Understanding Milk: Composition, Properties, and Quality

Milk, a staple beverage in many diets, appears white or yellowish due to the interaction of light with its components. The color of milk results from the scattering and absorption of light by milk fat globules and protein micelles. This is why skim milk, which has minimal fat, still retains its white hue. The yellowish tint in milk can be attributed to carotene, absorbed from the diet during grazing, present in the fat phase, and riboflavin in the aqueous phase.

Milk's flavor profile is mildly sweet with a faint odor and taste. Milk fat is present as droplets or globules, surrounded by a membrane and emulsified in milk serum, also known as whey. These fat globules tend to separate and float to the top as cream after prolonged storage or centrifugation. However, homogenization breaks these fat globules into much smaller sizes, preventing cream separation even after long periods of standing.

The proteins in milk, known as micelles, are dispersed within the milk serum. These micelles are primarily calcium salts of casein molecules. Additionally, milk contains lipoprotein particles, or milk microsomes, which include remnants of cell membranes and microvilli, as well as somatic cells, mainly leucocytes. Various proteins, carbohydrates, minerals, and other ingredients are dissolved in the milk serum.

The specific density of milk, which ranges from 1.029 to 1.039 at 15°C, varies with its composition. Higher fat content decreases the density, while higher amounts of protein, milk sugar, and salts increase it. Skim milk, having most of the fat removed, possesses a higher specific density compared to whole milk.

One notable property of milk is its freezing point, which ranges from -0.53 to -0.55°C. This relatively constant value is useful for detecting adulteration, such as the addition of water to milk.

In summary, milk's unique characteristics, from its color and taste to its density and freezing point, result from its complex composition of fats, proteins, carbohydrates, and minerals. Understanding these properties not only highlights the nutritional importance of milk but also ensures its quality and authenticity in the food industry.
Understanding Milk: Composition, Properties, and Quality