The microheater is a novel heat exchanger that is made in quartz, which has been developed to speed up process and product design through faster screening. Industrial time-temperature profiles can be mimicked, while the measurement time is short and sample volumes required are very small. The first step undertaken was validation of the microheater, using off-line turbidity measurements. As a model system, denaturation/aggregation kinetics of whey protein isolate (WPI) was investigated. The microheater operates at overall heat transfer coefficients of similar to 600-1000 W m(-2) K-1, and it enabled to distinguish between different kinetic models at a given temperature. In addition, the temperature dependency of the kinetics was also investigated; atypical value would bean Arrhenius constant of around 100kJ mol(-1) K-1 for the observed changes in turbidity. Finally, an in-line measurement cell was added to the set-up to allow continuous measurement of the turbidity. Promising results were obtained with this set-up, which indicate that faster measurements are within reach, and with this, process and product development can become considerably less time-consuming. (C) 2008 Elsevier Ltd. All rights reserved.