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Qualitative identification of mature milk adulteration in bovine colostrum using noise-reduced dielectric spectra and linear model.

BACKGROUND
The rapid and accurate identification of colostrum, a strong non-homogeneous food, remains a challenge. In this study, the dielectric spectra including dielectric constant (ε') and loss factor (ε″) of 154 colostrum samples adulterated with 0-50% mature milk were measured from 20 to 4500 MHz.


RESULTS
The results showed that the noise-reducing spectral preprocessing, including Savitzky-Golay (S-G), second derivative (SD), and S-G+SD, was significantly better than scattering-eliminating, including standard normal variate (SNV), multiplicative scatter correction (MSC), and SNV+MSC. The combination of S-G and SD was the best. Principal component analysis (PCA) results demonstrated that dielectric spectroscopy is less susceptible to the inhomogeneity of colostrum and can be used to identify doped colostrum. The identification performance of linear models was better than that of nonlinear models. The established linear discriminant analysis (LDA) model based on full spectra had the best accuracy rates of 99.14% and 97.37% in the calibration and validation sets, respectively. Confirmatory tests on samples from different sources proved the satisfactory robustness of the proposed model.


CONCLUSION
We found that the main unfavorable effect on the identification based on dielectric spectroscopy was noise interference, rather than scattering effect caused by inhomogeneity of colostrum. The satisfactory results undoubtedly cast light on rapid detection of strongly non-homogeneous foods based on dielectric spectroscopy. This article is protected by copyright. All rights reserved.