Polyphosphates are important functional additives used in meats and other food products. They control the loss of natural juices, reduce susceptibility to freeze burn and cook losses by increasing water binding capacity of the products due to the increased pH and ionic strength. The objectives of this study were to investigate the phosphate diffusion in beef dipped in sodium tripolyphosphate solutions (STP) and to experimentally determine the fundamentals of the phosphate diffusion under these conditions. For this objective, the beef samples were dipped for 90 min in different concentrations of STPs (0%, 2%, 4%, and 6%, w/v) and analyzed for their phosphate content changes using a modified spectrophotometric ammonium molybdate method. The analysis was accomplished in both meat samples and solutions. Naturally occurred orthophosphates in meats and STPs in the solutions resulted in a counter-current diffusion. The phosphate content of the meats started to decrease to a certain time before showing an increase. On the contrary, phosphate content of the solutions regularly increased during dipping due to the diffusion of orthophosphates from the meat samples. Using these, the diffusion coefficient of STPs was determined for the different stages of dipping time. The results showed that the diffusion of phosphates may be analyzed using their phosphate content changes to determine the diffusion coefficient of STPs to accomplish further diffusion and optimization related research. (C) 2004 Elsevier Ltd. All rights reserved.