Interaction mechanism between soybean protein isolate and citrus pectin.

Area of Science:

• Food Science and Technology
• Biochemistry
• Materials Science

Background:

• Soybean protein isolate (SPI) is a widely used food ingredient.
• Citrus pectin (CP) is a common hydrocolloid in food processing.
• Understanding the interaction between SPI and CP is crucial for developing novel food systems.

Purpose of the Study:

• To investigate the interaction mechanism and structural changes between citrus pectin (CP) and soybean protein isolate (SPI).
• To characterize the microstructure and thermal stability of SPI-CP complexes.
• To provide a theoretical basis for preparing protein-pectin complexes for food applications.

Main Methods:

• Fluorescence spectroscopy to analyze SPI's endogenous fluorescence quenching.
• Three-dimensional fluorescence spectra to assess changes in the SPI microenvironment.
• Fourier transform infrared spectroscopy (FTIR) to determine alterations in SPI secondary structure.
• Microstructure analysis (e.g., SEM) to visualize the composite system.
• Differential scanning calorimetry (DSC) to evaluate thermal stability.

Main Results:

• CP caused static quenching of SPI's endogenous fluorescence, indicating complex formation.
• Hydrophobic interactions were identified between CP and SPI.
• CP altered SPI's secondary structure, reducing α-helix and β-sheet content.
• The SPI-CP composite system exhibited a honeycomb structure with dense pores.
• CP enhanced SPI's thermal stability, increasing its denaturation temperature.

Conclusions:

• Citrus pectin interacts with soybean protein isolate through hydrophobic forces, leading to structural modifications.
• The formation of SPI-CP complexes results in improved thermal stability and a unique microstructure.
• These findings support the application of SPI-CP complexes in food-grade gels and Pickering emulsions.