Amino acids are the building blocks of all proteins, and each individual protein contains its own specific sequence of amino acid molecules. Amino acids are connected to one another by peptide bonds. Twenty two amino acids are used to make proteins and they are linked together in chains to form different proteins.
Proteins in Milk
The average total protein in milk is about 3.3 percent of its total weight. Both the total amount of protein and the composition of the amino acids will vary depending on the breed of cow and the cow's individual genetic makeup. Milk is made up of two main types of protein -- casein and whey. These two categories of milk proteins are loosely defined based on their chemical makeup and physical properties. On average, 82 percent of the protein in cow's milk is casein and 18 percent is whey. Both the casein family of proteins and the whey family of proteins contain multiple different types of proteins.
Amino Acids
Amino acids are broken down into two main types -- essential amino acids and nonessential amino acids. Essential amino acids are those that cannot be made by the human body and therefore must be obtained through your diet. Nonessential amino acids can be synthesized by your body, and you are not required to get them from food, although many of them are present in foods.
The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. All of these can be found in milk proteins. The 13 nonessential amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, cystine, glutamic acid, glutamine, glycine, hydroxyproline, proline, serine and tyrosine.
Amino Acid Content of Milk
According to the Food and Agriculture Organization of the United Nations, pasteurized cow's milk contains the following amounts of amino acids, expressed as mg/100 g of milk: 219 mg isoleucine, 430 mg leucine, 248 mg lysine, 86 mg methionine, 239 mg phenylalanine, 218 mg tyrosine, 153 mg threonine, 255 mg valine, 88 mg arginine, 118 mg histidine, 140 mg alanine, 233 mg aspartic acid, 633 mg glutamic acid, 79 mg glysine, 283 mg proline and 188 mg serine.
Amount of Protein Needed Daily
Most healthy adults need 0.8 grams of protein per kilogram of body weight (a kilogram equals 2.2 lbs.). On average, requirements for protein are between 45 and 60 g/day total. Certain people may have higher and more individualized protein needs, including infants, children, pregnant women, convalescent patients and people experiencing hemorrhage, burns and protein malnutrition or recovering from surgery or wounds.
Member Comments