Reproducibility and repeatability of milk coagulation properties predicted by mid-infrared spectroscopy

The objective of this study was to assess reproducibility and repeatability of milk coagulation properties (MCP) predicted by mid-infrared spectroscopy (MIRS). Individual milk samples from a single dairy herd were collected during 8 sampling dates, added with preservative (Bronopol) and analysed in two laboratories. Ten cows were randomly selected within each sampling date. Rennet coagulation time (RCT, min) and curd firmness (a30, mm) were predicted in the two laboratories using MIRS. Besides predicting MCP through MIRS, RCT and a30 were measured by Formagraph. Reproducibilities of RCT and a30 predicted by MIRS were 67.3 and 71.9%, respectively. Repeatabilities of RCT and a30 predicted by MIRS and determined by Formagraph were 92.8 and 95.8%, and 98.6 and 95.8%, respectively. Results indicated that MIRS predictions of MCP are repeatable, but not highly reproducible. Further efforts are needed to improve the standardisation among laboratories to enhance reproducibility.