Surface-directed structure formation of β-lactoglobulin inside droplets

Area of Science:

• Food science and technology
• Protein chemistry
• Materials science

Background:

• Beta-lactoglobulin (β-lactoglobulin) is a major whey protein with significant functional properties.
• Understanding its aggregation and gelation behavior is crucial for food product development.
• Protein morphology within emulsions influences texture and stability.

Purpose of the Study:

• To investigate the morphological changes of β-lactoglobulin structures within oil-in-water droplets during aggregation and gelation.
• To determine the effect of protein aggregation time and emulsifier concentration on β-lactoglobulin distribution.
• To evaluate how different β-lactoglobulin morphologies affect diffusion rates within the resulting gel network.

Main Methods:

• Confocal laser scanning microscopy (CLSM) with a temperature stage.
• Transmission electron microscopy (TEM).
• Fluorescence recovery after photobleaching (FRAP) to assess diffusion rates.

Main Results:

• β-lactoglobulin preferentially migrates to the oil-water interface, forming a dense shell around droplets.
• Increased aggregation time leads to thicker shells and less protein within droplets.
• Emulsifier (polyglycerol polyresinoleat - PGPR) concentration modulates protein localization: 0.5% PGPR allows distribution inside and at the interface, while 2% PGPR concentrates protein inside droplets.
• The resulting gel network's structural heterogeneity, dictated by protein morphology, significantly impacts diffusion rates of large molecules like FITC-dextran.

Conclusions:

• The morphology of β-lactoglobulin in emulsions is highly controllable through aggregation conditions and emulsifier type/concentration.
• These morphological changes directly influence the structural properties of the protein network, affecting its ability to act as a barrier.
• Tailoring β-lactoglobulin structure offers a pathway to control diffusion and potentially encapsulate or deliver active compounds within food matrices.