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'''Flavor''' is a combination of [[taste]] and [[smell]]. <ref> [http://www.medicinenet.com/script/main/art.asp?articlekey=212 Taste and Smell = Flavor] </ref>

'''Flavor''' is a combination of [[taste]] and [[smell]].<ref> [http://www.medicinenet.com/script/main/art.asp?articlekey=212 Taste and Smell = Flavor] </ref>

It is a property of materials (particularly edible materials), which is associated with the [[senses|sense]] of [[taste]]. [[School]] children learn that the [[tongue]] can detect four distinct flavors (sweet, sour, salty, bitter) and each flavor has dedicated taste buds in different regions of the tongue (the tip, the sides, the center and the back, respectively). This 4-distinct-flavor view of tastes was held as late as the 70’s <ref name="Pyke">Pyke, Magnus. Synthetic Food. Spottiswoode, Ballanyne & Co: 1970.</ref><ref name="asha">[http://www.asha.org/about/publications/leader-online/archives/2002/q4/f021022a.htm Beyond the Tongue Map]</ref>, but it was derived from a mistranslation of an early 1900's [[German]] study which was later misproven. More modern research has shown that, not only are there not distinct "regions" on the tongue, but a fifth flavor, umami, also exists. <ref name="asha" />.

It is a property of materials (particularly edible materials), which is associated with the [[senses|sense]] of [[taste]]. [[School]] children learn that the [[tongue]] can detect four distinct flavors (sweet, sour, salty, bitter) and each flavor has dedicated taste buds in different regions of the tongue (the tip, the sides, the center and the back, respectively). This 4-distinct-flavor view of tastes was held as late as the 70’s <ref name="Pyke">Pyke, Magnus. Synthetic Food. Spottiswoode, Ballanyne & Co: 1970.</ref><ref name="asha">[http://www.asha.org/about/publications/leader-online/archives/2002/q4/f021022a.htm Beyond the Tongue Map]</ref>, but it was derived from a mistranslation of an early 1900's [[German]] study which was later misproven. More modern research has shown that, not only are there not distinct "regions" on the tongue, but a fifth flavor, umami, also exists.<ref name="asha" />

Tactile sensations such as heat and cool as well as [[smell|aroma]] (from [[volatile]] flavor compounds) are now also considered part of the flavor properties of a [[food]]. Despite the seemingly limited combination of flavor properties, extremely large numbers of flavors are able to be sensed by the tongue.

Tactile sensations such as heat and cool as well as [[smell|aroma]] (from [[volatile]] flavor compounds) are now also considered part of the flavor properties of a [[food]]. Despite the seemingly limited combination of flavor properties, extremely large numbers of flavors are able to be sensed by the tongue.

==The Five Flavors==

==The Five Flavors==

Sour flavors are generally produced by [[acid]]s, and different acids produce different acidic flavors. Some familiar sour flavors are [[vinegar]] ([[acetic acid]]), sour [[milk]] (lactic acid), citrus [[fruit]] ([[citric acid]]), [[apple]]s (malic acid) and [[wine]] (tartaric acid) <ref name="Reineccius">Reineccuis, Gary. Flavor Chemistry and Technology. Taylor & Francis: 2006.</ref>.

Sour flavors are generally produced by [[acid]]s, and different acids produce different acidic flavors. Some familiar sour flavors are [[vinegar]] ([[acetic acid]]), sour [[milk]] (lactic acid), citrus [[fruit]] ([[citric acid]]), [[apple]]s (malic acid) and [[wine]] (tartaric acid).<ref name="Reineccius">Reineccuis, Gary. Flavor Chemistry and Technology. Taylor & Francis: 2006.</ref>

[[Salt]]y flavors are most commonly associated with the mineral of the same name (sodium chloride), however most low [[molecular weight]] salts ([[ammonium]] [[chlorine|chloride]], [[potassium]] chloride, [[lithium]] chloride, [[sodium]] [[bromine|bromide]], ammonium bromide, sodium [[iodine|iodide]] and lithium iodide) have a salty taste <ref name="Pyke" />.

[[Salt]]y flavors are most commonly associated with the mineral of the same name (sodium chloride), however most low [[molecular weight]] salts ([[ammonium]] [[chlorine|chloride]], [[potassium]] chloride, [[lithium]] chloride, [[sodium]] [[bromine|bromide]], ammonium bromide, sodium [[iodine|iodide]] and lithium iodide) have a salty taste.<ref name="Pyke" />

Less is known about sweet and bitter substances. There seems to be no relationship between [[organic chemistry|organic]] [[functional group]]s and sweet flavor (as almost every class of compound has a member which tastes sweet), yet at the same time the chemistry is very specific. For example, saccharine is 300 times sweeter than table [[sugar]] (sucrose), however if the [[hydrogen]] bonded to the [[nitrogen]] is replaced with a [[methyl]] group, all flavor sensation disappears <ref name="Pyke" />. Likewise, bitter sensations are difficult to classify, though many [[plant]]-derived [[molecule]]s which interact with the brain such as [[caffeine]] and [[nicotine]] <ref name="Reineccius" />, as well as large molecular weight ionic salts such as [[cesium]] chloride, [[rubidium]] bromide and potassium iodide <ref name="Pyke" /> produce bitter tastes.

Less is known about sweet and bitter substances. There seems to be no relationship between [[organic chemistry|organic]] [[functional group]]s and sweet flavor (as almost every class of compound has a member which tastes sweet), yet at the same time the chemistry is very specific. For example, saccharine is 300 times sweeter than table [[sugar]] (sucrose), however if the [[hydrogen]] bonded to the [[nitrogen]] is replaced with a [[methyl]] group, all flavor sensation disappears.<ref name="Pyke" /> Likewise, bitter sensations are difficult to classify, though many [[plant]]-derived [[molecule]]s which interact with the brain such as [[caffeine]] and [[nicotine]],<ref name="Reineccius" /> as well as large molecular weight ionic salts such as [[cesium]] chloride, [[rubidium]] bromide and potassium iodide<ref name="Pyke" /> produce bitter tastes.

''Umami'' ([[Japanese]] for “delicious”, “savory” or “[[meat]]y”) is a newcomer to the basic flavor group. ''Umami'' is associated with L-glutamate and is found in meat broths, [[sea weed]] broth and aged [[cheese]]. It can also be used in solid form, usually [[monosodium glutamate]], MSG <ref name="Reineccius" /><ref name="Pyke" />. Unlike the other four flavors, ''umami'' is not thought to have a flavor of its own, but rather it intensifies other flavors already present, hence the common use of MSG in many prepackaged food items.

''Umami'' ([[Japanese]] for "delicious", "savory" or "[[meat]]y") is a newcomer to the basic flavor group. ''Umami'' is associated with L-glutamate and is found in meat broths, [[sea weed]] broth and aged [[cheese]]. It can also be used in solid form, usually [[monosodium glutamate]], MSG.<ref name="Reineccius" /><ref name="Pyke" /> Unlike the other four flavors, ''umami'' is not thought to have a flavor of its own, but rather it intensifies other flavors already present, hence the common use of MSG in many prepackaged food items.

==Taste Mechanism==

==Taste Mechanism==

Little is known about the mechanisms involved in tasting foods, but it is thought that sour and salty tastes utilize channels which allow inward [[proton]] transfer combined with H+-gated channels, while sweet, bitter and ''umami'' flavors utilize surface binding pathways to transmit flavor information. All five flavors depolarize the taste [[cell]] (which initially has a net negative internal [[charge]]) by causing the transfer of calcium ions (Ca²⁺) into the cell. This forms an [[electrical]] signal which is then sent to the [[brain]] and interpreted as flavor. When ''umami'' binds to a flavor cell, not only is there an influx of Ca²⁺ into the cell, but the cell also become more sensitive to the effects of other flavor compounds <ref name="Reineccius" />.

Little is known about the mechanisms involved in tasting foods, but it is thought that sour and salty tastes utilize channels which allow inward [[proton]] transfer combined with H+-gated channels, while sweet, bitter and ''umami'' flavors utilize surface binding pathways to transmit flavor information. All five flavors depolarize the taste [[cell]] (which initially has a net negative internal [[charge]]) by causing the transfer of calcium ions (Ca²⁺) into the cell. This forms an [[electrical]] signal which is then sent to the [[brain]] and interpreted as flavor. When ''umami'' binds to a flavor cell, not only is there an influx of Ca²⁺ into the cell, but the cell also become more sensitive to the effects of other flavor compounds.<ref name="Reineccius" />

==Flavor Production in Nature==

==Flavor Production in Nature==

Historically, most science in the field of flavor has been dedicated to determining what flavor is rather than how it is produced in nature. In addition, the [[metabolic pathway]]s involved in flavor production are often very complicated, which makes their determination difficult. Recently, however, due to the demand for man-made flavors (especially the production of flavors able to be labeled “natural flavors”) more research has been focused in this area of study.

Historically, most science in the field of flavor has been dedicated to determining what flavor is rather than how it is produced in nature. In addition, the [[metabolic pathway]]s involved in flavor production are often very complicated, which makes their determination difficult. Recently, however, due to the demand for man-made flavors (especially the production of flavors able to be labeled “natural flavors”) more research has been focused in this area of study.

While some compounds are produced as part of normal biological processes (sugars and acids, for example), volatile aroma components seem to have no biological function for the plant. Most aroma compounds are actually formed through break down of the cell; in fruits the cells soften and degrade during ripening, and in [[vegetables]] the cell walls are ruptured by an outside force, such as a [[tooth]] or a [[knife]]. It is not until the cells break down that [[enzyme|enzymatic]] reactions take place which rapidly form aromas <ref name="Reineccius" />.

While some compounds are produced as part of normal biological processes (sugars and acids, for example), volatile aroma components seem to have no biological function for the plant. Most aroma compounds are actually formed through break down of the cell; in fruits the cells soften and degrade during ripening, and in [[vegetables]] the cell walls are ruptured by an outside force, such as a [[tooth]] or a [[knife]]. It is not until the cells break down that [[enzyme|enzymatic]] reactions take place which rapidly form aromas.<ref name="Reineccius" />

Flavor in fruit is created by various linked metabolic pathways. [[Fatty acid]]s, [[amino acid]]s, [[carbohydrate]]s and [[protein]]s are enzymatically converted to various flavor and aroma compounds associated with the fruit.

Flavor in fruit is created by various linked metabolic pathways. [[Fatty acid]]s, [[amino acid]]s, [[carbohydrate]]s and [[protein]]s are enzymatically converted to various flavor and aroma compounds associated with the fruit.

==Flavor Production in Industry==

==Flavor Production in Industry==

Flavors are manufactured and extracted for use in food and beverage by hundreds of different companies. They are primarily used in prepackaged food items, but they can also be sold to home consumers (in products such as imitation [[vanilla]]). Due to the difficulty (and sometimes impossibility) of patenting flavor compounds, many details of flavor manufacture are closely guarded secrets, however some general principles are known <ref name="Reineccius" />.

Flavors are manufactured and extracted for use in food and beverage by hundreds of different companies. They are primarily used in prepackaged food items, but they can also be sold to home consumers (in products such as imitation [[vanilla]]). Due to the difficulty (and sometimes impossibility) of patenting flavor compounds, many details of flavor manufacture are closely guarded secrets, however some general principles are known.<ref name="Reineccius" />

Flavor manufacture falls into two categories, natural and artificial. Legally speaking, ''natural flavors'' are those which are produced by nature or through an engineered [[biology|biological]] reaction, while ''artificial flavors'' are created by man through [[chemical reaction]]s. From a production standpoint, artificial flavors are more appealing, since natural flavors tend to be in low concentrations (especially fruit flavors), are susceptible to seasonal fluctuations, and have a high material cost (since natural flavors are generally derived from a whole spice or fruit) <ref name="Reineccius" />. Consumers generally prefer natural flavors over artificial, however. One reason for this is that natural flavors are not simply one or two compounds, which could be easily synthesized, but a large number of compounds in a characteristic distribution, called a flavor profile. For example, natural [[pineapple]] has at least 17 chemical compounds which make up its flavor profile. Any imitation pineapple will not taste exactly like real pineapple without this same profile <ref name="Pyke" />. Generally cost and quality dictate whether the expensive, but accurate natural flavors will be used in a product instead of the less costly, but also less accurate, artificial flavor.

Flavor manufacture falls into two categories, natural and artificial. Legally speaking, ''natural flavors'' are those which are produced by nature or through an engineered [[biology|biological]] reaction, while ''artificial flavors'' are created by man through [[chemical reaction]]s. From a production standpoint, artificial flavors are more appealing, since natural flavors tend to be in low concentrations (especially fruit flavors), are susceptible to seasonal fluctuations, and have a high material cost (since natural flavors are generally derived from a whole spice or fruit).<ref name="Reineccius" /> Consumers generally prefer natural flavors over artificial, however. One reason for this is that natural flavors are not simply one or two compounds, which could be easily synthesized, but a large number of compounds in a characteristic distribution, called a flavor profile. For example, natural [[pineapple]] has at least 17 chemical compounds which make up its flavor profile. Any imitation pineapple will not taste exactly like real pineapple without this same profile.<ref name="Pyke" /> Generally cost and quality dictate whether the expensive, but accurate natural flavors will be used in a product instead of the less costly, but also less accurate, artificial flavor.

The flavor industry also classifies flavors by phase ([[liquid]], [[emulsion]], paste and [[solid]]). The phase in which a flavoring product is produced is determined by the application (liquid phase flavors are produced for beverages, for example) and by the physical properties of the compounds involved. Emulsions are typically broken down further into beverage emulsions, which are used to add flavor or turbidity to beverages, and baker’s emulsions, which are [[viscosity|viscous]] macroemulsions (Reineccius).

The flavor industry also classifies flavors by phase ([[liquid]], [[emulsion]], paste and [[solid]]). The phase in which a flavoring product is produced is determined by the application (liquid phase flavors are produced for beverages, for example) and by the physical properties of the compounds involved. Emulsions are typically broken down further into beverage emulsions, which are used to add flavor or turbidity to beverages, and baker’s emulsions, which are [[viscosity|viscous]] macroemulsions (Reineccius).