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J Agric Food Chem. 2014 Dec 31;62(52):12668-77. doi: 10.1021/jf5037799. Epub 2014 Dec 18.

Gum arabic and Fe²⁺ synergistically improve the heat and acid stability of norbixin at pH 3.0-5.0.

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Department of Food Science and Technology, University of Tennessee , Knoxville, Tennessee 37996, United States.


Thermal and acid stabilities of norbixin are challenges for its application as a food colorant. In this work, gum arabic and Fe(2+) were studied for the possibility to improve the thermal and acid stabilities of norbixin. Norbixin was dissolved at 0.004% w/v in deionized water with and without 0.2% w/v gum arabic and/or 0.15 mM ferrous chloride, adjusted to pH 3.0-5.0, and heated at 90 or 126 °C for 30 min. Before heating, norbixin precipitated at pH 3.0-4.0, which was prevented by gum arabic. The thermal stability of norbixin was improved by the combination of gum arabic and Fe(2+). Fluorescence analyses indicated the complex formation between norbixin and gum arabic with and without Fe(2+). Particle size and atomic force microscopy results suggested Fe(2+) and gum arabic synergistically prevented the aggregation of norbixin at acidic pH and during heating. It was hypothesized that the core of gum arabic-norbixin complexes was strengthened by Fe(2+) to enable the synergy.


complex formation; ferrous ions; gum arabic; heat and acid stability; norbixin

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