Abstract: The invention relates to a system for the on-line measurement of a parameter in a processing stream. The system comprises a scanning head mounted adjacent a continuous stream of processed material, the scanning head comprising a remote light source and reflected light gathering and transmission apparatus; a near infrared spectrophotometer which includes a monochromator for resolving the reflected light into light of a discrete wavelength; a database containing a reference calibration equation linking absorption characteristics by wavelength and the quantified presence of the parameter of interest; and a computer for measuring the parameter by application of the calibration equation to the obtained spectrum for a sample and managing said system. The invention also comprises a method of on-line measurement of a parameter in a processing stream by NIR spectroscopy and networks comprising systems according to the invention.