The Science in Artificial Flavor Creation    

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Introduction:  

What is a science ?
It is a brand of knowledge or study especially one concerned with establishing and systematizing facts, principles, and methods as by experimentation and hypothesis.

Flavor Technology: The application of scientific knowledge to the solution of practical flavor problems.

The creation of artificial flavors to a large extent is an art . . . but as I will show today there is a good deal of science in . . . So much so that I think that there is a “science of flavor creation”.

The French philosopher and writer Voltair was quoted as saying “If you wish to converse with me, define your terms”.  

A flavor Compound basically is composed of two parts, A Flavor Portion and a Diluent Portion. 

The Flavor Portion is composed of three parts:  
1)    A flavor Character Item  
2)    A flavor Contributory Item  
3)    A flavor Differential Item

The function of the Flavor Portion is to:
    To simulate the named flavor
    To maintain this character (Character fixation - That it remains reminiscent 
         of the named flavor after processing.).  
    To enhance the flavor impression and it's acceptability.  

   
The function of the Diluent Portion is to:  
1. To keep the flavor principles in solution.  
2. Provide a carrier for the color, if any.  
3. A strength regulator, the greater the amount of solvent the weaker the flavor.  
4. It gives the flavor a physical fixation.  (That it remains after processing.).  
5. It inhibits chemical reactions from occurring.                             
6. It can act as a preservative. (i.e. Ethyl Alcohol, Propylene glycol)  
7. It is the vehicle for the presentation of the flavor portion.  
8. It determines the form of the flavor. The way the flavor appears on the market, i.e., as a liquid, powder, or paste form. It makes the flavor applicable. The flavor materials do not make a flavor work, ....  it is the form of the flavor that does. The solvent distributes the flavor uniformly  throughout the product.

Definitions:

Character fixation: The use in flavors of high boiling solids at high concentrations that is above their threshold values. They are usually used in combination, e.g., vanillin, oxanone, heliotropin and maltol. Since they are used above their threshold concentrations when diluted down they are still above their thresholds and therefore the perception of the flavor does not appear to change.  

Physical fixation: The use of a flavoring compound of relatively high boiling materials(boiling points), by that making it less heat labile. We use these materials whenever we have flavors to be used at temperatures above the boiling point of water.  Vegetable oil, or high boiling esters, e.g., diethyl succinate.


The following five (5), concepts  are derived from above: The Concept of:
1.  Characteristic Threshold Value.  
2.  Flavor Impact Item  
3.  Flavor Impact Group  
4.  Contributory Item  
5.  Flavor Differential Item

What is the concept of the Characteristic Threshold Value?  
The Characteristic Threshold Value is a way of tasting and characterizing the flavor materials under “standard conditions.” The tasting of a flavor material at various levels, and various media to decide what contribution it makes and under which condition of use, e.g., cherry at one ppm in sugar, acid and water  

This procedure presents the flavor materials closer to the levels at which they are found in nature. Flavor materials are not used in in flavors at percentage quantities, but realistic levels at the ppm and ppb range. 

This is the procedure that one uses to “characterize” the flavor materials, i.e., the placing of the flavor materials into the different categories for greater retention. ( Greater retention results in greater creativity – because creativity always starts with something already known ).

Definition: The Characteristic Threshold Value is the contribution a flavor material has at 1, 5, and 10 ppm, and whether it can be categorized as a Character, Contributory or Differential item.  

This procedure places the materials into one of three groups.  
1. Character Impact item.  
2. Contributory Item.  
3. A Differential item.

We record these values as parts per million. However, we convert them to what I call the concentration index

What is the concentration index? : The amount of flavor in the final product in parts per million written as a percent. For example,
1 p.p.m. = 0.0001%  
5 p.p.m. = 0.0005%  
10 p.p.m. = 0.0010%  
100 p.p.m. = 0.0100%

We use these values with the use of the following formula:

                                  X%   *   (TA)  
               CI % = --------------------------
                                     (FA)

X = % of active material in the concentrated flavor.

FA = Final volume of weight of the product

TA = Throw volume, the amount by weight or volume of the ingredient     added.  

Example: Lets assume I have a 1% by volume solution of an aromatic chemical. What will be the final concentration of this material if I used the 1% solution at 0.1cc in 100 cc? Solve for (CI)

                                  X * (TA)                   1% * 0.1 cc
                      (CI) = ---------------------- =  --------------------  =     ( 0.1%)  / 100     
                                     (FA)                           100 cc

                      CI = 0.0010% or 10 ppm

Example: Let’s assume that one wants to add five ppm of a flavor material to a product. What concentration should I have of the aromatic in my flavor, if I’m using my flavor at one ounce in 100 lbs. of a product?

                              (CI) * (FA)               (0.0005) * (1600)  
                  X =  --------------------  =   ----------------------------- 
                                  (TA)                              (1.0) 

                  X =   0.8 % in my flavor

What is a Character Impact Item? It is a material when smelled and/or tasted is reminiscent of the named flavor . . .  (More or less characteristic).

• It makes a large contribution to the flavor. It possesses a good deal of the character of the named flavor.

• A Character Impact Item is a chemical that provides most of some flavors organoleptic effect.  

Compounds recognized by experts as representative of a good deal of the organoleptic quality of the flavor type.They are Charactistic, Essential and Necessary for the flavor. I t may be an essential oil, botanical, aromatic chemical or combination of these.

For example:  
3-methoxy-2-isobutyl pyrazine is a character impact item for Bell Pepper or Pea

Ethyl-2-methybutyrate is a character impact item for Apple

Trans-2-cis-6-Nonadienal and cis-6-nonenal are character impact items for Cucumber

1-octen-3-ol, (mushroom), 4-methylnonanoic acid, 4- methyloctanoic acid  (Lamb)

p-menthene-8-thiol (Grapefruit)

2-methyl-3-furanthiol (Meat)

5-methyl-2-thiophenecarboxaldehyde (Almond)

5-methyl-2-hepten-4-one (Hazelnut)  

isoamyl acetate (Banana), benzaldehyde (Cherry), methyl anthranilate (Concord Grape)


What is a contributory Item?
 It is a flavor material that when smelled and/or tasted helps to create, enhance or potentiate the named flavor. They are not necessarily reminiscent of the name flavor, however when used in conjunction with the flavor impact items brings it closer to the named flavor. (They are Not Characteristic but Necessary.). Because it acts with the Impact Item to produce a definite character.

For example, Grape: ethyl butyrate, ethyl thiolactate, ethyl-3-hydroxy butyrate and furaneol (2,5-dimethyl -4-hydroxy-3(2H)-furanone).  

None of these are characteristic of a concord grape but when used with methyl anthranilate will create a truer concord grape flavor. 

Blueberry: ethyl safronate, butyl-2-butenoate, and ethyl-3-hydroxybutyrate all will help create a better more characteristic blueberry flavor.

Apple: damasceneone will help create a better Apple flavor.  

Cherry: acetophenone will help create a Black Cherry flavor.  

Pyridinemethanthiol will help create a better Pork Flavor. 

The use of 2,4-decadienal and 2-methyl-3-furanthiol, (furfuryl mercaptan and gamma-decalactone), in chicken will make a better, more characteristic Chicken Broth.

Orange juice: Acetaldehyde, ethylbutyrate, hexanal all will add to the character of orange juice. All will add to the making of a better orange juice flavor, but individually they  do not taste like orange juice,  but they do improve the flavor.  A contributory Item is necessary to produce a desired effect but not essential for the flavor.

 

What is a Differential item?

It is an additive or combination of additives when smelled or tasted has little if any character reminiscent of the named flavor. They are added to give flavor what I call individuality or difference. They are usually imaginative and I believe add the difference between flavor and flavor chemists. However, they are neither characteristic, essential nor necessary to the flavor.  

Examples of the above would be using: 
Menthol in a Butterscotch flavor

Methylthiobutyrate in Strawberry, (This material smells like Liederkrantz cheese)  

2-methyl-3-furanthiol in Mushroom
Cinnamon in a Blueberry flavor

Let us suppose that I have a strawberry flavor and I want to make it “greener”, (fresher),  I can use many materials, e.g., trans-2-hexenal, cis-3-hexenal, oil galbanum, violet absolute. I have many choices. You can see the possibilities for being creative.  

“Sweeter.” Vanillin:  benzodihydropyrone, oil balsam peru, butylbutyrolactate etc.  

“Fruitier” any of a large number of esters.  

“Fattier,” say for example a Meat flavor:  butyl-2-deceneoate, maybe as green fatty like hexanal.  

Pear . . .  Astrotone (Ethylene Brassylate)  

Blackberry . . . Exaltalide

Cheese . . .  4 methyl nonanoic acid  

How about making a Nut flavor “nuttier” -  gamma nonalactone, (primarily a Coconut note)  

Almond . . .  To add a roasted note . . .  several pyrazines will do this.

Walnut . . .  2,4-octadienal, 4-phenyl-4-pentenal  

Peanut . . .  hexanal, 2-nonenal, roasted peanut . . .  2-ethyl-3-methylpyrazine.  

The difference between a contributory and a differential item is really one of intent. With a contributory item I AM trying to make a “better” and more characteristic flavor, and these materials are necessary to do that.

With the differential item I am NOT really trying to make a more characteristic flavor  . . .  I am trying to make a “different” one.

Menthol added to a Butterscotch flavor is not making a better or more characteristic Butterscotch but a different one.  

2-methyl-3-furanthiol (very characteristic meat note) is not making a more characteristic Mushroom but it makes the Mushroom “meatier” and that is what I want to do.  

Exaltalide is not characteristic of Blackberry, it is not necessary in blackberry, but it adds a difference, which is what I want to do.

What is a Character Impact Group?

It is a group of flavor materials that share a common property that is, collectively they taste like/or make a large contribution to a named flavor type.

Methyl ketones: 2-heptanone, methyl amyl ketone) ................Blue Cheese

Amines: Trimethyl amine...........Fish, Seafood  

Diones:  (Cyclic enolones, contain carbonyl, enolic hydroxy and methyl groups.)
(cyclotene, maltol, ethyl maltol, furaneol) ..................Butter, Caramel  

Aliphatic ester’s: Ethyl Isoovalerate...................Fruit

Aliphatic acid’s (C-3 to C-12) : (Hexanoic acid) ........................Cheese

Lactones (Lactonic fruits do not have green notes): ...........Peach, Apricot, Cream, Coconut

Aliphatic, alicyclic aldehydes.................. Citrus  

Phenylacetic acid ester.......................... Honey  
(As Phenylethyl alcohol esters, the flavor varies according to the acid used.  
As Phenylacetic esters the flavor of sweet honey takes over.  
(Phenylethyl acetate (phenylethylalcohol, and acetic acid.), Ethyl phenylacetate (phenylacetic acid, and ethyl alcohol.).

Pyrazines ..........................................Roasted notes

Sulfides ............................................. Cooked Meat, food’s

Phenols (2,6-dimethoxy phenol) ....................  Smoke  

Pyrazines/Thiazoles............................... Nutty, Corny, Bready, Cracker.  
(Unsaturated N heterocyclics with one or two nitrogen atoms in the ring and substituted with acetyl and alkyl groups.)

8 Carbon compounds..................................... Mushroom  

Ketones/Alcohols.(Menthol, menthone) .................................... Minty

Amyl esters of acetic and butyric acid (Isoamyl butyrate, acetate) .....................Banana

Methyl and ethyl esters of T-2, 4-decadienoic acid........................      Pear (Bartlett)

Phthalides ..................................................... Celery  

Allyl alcohol esters ...................................... Pineapple  

2-methyl acid esters  (Ethyl-2-methylbutyrate) ........................ Apple  

Normal odd number carbon fatty acids and high level of branched chained fatty acids. ...................          Lamb, Mutton, Goat  

Hexyl, hexenyl alcohol esters. As the acid portion . . . the greenness disappears and a “goat” note  
appears. (Hexyl acetate, Ethyl caproate).

Delta lactones   C6, 8, 10, 12, 14 ............................... Coconut

Methyl ketones    C7, 8, 11, 13, 15.............................Cheese

The Concept of the Character Impact Group will account for the fact that combinations of materials occur over and over again in certain flavors and it is beneficial to be aware of these combinations.

Sometimes a flavor has a number of chemicals that help to create it rather than just one chemical. (Strawberry, Chocolate)

Sometimes a certain functionality may contribute a great amount of the organoleptic character. (Methyl ketones in blue cheese, aliphatic acid in cheese.

From the above the following flavor principles come about:  
Flavor Postulates: To assume without proof to be true, real and necessary.  
A basic or  fundamental principle, something taken for granted or assumed as a basis for reasoning. 

1) A flavor material can be tasted/smelled and characterized, that is an assessment of its flavor character and contribution can be determined, and it can be placed into the above concept areas.

2) Flavor material change quality (character) with concentration and environment, therefore a flavor can have several characteristic threshold values.

Examples of this would be the different effects one gets with benzaldehyde, at 40 ppm with and without acid (with acid cherry, without acid almond  . . .  (CHANGE IN ITS ENVIRONMENT.).

The different effect that ethyl butyrate, (at 30 ppm), undergoes with and without acid. (With acid it contributes fruity, pineapple flavor, without acid it exhibits a butterscotch flavor.).

Lactones (gamma‑decalactone) without acid at one ppm creamy, milk, butter, with acid , peach.(a CHANGE IN ENVIRONMENT). At one ppm creamy, milk, butter, at greater than 3ppm coconut. (CHANGE IN CONCENTRATION)

P-tertiarybutylphenylacetate with acid is strawberry.., without acid is creamy, milky, chocolate.  

2,5-dimethyl-4-hydroxy-3(2H)-furanone with acid is strawberry, without acid is caramel, meaty.  

An excellent example of this is the change in flavor and odor of butyric acid with changes in pH . . . (A change in environment) (It is the undissociated acid that has the flavor and odor of the acid)           

An important factor in perceiving flavor components in a food product . .  Is acid dissociation. Butyric acid for instance is only perceived in its undissociated form . . .  The degree of dissociation depending upon the pH of the medium. Butyric acid at pH 4.7 is about 43% dissociated and at PH 6.0 about 92% dissociated. What this means that to have the same flavor of butyric acid at two different pH’s one will have to use different levels, e.g., 10 ppm butyric acid at pH of 4.2 would be equivalent to 100 ppm at pH 6.7.  

Relative quantities of butyric acid to achieve equal flavor perception  
Product                              PH                            PPM  
Milk                                    6.7                             100  
Ice Cream                      5.6 - 6.7                    80 - 100     
Cheese                          5.3 - 5.6                     50 - 80  
Yogurt                             4.0 - 4.2                        10

This is why specifying the medium and level used is extremely important . . . in any of the characterizations  

3) A flavor material can perform different functions (make different contributions.), to a flavor.

A flavor material can have several functions within a flavor (intra) and between flavors (inter), e.g., 
a) Benzyl alcohol can be a character and a contributor item for a Nut and Cherry flavor, and also a diluent for them

b)  Benzyl alcohol can be a contributory item for Cherry and a differential item for a Nut flavor. 

c) Ethyl Oleate can provide the diluent and a contributory effect for Butter flavors.

Different effects in different flavors:  
d) Ethyl Oenanthate in a Brandy Grape flavor is a Character item . . .  In a  Concord Grape it is a Contributory or Differential item.  

e) Ethyl Oenanthate is a character item for the Vinus Vinifer Grape, a character item for cognac and a contributory or differential item for a Butter flavor.  

f). 2-methyl-3-furanthiol is a character item for roasted Meat, a differential item when used in a Mushroom flavor, it makes a different flavor. It is a contributory item when used in a Chicken flavor . . .  and it makes a better Chicken flavor.  

Why do we go through this exercise of defining these materials? So that they can be retained . . .  We give it a name, a place, and a use, and one will not forget it.

4) A flavor material must be given a name and character before it can be evaluated, appreciated and retained. Five things are necessary to characterize a flavor material.

         a). Name (isoamyl acetate, benzaldehyde etc.)

         b). Character (Concord Grape, Cherry, Peach, Pineapple etc.

         c). Contribution (character impact, contributory or differential item).

         d). Concentration (amount in ppm)

         e). Environment (with/without acid, milk, sugar acid and water.)

5) A flavor material must always be tasted in a base . . .  that is, diluted down and always compared with an unflavored base. (this stops us from seeing things that are not there.

We should speak of some flavor materials contribution   (Character, Contributory and Differential), as opposed to its character only.

b). The definition of contribution takes into account the character and function that the material plays in a specific flavor.  

It can make very different contributions in different flavors.

6)  In order to fully characterize a flavor material it must be tasted more than once.. The final characterization must be based on the collected characterizations. 

a). It must be tasted at more than one concentration.

b). It must be tasted in more than one media.

c). It must be tasted within more than on flavor type.

Characterizing a character impact item is fairly easy, but it is more difficult to characterize a contributory or a differential item.

By adding the flavor material to different flavors and asking the questions “Does it do anything?”. We then can decide its category. This is how we find the flavor materials that go into the categories of contributory and differential items.

7)  The Composition of the flavor material being characterized must be known.  

     a). Its impurities must be known and taste separately, i.e., to decide where the character is truly coming from.  (Have you ever tasted the same material from two different suppliers? 4- Octen-3-one, Mushroom from one supplier and strawberry from another, probably due to impurities.).

      b) Its isotopic ratio (if any) must be known and if possible the isomers must be separated and tasted.           

8) Usually the functionality of a flavor material determines its flavor contribution. e.g., esters, have fragrant fruity odors, Lactones have fragrant ester like odors.

9) The lower the characteristic threshold the more likely it will be a character impact item.

10) A flavor must always be considered as a whole and in relation to its envoirnment.

  Seeing a Banana flavor as being composed of a:  
Character item: Isoamyl acetate, Impact groups: An amyl ester of acetic and butyric acids,  
Contributory items: Ethyl.-2-methylbutyrate, ethyl-3-methylbutyrate, and  
Differential items: trans-2-hexenal, diacetyl.  

Is a very different way of looking at a Banana flavor.

11). A flavor should be “diagramed” before any compounding begins.  

a). The solvent of a flavor should be decided upon first before any compounding is started. Why? The solubilities of your flavor materials depend upon it. (citrus oil, in P.G., vanillin in vegetable oils, Flavor components solvent interactions e.g., acetal formation).

  b). The stabilities of you flavor, i.e., that it remains and remain reminiscent after processing depends to a great deal upon your solvent of choice.

c). The dispersibility of you flavor depends upon the compatibility/solubility of your solvent throughout the finished product.

d). Your choice of solvent determines the applicability of your flavor in the finished product, i.e., it determines the form of the flavor. (Remember that chemicals do not make the flavor work the form does.).

e). The character items/group should be chosen secondly.

f). The contributory and differential items should then be decided. Why? This is where the real difference between flavors comes into play.

g). The approximate (starting) usage level must be decided. (O.1, 0.25, etc.) Why? This will usually determine the concentration of you character items that is how much will be in the finished product.

12). Aroma “lift” in flavors is provided by low boiling and therefore highly volatile, low molecular weight molecules.

13). Flavors must contain only approved ingredients.

14). The area of flavor that offers the greatest possibilities for creativity is in the area of the contributory and differential flavor items.

15). Taste substances are usually polar, water soluble, and none volatile. Odor substances need volatility, odor substances are far less polar and elicit a much broader range of sensations, Salt, sour, bitter, sweet and umami, astringency, pungency and meatiness are the only taste sensations

16). A flavor should always be designed for a specific application. A flavor generally cannot be universally applied. The flavor has to be modified (materials and form).

17) There are basically seven (7), different flavor forms, i.e., different ways to deliver flavor to your product.

Liquid: Water soluble, Oil soluble and Water dispersible (emulsion form)  
Powders: Internal application, (Spray Dry, Occluded, extruded forms) and external applications, (Plated or extended)  
Paste: Carbohydrate and fat based

18). The solvent is the largest single item in a flavor.

 19). A flavor must remain clear and homogeneous with no precipitation, a cloudy or hazy flavor suggests insolubility, incompatibility of some ingredients in the flavor.

 20) Upon dilution the flavor should lose strength but not character. If is loses character, it is an unbalanced flavor.   (Materials drop below their thresholds).

 21). There are three (3), types of flavor creativity:

Innovation: We are asked to create an entirely new flavor. Wood Apple, Sorrel, Fruits of the forest, etc.  
Discovery: We find ways to use old flavors in a new way.  
Invention: We create flavors for a new product and or process, this is where we spend most of our Time.(We are asked to “duplicate” an existing flavor”)