Milk skin
Encyclopedia
Milk skin refers to a sticky film of protein
that forms on top of milk
and milk-containing liquids (such as hot chocolate and some soups). It is caused by the denaturation
of proteins such as casein
.
When milk is boiled, soluble milk proteins are denatured and then aggregate and form a sticky film across the top of the liquid, which then dries by evaporation
.
In Japan
, a dairy product called So
was made from layers of milk skin during the 7th-10th centuries. So was further processed to make Daigo.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
that forms on top of milk
Milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...
and milk-containing liquids (such as hot chocolate and some soups). It is caused by the denaturation
Denaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...
of proteins such as casein
Casein
Casein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....
.
When milk is boiled, soluble milk proteins are denatured and then aggregate and form a sticky film across the top of the liquid, which then dries by evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
.
In Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, a dairy product called So
So (Dairy)
So was a type of dairy product made in Japan between 7th and 10th centuries. The method of creation is noted in Engishiki as So acted as a gift in kind to the emperors. Daigo, a type of cheese, was produced by further processing So.-Summary:...
was made from layers of milk skin during the 7th-10th centuries. So was further processed to make Daigo.