Predicting cutting and clotting time of coagulating goat's milk using diffuse reflectance: effect of pH, temperature and enzyme concentration

A diffuse reflectance sensor, which used optical fibres and near-infrared radiation (NIR) at 880 nm, was used to monitor goat's milk coagulation. A randomised block design replicated three times was utilized to test the effects of pH, temperature and enzyme concentration on diffuse reflectance parameters. Milk pH was adjusted to three levels (5.5, 6.0 and 6.5) and coagulated at three different temperatures (28, 32 and 36 degreesC), using three enzyme concentrations (0.020, 0.035 and 0.050 mL kg(-1) of milk). A linear cutting time prediction equation, T-cut = betaT(max), was found to predict visual cutting time with a standard error of prediction of 84.5 s and an R-2 of 0.9785. beta was affected by pH, temperature and enzyme concentration. The diffuse reflectance parameter (T-max) was strongly correlated to the Berridge clotting time (R-2 = 0.9913). Parameters generated from the diffuse reflectance profiles, with the exception of response-based parameters, were found to be a function of coagulation rate. (C) 2001 Elsevier Science I;td. All rights reserved.