Homogenization (chemistry)

Last updated

Homogenization or homogenisation is any of several processes used to make a mixture of two mutually non-soluble liquids the same throughout. This is achieved by turning one of the liquids into a state consisting of extremely small particles distributed uniformly throughout the other liquid. A typical example is the homogenization of milk, where the milk fat globules are reduced in size and dispersed uniformly through the rest of the milk. [1]

Contents

Definition

Homogenization (from "homogeneous;" Greek, homogenes: homos, same + genos, kind) [2] is the process of converting two immiscible liquids (i.e. liquids that are not soluble, in all proportions, one in another) into an emulsion [3] (Mixture of two or more liquids that are generally immiscible). Sometimes two types of homogenization are distinguished: primary homogenization, when the emulsion is created directly from separate liquids; and secondary homogenization, when the emulsion is created by the reduction in size of droplets in an existing emulsion. [3] Homogenization is achieved by a mechanical device called a homogenizer. [3]

Application

One of the oldest applications of homogenization is in milk processing. It is normally preceded by "standardization" (the mixing of several different milking herds and/or dairies to produce a more consistent raw milk prior to processing and to prevent, reduce and delay natural separation of cream from the rest of the emulsion). The fat in milk normally separates from the water and collects at the top. Homogenization breaks the fat into smaller sizes so it no longer separates, allowing the sale of non-separating milk at any fat specification.

Methods

Homogenizing valve, a method to homogenize at high pressure. Homogenizing valve.svg
Homogenizing valve, a method to homogenize at high pressure.

Milk homogenization is accomplished by mixing large amounts of harvested milk, then forcing the milk at high pressure through small holes. Yet another method of homogenization uses extruders, hammermills, or colloid mills to mill (grind) solids. Milk homogenization is an essential tool of the milk food industry to prevent creating various levels of flavor and fat concentration.

Another application of homogenization is in soft drinks like cola products. The reactant mixture is rendered to intense homogenization, to as much as 35,000 psi, so that various constituents do not separate out during storage or distribution.

See also

Related Research Articles

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 should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid is dispersed in the other. Examples of emulsions include vinaigrettes, homogenized milk, and some cutting fluids for metal working.

Phase (matter) Region of space (a thermodynamic system), throughout which all physical properties of a material are essentially uniform; region of material that is chemically uniform, physically distinct, (often) mechanically separable

In the physical sciences, a phase is a region of space, throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, magnetization and chemical composition. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water. The glass of the jar is another separate phase.

Solution A homogeneous mixture which assumes the phase of the solvent

In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation. The solution usually has the state of the solvent when the solvent is the larger fraction of the mixture, as is commonly the case. One important parameter of a solution is the concentration, which is a measure of the amount of solute in a given amount of solution or solvent. The term "aqueous solution" is used when one of the solvents is water.

Decantation a process for the separation of mixtures

Decantation is a process for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension. The layer closer to the top of the container—the less dense of the two liquids, or the liquid from which the precipitate or sediment has settled out—is poured off, leaving the other component or the more dense liquid of the mixture behind. An incomplete separation is witnessed during the separation of two immiscible liquids.

Xanthan gum food additive and thickener

Xanthan gum is a polysaccharide with many industrial uses, including as a common food additive. It is an effective thickening agent and stabilizer to prevent ingredients from separating. It can be produced from simple sugars using a fermentation process, and derives its name from the species of bacteria used, Xanthomonas campestris.

Fractionation chemical separation process

Fractionation is a separation process in which a certain quantity of a mixture is divided during a phase transition, into a number of smaller quantities (fractions) in which the composition varies according to a gradient. Fractions are collected based on differences in a specific property of the individual components. A common trait in fractionations is the need to find an optimum between the amount of fractions collected and the desired purity in each fraction. Fractionation makes it possible to isolate more than two components in a mixture in a single run. This property sets it apart from other separation techniques.

Therapeutic foods are foods designed for specific, usually nutritional, therapeutic purposes as a form of dietary supplement. The primary examples of therapeutic foods are used for emergency feeding of malnourished children or to supplement the diets of persons with special nutrition requirements, such as the elderly. For liquid nutrition products fed via tube feeding see Medical foods.

Whey protein Protein supplement

Whey protein is a mixture of proteins isolated from whey, the liquid material created as a by-product of cheese production. The proteins consist of α-lactalbumin, β-lactoglobulin, serum albumin and immunoglobulins. Whey protein is commonly marketed as a dietary supplement, and various health claims have been attributed to it. An authoritative review published in 2010 concluded that the provided literature did not adequately support the proposed claims. For muscle growth, whey protein has been shown to be slightly better compared to other types of protein, such as casein or soy.

Maytag Blue cheese

Maytag is a blue cheese produced on the Maytag Dairy Farms outside of Newton, Iowa, the former home of the Maytag Corporation. In 1938, Iowa State University independently developed a process for making blue cheese from homogenized cow's milk instead of the traditional sheep's milk.

Separatory funnel Laboratory glassware

A separatory funnel, also known as a separation funnel, separating funnel, or colloquially sep funnel, is a piece of laboratory glassware used in liquid-liquid extractions to separate (partition) the components of a mixture into two immiscible solvent phases of different densities. Typically, one of the phases will be aqueous, and the other a lipophilic organic solvent such as ether, MTBE, dichloromethane, chloroform, or ethyl acetate. All of these solvents form a clear delineation between the two liquids. The more dense liquid, typically the aqueous phase unless the organic phase is halogenated, sinks and can be drained out through a valve away from the less dense liquid, which remains in the separatory funnel.

Churning (butter) process of shaking up cream or whole milk to make butter, usually using a butter churn.

Churning is the process of shaking up cream or whole milk to make butter, usually using a butter churn. In Europe from the Middle Ages until the Industrial Revolution, a churn was usually as simple as a barrel with a plunger in it, moved by hand. These have mostly been replaced by mechanical churns.

Microfoam

Microfoam is finely textured milk used for making espresso-based coffee drinks, particularly those with latte art. It is typically made with the steam wand of an espresso machine, which pumps steam into a pitcher of milk.

A dispersion is a system in which distributed particles of one material are dispersed in a continuous phase of another material. The two phases may be in the same or different states of matter.

A miniemulsion is a special case of emulsion. A miniemulsion is obtained by shearing a mixture comprising two immiscible liquid phases, one or more surfactants and, possibly, one or more co-surfactants.

A high-shear mixer disperses, or transports, one phase or ingredient into a main continuous phase (liquid), with which it would normally be immiscible. A rotor or impeller, together with a stationary component known as a stator, or an array of rotors and stators, is used either in a tank containing the solution to be mixed, or in a pipe through which the solution passes, to create shear. A high-shear mixer can be used to create emulsions, suspensions, lyosols, and granular products. It is used in the adhesives, chemical, cosmetic, food, pharmaceutical, and plastics industries for emulsification, homogenization, particle size reduction, and dispersion.

Miscibility

Miscibility is the property of two substances to mix in all proportions, forming a homogeneous solution. The term is most often applied to liquids but applies also to solids and gases. Water and ethanol, for example, are miscible because they mix in all proportions.

Macroemulsions are homogenous transparent thermodynamically unstable systems with particle sizes ranging from 5-140 nm, which form spontaneously when mixed in the correct ratio. Macroemulsions scatter light effectively and therefore appear milky, because their droplets are greater than a wavelength of light. They are part of a larger family of emulsions along with microemulsions. As with all emulsions, one phase serves as the dispersing agent. It is often called the continuous or outer phase. The remaining phase(s) are disperse or inner phase(s), because the liquid droplets are finely distributed amongst the larger continuous phase droplets. This type of emulsion is thermodynamically unstable, but can be stabilized for a period of time with applications of kinetic energy. Surfactants (emulsifiers) are used to reduce the interfacial tension between the two layers, and induce macroemulsion stability for a useful amount of time.

A nanocapsule is a nanoscale shell made from a nontoxic polymer. They are vesicular systems made of a polymeric membrane which encapsulates an inner liquid core at the nanoscale. Nanocapsules have many uses, including promising medical applications for drug delivery, food enhancement, nutraceuticals, and for self-healing materials. The benefits of encapsulation methods are for protection of these substances to protect in the adverse environment, for controlled release, and for precision targeting. Nanocapsules can potentially be used as MRI-guided nanorobots or nanobots, although challenges remain.

Sour cream dairy product produced by fermenting a regular cream with certain kinds of lactic acid bacteria

Sour cream or soured cream is a dairy product obtained by fermenting regular cream with certain kinds of lactic acid bacteria. The bacterial culture, which is introduced either deliberately or naturally, sours and thickens the cream. Its name comes from the production of lactic acid by bacterial fermentation, which is called souring.

Agglomerated food powder is a unit operation during which native particles are assembled to form bigger agglomerates, in which the original particle can still be distinguished. Agglomeration can be achieved through processes that use liquid as a binder or methods that do not involve any binder.

References

  1. "Homogenization", Encyclopædia Britannica. Encyclopædia Britannica Online Academic Edition, Encyclopædia Britannica Inc. , retrieved October 6, 2013
  2. homo-, word origin
  3. 1 2 3 McClements, David J. (2008). "Lipid-Based Emulsions and Emulsifiers". In Akoh, Casimir C.; Min, David B. (eds.). Food Lipids: Chemistry, Nutrition, and Biotechnology. Food Science and Technology (Third ed.). Boca Raton, Florida: CRC. p. 77. ISBN   978-1420046649.

Further reading