Determination of aroma compound diffusion in model food systems: Comparison of macroscopic and microscopic methodologies

Diffusion properties at macroscopic and microscopic scales for three aroma compounds (in solution and gel systems) were characterized using three different methodologies: the diffusion cell and the Volatile Air Stripping Kinetic methods for the determination of apparent diffusion coefficients and the pulsed-field-gradient Nuclear Magnetic Resonance method for the determination of self-diffusion coefficients. The accuracy of the methods was established by comparing ethyl hexanoate diffusion coefficient in water or D2O solution and in 1%-agar gel system at 25 and 30 °C. The robustness of the three methodologies was also investigated in 1%-iota-carrageenan system with different NaCl content leading to gel strengthening.In 1%-agar gel as well as in 1%-iota-carrageenan systems, the apparent or self-diffusion coefficients of aroma compounds had the same order of magnitude regardless of the approach, ranging between 2.3 × 10−10 and 10.4 × 10−10 m2 s−1. Diffusion properties were discussed in terms of the different observation scales (diffusion scales) and of the nature of gel network.