Syneresis (also spelled 'synæresis' or 'synaeresis'), in chemistry, is the

extraction Extraction may refer to: Science and technology Biology and medicine * Comedo extraction, a method of acne treatment * Dental extraction, the surgical removal of a tooth from the mouth Computing and information science * Data extraction, the pr ...

or expulsion of a

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, ...

from a

gel A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still di ...

, such as when

serum Serum may refer to: * Serum (blood), plasma from which the clotting proteins have been removed **Antiserum, blood serum with specific antibodies for passive immunity * Serous fluid, any clear bodily fluid *Truth serum, a drug that is likely to mak ...

drains from a contracting clot of

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

. Another example of syneresis is the collection of

whey Whey is the liquid remaining after milk has been curdled and strained. It is a byproduct of the manufacturing of cheese or casein and has several commercial uses. Sweet whey is a byproduct resulting from the manufacture of rennet types of har ...

on the surface of

yogurt Yogurt (; , from tr, yoğurt, also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as ''yogurt cultures''. Fermentation of sugars in the milk by these bac ...

. Syneresis can also be observed when the amount of diluent in a swollen

polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

exceeds the solubility limit as the temperature changes. A household example of this is the counterintuitive expulsion of water from dry

gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...

when the temperature increases. Syneresis has also been proposed as the mechanism of formation for the amorphous silicate composing the

frustule A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on ...

diatom A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...

Examples

In the processing of dairy

milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulat ...

, for example during

cheese making Cheesemaking (or caseiculture) is the craft of making cheese. The production of cheese, like many other food preservation processes, allows the nutritional and economic value of a food material, in this case milk, to be preserved in concentrat ...

, syneresis is the formation of the

curd Curd is obtained by coagulating milk in a sequential process called curdling. It can be a final dairy product or the first stage in cheesemaking. The coagulation can be caused by adding rennet or any edible acidic substance such as l ...

due to the sudden removal of the

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are n ...

macropeptides, which causes an imbalance in intermolecular forces. Bonds between

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, ...

sites start to develop and are enforced by

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

bonds, which form as the water molecules in the micelles start to leave the structure. This process is usually referred to as the phase of coagulation and syneresis. The splitting of the bond between residues 105 and 106 in the κ-casein molecule is often called the primary phase of the

rennet Rennet () is a complex set of enzymes produced in the stomachs of ruminant mammals. Chymosin, its key component, is a protease enzyme that curdles the casein in milk. In addition to chymosin, rennet contains other enzymes, such as pepsin an ...

action, while the phase of coagulation and syneresis is referred to as the secondary phase. In cooking, syneresis is the sudden release of moisture contained within protein molecules, usually caused by excessive heat, which over-hardens the protective shell. Moisture inside expands upon heating. The hard protein shell pops, expelling the moisture. This process is responsible for transforming juicy rare steak into dry steak when cooked thoroughly. It creates weeping in scrambled eggs, with dry protein curd swimming in the released moisture. It also causes emulsified sauces, such as hollandaise, to "break". Additionally, it creates unsightly moisture pockets within baked

custard Custard is a variety of culinary preparations based on sweetened milk, cheese, or cream cooked with egg or egg yolk to thicken it, and sometimes also flour, corn starch, or gelatin. Depending on the recipe, custard may vary in consistency fr ...

dishes, such as flan or crème brûlée. In dentistry, syneresis is the expulsion of water or other liquid molecules from dental impression materials (for instance, alginate) after an impression has been taken. Due to this process, the impression shrinks a little and therefore its size is no longer accurate. For this reason, many dental impression companies strongly recommend to pour the dental cast as soon as possible to prevent distortion of the dimension of the teeth and objects in the impression. The opposite process of syneresis is imbibition, which is the process of a material absorbing water molecules from the surroundings. Alginate is also an example of imbibition because it will absorb water if soaked in it.

References

Chemical processes Chemical mixtures Colloidal chemistry {{Chem-stub

Examples

See also

References