Lecture 3 - Flavour potentiators / enhancers

Question 1

Flavour enhancers

What are flavour enhancers?

Answer 1

Compounds with no taste / flavour of their own at usage levels, but intensify / enhance the flavour of a food.

Note : the definition of enhancers may not strictly apply in all cases

Question 2

Sweetness enhancers

Artificial sweeteners are flavour enhancers. True or False?

Answer 2

False, artificial sweeteners themselves taste sweet, and do not enhance the perception of sweetness.

Question 3

Sweetness enhancers

The strict definition of flavour enhancers applies to sweetness enhancers such as maltol and ethylmaltol. True or False?

Answer 3

False.
Maltol and ethylmaltol carry their own flavours ; they are odour active at usage level

Question 4

Sweetness enhancers & sugar reduction

What are the 2 ways / mechanisms in which sweetness can be enhanced?

Answer 4

1. Through smell/aroma → cross-modal interaction → by smelling sweet-smelling compounds, the brain is tricked
2. Sweetness modifiers → e.g. miracullin (ssweet protein) can alter sour taste into sweet taste

Question 5

Sweetness enhancers

What are the names of the 2 main sweetness enhancers? What is their aroma characteristic?

Answer 5

Ethylmaltol, maltol.
- Maltol : caramel-like / sweet aroma
- Ehylmaltol : caramelised sugar / cooked fruit

Question 6

Sweetness enhancers

Both ethylmaltol and maltol can be found in nature. True or False?
Explain how they are produced.

Answer 6

False.
- Maltol can be found in nature, where it can occur naturally in various plant materials and is produced during roasting processes (e.g. caramelisation during coffee roastin).
- However, ethylmaltol is synthethic ; derived by modifying the structure of maltol

FYI : Ethylmaltol is more potent than maltol

Question 7

Sweetness enhancers

5-75 ppm maltol can lead to up to ___% sugar reduction.

Answer 7

15

Question 8

Sweetness enhancers

What is the other class of sweetness enhancers? What is their aroma characteristic?

Answer 8

Cyclic enlones / furanones
- fruity, strawberry-like, caramel, sweet aroma

Question 9

Umami / savoury enhancers

What are the 2 main broad categories of common and natural umami enhancers?

Answer 9

1. L-amino acids
2. 5’ nucleotides

Question 10

Umami / savoury enhancers

L-amino acids are umami enhancers. What 3 forms can they exist in?

Answer 10

1. Free amino acids (most common : glutamate)
2. Gluamyl peptides
3. Salt form (MSG)

Question 11

Umami / savoury enhancers

What are the 3 most common umami enhancers?

Answer 11

1. MSG (salt form of glutamate)
2. Inosine monophosphate (IMP)
3. Guanine monophosphate (GMP)

Question 12

Umami / savoury enhancers

What are the common sources of MSG? [4]

Answer 12

Many sources
- meat, poultry, fish, shellfish, ripened cheese, mushroom, vegetables
- Yeast extracts
- Hydrolysed vegetable proteins
- Seaweed extract

Question 13

Umami / savoury enhancers

What are some common sources of IMP/GMP? [2]

Answer 13

• Yeast extracts
• IMP : seafood (during degradation of ATP)

Question 14

Umami / savoury enhancers

What are the 3 factors affecting the stability of MSG and 5’ nucleotides?

Answer 14

1. pH : affects stability
2. Temp (heat) : causes degradation of these compounds / maillard reaction (MSG + sugars)
3. Presence of enzymes : phosphatases in muscle of fish meat removes phosphate group and further degrades IMP

Question 15

Umami / savoury enhancers

MSG and 5’ nucleotides have synergistic effects. Explain what is synergism.

Answer 15

It is when the umami perceived in the mixture of MSG & 5’ nucleotides is greater than (umami of MSG + umami of 5’ nucleotides)

Theoretically, it should be the same

Question 16

Umami / savoury enhancers

1. MSG : IMP in a 1:1 ratio increases umami intensity by how many times?
2. MSG : GMP in a 1:1 ratio increases umami intensity by how many times?

Answer 16

1. 7 times
2. 30 times

Question 17

Umami compounds - 5’ nucelotides

What is the common ratio of MSG and IMP/GMP used in the industry and why?

Answer 17

MSG : IMP/GMP = 95 : 5, because 5’ nucleotides are costly

Question 18

Umami compounds - 5’ nucelotides

What kinds of amino acids can 5’ nucleotides exhibit synergism with?

Answer 18

1. Sweet L-amino acids : gly, ala, ser
2. L-amino acids with acidic side chain (umami AA) : glu / asp

Question 19

Umami compounds - yeast extract YE

Yeast extract is rich in what umami compounds? [2]

Answer 19

• Glutamate (MSG)
• RNA (5’ nucleotides are building blocks)

Question 20

Umami compounds - yeast extract YE

What is yeast extract? What are the 2 main steps in producing yeast extract?

Answer 20

Yeast extract : a taste enhancer produced by autolysis of yeast. It is all the cellular contents within the yeast (amino acids etc) without its cell wall

1. pre-treatment : inactivate the yeast ( 45-60°C / 24-36h) → mild conditions
2. Release cellular contents within yeast

Question 21

Umami compounds - yeast extract YE

What are the 2 main methods in releasing cellular contents in yeast? State reagents and conditions where applicable.

Answer 21

1. Hydrolysis - Conc HCl is added to 65-80% yeast solids ; 100°C / 6-12h ; followed by neutralisation by NaOH to pH 5-7
2. Plasmolysis - addition of salt to cause dehydration of yeast cells, disrupting its membrane and causing leakage of cellular components

Question 21

Umami compounds - yeast extract YE

What are some raw materials for yeast extracts? [2]`

Answer 21

1. Brewer’s yeast : Saccharomyces cerevisiae;; by-products of beer fermentation
2. Baker’s yeast : primarily grown specifically to produce YE (or used as yeast in baking)

Question 22

Umami compounds - monosodium glutamate MSG

How is MSG produced?

Answer 22

Fermentation of substrates (high sugar substrates like cane mlasses) with Corynebacterium glutamicum

• bacteria has defective TCA cycle, α-ketoglutarate cannot be converted to succinate, so it accumulates and gets converted into glu

Question 22

Umami compounds - Hydrolysed Vegetable Protein, HVP

What are the main raw materials of hydrolysed vegetable proteins?

Answer 22

“vegetable proteins” : low cost plant based protein sources such as defatted flours, wheat gluten, corn gluten

Note : flour and wheat gluten are slightly different. Both are powders but flour has starch + protein ;; but wheat gluten is just the protein only

Question 23

# **Umami compounds - yeast extract YE** Other than umami compounds, what is yeast extract high in?

Answer 23

Salt, NaCl. - hydrolysis : add HCl then add NaOH to neutralise - HCl + NaOH → **NaCl** + H₂O

Question 24

# **Umami compounds - monosodium glutamate MSG** What conditions facilitate Glu excretion from Corynebacterium glutamicum?

Answer 24

Low biotin (vit B7). Thus, substrates like cane molasses can be treated to reduce biotin levels

Question 24

# **Umami compounds - Hydrolysed Vegetable Protein, HVP** How are hydrolysed vegetable protein produced?

Answer 24

Acid hydrolysis with **32% HCl** + **high temp**, followed by neutralisation with **NaOH**. ## Footnote **High temp** : Maillard rxn may occur **NaOH** : high in NaCl

Question 24

# **Umami compounds - Hydrolysed Vegetable Protein, HVP** Sensory properties of HVP varies with..? [2]

Answer 24

1. Protein source & protein condition 2. Maillard reaction between carbs and proteins

Question 25

# **Umami compounds - 5' nucleotides* What are the 2 main ways in which 5' nucleotides be produced? [2]

Answer 25

1. 5' GMP can be recovered from fresh meat ; but rare cuz ex 2. Fermentation of sugars by bacteria

Question 26

# **Umami compounds - 5' nucleotides** In addition, degradation of microbial RNA can be used to obtain ___, ___, ___, ___, which can then be enzymatically converted to yield IMP

Answer 26

**GMP**, UMP, CMP, AMP

Question 26

Explain the rationale behind adding MSG or 5' nucleotides in salt reduction.

Answer 26

Foods with less salt are bland and have no taste. Thus, by adding umami compounds, the palability of food (taste) is enhanced through synergistic effects between saltiness and umami, increasing the overall perception of saltiness.

Question 27

# **Umami compounds - 5' nucleotides** Name the 2 bacteria can undergo fermentation to produce 5' nucleotides.

Answer 27

1. Brevibacterium ammoniagene mutants (considered precision fermentation as mutants are genetically engineered) 2. Bacillus subtiis

Question 28

What are the salt reduction strategies? [2]

Answer 28

1. Replacing salt (NaCl) with other salty substances such as metal chlorides / sulfates 2. Enhancing the palability of food through enhancement with umami or kokumi compounds

Question 28

# **Kokumi** What is kokumi flavour?

Answer 28

It is the sensation of fullness/mouthfullness/thickness/body ;; and adds onto flavour complexity

Question 29

# **Kokumi** Explain the rationale behind adding kokumi compounds in salt reduction. State the group / class of kokumi compounds that are usually used, in what types of applications?

Answer 29

Kokumi compounds enhance the palatability of food through contributing to richness / mouthfeel, thus increasing the perception of saltiness. - Associated with lactones which contribute to creaminess, richness, smoothness - COmmon in fluid-based foods

Question 30

# **Kokumi** Other than saltiness, what other flavour does kokumi have synergism with? Thus, what specific compounds can enhance kokumi perception (by reducing threshold of kokumi)?

Answer 30

Umami - MSG, 5' nucleotides (IMP, GMP) can reduce thresholds and enhance kokumi perception

Question 31

# **Kokumi** Name 3 kinds of kokumi taste substances and where they originate.

Answer 31

1. S-(1-propenyl)-L-cysteine sulfoxide : onion 2. S-(2-propenyl)-L-cysteine sulfoxide : garlic 3. Glutathione (GSH) : yeast extract