Determination of the ice-glaze content of fish and other seafood products depends today on batch samples from the production line. A non-contact scheme (denoted the enthalpy-method), based on infrared measurement of temperature changes of the product, has previously been introduced in the literature. In this paper the method is compared to the conventional CODEX procedure during regular online production. Especially, the ability to detect unwanted temporal variations in the glazing percentage is focused on. Two cases are studied. Firstly, the glazing process is monitored during stationary conditions. Secondly, an abrupt change in the glazing level is induced and the steady-state and dynamic properties of both methods are investigated. It is concluded that the enthalpy method is superior to the CODEX procedure and has the potential to be a key element in an automatic control system for the glazing percentage of cold-water prawns. (C) 2001 Elsevier Science Ltd. All rights reserved.