Abstract
Simple SummaryInformation about fatty acid proportions in milk fat is important for many purposes, such as animal breeding, animal health control, as well as human nutrition. The routine methods for determining fatty acid proportions (e.g., mid-infrared spectroscopy) are rapid and relatively cheap, but there is a need to compare them with the reference analytical method (gas chromatography) to ensure their validity and suitability for various milk samples. The aim of this study is to compare the proportions of single fatty acids and their sums determined by utilizing both of these analytical methods and the resulting correlation coefficients. Our results show that the mid-infrared spectroscopy method is more appropriate (both for bulk and individual milk samples) for fatty acids present in high proportions of the total fat and for the sum of fatty acids (such as saturated and unsaturated) than for fatty acids with low proportions.Rapid analytical methods can contribute to the expansion of milk fatty acid determination for various important practical purposes. The reliability of data resulting from these routine methods plays a crucial role. Bulk and individual milk samples (60 and 345, respectively) were obtained from Czech Fleckvieh and Holstein dairy cows in the Czech Republic. The correlation between milk fatty acid (FA) proportions determined by the routine method (infrared spectroscopy in the mid-region in connection with Fourier transformation; FT-MIR) and the reference method (gas chromatography; GC) was evaluated. To validate the calibration of the FT-MIR method, a linear regression model was used. For bulk milk samples, the correlation coefficients between these methods were higher for the saturated (SFAs) and unsaturated FAs (UFAs) (r = 0.7169 and 0.9232; p < 0.001) than for the trans isomers of UFAs (TFAs) and polyunsaturated FAs (PUFAs) (r = 0.5706 and 0.6278; p < 0.001). Similar results were found for individual milk samples: r = 0.8592 and 0.8666 (p < 0.001) for SFAs and UFAs, 0.1690 (p < 0.01) for TFAs, and 0.3314 (p < 0.001) for PUFAs. The correlation coefficients for TFAs and PUFAs were statistically significant but too low for practical analytical application. The results indicate that the FT-MIR method can be used for routine determination mainly for SFAs and UFAs.
Highlights
Comprehensive knowledge of the composition and properties of milk provides useful insight for many purposes, such as ensuring milk quality, animal health management, dairy cattle breeding, and benefiting the dairy industry in general
The highest variabilities were found for the polyunsaturated FAs (PUFAs) and trans isomers of UFAs (TFAs) in bulk milk samples, where RSDs were 46.1 and 28.2% (FT-MIR) and 19.9 and 26.4% (GC)
Regarding mean values [1,23,24,48], the more accurate PUFA proportions were determined by gas chromatography (GC) (3.5%) than those found by FT-MIR (6.6%)
Summary
Comprehensive knowledge of the composition and properties of milk provides useful insight for many purposes, such as ensuring milk quality, animal health management, dairy cattle breeding, and benefiting the dairy industry in general. This IM (FT-NIR) usually gives results with a slightly less tight relationship to DM (in terms of analysis of liquid, raw, and consumer milk) than for the MIR- and FT-MIR-specialized methods with flow measurement cells for milk due primarily to the absence of the mechanical homogenization procedure for milk fat globules in most of the FT-NIR instruments. The aim of this work is to evaluate the parameters of FT-MIR calibrations according to the GC results for MFAP measurements and validate the predictive reliability of the routine method under defined experimental conditions to extend the spectrum of relevant analytical and methodological knowledge
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