Many food processing operations involve mass transfer. The application of electric fields can influence the mass transfer properties of foods. A major limitation of infusion studies is the lack of successful measurement techniques to quantify the depth of penetration and localisation of infused material. Diffusion of two dyes (rhodamine 6G and methylene blue) in agar and alginate gels was visualised in situ for 10 min. The experiments were performed at three temperatures (30, 50, and 70 degrees C) and four voltage gradients (167, 333, 500, 667 V m(-1)) plus a control (0 V m(-1)). The effect of hydrocolloid concentration and electrical conductivity on diffusion and response to the electric field were tested. The limitations of Fickian analysis led to a new method of data analysis, the penetration model. The effect of the type of gel and the diffusing molecule charge and mass on the combined diffusion and electric field process is discussed. (C) 2011 Elsevier Ltd. All rights reserved.