The near-infrared optic probe for monitoring rennet coagulation in cow's milk

A near-infrared (NIR) reflectance optic probe and a coagulometer (thermal probe) were used for monitoring rennet coagulation of milk from individual cows. Completed near-infrared spectral information (1100-2500 nm) was registered at 2 min intervals for up to 50 min after renneting, which led to a pool of 1300 spectra. The data were analyzed by partial least squares (PLS) and after application of the second derivative, the standard error of calibration and the correlation coefficient were 0.20 and 0.94. The standard error of prediction was 0.36 with a correlation coefficient of 0.87. The study shows that NIR reflectance is a reliable method for monitoring milk coagulation. Furthermore, NIR technology provides a better estimate of the coagulation profile than the coagulometer (thermal probe). (C) 1998 Elsevier Science Ltd. All rights reserved.