nanoparticles. The similar anti-oxidation activity of curcumin before and after its encapsulation indicated that the encapsulation technique has commercial potential. It may be applied to encapsulate various lipophilic bioactive compounds.

Further information. Qixin Zhong, Department of Food Science and Technology, University of Tennessee, 211 Food Science and Technology Building, 2510 River Dr., Knoxville, TN 37996; phone: 865-974-6196; fax: 865-974-7332; email:

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Publication:Emerging Food R&D Report
Date:Mar 1, 2016
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