Analyzing the Interaction between Anthocyanins and Native or Heat-Treated Whey Proteins Using Infrared Spectroscopy

Area of Science:

• Food Science
• Biochemistry
• Spectroscopy

Background:

• Anthocyanins (ACN) are natural colorants prone to degradation.
• Whey proteins (WP) are known to enhance ACN color stability.
• Understanding the molecular interactions between ACN and WP is crucial for food applications.

Purpose of the Study:

• To investigate the molecular interactions between anthocyanins from purple corn, grape, and black carrot with whey proteins.
• To analyze changes in whey protein secondary structure upon interaction with anthocyanins using Fourier transform infrared spectroscopy.
• To determine how heat treatment of whey proteins affects their interaction with anthocyanins.

Main Methods:

• Fourier transform infrared (FTIR) spectroscopy was employed to analyze native and preheated whey proteins (WP) and their mixtures with anthocyanins (ACN).
• IR spectra were collected across a range of 4000-700 cm⁻¹ at pH 7.4.
• Soft independent modeling of class analogy (SIMCA) was used for data analysis.

Main Results:

• Heat treatment altered WP secondary structure, decreasing alpha-helices and increasing beta-sheets.
• ACN addition reduced WP alpha-helix content, indicated by changes in amide I and II bands.
• Higher preheating temperatures (70-80 °C) led to more disordered WP structures, enhancing WP-ACN interactions.
• ACN binding stabilized WP against heat denaturation, with varying affinities based on ACN structure.

Conclusions:

• Anthocyanin-whey protein interactions involve changes in protein secondary structure.
• The degree of whey protein structural change upon ACN binding depends on ACN complexity and preheating temperature.
• These findings provide a basis for utilizing whey proteins to enhance the color stability of anthocyanin-based food colorants.