Sodium Chloride Diffusion in Low-Acid Foods during Thermal Processing and Storage

Area of Science:

• Food Science and Technology
• Chemical Engineering
• Materials Science

Background:

• Understanding sodium chloride (NaCl) diffusion is crucial for food processing, affecting flavor, preservation, and texture.
• Thermal processing (pasteurization and sterilization) significantly impacts solute transport in food matrices.
• Post-processing storage conditions influence the final salt distribution within food products.

Purpose of the Study:

• To model NaCl diffusion in foods (potato, radish, salmon) during thermal processing using analytical and numerical methods.
• To investigate NaCl concentration changes during post-processing storage.
• To determine the optimal time for sensory evaluation of processed foods based on salt equilibration.

Main Methods:

• Samples of potato, radish, and salmon were immersed in 1% or 3% NaCl solutions.
• Heating was performed at 90, 105, or 121°C for durations ranging from 5 to 240 minutes.
• Analytical and numerical solutions were employed to model NaCl diffusion, with experimental validation.
• Post-processing storage at 4°C or 22°C for up to 28 days was conducted to monitor salt equilibration.

Main Results:

• Radish exhibited the highest equilibrium NaCl concentrations and distribution coefficients but the lowest effective diffusion coefficients.
• Effective diffusion coefficients ranged from 0.2 × 10⁻⁸ to 2.6 × 10⁻⁸ m²/s.
• Analytical and numerical models demonstrated strong agreement with experimental data (R² values of 0.98 and 0.95 for 1% NaCl at 121°C).
• Food samples reached a similar NaCl concentration during storage, irrespective of thermal processing intensity.

Conclusions:

• The study successfully modeled NaCl diffusion in various food matrices during thermal processing.
• Salt concentration equilibrates within multiphase food products approximately 14 days after processing.
• Sensory evaluation of processed foods should be delayed until salt distribution has stabilized for accurate assessment.