Thickening agent
Overview
 
"Thickener" redirects here. For a separation method see gravity separation
Gravity separation
Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: ie the components of the mixture have different specific weight. All of the gravitational methods are common...

.


Thickening agents, or thickeners, is the term applied to substances which increase the viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 of a solution or liquid/solid mixture without substantially modifying its other properties; although most frequently applied to foods where the target property is taste
Taste
Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....

, the term also is applicable to paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

s, ink
Ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...

s, explosives, etc.
Discussions
Encyclopedia
"Thickener" redirects here. For a separation method see gravity separation
Gravity separation
Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: ie the components of the mixture have different specific weight. All of the gravitational methods are common...

.


Thickening agents, or thickeners, is the term applied to substances which increase the viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 of a solution or liquid/solid mixture without substantially modifying its other properties; although most frequently applied to foods where the target property is taste
Taste
Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....

, the term also is applicable to paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

s, ink
Ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...

s, explosives, etc. Thickeners may also improve the suspension
Suspension (chemistry)
In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...

 of other ingredients or emulsion
Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...

s which increases the stability of the product. Thickening agents are often regulated as food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

s and as cosmetics
Cosmetics
Cosmetics are substances used to enhance the appearance or odor of the human body. Cosmetics include skin-care creams, lotions, powders, perfumes, lipsticks, fingernail and toe nail polish, eye and facial makeup, towelettes, permanent waves, colored contact lenses, hair colors, hair sprays and...

 and personal hygiene product ingredients. Some thickening agents are gelling agents, forming a gel
Gel
A gel is a solid, jelly-like material 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...

, dissolving in the liquid phase as a colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...

 mixture that forms a weakly cohesive internal structure. Others act as mechanical thixotropic
Thixotropy
Thixotropy is the property of certain gels or fluids that are thick under normal conditions, but flow over time when shaken, agitated, or otherwise stressed...

additives with discrete particles adhering or interlocking to resist strain
Strain
Strain can refer to:* Strain , variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes* Strain , a chemical stress of a molecule...

.

Food

Food thickeners frequently are based on either Polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

s (starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

es, vegetable gums, and pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...

), or protein
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...

s. A flavorless powdered starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

 used for this purpose is a fecula (from the Latin faecula, diminutive of faex meaning "dregs"). This category includes starches as arrowroot
Arrowroot
Arrowroot, or obedience plant , Bermuda arrowroot, araru, ararao, is a large perennial herb found in rainforest habitats...

, cornstarch
Cornstarch
Corn starch, cornstarch, cornflour or maize starch is the starch of the corn grain obtained from the endosperm of the corn kernel.-History:...

, katakuri starch
Erythronium japonicum
Katakuri is a species of lily native to Japan, Korea and northeastern China.-Uses:Katakuri starch, or katakuriko , is a starch originally processed from the corm of katakuri. Despite having kuri , lit...

, potato starch
Potato starch
Potato starch is starch extracted from potatoes. The cells of the root tubers of the potato plant contain starch grains . To extract the starch, the potatoes are crushed; the starch grains are released from the destroyed cells...

, sago
Sago
Sago is a starch extracted in the spongy center or pith, of various tropical palm stems, Metroxylon sagu. It is a major staple food for the lowland peoples of New Guinea and the Moluccas, where it is called saksak and sagu. A type of flour, called sago flour, is made from sago. The largest supply...

, tapioca
Tapioca
Tapioca is a starch extracted Manihot esculenta. This species, native to the Amazon, Brazil, Colombia, Venezuela, Cuba, Puerto Rico, Haiti, the Dominican Republic, Honduras, and most of the West Indies, is now cultivated worldwide and has many names, including cassava, manioc, aipim,...

 and their starch derivatives
Modified starch
Modified starch, also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch, thereby changing the properties of the starch. Modified starches are used in practically all starch applications, such as in food products as a thickening agent,...

. Vegetable gums used as food thickeners include alginin
Alginic acid
Alginic acid, also called algin or alginate, is an anionic polysaccharide distributed widely in the cell walls of brown algae, where it, through binding water, forms a viscous gum. In extracted form it absorbs water quickly; it is capable of absorbing 200-300 times its own weight in water. Its...

, guar gum
Guar gum
Guar gum, also called guaran, is a galactomannan. It is primarily the ground endosperm of guar beans. The guar seeds are dehusked, milled and screened to obtain the guar gum. It is typically produced as a free-flowing, pale, off-white-colored, coarse to fine ground powder.-Production:Guar gum is an...

, locust bean gum
Locust bean gum
Locust bean gum is a galactomannan vegetable gum extracted from the seeds of the carob tree, mostly found in the Mediterranean region. The long pods that grow on the tree are used to make this gum. The pods are kibbled to separate the seed from the pulp...

, and xanthan gum
Xanthan gum
Xanthan gum is a polysaccharide, derived from the bacterial coat of Xanthomonas campestris, used as a food additive and rheology modifier, commonly used as a food thickening agent and a stabilizer...

. Proteins used as food thickeners include collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

, egg white
Egg white
Egg white is the common name for the clear liquid contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms around either fertilized or unfertilized egg yolks...

s, furcellaran, and gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...

. Sugars include agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...

 and carrageenan
Carrageenan
Carrageenans or carrageenins are a family of linear sulfated polysaccharides that are extracted from red seaweeds. There are several varieties of carrageen used in cooking and baking. Kappa-carrageenan is used mostly in breading and batter due to its gelling nature...

. Other thickening agents act on the proteins already present in a food. One example is sodium pyrophosphate
Sodium pyrophosphate
Tetrasodium pyrophosphate, also called sodium pyrophosphate, tetrasodium phosphate or TSPP, is a colorless transparent crystalline chemical compound with the formula Na4P2O7. It contains the pyrophosphate ion and sodium cation. Toxicity is approximately twice that of table salt when ingested...

, which acts on 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....

 in milk during the preparation of instant pudding
Pudding
Pudding most often refers to a dessert, but it can also be a savory dish.In the United States, pudding characteristically denotes a sweet milk-based dessert similar in consistency to egg-based custards, though it may also refer to other types such as bread and rice pudding.In the United Kingdom and...

.

Different thickeners may be more or less suitable in a given application, due to differences in taste, clarity, and their responses to chemical and physical conditions. For example, for acidic foods, arrowroot
Arrowroot
Arrowroot, or obedience plant , Bermuda arrowroot, araru, ararao, is a large perennial herb found in rainforest habitats...

 is a better choice than cornstarch
Cornstarch
Corn starch, cornstarch, cornflour or maize starch is the starch of the corn grain obtained from the endosperm of the corn kernel.-History:...

, which loses thickening potency in acidic mixtures. At (acidic) pH levels below 4.5, guar gum has sharply reduced aqueous solubility, thus also reducing its thickening capability. If the food is to be frozen, tapioca or arrowroot are preferable over cornstarch, which becomes spongy when frozen.

Many other food ingredients are used as thickeners, usually in the final stages of preparation of specific foods. These thickeners have a flavor and are not markedly stable, thus are not suitable for general use. However, they are very convenient and effective, and hence are widely used.

Functional flour
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...

s are produced from specific cereal variety (wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

, maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

, rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 or other) conjugated to specific heat treatment able to increase stability, consistency and general functionalities. These functional flours are resistance to industrial stresses such as acidic pH, sterilisation, freeze conditions, and can help food industries to formulate with natural ingredients. For the final consumer, these ingredients are more accepted because they are shown as "flour" in the ingredient list.

Flour is often used for thickening gravies
Gravy
Gravy is a sauce made often from the juices that run naturally from meat or vegetables during cooking. In North America the term can refer to a wider variety of sauces and gravy is often thicker than in Britain...

, gumbo
Gumbo
Gumbo is a stew or soup that originated in southern Louisiana during the 18th century. It consists primarily of a strongly-flavored stock, meat or shellfish, a thickener, and the vegetable holy trinity of celery, bell peppers, and onions...

s, and stew
Stew
A stew is a combination of solid food ingredients that have been cooked in liquid and served in the resultant gravy. Ingredients in a stew can include any combination of vegetables , meat, especially tougher meats suitable for slow-cooking, such as beef. Poultry, sausages, and seafood are also used...

s. It must be cooked in thoroughly to avoid the taste of uncooked flour. Roux
Roux
Roux is a cooked mixture of wheat flour and fat, traditionally butter. It is the thickening agent of three of the mother sauces of classical French cooking: sauce béchamel, sauce velouté and sauce espagnole. Clarified butter, vegetable oils, or lard are commonly used fats. It is used as a...

, a mixture of flour and fat (usually butter) cooked into a paste, is used for gravies, sauce
Sauce
In cooking, a sauce is liquid, creaming or semi-solid food served on or used in preparing other foods. Sauces are not normally consumed by themselves; they add flavor, moisture, and visual appeal to another dish. Sauce is a French word taken from the Latin salsus, meaning salted...

s and stews. Cereal grains (oatmeal
Oatmeal
Oatmeal is ground oat groats , or a porridge made from oats . Oatmeal can also be ground oat, steel-cut oats, crushed oats, or rolled oats....

, couscous
Couscous
Couscous is a Berber dish of semolina traditionally served with a meat or vegetable stew spooned over it. Couscous is a staple food throughout Algeria, Morocco and Tunisia.-Etymology:...

, farina
Farina (food)
Farina is a cereal food, frequently described as mild-tasting, usually served warm, made from cereal grains. In contemporary American English use, the word usually refers to Cream of Wheat made from soft wheat. Wheat farina is a carbohydrate-rich food, often cooked in boiling water and served warm...

, etc.) are used to thicken soup
Soup
Soup is a generally warm food that is made by combining ingredients such as meat and vegetables with stock, juice, water, or another liquid. Hot soups are additionally characterized by boiling solid ingredients in liquids in a pot until the flavors are extracted, forming a broth.Traditionally,...

s. Yogurt is popular in Eastern Europe and Middle East for thickening soups. Soups can also be thickened by adding grated starchy vegetables before cooking, though these will add their own flavour. Tomato puree also adds thickness as well as flavour. Egg yolk
Egg yolk
An egg yolk is a part of an egg which feeds the developing embryo. The egg yolk is suspended in the egg white by one or two spiral bands of tissue called the chalazae...

s are a traditional sauce thickener in professional cooking; they have rich flavor and offer a velvety smooth texture but achieve the desired thickening effect only in a narrow temperature range. Overheating easily ruins such a sauce, which can make egg yolk difficult to use as a thickener for amateur cooks. Other thickeners used by cooks are nuts
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

 (including rehan) or glaces
Demi-glace
Demi-glace is a rich brown sauce in French cuisine used by itself or as a base for other sauces. The term comes from the French word glace, which used in reference to a sauce means icing or glaze...

 made of meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...

 or fish
Fish (food)
Fish is a food consumed by many species, including humans. The word "fish" refers to both the animal and to the food prepared from it. Fish has been an important source of protein for humans throughout recorded history.-Terminology:...

.

Many thickening agents require extra care in cooking. Some starches lose their thickening quality when cooked for too long or at too high a temperature; on the other hand, cooking starches too short or not hot enough might lead to an unpleasant starchy taste or cause water to seep out of the finished product after cooling. Also, higher viscosity causes foods to burn more easily during cooking. As an alternative to adding more thickener, recipes may call for reduction of the food's water content by lengthy simmering
Simmering
Simmering is a food preparation technique in which foods are cooked in hot liquids kept at or just below the boiling point of water , but higher than poaching temperature...

. When cooking, it is generally better to add thickener cautiously; if over-thickened, more water may be added but loss of flavour and texture may result.

Gelling agents are food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

s used to thicken and stabilize various foods, like jellies
Gelatin dessert
Gelatin desserts are desserts made with sweetened and flavored gelatin. They can be made by combining plain gelatin with other ingredients or by using a premixed blend of gelatin with additives...

, dessert
Dessert
In cultures around the world, dessert is a course that typically comes at the end of a meal, usually consisting of sweet food. The word comes from the French language as dessert and this from Old French desservir, "to clear the table" and "to serve." Common Western desserts include cakes, biscuits,...

s and candies
Candy
Candy, specifically sugar candy, is a confection made from a concentrated solution of sugar in water, to which flavorings and colorants are added...

. The agents provide the foods with texture through formation of a gel
Gel
A gel is a solid, jelly-like material 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...

. Some stabilizers and thickening agents are gelling agents.

Typical gelling agents include natural gum
Natural gum
Natural gums are polysaccharides of natural origin, capable of causing a large viscosity increase in solution, even at small concentrations. In the food industry they are used as thickening agents, gelling agents, emulsifying agents, and stabilizers...

s, starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

es, pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...

s, agar-agar and gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...

. Often they are based on polysaccharides or proteins.

Examples are:
  • Alginic acid
    Alginic acid
    Alginic acid, also called algin or alginate, is an anionic polysaccharide distributed widely in the cell walls of brown algae, where it, through binding water, forms a viscous gum. In extracted form it absorbs water quickly; it is capable of absorbing 200-300 times its own weight in water. Its...

     (E400), sodium alginate (E401), potassium alginate (E402), ammonium alginate (E403), calcium alginate
    Calcium alginate
    Calcium alginate is a water-insoluble, gelatinous, cream coloured substance that can be created through the addition of aqueous calcium chloride to aqueous sodium alginate. Adding artificial flavours and colours creates a more tasty edible slime...

     (E404) - polysaccharides from brown algae
  • Agar
    Agar
    Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...

     (E406, a polysaccharide obtained from red algae
    Algae
    Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

    s)
  • Carrageenan
    Carrageenan
    Carrageenans or carrageenins are a family of linear sulfated polysaccharides that are extracted from red seaweeds. There are several varieties of carrageen used in cooking and baking. Kappa-carrageenan is used mostly in breading and batter due to its gelling nature...

     (E407, a polysaccharide obtained from red seaweed
    Seaweed
    Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...

    s)
  • Locust bean gum
    Locust bean gum
    Locust bean gum is a galactomannan vegetable gum extracted from the seeds of the carob tree, mostly found in the Mediterranean region. The long pods that grow on the tree are used to make this gum. The pods are kibbled to separate the seed from the pulp...

     (E410, a natural gum
    Natural gum
    Natural gums are polysaccharides of natural origin, capable of causing a large viscosity increase in solution, even at small concentrations. In the food industry they are used as thickening agents, gelling agents, emulsifying agents, and stabilizers...

     polysaccharide from the seeds of the Carob tree
    Carob tree
    Ceratonia siliqua, commonly known as the Carob tree and St John's-bread, is a species of flowering evergreen shrub or tree in the pea family, Fabaceae...

    )
  • Pectin
    Pectin
    Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...

     (E440, a polysaccharide obtained from apple or citrus-fruit)
  • Gelatin
    Gelatin
    Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...

     (E441, made by partial hydrolysis of animal collagen
    Collagen
    Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

    )


Commercial jellies used in East Asian cuisine
Asian cuisine
Asian cuisine styles can be broken down into several tiny regional styles that have roots in the peoples and cultures of those regions. The major types can be roughly defined as East Asian with its origins in Imperial China and now encompassing modern Japan and the Korean peninsula; Southeast Asian...

s include the glucomannan
Glucomannan
Glucomannan is a water-soluble polysaccharide that is considered a dietary fiber. Glucomannan is a food additive used as an emulsifier and thickener. Products containing glucomannan, marketed under a variety of brand names, are also sold as nutritional supplements for constipation, obesity, high...

 polysaccharide gum used to make "lychee cups" from the konjac
Konjac
Konjac , also known as konjak, konjaku, konnyaku potato, devil's tongue, voodoo lily, snake palm, or elephant yam , is a plant of the genus Amorphophallus...

 plant, and aiyu or ice jelly
Aiyu jelly
Aiyu jelly , known as ice jelly in Singapore , is a jelly made from the gel from the seeds of a variety of fig found in Taiwan and East Asian countries of the same climates and latitudes...

 from the Ficus pumila
Ficus pumila var. awkeotsang
Ficus pumila var. awkeotsang is a member of the fig family and a variety of Ficus pumila. The plant is sometimes grown in close proximity to Betel nut palms thus providing a tall trunk, which the fig uses as a support to climb.-Use:...

climbing fig plant.

Food thickening can be important for people facing medical issues with chewing or swallowing
Swallowing
Swallowing, known scientifically as deglutition, is the process in the human or animal body that makes something pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration...

, as foods with a thicker consistency can reduce the chances of choking
Choking
Choking is the mechanical obstruction of the flow of air from the environment into the lungs. Choking prevents breathing, and can be partial or complete, with partial choking allowing some, although inadequate, flow of air into the lungs. Prolonged or complete choking results in asphyxia which...

, or of inhalation of liquids or food particles, which can lead to aspiration pneumonia
Aspiration pneumonia
Aspiration pneumonia is bronchopneumonia that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents...

.

Mechanical and thixotropic agents

Fumed silica
Fumed silica
Fumed silica, also known as pyrogenic silica because it is produced in a flame, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk...

 and similar products form stiff microscopic chains or fibers which interlock or agglomerate into a mass, holding the associated liquid by surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...

, but which can separate or slide when sufficient force is applied. This causes the thixotropic or shear-thinning property (also frequently exhibited by gels), where the viscosity is non-newtonian and becomes lower as the shearing force or time increases; their usefulness is primarily that the resulting increase in viscosity is large compared to the quantity of silica added. Fumed silica is generally accepted as safe
Gras
Gras is a commune in the Ardèche department in southern France.-Population:-References:*...

 as a food additive and is frequently used in cosmetics. Additives such as precipitated silica
Precipitated silica
-Production:The production of precipitated silica starts with the reaction of an alkaline silicate solution with a mineral acid. Sulfuric acid and sodium silicate solutions are added simultaneously with agitation to water. Precipitation is carried out under alkaline conditions...

, fine talc
Talc
Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg34 or Mg3Si4O102. In loose form, it is the widely-used substance known as talcum powder. It occurs as foliated to fibrous masses, its crystals being so rare as to be almost unknown...

, or chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

 also meet the definition of thickening agent in that they increase viscosity and body while not affecting the target property of a mixture.

Cosmetics

Thickening agents used in cosmetics or personal hygiene products include viscous liquids such as polyethylene glycol
Polyethylene glycol
Polyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. It has also been known as polyethylene oxide or polyoxyethylene , depending on its molecular weight, and under the tradename Carbowax.-Available forms:PEG, PEO, or POE refers to an...

, synthetic polymers such as carbomer
Carbomer
In organic chemistry, a carbomer is an expanded molecule obtained by insertion of a C2 unit in a given molecule. Carbomers differ from their templates in size but not in symmetry when each C–C single bond is replaced by at least one alkyne bond, and when a double bond is replaced by an allene bond...

 (a trade name for polyacrylic acid
Polyacrylic acid
Poly or PAA or Carbomer is a type of anionic polymer. The monomer of poly is acrylic acid. In a water solution at neutral pH, many of the side chains of PAA will lose their protons and acquire a negative charge. This makes PAA a polyelectrolyte.Dry PAA is a white solid...

) and vegetable gums. Some thickening agents may also function as stabilizers
Stabilizers
The Stabilizers were an American pop/rock duo founded in the early 1980s by musicians Dave Christenson and Rich Nevens. With Christenson on lead vocals and Nevens on guitars and occasional keyboards, they spent the first few years touring the Pennsylvania area and recording original compositions on...

 when they are used to maintain the stability of an emulsion
Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...

. Some emollients, such as petroleum jelly
Petroleum jelly
Petroleum jelly, petrolatum, white petrolatum or soft paraffin, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons , originally promoted as a topical ointment for its healing properties...

 and various wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...

es may also function as thickening agents in an emulsion.

Paint and printing thickeners

One of the main use of thickeners is in the paint and printing industries. For example, acrylic thickener is the main item used in both textile printing with water base and water base paints. Also, polyvenyle co-polymer and homopolymer are thickeners that can be used in the paint industries.

Petrochemistry

In petrochemistry, gelling agents, also called solidifiers, are chemicals capable of reacting with oil spill
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...

s and forming rubber-like solids. The gelled coagulated oil then can be removed from the water surface by skimming, suction devices, or nets. Calm or only moderately rough sea is required.

Explosives and incendiaries

Various materials are used to convert liquid explosives to a gel form. Nitrocellulose
Nitrocellulose
Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton...

 and other nitro esters
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

 are often used. Other possibilities include nitrated guar gum
Guar gum
Guar gum, also called guaran, is a galactomannan. It is primarily the ground endosperm of guar beans. The guar seeds are dehusked, milled and screened to obtain the guar gum. It is typically produced as a free-flowing, pale, off-white-colored, coarse to fine ground powder.-Production:Guar gum is an...

.

Many fuels used in incendiary device
Incendiary device
Incendiary weapons, incendiary devices or incendiary bombs are bombs designed to start fires or destroy sensitive equipment using materials such as napalm, thermite, chlorine trifluoride, or white phosphorus....

s require thickening for increased performance. Aluminium salts of fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

s are frequently used. Some formulations (e.g. Napalm
Napalm
Napalm is a thickening/gelling agent generally mixed with gasoline or a similar fuel for use in an incendiary device, primarily as an anti-personnel weapon...

-B) use polymeric thickeners, namely polystyrene
Polystyrene
Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...

. Hydroxyl aluminium bis(2-ethylhexanoate)
Hydroxyl aluminium bis(2-ethylhexanoate)
Hydroxyl aluminium bis is a chemical substance derived from 2-ethylhexanoic acid and aluminium. Nominally it is the coordination complex with the formula Al2 where Et = ethyl. The composition is not a homogeneous compound. It is used as a thickening agent in various products, including in napalm....

 is also used. Thickened pyrophoric agent, a pyrophoric replacement of napalm, is a triethylaluminium
Triethylaluminium
Triethylaluminium is an organoaluminium compound. This volatile, colorless liquid is highly pyrophoric, igniting immediately upon exposure to air. It is normally stored in stainless steel containers either as a pure liquid or as a solution in hydrocarbon solvents such as hexane, heptane, or ...

 thickened with polyisobutylene.

External links

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