Milk Components by in-Line Fiber Optic Probe-Based FT-NIR: Commercial Scale Evaluation of a Potential Alternative Measurement Approach for Milk Payment

BACKGROUND Mid-infrared (MIR) spectroscopy has traditionally been used to determine the macronutrients in bovine milk, as the basis of milk payment. Recent studies have demonstrated that NIR/FT-NIR spectroscopic systems can not only achieve MIR measurement performance, but are also generally simpler, more robust, and thus much more amenable to actual industrial process applications. OBJECTIVE The goal of this unique study was to investigate the feasibility of in-line FT-NIR spectroscopy for milk fat, protein, and total solids (TS) determination in a large industrial dairy processing facility, as an alternative basis for milk payment. METHOD Multivariant chemometric models using partial least squares (PLS) regression were built to predict the milk components. Over 1000 composite FT-NIR results gathered from the milk unloading process were compared directly to independent third-party FT-IR results. RESULTS Accuracy, precision, and linearity of the method were shown by Standard Error of Prediction (SEP) and Range/SEP of individual components. The SEP for fat, protein, and TS models were 0.09, 0.11, and 0.52, respectively. Range/SEP were 25.10, 12.60, and 6.40 for fat, protein, and TS, respectively. Accuracy and precision for the three components were further evaluated by the mean differences (0.01, 0.05, and 0.51) from dairy FT-IR results and the standard deviations of the mean difference (0.09, 0.09, and 0.13). Robustness was demonstrated by evaluating milk with natural variation over 6 months and using multiple instrumentation setups. The repeatability was also evaluated. CONCLUSIONS Overall, the in-line FT-NIR technology was found to have accurate, reliable, consistent performance similar to dairy FT-IR technology.