Evaluation of mid-infrared spectroscopy as a technique for predicting coagulation properties of milk

This study aimed to investigate the application of mid-infrared spectroscopy (MIRS) as a tool for predicting milk coagulation properties (MCP). Experimental data were from 79 Holstein Friesian cows; 6 milk samples were collected from each cow, and half of them were added with Azidiol preservative. Samples were analyzed at 3 different times: at collection (T0), after 4 (T4) or 8 d (T8) of storage. Milk coagulation time (RCT,min) and curd firmness (a30,mm) were measured using Computerized Renneting Meter (CRM) on T0 samples with or without preservative. MIRS analyses on T0, T4 and T8 samples with or without preservative were performed using MilkoScan FT120. Prediction equations were estimated by PLSR (WINISI II version 1.02). The reference average RCT and a30 values were 15.2 min and 36.1 mm, respectively, with a variation coefficient of 0.26 and 0.23 respectively. Correlation coefficients between CRM and MIRS analysis were 0.78 and 0.67 for RCT and a30, respectively. MCP at different times predicted by MIRS were comparable, while the coefficients of determination in calibration and in cross validation were better in the milk sample added with preservative. In conclusion, MIRS allowed for a rapid and rather accurate analysis of the MCP of cow milk and could be proposed as a tool for recording milk coagulation properties on a large scale, such as within milk recording schemes.