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Food Flavor
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Flavor Chemistry
Flavor is a combination of taste and aroma
Taste Sweet, sour, bitter, salty
Sensed on the tongue (protein receptors) Nerves sense metallic and astringent flavors
Aroma Volatiles released directly from the food Volatiles that are released in the mouth, then
sensed in the nasal cavity (retro-nasal).
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Flavor Chemistry
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Flavor Chemistry
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Sensory Impressions
Visual impressionColor, size, shape, luster
Odor
Volatile, odor-active compoundsTaste
Sweet, sour, bitter, salty
Somato-sensoryPain, burning, cold, warmth, astringent, fizzy
Trigeminal nerve response
Texture, resistance, elasticity
Sounds
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Taste Substances
Sweet attention because of interest in sugaralternatives and the desire to find suitablereplacements for the low-calorie sweetenerssaccharin and cyclamate
Bitter appears to be closely related to sweetnessfrom a molecular structure- receptor relationshipSourSalty reduction of sodium in diets havestimulated renewed interest in the mechanisms ofthe salty taste
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Structural basis of the sweetmodality
-OH groups Acree and Shallenberger AH/B concept
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Acree and Shallenberger
(Shallenberger & Acree) published a paper entitled the"Molecular Theory of Sweet Taste" in Nature [1969].
The model developed in that paper for sweetness was based on astructure-activity relationship between the simplest sweet tastingcompounds and their structural features of the stimulants and hasbecome known as the AH-B theory.The theory described with considerable success the structuralfeatures necessary for sweetness, but it was not sufficient to predictsweetness.
That is, not all compounds that satisfied the theory tasted sweet nor
was the theory able to predict potency level especially for very highpotency sweeteners.
However, all sweet compounds seemed to have an identifiable AH-B feature.
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covalently bound
H-bonding proton(AH)
an electronegativeatom (B)
lipophilic region ( g)
Sweet tasting compounds should have
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The perception of sweetnessis proposed to be due to achemical interaction thattakes place on the tongue
Between a tastant moleculeand tongue receptor protein
A sweet tastant molecule (i.e.glucose) is called the AH+/B-
glycophore . It binds to the receptor B-/AH+site through mechanisms thatinclude H-bonding.
THE AH/B THEORY OF SWEETNESS
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B
AH
B AH
Glycophore
Tongue receptor protein molecule
Hydrophobic interaction
For sweetness to be perceived, a molecule needs to have certain requirements.It must be soluble in the chemical environment of the receptor site on thetongue. It must also have a certain molecular shape that will allow it to bondto the receptor protein.
Lastly, the sugar must have the proper electronic distribution. This electronicdistribution is often referred to as the AH, B system. The present theory ofsweetness is AH-B-X (or gamma). There are three basic components
to a sweetener, and the three sites are often represented as a triangle.
AH+ / B-
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Gamma ( ) sites are relatively hydrophobic functional groupssuch as benzene rings, multiple CH 2 groups, and CH 3
Identifying the AH+ and B-regions of two sweet tastantmolecules: glucose and saccharin.
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Sucralose
Non-caloric sweetener producedby the selective chlorination of thesucrose molecule
Splenda1998, approved for table-topsweetener and use in various
foodsClean, sweet taste (600X sweeter thansucrose and no undesirable off-flavor
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Sucralose
Sucralose exhibits a high degree ofcrystallinity, high water solubility, and verygood stability at high temperatures, thusmaking it an excellent ingredient for bakery
applications. It is also quite stable at the pH ofcarbonated soft drinks, and only limitedhydrolysis to monosaccharide units occursduring usual storage of these products.Sucralose possesses a sweetness timeintensity profile similar to sucrose, andexhibits no bitterness or other unpleasantaftertastes.
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SaccharinSweetn Low, The 1 st artificial sweetener
Accidentally found in 1879 by Remsen and FahlbergSaccharin use increased during wars due to sugarrationing
By 1917, common table-top sweetener in AmericaBanned in 1977 due to safety issue1991, withdrew ban, but with warning label2000, removed warning label
Intensely sweet, but slight bitter aftertaste
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SaccharinSaccharin is about 300 times as sweet assucrose in concentrations up to theequivalent of a 10% sucrose solution, butthe range is from 200 to 700 times the
sweetness of sucrose depending on theconcentration and the food matrixSaccharin exhibits a bitter, metallicaftertaste, especially to some individuals,
and this effect becomes more evident withincreasing concentration
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Aspartame
Nutrasweet, EqualDiscovered in 1965 by J. SchlatterComposed of aspartic acid and phenylalanine4 kcal/g, but 200 times sweeter
Approved in 1981 for table-top sweetener andpowdered mixesSafety debating1996, approved for use in all foods and beverageShort shelf life, not stable at high temperature
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Aspartame
A caloric sweetener because it is adipeptide that is completely digested after
consumption.However, its intense sweetness (about200 times as sweet as sucrose) allowsfunctionality to be achieved at very low
levels that provide insignificant calories.It is noted for a clean, sweet taste that issimilar to that of sucrose.
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Acesulfame K
Sunette, Sweet OneDiscovered in 1967 by Hoechst1992, approved for gum and dry foods1998, approved for liquid useBlending with Aspartame due to synergistic effectStable at high temperature and long shelf life (3-4 years)Bitter aftertaste
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Acesulfame K
Acesulfame K is about 200 times as sweetas sucrose at a 3% concentration in solutionit exhibits a sweetness quality between thatof cyclamates and saccharin.
Acesulfame K possesses some metallic andbitter taste notes at higher concentrations itis especially useful when blended with other
low-calorie sweeteners, such as aspartame
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Acesulfame K
Acesulfame K is exceptionally stable at elevatedtemperatures encountered in baking, and it isalso stable in acidic products, such ascarbonated soft drinks.
Acesulfame K is not metabolized in the body,thus providing no calories, and is excreted bythe kidneys unchanged.Extensive testing has shown no toxic effects inanimals, and exceptional stability in foodapplications.
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Neotame
Brand new approved sweetener (Jan. 2000)7,000 ~ 13,000 times sweeter than sugarDipeptide methyl ester derivative; structurally
similar to AspartameEnhance sweetness and flavorBaked goods, non-alcoholic beverages (includingsoft drinks), chewing gum, confections and
frostings, frozen desserts, processed fruits andfruit juices, toppings and syrups.Safe for human consumption
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Polyhydric Alcohol Texturizers andReduced-Calorie Sweetener s
Polyhydric alcohols are carbohydratederivatives that contain only hydroxyl groupsas functional groups
they are generally water-soluble, hygroscopicmaterials that exhibit moderate viscosities athigh concentrations in water.Usage of some polyhydric alcohols is growing
because of demands for their reduced-caloriesweetener properties
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Polyhydric Alcohol Texturizers andReduced-Calorie Sweeteners
This class of substancesincludes
synthetic propylene
glycol (CH2OH-CHOH-CH3)naturally producedglycerol (CH2OHCHOH-CH2OH)
xylitol (CH2-OH-CHOH-CHOH-CHOH-CH2OH)from xylosesorbitol, and mannitol
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Polyhydric Alcohol Texturizers and Reduced-Calorie Sweeteners
The polyhydroxy structures of these compoundsprovide water-binding properties that have beenexploited in foods.Specific functions of polyhydric alcohols include
control of viscosity and textureretention of moisturereduction of water activitycontrol of crystallizationimprovement or retention of softnessimprovement of rehydration properties ofdehydrated foodsuse as a solvent for flavor compounds
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Bitter Taste Modality
BITTERNESS can beattributed to severalinorganics and organics
o KI CsCl MgSO 4o Certain amino acids
and peptides (dipeptideleucine-leucine)
o Alkaloids derived frompyridine (N-containing6-membered ring)andpurines
A = caffeine (1, 3, 7 trimethylxanthine) B = theobromine (from cacao )
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Bitter Taste Modality
GYCOSIDES are sugars that have been added to a naturalcompound .Citrus fruits generally have a bitter taste to them.
o This is due to the flavonoid compound Naringin.o Naringin actually has 2 sugars (both glucose) as part of its
structure.o Compound is still intensely bitter.o Removal of these sugars with naringinase, will render the
compound tasteless.o Naringin is then converted to Naringinin.o The de -bittering of grapefruit juice can be done, if desired.
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Salty Taste Modality
SALTY depends on the nature of the cation and anionin the ionic salt crystal structure; high molecular weight saltsmay be bitter; some salts may even exhibit sweetness
Examples: NaCl NaBr NaI KCl LiBr NaNO 3 = salty
KBr = salty + bitter
Lead acetate (toxic) = sweet
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Sour Taste Modality
SOURNESS and sour taste is often thought of as acid
However there is not a simple relationship between acid concentration
(pH) and sourness
Organic acids differ in sourness: CITRIC ACID (0.05 N solution): fresh taste sensation
LACTIC ACID (0.05 N solution): sour, tart
PROPIONIC ACID (0.05 N solution): sour, cheesy
ACETIC ACID (0.05 N solution): vinegar
PHOSPHORIC ACID (0.05 N solution): intense
MALIC ACID (0.05 N solution): green
TARTARIC ACID (0.05 N solution): hard
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Food flavorsMixtures of natural and/or artificial aromaticcompounds designed to impart a flavor, modify
a flavor, or mask an undesirable flavorNatural versus Artificial
Natural - concentrated flavoring constituents
derived from plant or animal sources Artificial - substances used to impart flavorthat are not derived from plant or animal
sources
Food Flavors
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Most natural flavors are concentrated from botanicals-plants, trees, fruits, and vegetables
Most artificial flavors are synthesized with high purity- pharmaceutical flavors
Isolation techniques - Steam distillation - mint and herbal oils- Solvent extraction - vanilla & oleoresins- Expression - citrus oils- Supercritical fluid extraction targeted extraction
Food Flavors
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Food Flavors
Natural flavors can also be enzymatically or chemically produced
- Fermentation reactions- Microbial enzymes
Saccharomyces Sp.
Lactobacillus Sp.Bacillus Sp.Molds
Maillard flavor compoundsGlucose + Glutamic acid = chickenGlucose + Lysine = burnt or fried potato
Glucose + Methionine = cabbageGlucose + Phenylalanine = caramelFructose + Glutamic acid = chickenFructose + Lysine = fried potatoFructose + Methionine = bean soupFructose + Phenylalanine = wet dog
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Artificial Flavors
Typically are esters
Esters have pleasant fruity aromas, derived from acids
a condensation reaction
ACID + ALCOHOL --> ESTER + WATER
Most artificial flavors are simple mixtures of esters
i.e.
Isobutyl formate + isobutyl acetate = raspberry
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Food Flavors
FERMENTATION and FLAVORO O
Diacetyl (CH3 C - C CH
3 ) is a compound produced by
Yeasts via fermentation of carbohydrates
Major compound in the flavor of cultured dairy productsButter and butter-like flavor
Compounds potentially used for diacetylformation
Lactic acid Oxalacetic acidPyruvic acid acetyl lactic acid
Acetaldehyde Citric acid
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Flavors complex mixtures of many compounds
-Amyl, butyl, ethyl esters - Amyl acetate = sweet fruity/ banana/ pear- Amyl caproate = sharp fruity/ pineapple- Amyl formate = sweet/ fruity
-Organic acids containing aldehydes , aromatic esters,alcohols, ketones
- Acetic acid = vinegary- Propionic acid = sour milk- Butyric acid = buttery
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Flavors complex mixtures of manycompounds
Brown flavors
- Caramelized, roasted or burnt character- Bread-yeast, caramel, chocolate, coffee, maple, peanut
- Sweet brown compounds Vanillin = sweet/ chocolate-likeMaltol = sweet/ malty/ brown (flavor enhancer)
Di-hydrocoumarin = sweet/ caramel/ nutlike
- Non-sweet brown compounds - Dimethyl pyrazine = nutty/roasted- 2,3,5 trimethyl pyrazine = chocolate/ roasted
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Flavors complex mixtures of manycompounds
- Woody compounds Alpha lonone = woody/balsamic/violet/red raspberryBeta lonone = woody/balsamic/black raspberry
- Spicy compounds Cinnamic aldehyde = cinnamonEugenol = clovesThymol = thymeZingerone = ginger oil
Capsicum = peppers- Sulfur compounds
- Diallyl disulfide = garlic onion- Methyl mercaptan = natural gas
- Methyl thio butyrate = sour milk
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Pungency
Cause characteristic hot, sharp, andstinging sensationsTwo kinds of pungent principles
non volatile and exert their effects on oraltissues (e.g. chili peppers, black pepper, andginger)
volatile (e.g. mustard, horseradish, radishes,onions, garlic, watercress, and clove)
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Pungency of Chile Pepper
Chili peppers (Capsicum sp.) contain a group ofsubstances known as capsaicinoidsCapsaicinoids are vanillylamides of monocarboxylic acidswith varying chain length (C8 C11) and unsaturation
Capsaicin is representative of these pungent principles
P f Bl k d Whi
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Pungency of Black and WhitePepper
Black and white pepper are made from the berries ofPiper nigrum
Black pepper is prepared from immature green berries
White pepper is made from more mature berries usuallyharvested at the time they are changing from green toyellow in color, but before they become red
Principal pungent compound in pepper is piperine an
amide
P f Bl k d Whit
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Pungency of Black and WhitePepper
The structure of piperine Trans geometry of thealkyl unsaturation isnecessary for strong
pungencyLoss of pungency duringexposure to light andstorage is attributedmainly to isomerizationsof these double bonds
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Pungency of Ginger
Ginger is a spice derived from the rhizomeof a tuberous perennial, Zingiber officinalePungency of fresh ginger is caused by agroup of phenylalkyl ketones calledgingerols
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Pungency of Ginger
Ginger is a spice derived from the rhizome of a tuberousperennial, Zingiber officinale
Pungency of fresh ginger is caused by a group ofphenylalkyl ketones called gingerols
Exposure of gingerol to an elevated temperature leads tocleavage of the alkyl chain external to the keto group,yielding a methyl ketone, zingerone, which exhibits onlymild pungency
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Vegetable, Fruit, and Spice Flavo rsSulfur-Containing Volatiles in Allium sp.
Plants in the genus Allium are characterized bystrong, penetrating aromasImportant members are onions, garlic, leek,
chives, and shallotsThese plants lack the strong characterizingaroma unless the tissue is damaged andenzymes are decompartmentalized so that flavorprecursors can be converted to odorous volatile
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Reactions involved in the formationof onion flavour
The precursor of the sulfur compounds that areresponsible for the flavor and aroma of thisvegetable is S-(1-propenyl)-L-cysteine sulfoxide
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Reactions involved in the formationof onion flavour
Rapid hydrolysis of the S-(1-propenyl)-L-cysteinesulfoxide by allinase yields a hypothetical sulfenicacid intermediate along with ammonia and
pyruvate
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Reactions involved in the formationof onion flavour
The sulfenic acidundergoes furtherrearrangements to yieldthe lachrymator,
thiopropanal S-oxidePart of the unstablesulfenic acid alsorearranges anddecomposes to
mercaptans, disulfides,trisulfides, andthiophenes
Vegetable Fruit and Spice Flavors
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Vegetable, Fruit, and Spice FlavorsSulfur-Containing Volatiles in the Cruciferae
The Cruciferae family contains Brassica plants such ascabbage, brussel sprouts, turnips, brown mustard,watercress, radishes and horseradishThe active pungent principles in the Cruciferae are alsovolatile and therefore contribute to characteristic aromasThe pungency sensation frequently involves irritationsensations, particularly in the nasal cavityThe flavor compounds in these plants are formed throughenzymic processes in disrupted tissues and throughcooking
Reactions involved in the formation of
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Reactions involved in the formation ofCruciferae flavors
Pungency in certain raw vegetables [mustards, (horse)radish,cabbages etc.] are due to thiosugar derivatives - glucosinolates
When cells are damaged, such as in cutting or chewing,the action of myrosinase triggers the breakdown ofglucosinolates into isothiocyanates
Reactions involved in the formation of
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Reactions involved in the formation ofCruciferae flavors
Processing at temperatures well above ambient (cookingand dehydrating) tends to destroy the isothiocyanates andenhance the amount of nitriles and other sulfur-containingdegradation and rearrangement compounds.
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Lipoxygenase-Derived Flavors in Plants
In plant tissues, enzyme-induced oxidativebreakdown ofunsaturated fatty acidsoccurs extensivelyyielding to characteristicaromas associated withsome ripening fruits and
disrupted tissuesHexenal gives the green flavor whilenonadienal gives the inherent cucumberand melon flavours
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Sunlight Flavor
Riboflavin is a catalyst for production of the sunlightflavor.
1) Milk protein and riboflavin sunlight sunlightflavor
2) Riboflavin increase in milk will increase thesunlight flavor
3) Riboflavin removal prevent the sunlight flavorSunlight and the fluorescent lighting in stores coulddecrease the freshness and flavor of milk and thepotency of vital vitamins in itthe majority of natural and artificial light could beblocked by containers that were yellow instead of white
Interactions of Flavours
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Interactions of Flavourswith Other Food Constituents
Aroma interactions with lipids, proteins andcarbohydrates affect the retention ofvolatiles within the food
The interactions affect the intensity andquality of food aroma.Proteins are known to bind flavour
compounds through hydrophobicinteractions with the volatiles
Interactions of Flavors
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Interactions of Flavorswith Protein
Retentions of volatiles by protein is lowerthan that by fatIn emulsions the presence of protein in theoil/water interface induces a significanteffect on flavour release and flavourperception of hydrophobic flavour
compounds
Interactions of Flavors
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Interactions of Flavorswith Carbohydrates
Amylose form complexes with aromaticcompoundHydrocolloids limit diffusion of aromaticcompounds due to change in viscosity
Interactions of Flavors
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Interactions of Flavorswith Lipids
Addition of fat induces the significantretention of hydrophobic flavor compoundsMelting point of fats influences the solubilityof the aromatic compounds and thus theflavor release