Detection of Adulteration of Goat Milk with Cow Milk Based on β-Carotene Analysis
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Abstract:
The fraudulent practice of substituting goat milk with cow milk is prevalent in the dairy industry. The level of β-carotene in cow milk is much higher than that in goat milk; hence, a quantitative analysis was established using high-performance liquid chromatography for the detection of adulteration of goat milk with cow milk, using the β-carotene level in the milk as a characteristic variable. Milk samples were saponified and extracted with petroleum ether, washed, and concentrated. Subsequently, the sample was eluted on a Shimadzu shim-pack VP-ODS C18 column (4.6 × 150 mm, 5 μm) by using methanol-acetonitrile-chloroform as the mobile phase and a detection wavelength of 450 nm. The variation range of β-carotene in pure cow and goat milk was used to construct the mixing ratio linear curve to perform quantitative analysis. The results showed that the recovery rates of this method were between 89.46% and 98.19%, while the relative standard deviations were between 1.50% and 2.79%. During the main production season, from April to September, the range of β-carotene levels in pure cow milk and goat milk was 0.08~0.13 μg/g and 1.9×10-3~2.2×10-3 μg/g, respectively. Linear correlation coefficients were between 0.9958 and 0.9988, whereas the relative errors of blind samples were between 2.20% and 4.75%. The results suggest that the method using β-carotene as a characteristic variable to evaluate the mixing ratio of cow milk in goat milk is feasible.
