How does the current method detect and add melamine and other substances to milk powder?
Currently, there are three main methods used for protein detection in food: Kjeldahl, Dumas, and infrared. The Kjeldahl method is the most widely used in the food industry. It measures the total nitrogen content in a sample and then estimates the protein content based on that. This method has been the standard for many years. However, it was first developed in 1883 and is not without its flaws. Despite being outdated, it's still commonly used because no better alternative has fully replaced it yet. The process is time-consuming, often taking several hours per sample, and involves handling dangerous chemicals like sulfuric acid, which must be heated to around 400°C. This makes it both slow and potentially hazardous.
The Dumas method is considered a more modern approach. It works by combusting the sample and measuring the nitrogen released. While this method is faster than Kjeldahl, it still has limitations. Since it burns the sample, it requires careful handling of all combustible materials, which can lead to safety concerns. Additionally, it’s not suitable for liquid samples or large volumes. Larger samples tend to cause more issues, which means users often have to limit the amount they test to ensure accurate results.
The third method is the infrared technique, which is a surface-based measurement. Although it's quick and non-destructive, it comes with its own challenges. Infrared instruments require frequent calibration, which demands a lot of calibration reagents. They also need regular cleaning and are sensitive to other components in the sample, making them less reliable for precise protein measurements.
None of these methods directly measure true protein. Both Kjeldahl and Dumas measure total nitrogen and convert it to protein content using a standard factor. However, this approach can be misleading. Non-protein nitrogen compounds, such as melamine, can also contribute to the measured nitrogen levels. Because of this, the presence of additives like melamine can artificially inflate protein readings. As a result, these methods may not detect adulterated products effectively. They might show high nitrogen levels, but they don’t confirm whether the nitrogen comes from actual protein or from harmful substances. This is why new, more accurate methods are needed to detect such contaminants and ensure food safety.
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