At-Line Near-Infrared Spectroscopy for Prediction of the Solid Fat Content of Milk Fat from New Zealand Butter

Abstract

Near-infrared (NIR) spectroscopy calibrations that will allow prediction of the solid fat content (SFC) of milk fat extracted from butter by one measurement during manufacture were developed. SFC is a measure of the amount of the solid fraction of fat crystallized at a temperature expressed as a percentage (w/w). At-line SFC determinations are currently performed by nuclear magnetic resonance (NMR) spectroscopy, which involves a 16 h delay period for tempering of the milk fat at 0 degrees C prior to the SFC measurements, from 0 to 35 degrees C in a series of 5 degrees C increments. The NIR spectra (400-2500 nm) were obtained using a sample holder maintained at 60 degrees C. Accurate predictions for the SFC (%) were developed by principal component analysis (PCA) and partial least-squares (PLS) regression models to relate the NIR spectra to the corresponding NMR values. The independent validation samples (N = 22) had a standard error of prediction (SEP) of 0.385-0.762% for SFC between 0 and 25 degrees C, with SFC reference values ranging between 70.42 and 8.96% with a standard deviation range of 3.36-1.47. The low bias (from -0.351 to -0.025), the slopes (0.935-1.077), and the excellent predictive ability (R2; 0.923-0.978) supported the validity of these calibrations.