In-line use of near infrared spectroscopy to measure structure parameters of frozen model sorbet

In a continuous freezer/extrusion process on-line viscosity and conductivit y measurements in frozen model sorbet were carried out. On-line viscosity m easurements were based on the pressure difference in the extruder exit Ligh t-microscopy (off-line), conductivity (on-line), viscosity (on-line) and th e measurement of exit temperature were used to calibrate an on-line NIR spe ctrometer with a light fibre probe introduced in the product flow. Based on these calibrations, on-line NIR measurements of viscosity and ice crystal size in continuously produced model sorbet were carried out. A first qualit ative check of elaborated NIR-models has been carried out successfully. (C) 1999 Published by Elsevier Science Limited All rights reserved.