Changes

Flavor is a fundamental property of every food or drink that we consume every day of our lives. Flavor is found naturally in all food, yet there is a $12.9 billion worldwide industry dedicated to producing synthetic and natural flavor extracts and integrating them into food and drink to increase their taste and appeal (GCCC, 2006). Flavors (specifically those from spices) have had amazing effects on human history; since the first records mentioning spices in 2000 B.C. flavors have caused wars, created wealthy empires and lead to the discovery of new worlds (Reineccius, 2006).

'''Flavor''' 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 (Pyke, 1970), but recent research suggests that not only is their a fifth flavor sensation (''umami''), but that the tongue has more overlap in flavor detection than previously thought. 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.

 

 

 

Sour flavors are generally produced by acids, and different acids produce different acidic flavors. Some familiar sour flavors are vinegar (acetic acid), sour milk (lactic acid), citrus fruit (citric acid), apples (malic acid) and wine (tartaric acid) (Reineccius). Salty flavors are most commonly associated with the mineral of the same name (sodium chloride), however most low molecular weight salts (ammonium chloride, potassium chloride, lithium chloride, sodium bromide, ammonium bromide, sodium iodide and lithium iodide) have a salty taste (Pyke). Less is known about sweet and bitter substances. There seems to be no relationship between organic functional groups 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, Figure 1, is 300 times sweeter than sugar (sucrose), however if the hydrogen bonded to the nitrogen is replaced with a methyl group, all flavor sensation disappears (Pyke). Likewise, bitter sensations are difficult to classify, though many plant-derived molecules which interact with the brain such as caffeine and nicotine (Reineccius), as well as large molecular weight ionic salts such as cesium chloride, rubidium bromide and potassium iodide (Pyke) produce bitter tastes.

Sour flavors are generally produced by acids, and different acids produce different acidic flavors. Some familiar sour flavors are vinegar (acetic acid), sour milk (lactic acid), citrus fruit (citric acid), apples (malic acid) and wine (tartaric acid) (Reineccius). Salty flavors are most commonly associated with the mineral of the same name (sodium chloride), however most low molecular weight salts (ammonium chloride, potassium chloride, lithium chloride, sodium bromide, ammonium bromide, sodium iodide and lithium iodide) have a salty taste (Pyke). Less is known about sweet and bitter substances. There seems to be no relationship between organic functional groups 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, Figure 1, is 300 times sweeter than sugar (sucrose), however if the hydrogen bonded to the nitrogen is replaced with a methyl group, all flavor sensation disappears (Pyke). Likewise, bitter sensations are difficult to classify, though many plant-derived molecules which interact with the brain such as caffeine and nicotine (Reineccius), as well as large molecular weight ionic salts such as cesium chloride, rubidium bromide and potassium iodide (Pyke) produce bitter tastes.

Umami (Japanese for “delicious”, “savory” or “meaty”) 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 (Reineccius, 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 “meaty”) 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 (Reineccius, 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.

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 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 (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 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 (Reineccius).

Flavor Production in Nature

Flavor Production in Nature