Milk Adulteration Testing

Milk is a wholesome nutritious dairy product and is consumed by a majority of the population worldwide. However, milk products are frequently adulterated to meet the increasing demand from consumers, or to increase profit. Adulterations invariably reduce the quality of milk products and may cause serious health hazards for consumers. Thus, it is essential for detecting milk adulterants to comply with regulatory requirements and protect consumer health.

Some of the common adulterations of milk products include substitution with cheaper and lower quality milk, addition of vegetable proteins, whey protein, vegetable oil, or addition of water. Some types of adulterations may even cause severe threat for human health, such as addition of nitrogen-rich adulterants (e.g., urea and melamine), preservatives, neutralizers, and so on. Lifeasible, as a leading food testing company worldwide, provides a wide range of adulterant detection services using state-of-the-art techniques, which include, but not limited to: 

Detection of milk from different sources

Milk is often adulterated by mixing lower valued milk with higher valued milk for greater profit. For example, cow milk is often adulterated by mixing with buffalo, bovine, ovine or caprine milk. Moreover, the geographical origins of milk are also frequently adulterated. These adulterations can be detected by chromatographic methods (e.g., high performance liquid chromatography/electrospray ionization-mass spectroscopy (HPLC/ESIMS) and solid-phase microextraction-mass spectrometry (SPME-MS)), spectroscopic methods (e.g., inductively coupled plasma emission spectroscopy (ICP-OES), DNA-based methods (e.g., real-time PCR and high resolution melting (HRM)), immunological methods (e.g., enzyme-linked immunosorbent assay (ELISA), biosensor), electromigration methods (e.g., polyacrylamide gel electrophoresis (PAGE) and capillary electrophoresis (CE)), and so on.

Detection of foreign proteins

Milk is often adulterated by low priced non-milk proteins such as soy, pea, almond, and wheat proteins. These proteins are not only 70% less value than normal milk, but also may cause food allergies. These adulterations can also be detected by chromatographic methods (e.g., reverse-phase high-performance liquid chromatography (RP-HPLC)), spectroscopic methods (e.g., near infrared (NIR) spectroscopy), DNA-based methods, immunological methods, electromigration methods and so on, as described above.

Detection of reconstituted milk

It is also common for adulteration of fresh milk with reconstituted milk such as cheap powdered milk and whey proteins. The existence of dry milk and whey protein can be detected based on the ratio of β-casein to α-lactalbumin, or the ratio of whey protein to casein, and/or glycomacropeptide (GMP), respectively. These ratios can be measured by CE and NIR spectroscopy.

Detection of water and compensation with other chemicals

The addition of water in milk can decrease milk nutritious value. Therefore, some chemicals are added to compensate the density, color, and nitrogen content after dilution with water, which can be a severe risk for human health. The water content in milk can be determined by biosensor, electronic nose, freezing point determination by thermistor cryoscopy, glass transition temperature (Tg) measurement through differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and so on.

Chlorine is often added to compensate for the density of the water-diluted milk. Chlorine can be detected by sequential injection analysis (SIA) based on titration with silver cation and/or flow injection analysis (FIA) based on pseudo titrations.

Urea is added to milk to increase non-protein nitrogen content. Urea is harmful to heart, liver, and kidneys. Urea can be detected by the potentiometric biosensor which uses an NH₄⁺ ion sensitive electrode as the transducer. It can also be detected by the manometric biosensor which measures carbon dioxide partial pressure. Urea in milk can also be detected by calorimetric method and optical biosensors.

Similar to urea, melamine is often added to increase protein content. The intake of melamine can induce the formation of kidney stones and further trigger kidney dysfunctions. Different types of mass spectroscopy (e.g., LC-MS/MS, atmospheric pressure chemical ionization-mass spectroscopy (APCIMS) and extractive electrospray ionization mass spectrometry (EESI-MS)) and spectroscopy (e.g., surface enhanced Raman spectroscopy (SERS), single bounce attenuated total reflectance-Fourier transform infrared spectroscopy (SB-ATR FTIR) techniques have been employed to detect melamine in milk products.

Detection of vegetable oil or animal fats

Because milk fat is of high values, it is frequently admixed or replaced with cheaper vegetable oils or animal fats. To detect the addition of foreign oils or fats, we adopt multiple precise and highly efficient spectroscopic methods such as fluorescence spectroscopy and NIR spectroscopy. In addition, we also provide triacylglycerols (TAGs) profile analysis using gas chromatography (GC) to detect foreign fats.

Detection of preservatives and neutralizers

Hydrogen peroxide (H₂O₂), boric acid, formalin (HCHO), and sodium azide are used as milk preservatives, which can preserve the milk for a longer time. However, under-regulated addition of preservatives may have poisonous effects on human. Sodium carbonate (Na₂CO₃), sodium bicarbonate (NaHCO₃), and caustic soda (NaOH), which can cause hypertension and heart ailments, are commonly used to neutralize the acidic effect. E-tongue is used to detect H₂O₂, and rosalic acid test is a common test to detect Na₂CO₃/NaHCO₃, and HCHO in milk.

Discrimination of organic and non-organic milk

Organic milk refers to milk products free of antibiotics, growth hormones, or pesticides. Lifeasible provides multiple advanced and reliable techniques, such as the chromatography and isotopic ratio mass spectrometry (IRMS) techniques, to discriminate organic and non-organic milk.

With full-fledged techniques and excellent experts, Lifeasible can provide you with customized services with superior quality. You can benefit from our milk adulteration testing services with accurate results, short turn-around times, and competitive prices. Welcome to contact us for technical consults, inquiries, and any further information.