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 r adiation (NIR) at 880 nm, was used to monitor goat's milk coagulation. A ra ndomised block design replicated three times was utilized to test the effec ts of pH, temperature and enzyme concentration on diffuse reflectance param eters. Milk pH was adjusted to three levels (5.5, 6.0 and 6.5) and coagulat ed at three different temperatures (28, 32 and 36 degreesC), using three en zyme concentrations (0.020, 0.035 and 0.050 mL kg(-1) of milk). A linear cu tting time prediction equation, T-cut = betaT(max), was found to predict vi sual 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. T he diffuse reflectance parameter (T-max) was strongly correlated to the Ber ridge clotting time (R-2 = 0.9913). Parameters generated from the diffuse r eflectance 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.