Flavor
is the sensory
impression of a food or other substance, and is determined mainly by the
chemical senses of taste and smell. The "trigeminal senses", which
detect chemical irritants in the mouth and throat as well as temperature and
texture, are also very important to the overall Gestalt of flavor perception.
The flavor of the food, as such, can be altered with natural or artificial
flavorants, which affect these senses.
Flavorant is defined as a substance that
gives another substance flavor, altering the characteristics of the solute,
causing it to become sweet, sour, tangy, etc.
Of the three chemical
senses, smell is the main determinant of a food item's flavor. While the taste
of food is limited to sweet, sour, bitter, salty, umami (savory) pungent or
piquant, and metallic – the seven basic tastes – the smells of a food are
potentially limitless. A food's flavor,
therefore, can be easily altered by changing its smell while keeping its taste similar.
Nowhere is this better exemplified than in artificially flavored jellies, soft
drinks and candies, which, while made of bases with a similar taste, have
dramatically different flavors due to the use of different scents or
fragrances. The flavorings of commercially produced food products are typically
created by flavorists.
Although the terms
"flavoring" or "flavorant" in common language
denote the combined chemical sensations of taste and smell, the same terms are
usually used in the fragrance and flavors industry to refer to edible chemicals
and extracts that alter the flavor of food and food products through the sense
of smell. Due to the high cost or unavailability of natural flavor extracts,
most commercial flavorants are nature-identical, which means that they
are the chemical equivalent of natural flavors but chemically synthesized
rather than being extracted from the source materials. Identification of
nature-identical flavorants are done using technology such as headspace
techniques.
The History of Tastes
Before digging into the main course—the methods of preparation—let us
make a little detour useful to understanding how we eat, because we will be
better cooks if we know how to distinguish the various sensations that dishes
produce: tastes and flavors, colors, scents, aromas.
Aristotle knew everything, but what did he know about tastes? Let us
entrust ourselves to this old philosopher. Tirelessly traversing the lyceum
with his disciples, he worked up an appetite and turned his metaphysical mind
toward gourmand meditations: there are “in
the tastes as in the colors, on the one hand, the simple kinds which are also
the opposites, that is, the sweet and the bitter; on the other hand, the kinds
derived either from the first, like the unctuous, or from the second, like the
salty; finally, halfway between these last two flavors, the sour, the pungent,
the astringent, and the acid, more or less; these seem to be, in effect, the
different tastes.”
Aristotle is not the only authority to have appreciated oral sensations.
In particular, in the eighteenth century the great Linnaeus also applied his
talents to tastes, but paradoxically the most famous of systematicians, the
father of botanical classification, lacked some systematic spirit, because he mixed
together the moist, the dry, the acid, the bitter, the fatty, the astringent,
the sweet, the sour, the viscous, the salty. He put them all pell-mell in the
same bag for us, this mix of tastes and mechanical sensations.
A Frenchman deserves the credit for establishing a little order in the
domain of oral impressions. In 1824 the great chemist Michel-Eugene Chevreul (1786-1889),
famous especially for his work on fats, distinguished the olfactory, gustatory,
and tactile sensations. He recognized that the perception of hot or cold is
distinct from that of sweet or bitter. He separated out the tactile sensations
of the oral cavity, as well as the proprioceptive sensations (for example,
toughness). With Chevreul, the taste
of physiologists—one component of flavor—was distinguished from everyday
sensation, where all the sensations associated with the absorption of food and
drink are mixed.
In the same period but in a different circle, among the gourmands
centered around Brillat-Savarin, the only confusion that continued to reign was
between tastes and smells. The tongue was known to perceive tastes, but the
nose was also believed to be a receptor. Apart from a few more or less harmless
errors, the remarks made in the Treatise
on the Physiology of Taste are
as insightful as their author is passionate about cooking: “The number of
tastes is infinite, since every soluble
body has a special flavor which does not
wholly resemble any other. Up to the present time there is not a single
circumstance in which a given taste has been analyzed with stern exactitude, so
that we have been forced to depend on a small number of generalizations such as sweet, sugary , sour, bitter,
and other like ones which express, in the end, no more than the words agreeable or disagreeable.” On the
other hand, a bit later, Brillat-Savarin adds that “any sapid substance is
perforce odorant.” He had forgotten that some molecules that are hardly
volatile at all at ambient temperatures and thus odorless nevertheless bind
easily to taste receptors on the tongue and palate and therefore have a taste.
Salt, for example, is sapid but odorless.
As indicated
previously, the two main factors affecting flavor are taste and odor. In a general way, food flavors can be divided into two
groups. The first consists of foods
whose flavor cannot be attributed to one or a few outstanding flavor notes;
their flavor is the result of the complex interaction of a variety of taste and
odor components. Examples include bread, meat, and cheese. The second group
consists of foods in which the flavor can
be related to one or a few easily recognized components (contributory
flavor compounds). Examples include certain fruits, vegetables, and spices.
Another way of differentiating food flavors is by considering one group in
which the flavor compounds are naturally present and another group in which the
flavor compounds are produced by processing methods.
Bread
The flavor of white
bread is formed mainly from the fermentation and baking processes. Freshly
baked bread has a delightful aroma that is rapidly lost on cooling and storage.
It has been suggested that this loss of flavor is the result of disappearance
of volatile flavor components. However, it is well known that the aroma may be
at least partially regenerated by simply heating the bread. Schoch (1965)
suggested that volatile flavor compounds may become locked in by the linear fraction
of wheat starch. The change in texture upon aging may be a contributory factor in
the loss of flavor. During fermentation, a number of alcohols are formed,
including ethanol, rc-propanol, isoamyl and amyl alcohol, isobutyl alcohol, and
p-phenol alcohol. The importance of the alcohols to bread flavor is a matter of
controversy. Much of the alcohols are lost to the oven air during baking.
A large number of
organic acids are also formed (Johnson et al. 1966). These include saturated
aliphatic acids, from formic to capric, as well as lactic, succinic, pyruvic, hydrocinnamic,
benzilic, itaconic, and levulinic acid. A large number of carbonyl compounds has
been identified in bread, and these are believed to be important flavor components.
Johnson et al. (1966) list the carbonyl compounds isolated by various workers
from bread; this list includes 14 aldehydes and 6 ketones. In white bread made
with glucose, the prevalent carbonyl compound is hydroxymethylfurfural (Linko et
al. 1962). The formation of the crust and browning during baking appear to be
primary contributors to bread flavor. The browning is mainly the result of a
Maillard-type browning reaction (Maillard
Reaction Mechanism and Its Applications to Your Cooking) rather than
caramelization. This accounts for the presence of the carbonyl compounds,
especially furfural, hydroxymethylfurfural, and other aldehydes. In the Maillard reaction, the amino acids
are transformed into aldehydes with one less carbon atom. Specific
aldehydes can thus be formed in bread crust if the necessary amino acids are
present. The formation of aldehydes in bread crust is accompanied by a lowering
of the amino acid content compared to that in the crumb. Johnson et al. (1966)
have listed the aldehydes that can be formed from amino acids in bread crust as
a result of the Strecker degradation. Grosch and Schieberle (1991) reported the
aroma of wheat bread to include ethanol, 2- methylpropanal, 3-methylbutanal,
2,3-butanedione, and 3-methylbutanol. These compounds contribute significantly
to bread aroma, whereas other compounds are of minor importance.
Meat
Meat is another food
in which the flavor is developed by heating from precursors present
Aldehydes That Can Be Formed from Amino Acids in
Bread Crust as a Result of the Strecker Degradation
|
Amino
Acid
|
Aldehyde
|
|
Alanine
|
Acetaldehyde
|
|
Glycine
|
Formaldehyde
|
|
lsoleucine
|
2-Methylbutanal
|
|
Leucine
|
Isovaleraldehyde
|
|
Methionine
|
Methional
|
|
Phenylalanine
|
Phenylacetaldehyde
|
|
Threonine
|
2-Hydroxypropanal
|
|
Serine
|
Glyoxal
|
Source: From J.A.
Johnson et al., Chemistry of Bread Flavor, in Flavor Chemistry, I. Hornstein, ed., 1966, American Chemical
Society.
in the meat;
this occurs in a Maillard-type browning reaction. The overall flavor impression
is the result of the presence of a large number of nonvolatile compounds and
the volatiles produced during heating. The contribution of nonvolatile
compounds in meat flavor has been summarized by Solms (1971). Meat extracts contain a large number of
amino acids, peptides, nucleotides, acids, and sugars. The presence of
relatively large amounts of inosine-5'-monophosphate
has been the reason for considering this compound as a basic flavor component.
In combination with other compounds, this nucleotide would be responsible for
the meaty taste. Living muscle contains adenosine-5'-triphosphate; this is
converted after slaughter into adenosine-5'-monophosphate, which is deaminated to
form inosine-5'-monophosphate (Jones 1969). The volatile compounds produced on
heating can be accounted for by reactions involving amino acids and sugars present
in meat extract. Lean beef, pork, and lamb are surprisingly similar in flavor;
this reflects the similarity in composition of extracts in terms of amino acid
and sugar components. The fats of these different species may account for some
of the normal differences in flavor. In the volatile fractions of meat aroma,
hydrogen sulfide and methyl mercaptan have been found; these may be important
contributors to meat flavor. Other volatiles that have been isolated include a variety
of carbonyls such as acetaldehyde, propionaldehyde, 2-methylpropanal,
3-methylbutanal, acetone, 2-butanone, rc-hexanal, and 3-methyl-2-butanone
(Moody 1983).
Fish
Fish contains sugars
and amino acids that may be involved in Maillard-type reactions during heat
processing (canning). Proline is a prominent
amino acid in fish and may contribute to sweetness. The sugars ribose, glucose,
and glucose-6-phosphate are flavor contributors, as is 5'-inosinic acid, which contributes
a meaty flavor note. Volatile sulfur compounds contribute to the flavor of fish;
hydrogen sulfide, methylmercaptan, and dimethylsulfide may contribute to the
aroma of fish. Tarr (1966) described an off-flavor problem in canned salmon
that is related to dimethylsulfide. The salmon was found to feed on zooplankton
containing large amounts of dimethyl-2-carboxyethyl sulfonium chloride. This
compound became part of the liver and flesh of the salmon and in canning
degraded to dimethylsulfide according to the following equation:
(CH3)2-SH-CH2-CH2-COOH
->
(CH3)2S
+ CH3-CH2-COOH
The flavor of cooked,
fresh fish is caused by the presence of sugars, including glucose and fructose, giving a sweet impression as well
as a umami component arising from
the synergism between inosine monophosphate and free amino acids. The fresh
flavor of fish is rapidly lost by bacterial spoilage. In fresh fish, a small
amount of free ammonia, which has a pH level of below 7, exists in protonated form.
As spoilage increases, the pH rises and ammonia is released. The main source of
ammonia is trimethylamine, produced as a degradation product of
trimethylamineoxide. The taste-producing properties of hypoxanthine and
histidine in fish have been described by Konosu (1979). 5'-inosinate accumulates
in fish muscle as a postmortem degradation product of ATP. The inosinate slowly
degrades into hypoxanthine, which has a strong bitter taste. Some kinds of
fish, such as tuna and mackerel, contain very high levels of free histidine,
which has been postulated to contribute to the flavor of these fish.
Milk
The flavor of normal
fresh milk is probably produced by the cow's metabolism and is comprised of
free fatty acids, carbonyl compounds, alkanols, and sulfur compounds. Free
fatty acids may result from the action of milk lipase or bacterial lipase.
Other decomposition products of lipids may be produced by the action of heat.
In addition to lipids, proteins and lactose may be precursors of flavor
compounds in milk (Badings 1991). Sulfur compounds that can be formed by heat
from (3-lactoglobulin include dimethyl sulfide, hydrogen sulfide, dimethyl
disulfide, and methanethiol. Some of these sulfur compounds are also produced
from methionine when milk is exposed to light. Heterocyclic compounds are
produced by nonenzymatic browning reactions. Bitter peptides can be formed by
milk or bacterial proteinases. The basic taste of milk is very bland, slightly
sweet, and salty. Processing conditions influence flavor profiles. The extent of heat treatment determines the
type of flavor produced. Low heat treatment produces traces of hydrogen
sulfide. Ultra-high temperature treatment results in a slight fruity, ketone-like
flavor. Sterilization results in strong ketone-like and
caramelization/sterilization flavors. Sterilization flavors of milk are caused
by the presence of 2-alkanones and heterocyclic compounds resulting from the
Maillard reaction. Because of the bland flavor of milk, it is relatively easy
for off-flavors to take over.
Cheese
The flavor of cheese
largely results from the fermentation process that is common to most varieties
of cheese. The microorganisms used as cultures in the manufacture of cheese act
on many of the milk components and produce a large variety of metabolites. Depending
on the type of culture used and the duration of the ripening process, the cheese
may vary in flavor from mild to extremely powerful. Casein, the main protein in
cheese, is hydrolyzed in a pattern and at a rate that is characteristic for
each type of cheese. Proteolytic enzymes produce a range of peptides of
specific composition that are related to the specificity of the enzymes present.
Under certain conditions bitter peptides may be formed, which produce an offflavor.
Continued hydrolysis yields amino acids. The range of peptides and amino acids provides
a "brothy" taste background to the aroma of cheese. Some of these
compounds may function as flavor enhancers. Breakdown of the lipids is
essential for the production of cheese aroma since cheese made from skim milk
never develops the full aroma of normal cheese. The lipases elaborated by the culture
organisms hydrolyze the triglycerides to form fatty acids and partial
glycerides.
The particular flavor
of some Italian cheeses can be enhanced by adding enzymes during the
cheese-making process that cause preferential hydrolysis of short-chain fatty
acids. Apparently, a variety of minor components are important in producing the
characteristic flavor of cheese. Carbonyls, esters, and sulfur compounds are
included in this group. The relative importance of many of these constituents
is still uncertain. Sulfur compounds found in cheese include hydrogen sulfide,
dimethylsulfide, methional, and methyl mercaptan. All of these compounds are
derived from sulfur-containing amino acids. The flavor of blue cheese is mainly the result of the presence of a
number of methyl ketones with odd carbon numbers ranging in chain length from 3
to 15 carbons (Day 1967). The most important of these are 2- heptanone and
2-nonanone. The methyl ketones are formed by p-oxidation of fatty acids by the
spores of P. roqueforti.
Fruits
The flavor of many
fruits appears to be a combination of a delicate balance of sweet and sour
taste and the odor of a number of volatile compounds. The characteristic flavor of citrus products is largely due to
essential oils contained in the peel. The essential oil of citrus fruits
contains a group of terpenes and sesquiterpenes and a group of oxygenated compounds.
Only the latter are important as contributors to the citrus flavor. The
volatile oil of orange juice was found to be 91.6 mg per kg, of which 88.4 was
hydrocarbons (Kefford 1959). The volatile water-soluble constituents of orange
juice consist mainly of acetaldehyde, ethanol, methanol, and acetic acid. The
hydrocarbons include mainly Dlimonene, p-myrcene, and a compound of composition
C15H24. The esters include isovalerate, methyl alphaethyl-n-caproate,
citronellyl acetate, and terpinyl acetate.
In the group of
carbonyls, the following compounds were identified: w-hexanal, H-octanal,
w-decanal, and citronella; and in the group of alcohols, linalool, a-terpineol,
rc-hexane-1-ol, noctan- 1-ol, rc-decan-1-ol, and 3-hexen-l-ol were
identified. The flavor deterioration of canned orange juice during storage
results in stale off-flavors. This is due to reactions of the nonvolatile
water-soluble constituents. As in the case of citrus fruits, no single compound
is completely responsible for any single fruit aroma. However, some
organoleptically important compounds characteristic for particular fruits have
been found. These include amyl esters in banana aroma, citral in lemon, and
lactones in peaches. The major flavor component of Bartlett pears was identified
by Jennings and Sevenants (1964) as ethyl /ratt5--2-d,y-4-decadienoate.
Vegetables
Vegetables
contain an extensive array of volatile flavor compounds, either in original form
or produced by enzyme action from precursors. Maarse (1991) has reviewed these
in detail. Onion and garlic have distinctive and pungent aromas that result
mostly from the presence of sulfur-containing compounds. A large number of
flavor compounds in vegetables are formed after cooking or frying. In raw
onions, an important compound is thio-propanal s-oxide—the lachrymatory factor.
The distinctive odor of freshly cut onions involves two main compounds, propyl
methane-thiosulfonate and propyl propanethiosulfonate. Raw garlic contains
virtually exclusively sulfur compounds: four thiols, three sulfides, seven
disulfides, three trisulfides, and six dialkylthiosulfinates.
Tea
The flavor of black
tea is the result of a number of compounds formed during the processing of
green tea leaves. The processing involves withering, fermentation, and firing. Bokuchava
and Skobeleva (1969) indicate that the
formation of the aroma occurs mainly during firing. Aromatic compounds isolated
and identified from black tea include acrolein, n-butyric aldehyde, ethanol, nbutanol,
isobutanol, hexanal, pentanal, 2- hexanol, 3-hexen-l-ol, benzaldehyde,
linalool, terpeneol, methylsalicylate, benzyl alcohol, (3-phenylethanol,
isobutyric aldehyde, geraniol, and acetophenone. The flavor substances of tea
can be divided into the following four fractions: a carbonyl-free neutral fraction
including a number of alcohols, a carbonyl fraction, a carboxylic acid
fraction, and a phenolic fraction. A compilation (Maarse 1991) identifies a
total of 467 flavor constituents in tea. The distinctive flavor of tea is due
to its content of lactones, aldehydes, alcohols, acids, and pyridines.
Coffee
The
flavor of coffee is developed during the roasting of the green coffee bean. Gasliquid chromatography can be
used to demonstrate the development of volatile constituents in increasing
amounts as intensity of roasting increases (Gianturco 1967). The total number
of volatile compounds that have been isolated is in the hundreds, and many of
these have been identified. To determine the flavor contribution of each of
these is a Herculean task. Many compounds result from the pyrolytic
decomposition of carbohydrates into units of 2, 3,4, or 5 carbons. Other
compounds of carbohydrate origin are 16 furanic compounds, cyclic diketones,
and maltol.
Roasting of the
proteins of the coffee bean can yield low molecular weight products such as
amino acids, ammonia, amines, hydrogen sulfide, methyl mercaptan,
dimethylsulfide, and dimethyl disulfide. A series of furanic and pyrrolic compounds
identified include the following: furan, furfural, acetylfuran, 5-methylfuran, 5-methylfurfural,
5-methyl-2-acetylfuran and pyrrole, 2-pyrrolaldehyde, 2-acetylpyrrole, Af-methylpyrrole,
Af-methyl-2-pyrrolaldehyde, and Af-methyl-2-acetylpyrrole. Differences in the
aroma of different coffees can be related to quantitative differences in some
of the compounds isolated by gas chromatography, may be different. Pyrazines,
furanes, pyrroles, and thiophen derivatives are particularly abundant in coffee
aroma. Furfurylmethyl- sulfide and its homologs are important contributors to
the aroma of coffee.
It is impossible to
compare the aroma of different coffees on the basis of one or a few of the
flavor constituents. Computer-generated histograms can be used for comparisons after
selection of important regions of gasliquid chromatograms by using mathematical
treatments. Biggers et al. (1969) differentiated the beverage quality of two
varieties of coffee (arabica and robusta) on the basis of contributions of
flavor compounds. Recent studies have identified 655 compounds in the flavor of
coffee, the principal ones being furans, pyrazines, pyrroles, and ketones
(Maarse 1991). The distinctiveness of coffee flavor is related to the fact that
it contains a large percentage of thiophenes, furans, pyrroles, as well as
oxazoles, thiazoles, and phenols.
Alcoholic Beverages
In distilled
beverages, one of the major flavor compounds is acetaldehyde. Acetaldehyde represents about 90 percent of the total
aldehydes present in beverages like whiskey, cognac, and rum. Together with
other shortchain aliphatic aldehydes, it produces a pungent odor and sharp
flavor, which is masked by other flavor components in cognac, fruit brandies,
rum, and whiskey. In vodka the presence of acetaldehyde may result in an off-flavor.
Propanol and 2-methylpropanol, as well as unsaturated aldehydes, are also present
in distilled beverages. The aldehydes are very reactive and can form acetals by
reacting with ethanol. This reaction results in a smoother flavor profile.
Another important flavor compound in distilled beverages is the diketone,
2,3-butanedione (diacetyl), which is a product of fermentation. Depending on fermentation
and distillation conditions, the level of diacetyl varies widely in different beverages.
Fusel alcohols, which
are present in most distilled beverages, influence flavor. They are formed
during fermentation from amino acids through decarboxylation and deamination, and
include 1-propanol, 2-methylpropanol, 2-methylbutanol, 3-methylbutanol, and
2-phenylethanol.
Distilled beverages
also contain fatty acids—from acetic acid (which is one of the major fatty
acids) to long-chain unsaturated fatty acids.
Maturation
in oak barrels has a major effect on flavor of distilled beverages. Maturing fresh distillates in oak
barrels can transform a raw-tasting product into a mellow, well-rounded
beverage. The reactions that take place during maturation involve reactions between
components of the distillate and reactions between distillate components and
compounds present in the oak wood. The alcoholic solution in the barrel
extracts lignin from the oak to form
an alcohol-soluble ethanol- lignin. Alcoholysis converts this to coniferic
alcohol and then by oxidation to coniferaldehyde. Similarly, sinapic alcohol is
converted to sinapaldehyde. These aldehydes then produce syringaldehyde and
vanillin. The latter compound is important in the flavor of cognac and whiskey.
A similar process occurs in the aging of wines in oak barrels to produce the
distinctive smoothness of oakaged wines.
Spices and Herbs
Spices and herbs are
natural vegetable products used for adding flavor and aroma to foods. They are
usually highly flavored themselves and are used in small quantities. There is
no clear distinction between spices and herbs, other than the general rule that
spices are produced from tropical plants and herbs from plants grown in cooler
climates. Spices and herbs provide aroma because of the presence of aromatic constituents;
in addition, spices often provide pungency or hotness. The flavor and pungency
of spices can be provided by the dried or ground products themselves, by their
essential oils (produced by steam distillation), or by their oleoresins
(produced by extraction with solvents). Essential oils contain only volatile compounds;
oleoresins also include nonvolatile fats or oils.
Spices and herbs
differ in the nature of their volatile constituents (Boelens 1991). Spices contain higher levels of phenylpropanoids
such as eugenol, dillapiol, and cinnamaldehyde. Herbs have higher levels of
para-menthanoids, such as menthol, carvone, thymol, carvacrol, and
cuminaldehyde. Numerous volatile compounds have been identified in the
essential oils of spices. Maarse (1991) has reported the number of hydrocarbons,
alcohols, aldehydes, ketones, esters, phenols, acids, and others. Ginger
contains about 2 percent of volatile oil, composed mostly of sesquiterpene
hydrocarbons. Other constituents are oxygenated sesquiterpenes, monoterpene
hydrocarbons and oxygenated monoterpenes. The pungent component of ginger is
gingerol, which is a series of compounds consisting of zingerone-forming
condensation products with saturated straight-chain aldehydes of chain lengths
6, 8, and 10. Fresh ginger has a lemony flavor resulting from the presence of citral
and terpineol compounds. The lemony character may be lost because of flashing
off during drying.
Pepper aroma and
flavor are determined by the composition of the steam volatile oil (Purseglove
et al. 1991). The steam volatiles consist of monoterpene hydrocarbons and smaller
amounts of sesquiterpene hydrocarbons. The major pungent compound in pepper is
piperine. Also contributing to pungency are five minor alkaloids. Nutmeg oil, which
is obtained by steam distillation, contains the following major components: monoterpene
hydrocarbons, oxygenated monoterpenes, and aromatic ethers. The monoterpene hydrocarbons
contain alpha- and betapinene and sabinene. The aromatic ether fraction has as
major constituent myristicin; this fraction is thought to
Number of Volatile Components in the Essential Oils
of Some Spices
|
Spice
|
Number
|
|
Cinnamon
|
113
|
|
Cloves
|
95
|
|
Ginger
|
146
|
|
Nutmeg
|
80
|
|
Pepper
|
122
|
|
Vanilla
|
190
|
Source: Reprinted
with permission from H. Maarse, Volatile
Compounds in Foods and Beverages, p. 1991, by courtesy of Marcel Dekker,
Inc.
forms used as a spice.
The composition of the pungent Capsicum fruits varies widely and is
influenced by the species, cultivars, growing conditions, stage of maturity at
harvest, and postharvest processing. The bell peppers possess no pungency, and
paprika is mainly used for its coloring power. The main pungent principle of
hot chilies is capsaicin. In addition, Purseglove et al. (1991) have reported a
number of analogs and homologs of capsaicin that contribute to the pungency of
chilies.
Vanilla
Vanilla is obtained
from dried and cured vanilla beans. These can be used directly, in the form of
an alcoholic extract, or as oleoresin. The major flavor compound is vanillin, which
is present in the beans at a level of 1.3 to 3.8 percent (Maarse 1991). The
extracts contain resins that contribute to the taste and serve in the fixation
of flavor. The precursor of vanillin is probably lignin, of which the cured
beans contain from 2.1 to 3.9 percent. Numerous other compounds are present at very
low concentrations. These include phydroxybenzaldehyde and
/?-hydroxylbenzyl methyl ether. The
composition of vanilla is influenced by the geographic origin of the beans.
Flavorants or flavorings
Flavorings are focused on altering the flavors
of natural food product such as meats and vegetables, or creating flavor for
food products that do not have the desired flavors such as candies and other
snacks. Most types of flavorings are focused on scent and taste. Few commercial
products exist to stimulate the trigeminal senses, since these are sharp,
astringent, and typically unpleasant flavors.
There are three
principal types of flavorings used in foods, under definitions agreed in the
E.U. and Australia:
|
Type
|
Description
|
|
Natural flavoring
substances
|
Flavoring substances
obtained from plant or animal raw materials, by physical, microbiological or
enzymatic processes. They can be either used in their natural state or
processed for human consumption, but cannot contain any nature-identical or
artificial flavoring substances.
|
|
Nature-identical
flavoring substances
|
Flavoring substances
that are obtained by synthesis or isolated through chemical processes, which
are chemically and organoleptically identical to flavoring substances
naturally present in products intended for human consumption. They cannot
contain any artificial flavoring substances.
|
|
Artificial flavoring
substances
|
Flavoring substances
not identified in a natural product intended for human consumption, whether
or not the product is processed. These are typically produced by fractional
distillation and additional chemical manipulation of naturally sourced
chemicals, crude oil or coal tar. Although they are chemically different, in
sensory characteristics are the same as natural ones.
|
Regulations on Natural Flavoring
UK
Food Law defines a natural flavor as: a
flavouring substance (or flavouring substances) which is (or are) obtained, by
physical, enzymatic or microbiological processes, from material of vegetable or
animal origin which material is either raw or has been subjected to a process
normally used in preparing food for human consumption and to no process other
than one normally so used.
The U.S. Code of
Federal Regulations describes a "natural
flavorant" as: the essential oil, oleoresin, essence or extractive,
protein hydrolysate, distillate, or any product of roasting, heating or
enzymolysis, which contains the flavoring constituents derived from a spice,
fruit or fruit juice, vegetable or vegetable juice, edible yeast, herb, bark,
bud, root, leaf or any other edible portions of a plant, meat, seafood,
poultry, eggs, dairy products, or fermentation products thereof, whose primary
function in food is flavoring rather than nutritional.
The European Union's
guidelines for natural flavorants are slightly different. Certain artificial
flavorants are given an E number, which may be included on food labels.
Smell
Smell flavorants, or
simply, flavorants, are engineered and composed in similar ways as with
industrial fragrances and fine perfumes. To produce natural flavors, the
flavorant must first be extracted from the source substance. The methods of
extraction can involve solvent extraction, distillation, or using force to
squeeze it out. The extracts are then usually further purified and subsequently
added to food products to flavor them. To begin producing artificial flavors, flavor
manufacturers must either find out the individual naturally occurring aroma
compounds and mix them appropriately to produce a desired flavor or create a
novel non-toxic artificial compound that gives a specific flavor.
Most artificial
flavors are specific and often complex mixtures of singular naturally occurring
flavor compounds combined together to either imitate or enhance a natural
flavor. These mixtures are formulated by flavorists to give a food product a
unique flavor and to maintain flavor consistency between different product
batches or after recipe changes. The list of known flavoring agents includes
thousands of molecular compounds, and the flavor chemist (flavorist) can often
mix these together to produce many of the common flavors. Many flavorants
consist of esters, which are often described as being "sweet" or
"fruity".
|
Chemical
|
Odor
|
|
Diacetyl
|
Buttery
|
|
Isoamyl acetate
|
Banana
|
|
Benzaldehyde
|
Bitter almond
|
|
Cinnamic aldehyde
|
Cinnamon
|
|
Ethyl propionate
|
Fruity
|
|
Methyl anthranilate
|
Grape
|
|
Limonene
|
Orange
|
|
Ethyl decadienoate
|
Pear
|
|
Allyl hexanoate
|
Pineapple
|
|
Ethyl maltol
|
Sugar, Cotton candy
|
|
Ethylvanillin
|
Vanilla
|
|
Methyl salicylate
|
Wintergreen
|
The compounds used to
produce artificial flavors are almost identical to those that occur naturally.
It has been suggested that artificial flavors may be safer to consume than
natural flavors due to the standards of purity and mixture consistency that are
enforced either by the company or by law. Natural flavors in contrast may
contain impurities from their sources while artificial flavors are typically
more pure and are required to undergo more testing before being sold for
consumption.
Flavors from food products
are usually the result of a combination of natural flavors, which set up the
basic smell profile of a food product while artificial flavors modify the smell
to accent it.
Unlike smelling, which
occurs upon inhalation, the sensing of flavors in the mouth occurs in the exhalation
phase of breathing and is perceived differently by an individual. In other
words, the smell of food is different depending on when you are smelling it in
front of you or whether it has already entered your mouth.
Taste
While salt and sugar
can technically be considered flavorants that enhance salty and sweet tastes,
usually only compounds that enhance umami, as well as other secondary flavors
are considered and referred to as taste flavorants. Artificial
sweeteners are also technically flavorants.
Umami or "savory" flavorants,
more commonly called taste or flavor enhancers are largely based on amino acids
and nucleotides. These are typically used as sodium or calcium salts. Umami
flavorants recognized and approved by the European Union include:
|
Acid
|
Description
|
|
Glutamic
acid salts
|
This amino acid's sodium
salt, monosodium glutamate (MSG),
a notable example, is one of the most commonly used flavor enhancers in food
processing. Mono and diglutamate salts are also commonly used.
|
|
Glycine salts
|
Simple amino acid
salts typically combined with glutamic acid as flavor enhancers.
|
|
Guanylic acid salts
|
Nucleotide salts
typically combined with glutamic acid as flavor enhancers.
|
|
Inosinic acid salts
|
Nucleotide salts
created from the breakdown of AMP. Due to high costs of production, typically
combined with glutamic acid as flavor enhancers.
|
|
5'-ribonucleotide
salts
|
Nucleotide salts
typically combined with other amino acids and nucleotide salts as flavor
enhancers.
|
Certain organic and
inorganic acids can be used to enhance sour tastes, but like salt and sugar
these are usually not considered and regulated as flavorants under law. Each
acid imparts a slightly different sour or tart taste that alters the flavor of
a food.
|
Acid
|
Description
|
|
Acetic acid
|
Gives vinegar its
sour taste and distinctive smell
|
|
Ascorbic acid
|
Found in oranges and
green peppers and gives a crisp, slightly sour taste. Better known as vitamin
C
.
|
|
Citric acid
|
Found in citrus
fruits and gives them their sour taste
|
|
Fumaric acid
|
Not found in fruits,
used as a substitute for citric and tartaric acid
|
|
Lactic acid
|
Found in various
milk or fermented products and give them a rich tartness
|
|
Malic acid
|
Found in apples and
gives them their sour/tart taste
|
|
Phosphoric acid
|
Used in all Cola
drinks to give an acid taste
|
|
Tartaric acid
|
Found in grapes and
wines and gives them a tart taste
|
Color
The color of food can
affect flavor. For example, adding more red color to a drink increases its
sweetness with darker colored solutions being rated 2–10% higher than lighter
ones even though it had 1% less sucrose concentration. The effect of color is
believed to be due to cognitive expectations.
Dietary Restrictions
Food manufacturers are
sometimes reluctant about informing consumers about the source from where the
flavor is obtained and whether it has been produced with the incorporation of
substances such as animal by-products glycerin (note that glycerin is also
available from vegetable sources), gelatin, and the like, and the use of
alcohol in the flavors.
Many Jews, Jains, Hindus, and Muslims adhere to religious dietary laws, and vegans
to personal convictions, which restrict the use of animal by-products and/or
alcohol in foods unless subject to oversight and inspection by their respective
religious authority or less-strict or circumstantial moral belief.
In many Western
countries, some consumers rely on a Jewish
Kosher Pareve certification mark to indicate that natural flavorings used
in a food product are free of meat and dairy (although they can still contain
fish). The Vegan Society's Sunflower
symbol (which is currently used by over 260 companies worldwide) can also
be used to see which products do not use any animal ingredients (including
flavorings and colorings).
Similarly, persons
with known sensitivities or allergies to food products are advised to avoid
foods that contain generic "natural flavors" or to first determine
the source of the flavoring before consuming the food. Such flavors may be
derived from a variety of source products that are themselves common allergens,
such as dairy, soy, sesame, eggs, and nuts.
Flavor Creation
Most food and beverage
companies do not create their own flavors but instead employ the services of a flavor
company. Food and beverage companies may require flavors for new products, product
line extensions (e.g., low fat versions of existing products) or changes in
formula or processing for existing products. In 2011, about U$S10.6 billion
were generated with the sale of flavors; the majority of the flavors used is
consumed in processed and packaged food.
The flavor creation is
done by a specially trained scientist called a "flavorist". The flavorist's job
combines extensive scientific knowledge of the chemical palette with artistic
creativity to develop new and distinctive flavors. The flavor creation begins
when the flavorist receives a brief from the client. In the brief the client
will attempt to communicate exactly what type of flavor they seek, in what
application it will be used, and any special requirements (e.g., must be all natural).
The communication barrier can be quite difficult to overcome since most people
aren't experienced at describing flavors. The flavorist will use his or her
knowledge of the available chemical ingredients to create a formula and
compound it on an electronic balance. The flavor will then be submitted to the
client for testing. Several iterations, with feedback from the client, may be
needed before the right flavor is found.
Additional work may
also be done by the flavor company. For example, the flavor company may conduct
sensory taste tests to test consumer acceptance of a flavor before it is sent
to the client or to further investigate the "sensory space." The
flavor company may also employ application specialists who work to ensure the
flavor will work in the application for which it is intended. This may require
special flavor delivery technologies that are used to protect the flavor during
processing or cooking so that the flavor is only released when eaten by the end
consumer.
Determination
Few standards are
available or being prepared for sensory analysis of flavors. In chemical
analysis of flavors, solid phase
extraction (SPE), solid phase
microextraction (SPME), and headspace
gas chromatography are applied to extract and separate the flavor compounds
in the sample. The determination is typically done by various mass
spectrometric techniques.
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