Hemp globulin forms colloidal nanocomplexes with sodium caseinate during pH-cycling.

Area of Science:

• Food Science and Technology
• Protein Chemistry
• Colloid and Surface Science

Background:

• Industrial hemp seed protein (globulins) offers high digestibility but suffers from low solubility, limiting its food applications.
• Sodium caseinate (SC) is a common food ingredient that can potentially improve protein functionality.
• pH-cycling is a processing technique used to modify protein properties.

Purpose of the Study:

• To enhance the solubility and functionality of hemp globulins (HG) for food applications.
• To develop a method for creating soluble and heat-stable protein nanoparticles from HG.
• To investigate the role of sodium caseinate (SC) and processing conditions in nanoparticle formation.

Main Methods:

• Blending hemp globulins (HG) with varying concentrations of sodium caseinate (SC).
• Subjecting HG|SC blends to a pH-cycling process (pH 12 for 1 hr, then neutralized to pH 7).
• Characterizing the resulting nanoparticles using dynamic light scattering (Z-average diameter, PDI), zeta potential measurements, and heat/chemical treatments (urea, N-ethylmaleimide).

Main Results:

• pH-cycling of HG|SC blends formed monodisperse nanoparticles (Z-average diameter ≈ 130 nm, PDI < 0.17) with improved HG solubility (>80%) at SC concentrations >1%.
• Hydrogen bonding was identified as the primary force assembling HG|SC nanoparticles, evidenced by dissociation with heat (<60°C) and urea.
• The HG|SC nanoparticles exhibited good heat stability (Z-average diameter ≈ 229 nm after 90°C for 30 min) and irreversible aggregation above 60°C, likely via thiol-disulphide exchange.

Conclusions:

• Blending hemp globulins with sodium caseinate and applying pH-cycling effectively produces soluble and heat-stable nanoparticles.
• The developed HG|SC nanoparticles demonstrate potential for increasing hemp protein content in various food systems like beverages and emulsions.
• Understanding the role of hydrogen bonding and disulphide bonds is crucial for controlling nanoparticle formation and stability.