Determining the cold-spot in packaged foods is a critical step to ensure commercial sterility of the processed products in developing novel thermal processes. In dielectric heating (i.e. heating with microwave and radio frequency energy), the cold-spot is different from that of conventional heating. Chemical marker methods can be used to map heating patterns within foods systems. This study determined the kinetic parameters of the M-1 formation in whey protein gels at sterilization temperatures. Pre-formed whey protein gels containing 2% glucose sealed in capillary tubes were heated for different time intervals in oil baths at 116, 121, 126 and 131 degreesC. M-1 yields were determined by high performance liquid chromatography. Modified two-step, multi-linear and nonlinear regression analyses were conducted to determine the kinetic parameters of marker formation. Kinetic parameters were validated with experiments using a pilot-scale radio frequency sterilization system. M-1 formation followed a first order kinetics. The predicted M-1 yields based on the kinetics model agreed with experimental results. Accurate kinetic parameters for M-1 formation should enable us to use M-1 for developing and validating advanced thermal processes. (C) 2003 Elsevier Ltd. All rights reserved.