Main nutritional components of butter

Butter products are broadly classified as sweet cream unsalted, sweet cream salted, cultured unsalted, cultured salted butter, or traditional sour cream butter.

Butter is principally composed of milk fat, moisture, salt and curd. It also contains small amount of fat, lactose, acids, phospholipids, air, microorganisms, enzymes and vitamins.

The nutrition facts for 1 tablespoon (14 grams) of salted butter are:
Water: 16%
Protein: 0.12 grams
Carbs: 0.01 grams
Sugar: 0.01 grams
Fiber: 0 grams
Fat: 11.52 grams
Monounsaturated: 2.99 grams
Polyunsaturated: 0.43 grams
Trans: 0.47 grams

Butter is considered as high calorie food as 100 g of butter provides almost 700 Kcal. Butter has a saturated fat content around 51.4%, with saturated fats, such as palmitic and stearic acid, which are double the concentration of those in cream and other dairy products. However, stearic acid is beneficial to health and lowers the level of low-density lipoprotein (LDL) in blood.

Butyric acid is at a greater concentration in butter than other short chain fatty acids (SCFAs). It causes a rancid off-flavor in butter, which is undesirable during storage. However, phospholipids have many biological activities which are essential for human health.

The presence of carotene in natural butter is a source of important nutrition for human beings. Carotene benefits various parts of the body. It promotes cell regrowth and repair, protecting the body from various infections.
Main nutritional components of butter 

Casein component in milk

Milk contains two major protein groups: caseins and whey proteins. Caseins, which occupy about 80% of the total protein in bovine milk, exist mainly in macromolecular complexes as casein micelles consisting of more than 1000 casein submicelles.

The casein proteins are the major component of milk true protein and are comprised of alpha S1 (αS1), alpha S2 (αS2), beta (β), kappa (κ), gamma (γ) caseins. Γ-casein is a product of the proteolytic degradation of β casein.

As caseins are polyelectrolytes, they are very susceptible to changes in pH. They have, in general, an isoelectric point in the region of pH 4.6. Changing the pH of skimmed milk from ~6.7 (natural pH) to 4.6 causes the caseins to self-aggregate on a macroscopic scale.

Caseins are known to be precursors of a number of different bioactive peptides. Casein is a group of phosphoproteins and consists of about 30 different components including genetic variants.

The casein micelle determines the colloidal stability of the polydisperse system in milk. The dimension and composition of casein micelles are of great importance for the coagulation process.
Casein component in milk 

Fat in Milk

Fat in Milk
Fat and associated lipid materials are present in milk as an emulsion of small individual globules in an aqueous phase. These fat globules are predominantly in the liquid state at 37 degree. The fat globules vary in size from about 0.1 to 10 um in diameter.

Surrounding each milk fat globule is a membrane composed of cholesterol, phospholipids, proteins, and other surface-active molecules. The fat globules membrane appears to have two layers: an inner layer that contains a phospholipids-protein complex, and an outer layer that contains enzymes originating in the mammary gland.

The membrane serves to prevent individual fat globules from combining with other to form a larger globule. Mechanical agitation can lead to a disruption of the membrane and thus cause the individual fat globules to coalesce to form larger globules and eventually to form butter. Disruption of the globule membrane may also contribute to the development of rancid flavor in milk.

Milk fat is made up of approximately 12.5% glycerol and 85.5% fatty acids by weight. The predominant glycerides are triglycerides (8-99%); diglycerides account for 0.05%; and monoglycerides for 0.04% of the total. These glycerides contain more than 16 different fatty acids combined with glycerol in a number of different ways.

The principal fatty acids contain an even number of carbon atoms. Milk fat is unique in that it is the only natural food fat that contains butyric acid in its glycerides structure. This fatty acid has a strong characteristics odor. Their release from triglycerides during lipolysis is the cause of rancid odor and flavor in milk.

Milk fat contains a number of minor components. Among these are free fatty acids, cholesterol, phospholipids, and the fat soluble vitamins.
Fat in Milk

Composition of Milk

Composition of Milk
The average gross composition of cow’s milk is as follows:

• Water – 87%
  
• Fat – 3.7%
  
• Lactose – 4.9%
  
• Proteins – 3.5%
• Ash – 0.7%

However, the composition of milk from individual cows may vary considerably from these average values. Breed differences, the time of year, the time of day, individual differences, the age of the cow, the period of lactation, the portion of any one milking, feeding, etc., are some factors that may contribute to variation in the composition of milk.

Variation in milk composition due to breed are of the greatest magnitude. Jersey, Guernsey and Ayrshire cows gives milk richer in fat than Holstein cows. Usually milk obtained in the fall and early winter is richer than obtained in the spring and the summer. The morning milk usually is richer in fat than evening milk, at times by almost 2%.

The first portion (or fore milk) of milk drawn in the milking process are lower in fat than the last portions (or strippings). Milk obtained the first few days after calving is known as colostrum and differs materially from normal milk. During the final stages of lactation, when the daily production of milk is decreasing, there is some increase in percentages of fat and casein. The differences in milk composition occur mainly in the relative amounts of fat, protein, and water. The percentages of ash and lactose remain fairly constant in normal milk regardless of the amount of other components.
Composition of Milk