Many people, when they see dark particles in their glass of milk, will think it is dirt, mold or unhygienic milk production. If you type the phrase “black particles in powdered milk” on the Google search engine to find the answer to what it is, most of the results lead to negative interpretations such as “moldy milk”, “spoiled milk”, “milk with impurities”.
However, after eliminating causes such as foreign objects and mold, it is possible that the dark and black particles in the glass of milk are actually scorched particles, appearing during the drying process – a common technical phenomenon of powdered milk. Scorched particles are colored spots of small powder particles ranging in color from yellow, orange, brown to black, formed by the drying process of milk at high temperatures, also known as products of the Maillard reaction. Depending on the drying temperature, these seeds will have a color ranging from yellow-brown to black (the higher the temperature, the darker the color).
In terms of chemistry, the Maillard reaction is a series of chemical reactions that occur between nitrogen-containing compounds (mainly proteins in milk) and reducing sugars (here lactose in milk) when they are exposed to high enough temperatures for a certain period of time. The products of this reaction produce dark brown compounds that cause the milk particles to turn light brown, brown, to black, depending on the degree of overheating they are subjected to.
The origin of the formation of these scorched particles is directly associated with the spray drying process – a common process in the production of milk powder. In this process, liquid milk is sprayed in a fine mist into a large drying chamber, where hot air evaporates the water, leaving behind dry milk particles. During that process, a small part of the powder particles may come into direct contact with the high heat area, leading to slight scorching. Although manufacturers always strictly control temperature and drying time, high temperature is still a mandatory condition to ensure the product is completely dry, microbiologically safe and has a long shelf life.
Powdered milk for children. Image: But Nga
To distinguish burnt elements from mold and foreign impurities, people can refer to the following: Dark grains due to burnt elements come from the Maillard reaction (sugar – protein) when powdered milk is overheated. These particles are characterized by small particles identical to milk powder, small in size, color from light yellow to brown or black, and dissolve more slowly in water than the rest of the milk powder.
Mold particles or foreign impurities (such as pieces of plastic, metal, insects) often have distinctly different shapes and colors (silk threads, bright hard, irregular white-blue-black) or hard, bright, sharp surfaces and do not dissolve in milk.
According to ADPI analytical standards, “impurities” in powdered milk are defined to include foreign materials such as dust, hair, metal, wood, and insect corpses. These materials often have physical characteristics (hard, shiny, brittle) or colors that are easily distinguishable from particles burned by heat.
Most nutrition experts confirm that burnt milk grains are not harmful to users and do not affect the nutritional value or safety of milk. Burnt milk particles are not bacteria, not mold, and not heavy metals or harmful chemicals.
The amount of burnt particles in powdered milk is very small (usually only a few thousandths of the powder volume), and does not affect the overall nutritional value of the product. Milk manufacturers always strictly control drying temperatures to ensure burnt ingredients are kept to a minimum, complying with international food safety standards.