Structural collapse prevents beta-carotene loss in a supercooled polymeric matrix

Area of Science:

• Food Science and Technology
• Polymer Science
• Chemical Kinetics

Background:

• Beta-carotene, a vital nutrient, is susceptible to degradation when encapsulated in polymeric matrices.
• Understanding degradation kinetics is crucial for maintaining beta-carotene stability in food products.
• Polyvinylpyrrolidone (PVP-40) is a common matrix for encapsulating sensitive compounds.

Purpose of the Study:

• To investigate the degradation kinetics of beta-carotene within a PVP-40 matrix.
• To correlate beta-carotene degradation with physical changes (structural collapse) of the matrix.
• To assess the impact of water activity and relative humidity (RH) on degradation and color changes.

Main Methods:

• Encapsulation of beta-carotene in PVP-40.
• Storage of samples at various water activities and constant temperature.
• Monitoring beta-carotene degradation, matrix structural collapse, and surface color changes over time.

Main Results:

• Degradation rate constants decreased with increasing RH.
• Beta-carotene loss was significant below the glass transition temperature (Tg) but lower in collapsed, plasticized matrices (64-75% RH).
• An inverse correlation was found between matrix collapse and degradation rates; surface color changes were not indicative of beta-carotene retention.

Conclusions:

• Matrix molecular mobility is not the primary factor limiting beta-carotene degradation.
• Microstructure and porosity of the polymeric matrix likely play a more significant role in modifying degradation kinetics.
• Surface color is an unreliable indicator of beta-carotene stability due to its sensitivity to hydration and collapse.