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Probing the binding between norbixin and dairy proteins by spectroscopy methods
1Department of Food Science and Technology, University of Tennessee, Knoxville, United States.
Food Chemistry
|April 9, 2013
Summary
Annatto (norbixin) pigment interacts with dairy proteins like sodium caseinate and whey protein isolate, forming complexes. This binding affects protein structure, with varying affinities observed for different milk proteins.
Area of Science:
- Food Science
- Biochemistry
- Protein Chemistry
Background:
- Annatto (norbixin) is a natural pigment used for dairy coloration.
- Understanding pigment-protein interactions is crucial for food quality and stability.
- Limited knowledge exists on norbixin's specific interactions with dairy proteins.
Purpose of the Study:
- To investigate the binding interactions between norbixin and various dairy proteins.
- To characterize the nature and strength of these pigment-protein complexes.
- To assess the impact of binding on protein conformation.
Main Methods:
- Fluorescence spectroscopy
- Fourier transform infrared spectroscopy (FTIR)
- Circular dichroism (CD)
- Differential scanning calorimetry (DSC)
Main Results:
- Norbixin effectively quenched fluorescence in whey protein isolate (WPI) and sodium caseinate (NaCN), indicating complex formation.
- Sodium caseinate exhibited higher binding affinity for norbixin than WPI.
- Bovine serum albumin showed greater affinity than β-lactoglobulin and α-lactalbumin; κ-casein bound better than α- and β-caseins.
- Binding induced conformational changes in WPI and NaCN, with variations among individual proteins.
Conclusions:
- Norbixin forms complexes with WPI and NaCN, influencing their structural properties.
- Differential binding affinities exist between norbixin and specific dairy proteins.
- These findings provide insights into the molecular basis of annatto's behavior in dairy systems.
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