Investigation of the diffusion of dyes in agar gels

• Published in: Journal of food engineering Vol. 111; no. 4; pp. 537 - 545
• Main Authors: Samprovalaki, K., Robbins, P.T., Fryer, P.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2012; Elsevier
• Subjects: Agar; aqueous solutions; Biological and medical sciences; Diffusion; Diffusion coefficient; Diffusion effects; diffusivity; Dyes; Fick’s law; Food engineering; Food industries; Foods; Fundamental and applied biological sciences. Psychology; Gels; General aspects; Image analysis; methylene blue; Rhodamine 6G; Fick’s law; Diffusion; Image analysis; Agar; Fick's law
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2012.03.024

► The diffusion of rhodamine 6G and methylene blue dyes in agar gels was investigated. ► Experiments were run at 30, 50, and 70°C until equilibrium was reached. ► A Fickian approach was used to analyse and model the experimental data. ► Diffusion depended on temperature and size of the diffusing molecule. ► Diffusion coefficients were estimated and values agreed with literature. An experimental set-up and a measurement technique were developed so that diffusion in model foods (gels of agar) could be visualised and quantified. The diffusion of aqueous solutions of varying concentrations of two dyes (rhodamine 6G and methylene blue) in gels of agar was followed in situ at three temperatures (30, 50, 70°C) until equilibrium was reached. The nature of the diffusion process (in terms of the amount of dye diffused into the gel) was studied using image analysis techniques. The diffusion coefficient, D, was estimated using Fick’s second law of diffusion and found to be ∼10−10m2s−1. The effect of the size of the diffusing molecule, as well as that of the processing temperature on diffusion was investigated and found to be significant.