Bitterness

Question 1

Bitter sensation is also [LESS/ MORE ?] prolonged than sweet, salty or sour sensations.

Answer 1

more

Question 2

Caffeine belongs to which chemical group ?

Answer 2

Purine alkaloide belonging to the group known as methylxanthines

Question 3

Caffeine is classified by the Food and Drug Administration as?

Answer 3

“generally recognized as safe” (GRAS)

Question 4

Caffeine can be a stimulant to which human system

Answer 4

Central nervous system (CNS) stimulant

Question 5

Caffeine threshold

Answer 5

75-155 mg/L

Question 6

Which compounds are responsible for bitterness & astringency?

Answer 6

Phenolic compounds

Question 7

The effect of phenolic compounds structure on taste perception

Answer 7

• Simple phenolic molecules tend to be bitter - e.g. Quercitin
• Polymers of high molecular weight (also known as tannins) tend to be astringent - e.g. tea tannins

Question 8

Bitterness in citrus fruit derived from

Answer 8

Flavanones, flavones & flavonols

Bitterness dependant on the type of glycoside chain

Question 9

Naringin 
sources ?
chemical group 
effects? 
Chemical name

Answer 9

• citrus fruit
• flavanone
• Bitter
• Rhamnosyl-α-1,2-glucose

Question 10

Hesperidin 
sources ?
chemical group 
effects? 
Chemical name

Answer 10

• citrus fruit
• flavanone
• Tasteless
• Rhamnosyl-α-1,6-glucose

Question 11

Neohesperidin
sources ?
chemical group
effects?

Answer 11

• citrus fruit
• flavanone
• Very bitter

Question 12

Neohesperidin dihydrochalcone
sources ?
effects?

Answer 12

• citrus fruit

Intensely sweet

Question 13

Flavan is the base form of ____

Learn chemcial structure difference on P. 27 slide

Answer 13

Flavanonols    
Chalcones 
Flavanones 
Anthocyanidins
Flavones
Flavonols

Question 14

bitterness in tea derived from which compounds?

Answer 14

Combination of catechins, caffeine, amino acids & saponin

Question 15

bitterness in chocolate derived from which compounds?

Answer 15

• High amounts of catechins

* Fermented cocoa: epicatechin, polyphenols and anthocyanins ( glycoside forms of anthocyanidins)

Question 16

bitterness and astringent in wine derived from which compounds?

Answer 16

• Low molecular weight catechins (bitter)

* High molecular weight tannins (astringent)

Question 17

Glucosinolates is___?
found in?
Characters?

Answer 17

• Amino acid-derived secondary plant metabolites
• Exclusively in cruciferous plants, predominantly Brassicaceae family
• Characteristic flavour and odour properties
• Pungent and bitter

Question 18

Ex of Glucosinolates & chem structure

7 Ex

Answer 18

(Z)-cis-N-hydroximinosulfate esters
•Side chain R
•Sulfur-linked D-glucopyranose moiety

Glucoiberin / Progoitrin
Sinigrin/ Glucoraphanin
Gluconapin/ Glucobrassicin

Question 19

Glucosinolate Hydrolysis

Answer 19

Pungent & highly reactive

Pungent Acrid Corrosive Lachrymatory or tear-inducing

Question 20

Other Bitter Taste Substances (3)

characteristic

Answer 20

α-acids
•Sought-after characteristic in beer
•Achieved by adding hops to the wort rich in α-acids

Isoflavones
•Bitter isoflavone glucosides & the corresponding aglycones

Amino acids and oligopeptides
•Partial hydrolysis of whey proteins
•Hydrophobic L-amino acids (val, leu, ile, phe, tyr, trp)

Question 21

Astringency is perceived by?

Answer 21

Perceived through the oral cavity and the tongue

Question 22

Astringency is regarded as ____ and how ?

Answer 22

“mouth-feel”

• Reactions involving polyphenolic substances and proteins in the saliva, surface of the tongue, palate.

Question 23

astringency in red wine & tea derived from

Answer 23

•High content of polyphenols, such as tannin which also contribute to the colour

Question 24

Diketopiperazines is described as having what properties?

Answer 24

Described as having bitter, mouth coating, drying, astringent, salty and metallic taste properties

Question 25

Diketopiperazines is detected in

Answer 25

a variety of natural products as well as in processed foods, where they appear to derive from thermal processing.

Question 26

when Diketopiperazines is in aqueous solution, its characteristics are?

Answer 26

have bitter (or astringent) characteristics and probably contribute to bitterness in cocoa, coffee and beer.

However, in systems that contain other taste characteristics (sweet, sour, savoury) they may modify these other tastes, while not adding bitter taste itself

Question 27

Formation of Diketopiperazines

Answer 27

DKP formation in cocoa involved intramolecular cyclation of linear peptide precursors