Development of Infrared Prediction Models for Diffusible and Micellar Minerals in Bovine Milk

Abstract

Milk and dairy products are major sources of minerals in human diet. Minerals influence milk technological properties; in particular, micellar and diffusible minerals differentially influence rennet clotting time, curd firmness and curd formation rate. The aim of the present study was to investigate the ability of mid-infrared spectroscopy to predict the content of micellar and diffusible mineral fractions in bovine milk. Spectra of reference milk samples (n = 93) were collected using Milkoscan™ 7 (Foss Electric A/S, Hillerød, Denmark) and total, diffusible and micellar content of minerals were quantified using inductively coupled plasma optical emission spectrometry. Backward interval partial least squares algorithm was applied to exclude uninformative spectral regions and build prediction models for total, diffusible and micellar minerals content. Results showed that backward interval partial least squares analysis improved the predictive ability of the models for the studied traits compared with traditional partial least squares approach. Overall, the predictive ability of mid-infrared prediction models was moderate to low, with a ratio of performance to deviation in cross-validation that ranged from 1.15 for micellar K to 2.73 for total P.

Keywords: diffusible; infrared; micellar; milk; mineral; spectroscopy.

Figure 1

Spectral regions selected using backward interval partial least squares analysis. (I) Ca, (II) P, (III) K, (IV) Mg, (V) Na. (Black) full spectrum (mean); (green) total mineral (mg/100 mL); (blue) micellar mineral (mg/100 mL); (red) diffusible mineral (mg/100 mL); (orange) ratio between micellar and diffusible fractions (w/w). Absorbance is given in arbitrary units (AU).