Milk composition
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Key Components of Milk Composition
Milk is a complex mixture containing water, fat, proteins (mainly casein and whey proteins), lactose (milk sugar), minerals, vitamins, enzymes, and a wide range of other bioactive compounds. The main constituents in cow’s milk are typically about 3.3–3.4% protein, 4.0–4.5% fat, and 4.6–4.8% lactose, with the remainder being water and minerals such as calcium, magnesium, and phosphorus 234. Human milk also contains these components, but the exact proportions and types of bioactive molecules can differ and are influenced by many factors 89.
Milk Fat Composition and Structure
Milk fat is present as emulsified globules, making up about 3.5–5% of bovine milk. Most of the fat is in the form of triacylglycerols, with smaller amounts of phospholipids and sterols, such as cholesterol. The fatty acid profile includes short-chain (C4:0 to C10:0), medium-chain, and some long-chain fatty acids, with unique structural arrangements that are not easily altered by ordinary dietary changes 25. The fat globule membrane contains phospholipids and proteins, which play roles in milk stability and nutrition 25.
Protein and Carbohydrate Content
The major proteins in milk are casein and whey proteins. In cow’s milk, casein makes up about 2.5–2.6% and whey proteins about 0.7–0.8% . Lactose, the main carbohydrate, is present at about 4.6–4.8% in cow’s milk . These components are important for both the nutritional value and the technological properties of milk and dairy products 234.
Minerals, Vitamins, and Bioactive Compounds
Milk contains essential minerals such as calcium, magnesium, phosphorus, selenium, and iodine. The levels of some minerals, like selenium and iodine, have increased in certain regions over time . Vitamins, enzymes, and other bioactive molecules are also present, contributing to the health benefits of milk 24.
Variability in Milk Composition
Seasonal and Geographic Variation
Milk composition is not static. Many components, including fat, protein, and minerals, show significant seasonal variation, often influenced by changes in feed and environmental conditions 13. Geographic differences also exist, affecting the levels of certain nutrients and bioactive compounds 13.
Influence of Diet and Feeding
The cow’s diet can rapidly alter milk composition, especially the fat content. Factors such as the amount of roughage, forage-to-concentrate ratio, and lipid supplements can significantly change milk fat levels, while protein and lactose are less affected by diet . Accurate prediction of these changes is complex due to the many interacting factors involved .
Human Milk: Biological and Methodological Influences
Human milk composition is highly variable, influenced by maternal diet, infant factors (such as age and birth weight), and methodological aspects of milk collection and analysis 68. Lipids and lipid-soluble components show the greatest variability, while other nutrients are more stable. Standardizing analytical methods is important for accurate comparisons .
Advances in Milk Composition Analysis
Modern analytical techniques, such as nuclear magnetic resonance (NMR), liquid chromatography-mass spectrometry (LC-MS), and mid-infrared (MIR) spectrometry, have enabled the identification and quantification of hundreds of milk metabolites and components, providing a more comprehensive understanding of milk’s chemical complexity 47. These advances support improved breeding, management, and nutritional strategies in dairy production .
Conclusion
Milk is a nutritionally rich and chemically complex fluid, with its composition influenced by species, diet, season, geography, and individual biological factors. Advances in analytical methods have greatly expanded our understanding of milk’s components, supporting both nutritional science and dairy industry practices. Understanding and managing the variability in milk composition is key to optimizing its nutritional value and processing qualities for both human and animal consumption 12345678+2 MORE.
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