Permeability measurement and gas retention in double-layered flatbread.

Area of Science:

• Food science and technology
• Material science
• Chemical engineering

Background:

• Delamination in double-layered flatbreads is linked to internal water vapor pressure exceeding escape rates.
• Gas permeability of dough is a critical factor influencing pressure build-up during baking.
• Limited data exists on the permeability of bread crusts and double-layered flatbreads.

Purpose of the Study:

• To investigate the gas permeability of double-layered flatbreads during baking.
• To understand the role of permeability in delamination and pressure build-up.
• To correlate experimental findings with numerical simulations.

Main Methods:

• Baking double-layered flatbreads at 300°C with and without steam injection.
• Utilizing a specialized two-chamber apparatus to measure gas permeability.
• Employing numerical simulations to model gas generation and pressure dynamics.

Main Results:

• Measured low gas permeability values for both upper and lower flatbread layers (6 × 10⁻¹⁷ to 3 × 10⁻¹⁵ m²).
• Observed increased permeability of the upper layer upon detachment during delamination.
• Simulations confirmed water vapor as the primary driver of pressure build-up over carbon dioxide.

Conclusions:

• Gas permeability significantly impacts pressure build-up and delamination in double-layered flatbreads.
• Permeability values below 8 × 10⁻¹³ m² are necessary for substantial pressure increase (>10 kPa) across various oven temperatures.
• Higher permeability delays pressure build-up, especially at lower baking temperatures.