Lecture 4 : Flavour creation, release, production, application

Question 1

What are the 2 approaches to creating imitation flavourings?

Answer 1

1. Traditional (empirical approach) : formulation of flavours by using known major ingredients of target flavour and adding aromatics with sensory notes found in the target flavour.
2. Analytical approach : use of instruments to analyse target flavour to determine its composition, and flavour is formulated based on it.

Question 2

What is the disadvantage of the traditional approach of creating imitation flavourings?

Answer 2

Subjective, time-consuming

Question 3

What is the main disadvantage of the analytical approach in creating flavours? How can it be overcome? [2]

Answer 3

It may lead to the formulation of flavouring with an incomplete / unbalanced flavour profile as instruments have high detection threshold, and may miss out on trace volatiles
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Overcome by :
1. Supplementing information with GC-Olfactometry (GCO)
2. Collaboration between flavourist and flavour analyst

Basically, combine analytical approaches + humans

Question 4

What are the steps in flavour creation? [6]

Answer 4

1. Establish target flavour → through sensory assessment
2. Gather data on target flavour → composition, profile and concentrations (existing formulations, research reports, technical literature, internet/databases)
3. Prepare a trial blend with list of ingredients for flavour compounding
4. Initial appraisal of trial blend
5. Application trial
6. Marketing / sale of the flavouring

Question 5

What 4 types of compounds are needed in flavour compounding / blending and what purposes do they serve?

Answer 5

1. Character impact compounds (≥1) : impart desired flavour, but lacks complexity / nuance
2. Contributory compounds : enhance/balance desired flavour
3. Differential compounds : adds uniqueness to sensory attributes
4. Flavour carriers : to disperse / dissolve flavourings

Question 6

Release of flavour can be enhanced or inhibited by …? [4]

Answer 6

1. chemical interactions (binding) between flavourings and food components
2. Physical properties of foods : hardness, viscosity, gel strength)
3. Human factors : chewing efficiency and time, breathing
4. Evaporation of CO₂ or ethanol

Question 7

What kinds of interactions can flavour compounds and food matrix have? [5]

Answer 7

1. covalent bonding
2. hydrogen bonding
3. hydrophobic interaction
4. ionic interaction
5. physical binding: absorption, adsoprtion, coating

Question 8

What are the implications when a flavour compound is covalently bonded to the food matrix?

Answer 8

The reaction is irreversible, and thus the flavour compounds will not be volatile / odour active, resulting in a loss of aroma
- more of the flavour compound will need to be added into the food, leading to increased costs.

Question 9

What are the factors affecting flavour/aroma retention and release? [3]

Answer 9

1. Physiochemical properties of the flavour compounds : molecular weight, size, carbon chain length, functional group, hydrophobicity / partition coefficient (log P)
2. Types of food matrix components : types of macromolecules (lipid/carbs) and their functional groups, viscosity, hydrophobicity
3. Concentration of food matrix components

Question 10

What is the partition coefficient?

Answer 10

It is the tendency of a neutral (uncharged/unionised) compound to dissolve in an immiscible biphasic system of lipid and water

Question 11

What is the equation for partition coeffiecient, P?

Answer 11

[solute/odourant in organic phase ] / [solute/odourant in aq phase]

Question 12

What does a partition coefficient, P of :
P = 1
P < 1
P > 1
mean?

Answer 12

• P = 1 means that compound is equally distributed between lipid/organic and aq phase
• P < 1 means that compoundhas higher affinity for aq phase ;; hydrophilic
• P > 1 means that compound has higher affinity for lipid phase ;; hydrophobic

**As carbon chain length increases, hydrophobicity increases, P and logP increases **

Question 13

What 2 partition coefficients can measure flavour release?

Answer 13

1. Amount of odourants in continous / dispersing phase of food (oil: water partition coefficient)
2. Food : air partioning of odourants

Question 14

What affects the food:air partitioning of odourants? [2]

Answer 14

1. Nature of continuous phase (aq/lipid) –> the continous phase is the phase that holds the smaller, dispersed phase. Usually, continous phase is water (aq)
2. Nature of odourants (hydrophilic / hydrophobic)

Question 15

What acts as a flavour solvent / retainer of odourants?

Answer 15

Lipids (odourants are hydrophobic)

Question 16

what is the formula for the food-air partition coefficient of an odourant?

Answer 16

K_a/c = [odourants in air] / [odourants in continous phase of food]

Question 17

Assume there are 2 odourants in a food.
When lipid (fat / oil) content of a food changes, only the aroma intensity changes, while the aroma character remains the same. True or False?

Answer 17

It depends on the oil : water partition coefficient.
- If oil : water partition coefficient for both odourants are the same, then only aroma intensity changes.
- If oil : water partition coefficient for both odourants are the different, both aroma character + intensity changes.

Question 18

The fat content of a food is decreased. How does aroma intensity and character change when :
* oil-water partition coefficient of 2 odourants are similar?

• oil-water partition cofficient of 2 odourants are different?

Answer 18

• Same oil-water partition coefficient : aroma intensity decreases, aroma character remains the same
• Different oil-water partition coefficient : aroma intensity decreases, aroma character also changes

Question 19

What is the implication for reducing fat content on the flavour of food?

Answer 19

Low fat food would reduce the flavour of food, as less fat increases the air: food partition coefficient (more flavour compounds go into the air), less retention of flavour compounds within the food matrix

Question 20

In static conditions (equilibrium), only odourant partitioning occurs. However, in dynamic conditions, what else occurs other than odourant partitioning?

Answer 20

Mass transfer also occurs under dynamic conditions, which affects the movement of odourant molecules and thus the release of flavour (e.g during chewing, or physical processing of food ingredients)

Question 21

Interactions between protein & flavour compounds

What chemical interactions can occur between proteins and flavour compounds? [4]

Answer 21

Reversible interactions : ionic / hydrophobic / H-bonding
Irreversible interactions : covalent bonding

Question 22

Interactions between protein & flavour compounds

For covalent bonding, what kind of odourants react with:
* amino groups of proteins?
* -S-H / -S-S- bonds of proteins?

Answer 22

• aldehydes react with amino groups of proteins
• odourants with disulfide groups can react with –S-H- (thiol) or -S-S- (disulfide) bonds

Question 23

Interactions between protein & flavour compounds

What are some factors affecting the stength of interactions between proteins and flavour compounds? [4]

Answer 23

1. extent of denaturation (more open structure exposes more hydrophobic sites, thus more binding) -> affected by pH / NaCl / temperature
2. Viscosity of proteins, gel structure and strength -> affects mass transfer (higher viscosity / stronger gels make it harder for flavour compounds to diffuse into head space)
3. Protein concentrations
4. Chain length of aroma compounds -> longer chain length = more interaction

Question 24

Interactions between protein & flavour compounds

What is the order of binding of aromatic volatiles to these 5 proteins, in descending order (strongest interaction to weakest interaction)?

• Ovalbumin
• Caesin
• Gelatin
• Soy
• Corn

Answer 24

1. Soy : more exposed binding sites
2. Gelatin : rich in hydrophobic scids (proline)
3. Ovalbumin
4. Caesin
5. Corn

• Caesin, corn protein have less exposed binding sites, weaker bonding

SGOCCo

Question 25

How do simple sugars, such as mono and disaccharides, enhance aroma release through the "salting out effect"?

Answer 25

- When simple sugars are dissolved in water, they compete for water molecules. - This reduces the ability of water to dissolve volatile aroma compounds. - As a result, the volatiles are forced out of the aqueous phase and released into the gas phase.

Question 26

How do complex carbohydrates inhibit aroma **release**? [2]

Answer 26

1. Through chemical interactions between various functional groups on carbohydrates and flavour compounds. 2. Through physical binding of flavour compounds to carbohydrates (hydrophobic sites / pockets)

Question 27

What is inclusion (physical binding)? What are examples of some carbohydrates that can bind flavour compounds through inclusion? [2]

Answer 27

Inclusion : physical trapping of flavour compounds 1. Starch, helical structure with hydrophobic core 2. Cyclodextrin : hollow, bucket-like structure with hydrophobic pockets

Question 28

What are some phyiscal forms of flavourings? [4]

Answer 28

1. Liquids (water-based solvents or fat-based carriers) 2. Emulsions 3. Pastes 4. Solids : powders, dry flavourings

Question 29

For flavour emulsions, what is the continous phase and what is the dispersed phase?

Answer 29

Continous phase : water Dispersed phase : oil

Question 30

Oil-soluble flavourings (e.g. citrus essential oils) are to be included into soft drink. What form of flavouring should be used - liquid or emulsion? Why?

Answer 30

Emulsion. Since flavourings are oil-soluble, it is necessary to disperse the oil phase into aq phase before incoporating into beverage, as beverage is mainly aq - Could technically dissolve oil-soluble flavourings in oil carrier (liquid form), but it will cause separation when added into beverage (aq)

Question 31

Other than imparting flavour, what can flavour emulsions impart?

Answer 31

Turbidity Non odourous vege oil / terpenes

Question 32

What are the 5 components of a flavour emulsion and their functions?

Answer 32

1. Oil (flavourings) → dispersed phase 2. Water → aq phase 3. Emulsifiers like xanthan gum → prevent phase separation 4. Weighing agents → increase density of oil phase to further prevent separation 5. Preservatives → protect against microbial spoilage (sodium benzoate + citric acid / propylene glycol)

Question 33

What 2 preservatives are usually used in flavour emulsions?

Answer 33

1. Sodium benzoate + citric acid OR 2. Propylene glycol

Question 34

What is the stoke's law equation for separation?

Answer 34

V =gr²(ρ₁ - ρ₂) /18n

Question 35

What 2 ways can separation of oil phase from aq phase be reduced?

Answer 35

1. Increasing density of oil phase (dispersed) by adding weighing agent. 2. Reduce oil particle size

Question 36

In what 3 ways can dry flavourings be prepared?

Answer 36

1. Plating / spreading of flavourings onto granular, edible food ingredient such as sugar, salt, starch 2. Formation of inclusion complexes with cylodextrins 3. Encapsulation, where oil flavour compounds are coated with / entrapped within protective material (polysaccharides, proteins, lipids, emulsifiers)

Question 37

What are cyclodextrins?

Answer 37

Cyclic oligosaccharides that are enzymatically derived from starch.

Question 38

# **Flavour application** What is the drawback of using aspartame as an artificial sweetner in cheewing gum? What 2 other sweeteners can be used instead?

Answer 38

Aldehyde odourants can react with the asp-phe dipeptide in aspartame, leading to loss in aroma and sweetness (since aspartame react, sweetness lost) **Use**: - Acesulfame k - Sucralose