Food Chem- Flavour
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What are the 3 components of food flavor?
- Odor or smell
How does the tongue percieve flavor?
What are the 4 true or basic tastes?
Sweet, sour, salt, bitter
Where is sweet taste percieved?
Mostly located at the tip of the tongue
Where is salty taste percieved?
To the front sides of the tongue
Where is sour taste percieved?
To the back sides of the tongue
Where is bitter taste percieved?
At the back of the tongue
How do we percieve smell in the mouth?
We percieve in the olfactory epitelium which is in the upper palate of the mouth
What is mouthfeel?
The way the food feels in the mouth and is sensed by the jaws and teeth
How is taste percieved by the brain?
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
What is responsible for the sweet taste in foods?
- 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)
How does enantiomerism effect the sweetness of amino acids?
D-amino acids tend to be sweeter than other amino acids
How is the relative sweetness of sugars measured?
Sucrose is assigned an arbitrary number of 1 and other sugars are compared with sucrose on a scale known as the Relative Sweetness Scale
What is the relative sweetness of sucrose?
What is the relative sweetness of lactose?
What is the relative sweetness of glucose?
What is the relative sweetness of fructose?
What is the relative sweetness of aspartame?
What is the relative sweetness of sucralose?
Describe the tastes of L- and D-Asp-NH2
- L-Asp-NH2 is tasteless
- D-Asp-NH2 is sweet
Describe the tastes of L- and D-glutamic acid
- L-glu is meaty
- D-glu is tasteless
Describe the tastes of L- and D-histidine
- L-His is tasteless to bitter
- D-His is sweet
Describe the tastes of L- and D-isoleucine
- L-Ile is bitter
- D-Ile is sweet
Describe the tastes of L- and D-tryptophan
- L-Try is bitter
- D-Try is very sweet
What are some examples of traditional sweetners?
Sugar, invert sugar, conventional corn syrup, high fructose corn syrup, maltodextrin, maple syrup
What is today's challenge regarding sweeteners?
Today's challenge is to provide good tasting sugar-free products (low calorie, non-carcinogenic sweeteners)
What is the criteria for selecting alternate sweeteners?
- Sweetness equivalent
- Laxitive effect
- Heat of solution
What effects the cariogenicity of a sweetener?
- 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
How does sweetness equivalent affect the choice of an alternate sweetener?
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
What is xylitol?
The sweetness of these polyols, it is isosweet to sugar, and without aftertaste
What is the relative sweetness of alternate sweeteners?
How does solubility affect the choice for an alternate sweetener?
- 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
How do alternate sweeteners with low solubility affect the mouthfeel?
Alternate sweeteners with low solubility result in products with a chalky mouthfeel
Why is it desirable for alternate sweeteners to have a similar solubility profile as a traditional sugar?
The solubility of the sweetener can influence the mouthfeel, texture, and perception of sweetness onset of the final product
How does the viscosity of the alternate sweetener affect the 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
Why are xylitol and polydextrose often combined in products?
Xylitol has a lower viscosity than sugar and polydextrose has a higher viscosity. Combinations of xylitol and polydextrose help to produce acceptable products
Why is hygroscopicity important when choosing an alternate sweetener?
- 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
Which alternate sweeteners are non-hygroscopic?
Mannitol and isomalt are non-hygroscopic, while the remaining polyols are fairly hygroscopic
Why is heat of solution important when choosing an alternate sweetener?
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
Which alternate sugar has the largest cooling effect?
Xylitol is the largest; mannitol and sorbitol also produce significant cooling effects
What are some applications that take advantage of the polyol cooling effect?
Chewing gum, tablets, mints and lozenges, hard and soft coatings, fondants, hard candies, certain chocolates and chocolate coatings
Relate the prices of maltitol and corn syrup
On a dry solids basis, maltitol is about 5x more expensive than corn syrup
Relate the prices of sorbitol and sugar
Sorbitol is about 2-3 times as expensive as sugar
Which are the most expensive alternate sweeteners?
Mannitol, xylitol, isomalt, and maltitol are the most expensive
Which alternative sweeteners have a laxative effect and why?
Polyols and polydextrose have a laxative effect due to the fact that they are incompletely digested and slowly absorbed
Which foods require a label due to laxative effects?
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
Why is xylitol good for diabetics?
Xylitol is metabolized independently of insulin- thus, a very useful ingredient in foodstuffs prepared for diabetics
Why doesnt xylitol cause tooth decay?
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
What are some technological characteristics of xylitol?
- High thermal stability
- High microbiological stability
- Inhibits many food-spoilage organisms
- Does not react with amino acids
- Moderate hygroscopicity
- Effective bulking agent
What are some applications of xylitol?
- Chewing gum and other confectionery
- Pharmaceuticals- syrups, chewable tablets
- Oral hygiene products (toothpastes, mouthwashes, dietetic and diabetic foods)
How are sugar free fondants made?
With sorbitol or maltitol in the syrup phase, and xylitol in the solid phase
How is sugar free chocolate made?
Exceptional sugar-free chocolate can be prepared by combining maltitol and xylitol as the sweetening phase in a ration of 80:20
What are the benefits of using maltitol in chocolates?
- Eliminates burning sensation in back of throat due to osmotic properties of other polyols
- Diminishes perception of cooling effect caused by other polyols
Why are xylitol and mannitol used in chocolates?
Xylitol and mannitol in 1:1 ratio produces sugar-free chocolates with enhanced sweetness and diminished gritty mouthfeel
How are sugar free jellies prepared?
- 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
How are sugar-free hard candies made?
Sugar-free hard candies are made with sorbitol or maltitol syrup
How are sugar-free chewy candies made?
Maltitol syrup, sorbitol and xylitol can be combined with alginate and gelatin gum systems to create a sugar-free chewy candy
How are compressed mints made?
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
What is honey?
- 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
What is maple syrup?
Mixture of glucose, fructose and sucrose- obtained by boiling the sap of the sugar maple tree
What is molasses?
The dark syrupy liquid left after recovery of sugar from either sugar cane or sugar beet. Has variable composition
What is the general rule for the flavor of D- and L- amino acids?
- 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
Why is D-tryptophan used as a sweetener?
- D-Try is ~35x sweeter than sucrose
- Its synthetic derivative 6-chloro-D-Try is ~1000x sweeter than sucrose
What is miraculin?
A glycoprotein from berries found in West Africa- the fruit of this plant is commonly referred to as the miracle fruit.
Why is miraculin referred to as the miracle fruit?
Has the unusual property of tasting intensely sweet only in the presence of acids
What is Thaumatin?
A mixture of sweet-tasting proteins found in the African fruit known as katemfe. It is about 1,500-2,500x sweeter than sucrose
What are some other sweet tasting proteins?
- Monellin, brazellin, neoculin (all from plants found in tropical rainforests)
- Mabinlin (china)
What is saccharin?
- High intensity synthetic sweetener
- Na or Ca salts
- ~300x sweeter than sucrose
What are cyclamates?
- High intensity synthetic sweetener
- Na or Ca salts
- ~30-40x sweeter than sucrose
- Converted to cyclohexylamine- a carcinogen, by intestinal bacteria in certain individuals
Why are cyclamates harmful?
Converted to cyclohexylamine- a carcinogen, by intestinal bacteria in certain individuals
What is aspartame?
The methyl ester of the dipeptide, L-aspartyl-L-phenylalanine; about 200x sweeter than sugar
When was aspartame approved and what for?
Approved in early 1980s for use as a table-top sweetener, in dry beverage mixes, and in foods that are not heat processed
How sweet is aspartame?
About 200x sweeter than sugar
What is acesulfame K?
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
How sweet is acesulfame K?
200x sweeter than sugar
What is sucralose?
- Trichloro derivative of sucrose; ~600x sweeter than sucrose
- More stable than sugar, and appears to be very suitable for several food uses
How sweet is sucralose?
~600x sweeter than sucrose
What is alitame?
- 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
Why is alitame better than aspartame?
Alitame is stable to heat, which is a definite advantage over aspartame in some food applications
What is responsible for the sour taste in food?
Due to H+ ions from acids (lactate, pyruvate, acetate, malate, etc)
What determines the sourness of food?
[H+] determines the degree of sourness, not the total acidity
What else, other than H+ contributes to sour taste?
Other contibutor factors include: nature of acidic group, buffering capacity, presence of other compounds
How do proteins and amino acids effect sourness?
Some components such as proteins and amino acids have buffering effects and resist changes in pH even after small amounts of OH- are added
How is citric acid produced commercially?
Citric acid is produce commercially from pineapple skins by fermentation, and is a broad spectrum
How is adipic acid produced?
Produced via oxidation of cyclohexanol
What are some examples of organic acids?
Why are acids added to foods?
- 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)
How does acid effect antioxidants?
Acids can stabilize (thereby enhance) the activities of anti-oxidants like vitamin C
What are the majority of acids used in foods?
The majority of the acids used in foods are organic acids
Which inorganic acids are used in foods?
Inorganic acids used in foods are H3PO4 (phosphoric acid) and HCl (hydrochloric acid)
Why are acidulants used?
- 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
Why is acidity important in jams and jellies?
In pectin-based jams and jellies, gel strength depends on the use of the correct acidity
Why is acidity important in wine production?
Important to have the right acidity pH during wine processing to obtain stable products
What are the common organic acids used in foods?
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
How is acetic acid prepared?
Prepared commercially by oxidation of acetaldehyde or butane
How is acetic acid used in the industry?
- 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
What does acetic acid look like?
Clear, colorless liquid
What does adipic acid look like?
An odorless, white crystalline powder
How is adipic acid produced?
Produced on a commercial scale by oxidation of cyclohexanol
What is the solubility of adipic acid?
Has limited solubility in H2O, but is very soluble in alcohol and acetone
What is adipic acid used for?
A general purpose acidulant- as buffering and neutralizing agent
How is citric acid produced?
Produced commercially from pineapple waste
What is the solubility of citric acid?
Highly soluble in H2O and alcohol
What is the most widely distributed of the natural acids?
What does fumaric acid look like?
An odorless, white granular or crystalline powder
How is fumaric acid produced?
Produced during fermentation of glucose or molasses by Rhizopus species
What is the solubility of fumaric acid?
Sparingly soluble in H2O, soluble in ethanol (EtOH)
How is fumaric acid used in food products?
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
What does lactic acid look like?
A viscous, colorless to pale yellow, non-volatile liquid with distinct odor
How is lactic acid produced?
Produced commercially by controlled fermentation of sucrose, potato starch, molasses, etc
How is lactic acid used in food products?
Commonly used acidulant in fermented and dairy products
What does malic acid look like?
- An odorless, white crystalline powder, soluble in H2O and EtOH
- The commercial product is a racemic mixture of the D- and L- isomers
How is malic acid used in food products?
Used in non-alcoholic beverages, canned tomatoes, fruit products, and fruit pie fillings
What does propionic acid look like?
- An oily liquid with a slight pungent/rancid odor
- On dilution, resembles butyric acid
What is the solubility of propionic acid?
Completely miscible with H2O and EtOH
How is propionic acid used in food?
Used more in baking to suppress mold growth
What does sorbic acid look like?
An almost odorless, white crystalline substance with a slight acidic taste
What is the solubility of sorbic acid?
Limited solubility in H2O and EtOH. K, Na, and Ca salts soluble in H2O, and release free acid in low pH media
How is sorbic acid used in foods?
Salt forms used more for their anti-fungal and preservative properties
What does succinic acid look like?
An odorless, white crystalline solid with a sharp acidic as well as slight bitter taste
What is the solubility of succinic acid?
Soluble in both H2O and EtOH
How is succinic acid used in foods?
As a general purpose GRAS status acidulant
What does succinic anhydride look like?
A white crystalline powder- stable when dry, but converted to succinic acid when dissolved in H2O
What is the only anhydride permited for commercial use?
How is succinic anyhydride used in foods?
Mostly used as a leavening agent in baked goods
What does tartaric acid look like?
- A colorless, translucent crystalline powder
- Odorless, but has a strong acidic taste
What is the solubility of tartaric acid?
Very soluble in H2O and EtOH
Where does tartaric acid occur?
Occurs in many fruits, especially grapes, and is obtained as the K or Ca salt during wine fermentation
How is tartaric acid used in foods?
GRAS status general purpose acidulant
What is phosphoric acid?
A colorless, crystalline solid; commonly used in the form of a clear, syrupy liquid with concentration ranging from 75-85%
What does phosphoric acid taste like?
Has a flat taste which enables it to blend very well with non-fruit flavors
How is phosphoric acid used in foods?
Used in formulating cola drinks, and in cheese making/brewing for pH control
What is responsible for the salty taste in foods?
- 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)
How does the size of salt ions effect their flavor?
The smaller sized ions are salty; the larger sized ions tend to be bitter
How are salt ions formed?
- Formed by the neutralization of acids and bases
- Acid+Base = Salt+H2O
How much salt can the average person tolerate?
Most individuals can tolerate up to 2% salt in foods, beyond that, salt may cause nausea in some people
How does salt aid in digestion?
Some digestive enzymes like cathepsins and gastrucins are activated by Cl-, and thus salt aids in digestion
How is salt used for food preservation?
Lowers Aw in the product to prevent microbial proliferation; enzyme activity control
Why are there concerns about using salt in foods?
Concerns with the use of salt in foods because of high blood pressure
What are some alternatives to using salt in foods?
- Na-compounds are replaced with non-Na-compounds (K+. NH4+)
What are some examples of salty salts?
What are some examples of bitter salts?
What are some examples of sweet salts?
What has been used since ancient times to impart salty taste to foods and/or preserve foodstuffs?
What re vegetized salt substitutes?
Common salt with powdered dehydrated vegetables (eg. celery salt) as a base
What is responsible for bitter taste in foods?
- Bitterness in foods due to various organic and inorganic compounds
- Mostly of plant origin
Why is bitter taste important?
Bitter taste is unpleasant, however, in combination with other taste sensations, it contributes significantly to consumer acceptance of various products
What are the 3 classes of organic compounds responsible for bitterness in foods?
Alkaloids, glycosides, certain amino acids/peptides
What are alkaloids?
- Nitrogenous compounds widely distributed in plants as salts with acetic acid, or a carboxylic acid
- Ex. Quinine, caffeine, and theobromine
What is Quinine?
Bitter tasting alkaloid
What does quinine look like?
A white amorphous powder
What is the solubility of quinine?
Limited solubility in H2O, although the sulfate and hydrochloride salts are H2O-soluble
What is one of the most bitter substitues known?
How is quinine used in food?
Used in beverages
What is caffeine?
A crystalline purine deriative found in coffee beans (1.5%), tea leaves (5%), and cola nuts (2.5%)
What is the solubility of caffeine?
Solubility in H2O is 1:50 (~25°C) or 1:2 (~65°C)
How is caffeine used?
A powerful stimulant with GRAS status
What is theobromine?
Structurally related with caffeine, and often found together with caffeine in various plants (coffee beans, cola nuts)
What are glycosides?
Agylcones esterified with various sugars (naringin, hesperidin, coniferin, and sinigrin)
Where is naringin found?
Found predominantly in grapefruit and bitter orange
What happens when naringin is hydrolyzed?
Hydrolysis yields D-rhamnoglycose, and the aglycone- naringenin
Where is hesperidin found?
Found in sweet orange and several other citrus fruits
What happens with hesperidin is hydrolyzed?
Yields rutinose and the aglycone hesperetin on hydrolysis
Where is coniferin found?
Found in conifer wood
What happens with coniferin is hydrolyzed?
Produces coniferyl alcohol on hydrolysis- which may subsequently be oxidized to vanillin
Where is sinigrin found?
Found in black mustard seed, it yields glucose and allyl isothiocyanate on hydrolysis
How does the miracle fruit effect taste?
- A dipeptide responsible for the taste effect
- It acts by interacting with the taste receptors and inhibiting them from sensing sweet and bitter tastes
How do colds and flus affect taste?
Colds and the flu inhibit our capacity to perceive taste because the receptors are rendered less sensitive to volatile compounds in the food
What is gymnemic acid?
Able to inhibit the taste receptors from sensing sweet and bitter tastes
What is phenylthiocarbamate?
About 25% of the population is unable to sense bitterness of phenylthiocarbamate
What 2 factors affect taste sensitivity?
- Concentration or amount of the material
What is the threshold amount?
- 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
How is the saltiness of vegetables modified?
Saltiness may be enhanced by adding small amount of acid (like vinegar)
Why is it common to oversalt vegetables?
It is easy to over-salt vegetables because the acids present can enhance salty taste
How is bitterness in foods altered?
Add a sub-threshold amount of sugar to reduce the bitterness, or by sprinkling a sub-threshold amount of salt to reduce bitterness
How can sweet taste be enhanced?
Sweet taste may be enhanced by adding a sub-threshold amount of salt
What are flavor enhancers?
- 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
What are some examples of flavor enhancers?
- Monosodium glutamate (MSG)
- Nucleotides (IMP and GMP)
- Maltol (3-hydroxy-2-methyl-4-pyrone)
How are nucleotides used as an index of muscle freshness?
- 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
Where is maltol found?
Occurs naturally in roasted malt; also found in the larch and pine trees
How is maltol used?
Used as a flavor enhancer for baked foods and certain confections
What are some factors of mouthfeel?
- Tactile sesations (texture, astringency, and consistency)
What are the 7 primary odors?
- 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)
What do ethereal odor molecules look like?
Thin rod-shaped moleules
What do camphoraceous odor molecules look like?
- Hemispherical-shaped molecules
- ~7A in diameter
What do musky odor compounds look like?
- Flat disk shaped
- ~10A diameter
What do floral odor compounds look like?
Shaped as keyholes
What do minty odor compounds look like?
How do pungent and putrid odor compounds differ?
Pungent compounds are negatively charged, Putrid compounds are positively charged
What are the 2 methods of sensory evalutation of foods?
- Preference testing
- Difference testing
What is preference testing?
Ususally used in product development to verify acceptability of a developed product and may comprise of trained or untrained testers
What is difference testing?
- 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)
What are the 3 methods of preference testing?
- The paired comparison test
- The hedonic scale
- The ranking test
What is the hedonic scale?
Uses a 9 point scale to evaluate sensory attributes ranking from the 2 extremes
What is a ranking test?
Using samples A, B, C, D for example, rank them in order from best to worst based on particular attributes
What are some examples of difference testing?
- Simple paired comparison test
- Scheffe paired comparison test
- Multiple comparison test
- Triangle test
- The duo-trio test
- Ranking test
What is the Scheffe paired comparison test?
- Makes you actually quantify each degree to which they differ
- Ex. A is 50% sweeter than B
What is the multiple comparison test?
- 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
What is the triangle test?
- Panel provided with 3 samples, 2 samples are the same, one is different
- Panel is asked to pick the odd one
What is the duo-trio test?
- 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
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