Bitterness Flashcards
Bitter sensation is also [LESS/ MORE ?] prolonged than sweet, salty or sour sensations.
more
Caffeine belongs to which chemical group ?
Purine alkaloide belonging to the group known as methylxanthines
Caffeine is classified by the Food and Drug Administration as?
“generally recognized as safe” (GRAS)
Caffeine can be a stimulant to which human system
Central nervous system (CNS) stimulant
Caffeine threshold
75-155 mg/L
Which compounds are responsible for bitterness & astringency?
Phenolic compounds
The effect of phenolic compounds structure on taste perception
- 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
Bitterness in citrus fruit derived from
Flavanones, flavones & flavonols
Bitterness dependant on the type of glycoside chain
Naringin sources ? chemical group effects? Chemical name
- citrus fruit
- flavanone
- Bitter
- Rhamnosyl-α-1,2-glucose
Hesperidin sources ? chemical group effects? Chemical name
- citrus fruit
- flavanone
- Tasteless
- Rhamnosyl-α-1,6-glucose
Neohesperidin
sources ?
chemical group
effects?
- citrus fruit
- flavanone
- Very bitter
Neohesperidin dihydrochalcone
sources ?
effects?
- citrus fruit
Intensely sweet
Flavan is the base form of ____
Learn chemcial structure difference on P. 27 slide
Flavanonols Chalcones Flavanones Anthocyanidins Flavones Flavonols
bitterness in tea derived from which compounds?
Combination of catechins, caffeine, amino acids & saponin
bitterness in chocolate derived from which compounds?
- High amounts of catechins
* Fermented cocoa: epicatechin, polyphenols and anthocyanins ( glycoside forms of anthocyanidins)
bitterness and astringent in wine derived from which compounds?
- Low molecular weight catechins (bitter)
* High molecular weight tannins (astringent)
Glucosinolates is___?
found in?
Characters?
- Amino acid-derived secondary plant metabolites
- Exclusively in cruciferous plants, predominantly Brassicaceae family
- Characteristic flavour and odour properties
- Pungent and bitter
Ex of Glucosinolates & chem structure
7 Ex
(Z)-cis-N-hydroximinosulfate esters
•Side chain R
•Sulfur-linked D-glucopyranose moiety
Glucoiberin / Progoitrin
Sinigrin/ Glucoraphanin
Gluconapin/ Glucobrassicin
Glucosinolate Hydrolysis
Pungent & highly reactive
Pungent Acrid Corrosive Lachrymatory or tear-inducing
Other Bitter Taste Substances (3)
characteristic
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)
Astringency is perceived by?
Perceived through the oral cavity and the tongue
Astringency is regarded as ____ and how ?
“mouth-feel”
• Reactions involving polyphenolic substances and proteins in the saliva, surface of the tongue, palate.
astringency in red wine & tea derived from
•High content of polyphenols, such as tannin which also contribute to the colour
Diketopiperazines is described as having what properties?
Described as having bitter, mouth coating, drying, astringent, salty and metallic taste properties
Diketopiperazines is detected in
a variety of natural products as well as in processed foods, where they appear to derive from thermal processing.
when Diketopiperazines is in aqueous solution, its characteristics are?
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
Formation of Diketopiperazines
DKP formation in cocoa involved intramolecular cyclation of linear peptide precursors
