Food Chem- Flavour

• Taste
• Odor or smell
• Mouthfeel

Taste buds

Sweet, sour, salt, bitter

Mostly located at the tip of the tongue

To the front sides of the tongue

To the back sides of the tongue

At the back of the tongue

We percieve in the olfactory epitelium which is in the upper palate of the mouth

The way the food feels in the mouth and is sensed by the jaws and teeth

Molecules in food interact with taste receptors in the mouth and as a result of the interactions, signals are sent to the central nervous system where they are translated into the different flavor sensations we percieve

• Due to electronegative elements of organic molecules
• An atom that is electronegative has a high tendency to attract electrons
• Ex. alcohols (glycerol, xylitol), aldehydes (cinnamic aldehyde), certain amino acids (D-histidine)

D-amino acids tend to be sweeter than other amino acids

Sucrose is assigned an arbitrary number of 1 and other sugars are compared with sucrose on a scale known as the Relative Sweetness Scale

1

0.27

0.5-0.7

1.1-1.5

100-200

300

• L-Asp-NH2 is tasteless
• D-Asp-NH2 is sweet

• L-glu is meaty
• D-glu is tasteless

• L-His is tasteless to bitter
• D-His is sweet

• L-Ile is bitter
• D-Ile is sweet

• L-Try is bitter
• D-Try is very sweet

Sugar, invert sugar, conventional corn syrup, high fructose corn syrup, maltodextrin, maple syrup

Today's challenge is to provide good tasting sugar-free products (low calorie, non-carcinogenic sweeteners)

• Cariogenicity
• Sweetness equivalent
• Solubility
• Hydroscopicity
• Viscosity
• Laxitive effect
• Cost
• Heat of solution

• Cariogenicity depends on whether the sweetner is susceptible to fermentation by oral microorganisms
• Generally, polyols are either resistant to fermentation or not fermented appreciably
• Thus, formation of cavity causing fermentation plaque acids is minimal

Consumers are concerned with both sweetness and the quality of that sweetness.  The alternate sweetener must provide the same sweet taste the consumer associates with the sugar sweetened counterpart, without objectionable aftertaste

The sweetness of these polyols, it is isosweet to sugar, and without aftertaste

Xylitol>maltitol>mannitol>sorbitol>isomalt>polydextrose

• The solubility of the sweetener can influence the mouthfeel, texture, and perception of sweetness onset of the final product
• It is desirable for the alternate sweetener to have similar solubility profile as traditional sugar

Alternate sweeteners with low solubility result in products with a chalky mouthfeel

The solubility of the sweetener can influence the mouthfeel, texture, and perception of sweetness onset of the final product

Viscosity of the alternate sweetener can influence the characteristics of the product, eg., xylitol has a lower viscosity than sugar and can yield a poor bodying effect unless compensated for

Xylitol has a lower viscosity than sugar and polydextrose has a higher viscosity.  Combinations of xylitol and polydextrose help to produce acceptable products

• Hygroscopicity of an alternate sweetener can affect shelf-stability of a product
• Shelf-life of products from high hygroscopic materials is relatively short; the products may even require individual wrapping

Mannitol and isomalt are non-hygroscopic, while the remaining polyols are fairly hygroscopic

When crystalline polyols dissolve, the relative lower heat of solution (versus sugar) produces a pleasant cooling effect in the mouth, and gives them a 'taste edge' over sugar in many applications such as mint flavors

Xylitol is the largest; mannitol and sorbitol also produce significant cooling effects

Chewing gum, tablets, mints and lozenges, hard and soft coatings, fondants, hard candies, certain chocolates and chocolate coatings

On a dry solids basis, maltitol is about 5x more expensive than corn syrup

Sorbitol is about 2-3 times as expensive as sugar

Mannitol, xylitol, isomalt, and maltitol are the most expensive

Polyols and polydextrose have a laxative effect due to the fact that they are incompletely digested and slowly absorbed

Food which provide >50g sorbitol/day or >20g mannitol/day are required to pose a label warning statement concerning the potential laxative effect.  It is the same with foods providing >15g polydextrose/day

Xylitol is metabolized independently of insulin- thus, a very useful ingredient in foodstuffs prepared for diabetics

Xylitol is resistant to fermentation by oral bacteria (streptococcus mutans).  Thus, intake of xylitol does not cause pH decline (as with sucrose) to demineralize tooth enamel and cause decay

• High thermal stability
• High microbiological stability
• Inhibits many food-spoilage organisms
• Does not react with amino acids
• Moderate hygroscopicity
• Effective bulking agent

• Chewing gum and other confectionery
• Pharmaceuticals- syrups, chewable tablets
• Oral hygiene products (toothpastes, mouthwashes, dietetic and diabetic foods)

With sorbitol or maltitol in the syrup phase, and xylitol in the solid phase

Exceptional sugar-free chocolate can be prepared by combining maltitol and xylitol as the sweetening phase in a ration of 80:20

• Eliminates burning sensation in back of throat due to osmotic properties of other polyols
• Diminishes perception of cooling effect caused by other polyols

Xylitol and mannitol in 1:1 ratio produces sugar-free chocolates with enhanced sweetness and diminished gritty mouthfeel

• High quality sugar-free jellies prepared using combination of maltitol syrup, xylitol and sorbitol in a 4:1:1 ratio
• Jellies with decreased sweetness may be prepared using a 2:1 combination of maltitol syrup and sorbitol

Sugar-free hard candies are made with sorbitol or maltitol syrup

Maltitol syrup, sorbitol and xylitol can be combined with alginate and gelatin gum systems to create a sugar-free chewy candy

Sugar-free compressed candies and mints are currently sweetened with sorbitol or mannitol; or a 1:1 ratio combination of xylitol and sorbitol to enhance sweetness

• Sweet, syrupy liquid made by honey bees in bee hives
• It is a mixture of fructose (33-40%) and glucose (32-42%) with 15-20% H2O and significant content of phenolics

Mixture of glucose, fructose and sucrose- obtained by boiling the sap of the sugar maple tree

The dark syrupy liquid left after recovery of sugar from either sugar cane or sugar beet.  Has variable composition

• In general, the D-amino acids tend to be sweet and the L-isomers are bitter
• Some exceptions are D-Ala which has an insipid taste (tasteless) and L-Ala which is sweet

• D-Try is ~35x sweeter than sucrose
• Its synthetic derivative 6-chloro-D-Try is ~1000x sweeter than sucrose

A glycoprotein from berries found in West Africa- the fruit of this plant is commonly referred to as the miracle fruit.

Has the unusual property of tasting intensely sweet only in the presence of acids

A mixture of sweet-tasting proteins found in the African fruit known as katemfe.  It is about 1,500-2,500x sweeter than sucrose

• Monellin, brazellin, neoculin (all from plants found in tropical rainforests)
• Mabinlin (china)

• High intensity synthetic sweetener
• Na or Ca salts
• ~300x sweeter than sucrose

• High intensity synthetic sweetener
• Na or Ca salts
• ~30-40x sweeter than sucrose
• Converted to cyclohexylamine- a carcinogen, by intestinal bacteria in certain individuals

Converted to cyclohexylamine- a carcinogen, by intestinal bacteria in certain individuals

The methyl ester of the dipeptide, L-aspartyl-L-phenylalanine; about 200x sweeter than sugar

Approved in early 1980s for use as a table-top sweetener, in dry beverage mixes, and in foods that are not heat processed

About 200x sweeter than sugar

A relatively new sweetener approved for food use in 1988; about 200x sweeter than sugar; more stable than other synthetic sweeteners; and sweet taste is clean and does not linger

200x sweeter than sugar

• Trichloro derivative of sucrose; ~600x sweeter than sucrose
• More stable than sugar, and appears to be very suitable for several food uses

~600x sweeter than sucrose

• A derivative of the dipeptide- L-alpha-aspartyl-alaninamide
• It is about 2,000-3,000x sweeter than sucrose
• Alitame is stable to heat, which is a definite advantage over aspartame in some food application

Alitame is stable to heat, which is a definite advantage over aspartame in some food applications

Due to H+ ions from acids (lactate, pyruvate, acetate, malate, etc)

[H+] determines the degree of sourness, not the total acidity

Other contibutor factors include: nature of acidic group, buffering capacity, presence of other compounds

Some components such as proteins and amino acids have buffering effects and resist changes in pH even after small amounts of OH- are added

Citric acid is produce commercially from pineapple skins by fermentation, and is a broad spectrum

Produced via oxidation of cyclohexanol

• Acetic
• Adipic
• Benzoate
• Sorbate
• Formic
• Propionic
• Malate

• Impart flavor
• Preserve foods
• Inactivate enzymes
• Texture- jams and jellies, acids are needed for gel formation and stabilization
• In dairy products enhance product formation (cheese)

Acids can stabilize (thereby enhance) the activities of anti-oxidants like vitamin C

The majority of the acids used in foods are organic acids

Inorganic acids used in foods are H3PO4 (phosphoric acid) and HCl (hydrochloric acid)

• Optimum acidity in desserts, sugar confectinery, fruit-flavored beverages enhances flavor of product
• Acid milieu curtails mircobial activity/metabolism and prevents spoilage
• An acid milieu also slows down or even stops the action of several enzymes- thus, preventing food spoilage by autolysis
• Acids enhance the action of natural antioxidants

In pectin-based jams and jellies, gel strength depends on the use of the correct acidity

Important to have the right acidity pH during wine processing to obtain stable products

Acetic acid, adipic acid, citric acid, fumaric acid, lactic acid, malic acid, propionic acid, lactic acid, malic acid, propionic acid, sorbic acid, succinic acid, succinic anhydride, and tartaric acid

Prepared commercially by oxidation of acetaldehyde or butane

• Used in industry as vinegar- to preserve pickles, sauces, relishes, and also impart sharp piquancy and aromatic flavor to foods
• Vinegar produced by yeast fermentation of fruit juices, sucrose, glucose, malt, etc

Clear, colorless liquid

An odorless, white crystalline powder

Produced on a commercial scale by oxidation of cyclohexanol

Has limited solubility in H2O, but is very soluble in alcohol and acetone

A general purpose acidulant- as buffering and neutralizing agent

Produced commercially from pineapple waste

Highly soluble in H2O and alcohol

Citric acid

An odorless, white granular or crystalline powder

Produced during fermentation of glucose or molasses by Rhizopus species

Sparingly soluble in H2O, soluble in ethanol (EtOH)

Widely used in dry powdered food producs where solubility is not a significant quality factor- but where its preservative/antioxidant properties are of more value

A viscous, colorless to pale yellow, non-volatile liquid with distinct odor

Produced commercially by controlled fermentation of sucrose, potato starch, molasses, etc

Commonly used acidulant in fermented and dairy products

• An odorless, white crystalline powder, soluble in H2O and EtOH
• The commercial product is a racemic mixture of the D- and L- isomers

Used in non-alcoholic beverages, canned tomatoes, fruit products, and fruit pie fillings

• An oily liquid with a slight pungent/rancid odor
• On dilution, resembles butyric acid

Completely miscible with H2O and EtOH

Used more in baking to suppress mold growth

An almost odorless, white crystalline substance with a slight acidic taste

Limited solubility in H2O and EtOH. K, Na, and Ca salts soluble in H2O, and release free acid in low pH media

Salt forms used more for their anti-fungal and preservative properties

An odorless, white crystalline solid with a sharp acidic as well as slight bitter taste

Soluble in both H2O and EtOH

As a general purpose GRAS status acidulant

A white crystalline powder- stable when dry, but converted to succinic acid when dissolved in H2O

Succinic anhydride

Mostly used as a leavening agent in baked goods

• A colorless, translucent crystalline powder
• Odorless, but has a strong acidic taste

Very soluble in H2O and EtOH

Occurs in many fruits, especially grapes, and is obtained as the K or Ca salt during wine fermentation

GRAS status general purpose acidulant

A colorless, crystalline solid; commonly used in the form of a clear, syrupy liquid with concentration ranging from 75-85%

Has a flat taste which enables it to blend very well with non-fruit flavors

Used in formulating cola drinks, and in cheese making/brewing for pH control

• Due to salt ions (Na+, K+, Cl-, etc)
• Salty taste dependent on size of ions (the smaller sized ions are salty, the larger sized ions tend to be bitter)

The smaller sized ions are salty; the larger sized ions tend to be bitter

• Formed by the neutralization of acids and bases
• Acid+Base = Salt+H2O

Most individuals can tolerate up to 2% salt in foods, beyond that, salt may cause nausea in some people

Some digestive enzymes like cathepsins and gastrucins are activated by Cl-, and thus salt aids in digestion

Lowers Aw in the product to prevent microbial proliferation; enzyme activity control

Concerns with the use of salt in foods because of high blood pressure

• Na-compounds are replaced with non-Na-compounds (K+. NH4+)
• Spices

• LiCl
• LiBr
• NaNO
• NaCl
• KCl

• CsCl
• KI
• MgSO4

• PbAc
• BeAc

NaCl

Common salt with powdered dehydrated vegetables (eg. celery salt) as a base

• Bitterness in foods due to various organic and inorganic compounds
• Mostly of plant origin

Bitter taste is unpleasant, however, in combination with other taste sensations, it contributes significantly to consumer acceptance of various products

Alkaloids, glycosides, certain amino acids/peptides

• Nitrogenous compounds widely distributed in plants as salts with acetic acid, or a carboxylic acid
• Ex. Quinine, caffeine, and theobromine

Bitter tasting alkaloid

A white amorphous powder

Limited solubility in H2O, although the sulfate and hydrochloride salts are H2O-soluble

Quinine

Used in beverages

A crystalline purine deriative found in coffee beans (1.5%), tea leaves (5%), and cola nuts (2.5%)

Solubility in H2O is 1:50 (~25°C) or 1:2 (~65°C)

A powerful stimulant with GRAS status

Structurally related with caffeine, and often found together with caffeine in various plants (coffee beans, cola nuts)

Agylcones esterified with various sugars (naringin, hesperidin, coniferin, and sinigrin)

Found predominantly in grapefruit and bitter orange

Hydrolysis yields D-rhamnoglycose, and the aglycone- naringenin

Found in sweet orange and several other citrus fruits

Yields rutinose and the aglycone hesperetin on hydrolysis

Found in conifer wood

Produces coniferyl alcohol on hydrolysis- which may subsequently be oxidized to vanillin

Found in black mustard seed, it yields glucose and allyl isothiocyanate on hydrolysis

• A dipeptide responsible for the taste effect
• It acts by interacting with the taste receptors and inhibiting them from sensing sweet and bitter tastes

Colds and the flu inhibit our capacity to perceive taste because the receptors are rendered less sensitive to volatile compounds in the food

Able to inhibit the taste receptors from sensing sweet and bitter tastes

About 25% of the population is unable to sense bitterness of phenylthiocarbamate

• Solubility
• Concentration or amount of the material

• The minimum amount of the taste compound that must be present (or dissolved) in the saliva for the sensation to be percieved
• Also applies to odor/smell

Saltiness may be enhanced by adding small amount of acid (like vinegar)

It is easy to over-salt vegetables because the acids present can enhance salty taste

Add a sub-threshold amount of sugar to reduce the bitterness, or by sprinkling a sub-threshold amount of salt to reduce bitterness

Sweet taste may be enhanced by adding a sub-threshold amount of salt

• Compounds that improve or intensify flavor quality in foods
• Compounds that on their own have little flavor sensation, but when used together with other flavor-active compounds are able to enhance or intensify the taste percieved

• Monosodium glutamate (MSG)
• Nucleotides (IMP and GMP)
• Maltol (3-hydroxy-2-methyl-4-pyrone)

• Have a sweet, meaty taste, but breakdown to form bitter compounds
• Use the K value (ratio of IMP concentration to ATP and its other breakdown products)
• Used as an index of muscle food freshness

Occurs naturally in roasted malt; also found in the larch and pine trees

Used as a flavor enhancer for baked foods and certain confections

• Pain
• Temperature
• Tactile sesations (texture, astringency, and consistency)

• Ethereal (thin rod-shaped molecules)
• Camphoraceous (hemispherical-shaped molecules; ~7A im diameter)
• Musky (flat disk shaped ~10A in diameter)
• Floral (shaped as keyholes)
• Minty (wedge-shaped molecules)
• Pungent (negatively charged molecules)
• Putrid (positively charged molecules)

Thin rod-shaped moleules

• Hemispherical-shaped molecules
• ~7A in diameter

• Flat disk shaped
• ~10A diameter

Shaped as keyholes

Wedge-shaped molecules

Pungent compounds are negatively charged, Putrid compounds are positively charged

• Preference testing
• Difference testing

Ususally used in product development to verify acceptability of a developed product and may comprise of trained or untrained testers

• Used to verify whether products differ in particular taste attributes
• Requires trained panel (member have been trained to be able to discriminate between the various flavor attributes)

• The paired comparison test
• The hedonic scale
• The ranking test

Uses a 9 point scale to evaluate sensory attributes ranking from the 2 extremes

Using samples A, B, C, D for example, rank them in order from best to worst based on particular attributes

• Simple paired comparison test
• Scheffe paired comparison test
• Multiple comparison test
• Triangle test
• The duo-trio test
• Ranking test

• Makes you actually quantify each degree to which they differ 
• Ex. A is 50% sweeter than B

• Compare A to B, then A to C, then B to C, etc
• Presented with more than 2 samples and asked to compared them with each other

• Panel provided with 3 samples, 2 samples are the same, one is different
• Panel is asked to pick the odd one

• Slight modification on triangle test
• 3 samples, one is given as a reference, choose which of the other 2 samples is identical to the reference