Heat denaturation of beta-lactoglobulin was measured in the channels of a six-channels-per-pass plate heat exchanger (PHE) by use of an immunodiffusion method. Experimental results were successfully compared with numerical calculations involving the bulk temperature profile and the second-order denaturation kinetic of beta-lactoglobulin. The link between heat denaturation of beta-lactoglobulin and the fouling of the PHE was studied through the overall heat transfer coefficient and dry masses of deposit measurements. If appeared that mixing intensity in the PHE channels could give some answers to this problem. However the assumption that only proteins denaturated in the thermal boundary layer are involved in deposit formation was found not to be valid.