title: Effectiveness of mid-infrared spectroscopy to predict the color of bovine milk and the relationship between milk color and traditional milk quality traits.
abstract: The color of milk affects the subsequent color features of the resulting dairy products; milk color is also related to milk fat concentration. The objective of the present study was to quantify the ability of mid-infrared spectroscopy (MIRS) to predict color-related traits in milk samples and to estimate the correlations between these color-related characteristics and traditional milk quality traits. Mid-infrared spectral data were available on 601 milk samples from 529 cows, all of which had corresponding gold standard milk color measures determined using a Chroma Meter (Konica Minolta Sensing Europe, Nieuwegein, the Netherlands); milk color was expressed using the CIELAB uniform color space. Separate prediction equations were developed for each of the 3 color parameters (L*=lightness, a*=greenness, b*=yellowness) using partial least squares regression. Accuracy of prediction was determined using both cross validation on a calibration data set (n=422 to 457 samples) and external validation on a data set of 144 to 152 samples. Moderate accuracy of prediction was achieved for the b* index (coefficient of correlation for external validation=0.72), although poor predictive ability was obtained for both a* and L* indices (coefficient of correlation for external validation of 0.30 and 0.55, respectively). The linear regression coefficient of the gold standard values on the respective MIRS-predicted values of a*, L*, and b* was 0.81, 0.88, and 0.96, respectively; only the regression coefficient on L* was different from 1. The mean bias of prediction (i.e., the average difference between the MIRS-predicted values and gold standard values in external validation) was not different from zero for any of 3 parameters evaluated. A moderate correlation (0.56) existed between the MIRS-predicted L* and b* indices, both of which were weakly correlated with the a* index. Milk fat, protein, and casein were moderately correlated with both the gold standard and MIRS-predicted values for b*. Results from the present study indicate that MIRS data provides an efficient, low-cost screening method to determine the b* color of milk at a population level.
authors.affiliation: Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland; Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy.
authors.forename: A
authors.initials: A
authors.lastname: McDermott
authors.affiliation: Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland; Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy.
authors.forename: G
authors.initials: G
authors.lastname: Visentin
authors.affiliation: Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland.
authors.forename: S
authors.initials: S
authors.lastname: McParland
authors.affiliation: Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland.
authors.forename: D P
authors.initials: DP
authors.lastname: Berry
authors.affiliation: Teagasc, Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland.
authors.forename: M A
authors.initials: MA
authors.lastname: Fenelon
authors.affiliation: Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova, Viale dell'Università 16, 35020 Legnaro (PD), Italy. Electronic address: massimo.demarchi@unipd.it.
authors.forename: M
authors.initials: M
authors.lastname: De Marchi
mesh_terms: D000818:Animals; D002138:Calibration; D002364:Caseins; D002417:Cattle; D005260:Female; D008892:Milk / Q000737:chemistry*; D010641:Phenotype; D013055:Spectrophotometry, Infrared / Q000662:veterinary*
chemical_list: D002364:Caseins
keywords: Fourier transform infrared; cow milk; grazing system; yellowness