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Decoding Casein: The Natural Nutritional Treasure Hidden in Breast Milk

2025-12-04
Casein, also known as cheese protein, caseinogen or whey protein, is a protein abundant in mammalian milk. Its notable characteristic is its sensitivity to acid; it will precipitate in an environment with a lower pH value. In milk, casein accounts for approximately 80% of the total protein content and is the dominant protein; in human milk, this proportion is about 30%, although it is less than that in milk, it is still a core component for infant nutrition supply. 

This protein is suspended in the emulsion in the form of casein micelles. Each micelle is formed by the polymerization of approximately 20,000 casein molecules, presenting as colloidal spherical particles with an average diameter of around 100 nanometers. The currently accepted scientific model of casein micelle structure is the Holt model (nanocluster model), which posits that within the micelle, there is a micro-cluster complex formed by the entanglement and connection of calcium phosphate and casein molecules, with a precise and stable structure. 

Based on the differences in molecular properties, casein is mainly divided into four types: αs1-CN, αs2-CN, β-CN and κ-CN. The molecular weights of these four monomers are all within the range of 20 kDa to 25 kDa. 

The content and composition ratio of casein in the milk of different mammals show significant differences. Human milk does not contain α-CN, while β-CN is the main component, accounting for approximately 70% of the total casein content; in cow's milk, the content of αs1-CN is the highest, accounting for about 45% of the total casein. These compositional differences directly affect its digestive properties and nutritional adaptability.
2.Nutritious nutrients for nurturing life - Casein
Casein is a complete protein that contains the 8 essential amino acids for the human body. Its amino acid composition is highly compatible with the human body's requirements, making it of high nutritional value. Unlike some proteins that need to be denatured beforehand for digestion, casein can be directly hydrolyzed by the protease in the human body without any additional processing, resulting in a higher efficiency of digestion and absorption. 

The unique advantage of casein lies in its mineral carrier function. It can combine with metal ions such as calcium and iron, especially calcium ions, to form soluble complexes. This characteristic brings two benefits: on the one hand, it prevents calcium from forming insoluble precipitates in the acidic or slightly alkaline environment of the small intestine, ensuring the effective retention of calcium; on the other hand, even without the participation of vitamin D, it can promote the absorption of calcium by intestinal wall cells, significantly improving the utilization efficiency of minerals. 

For infants and young children, casein is an essential nutrient foundation in their growth process. It is not only the main source of essential amino acids, but also an important channel for providing calcium and phosphorus. What's more, casein forms soft curds in the stomach of infants and young children, which is a more suitable form for their delicate digestive systems, facilitating efficient absorption of nutrients. 

Furthermore, casein can also be broken down by proteases into various small bioactive peptides. These peptide segments possess multiple physiological activities, such as anti-cancer, anti-microbial, assisting in regulating blood pressure, antioxidation, lowering cholesterol, regulating the balance of intestinal flora, and enhancing immune function, providing multi-dimensional protection for human health.
3.Multifunctional raw materials in the food industry 

With its rich nutritional value and unique physical and chemical properties, casein has been continuously expanding its application scope in the field of food processing and has become a practical multi-functional raw material.

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