Correlations between chemical assays and near-infrared reflectance spectroscopy for nutrient components and correlations between nutrients and color scores of distillers dried grains with solubles

Abstract

The objective of this research was to evaluate the correlations between chemical assay and near-infrared reflectance spectroscopy (NIRS) for the nutrient content of distillers dried grains with solubles (DDGS) samples. The samples were analyzed by NIRS or wet chemical procedures. Color [CIE lightness (L*), redness (a*), and yellowness (b*)] characteristics of the samples were measured in triplicates with a chroma meter. Highest CV were observed for fiber fragments in wheat DDGS and for fat in corn DDGS among the nutrients tested. Correlation coefficients showed good agreement between NIRS and wet methods for the determination of selected nutrients except DM. Strong negative correlations were found between ash and ADF (-0.811), ash and NDF (-0.649), and ash and CF (-0.757) when determined by wet analyses. Phosphorus and gross energy had negative correlations with fiber fragments. The values for a* were found to be inversely correlated to the CF, ADF, and NDF contents found in both methods. On the contrary, there was a positive correlation between a* values and ash content in both methods. Positive correlations also were found between fat content and L* and b* values of the ingredients. Negative correlations were found between b* value and CP, Arg, Ile, Gly, and Pro levels. Based on these results, NIRS is a reliable method depending on the calibration quality, and the correlations found among nutrients and between color and nutrients must be taken into consideration to predict nutrient content of DDGS. No antibiotic residue was found in the samples.