Astringency Flashcards
T or F : there is a receptor associated with astringency
False, it is a mouth feeling that results from the interaction between saliary proteins and polyphenols
Why is tea less astringent when you add milk?
Because of the interaction between the milk proteins and the tannins of tea
What at the two types of tannins seen in class and what is the difference between them?
- Hydrolysable - ester linkage
- Condensed - no esther linkage
Is this a condensed hydrolysable tannin ?
condensed because there is a c-c covalent linkage between the multiring phenols and because there is no esther linkage in the structure.
Is this a condensed or a hydrolysable tannin ?
Hyrolysable because there are some esther linkage in the strucutre
What is the structure of galllic acid
What do you get after the hydrolysis of this condensed tannin
1 glucose molecule, a dimer of gallic acid and a tetramer of gallic acid
What is the major difference between the bitterness and the astringency
bitterness is receptor mediated
What is the molecular weight of epi-catechin and catechin
290
What are the building blocks of flavan-3-ol
Catechin and epi-catechin
Catechin and epicatechin are part of the ____ family
Flavan-3-ols (sometimes referred to as flavanols)
What is the difference between flavanols and flavonols
flavonol contains a ketone group.
In the picture we can see the major classes of flavonoids
What are the different classes of proanthocyanidins ?
Propelargonidins: R1=R2=H
Procyanidins: R1=H, R2=OH
Prodelphinidins: R1=R2=OH
They depends on the R1 and R2 groups
When cathecins polymerise, they can form _____
proanthocyanidins
What is this molecule ?
Proanthocyanidins
The hydrolysable tannins can be hydrolysed by ___ enzyme or a ___ environment
tannase
alkali
What are the two types of proanthocyanidins seen in class and what is the difference between them?
- A-type : two links between the cathecins subunits
- B-type : one links between the cathecin subunits
what information can you get in the normal phase chromatography?
info on the molecular weight (time eluted) and on the concentration (height of peak)
in normal phase chromatography, ___ molecules elutes first
small
In normal phase chromatography, the ____ (polar/apolar) compounds elutes first because the column solvent gradient goes from ___ to ____
apolar ellutes first
apolar to polar
In the reversed-phase chromatography, the first compounds to ellute are ____ (polar/apola)
polar
In reverse phase chromatography, the column goes from ___ to ___
polar to apolar
in the case of reverse phase chromatography your column is ___ while in normal phase the column is ____
reversed phase : apolar
normal phase: polar
When there is a peak at 575 on your MS spectrum, you have a ___ in your mixture
dimeric proanthocyanidins with A type linkage
If you have a peak at 577 on your MS spectrum you have a type ___ proanthocyanidins
B
What are the two types of complexation we saw in class
- Monodentate
- Multidentate
in the case of monomeric polyphenol, you will have a ___ complexation
monodentate
How does proteins aggregate in the case of monodentate complexation
they aggregate when a lot of monomeric polyphenols are present and increases the hydrophobicity of proteins which will then precipitate
How does multidentate complexation precipitate the proteins?
large polyphenol can cross-link between them and the other proteins and so they will form complex that will precipitate
Which a.a does the polyphenol need in order to bind the salivary proteins
proline
What are the two hypothesis of the interaction between polyphenols and proline residues
- Stalking interaction (hydrophobic) between the A-ring of the polyphenol and the pyrrolidine ring of the proline
- Hydrogen bonding between the B ring of the polyphenol and the hydrogens of the pyrrolidine ring
Why are proline good at binding the polyphenols?
Because the oxygen in proline are next to a tertiary amide and so they re partially positive and so they are good H-bond acceptors
What are the three functions of saliva
- protective: tissue coating, lubri-cation, remineralizationof teeth
- host-defense: immunological activity, anti-viral, anti-microbial
- digestion: digestive enzymes, bolus
T or F : the composition of the saliva depends on the gland it originate from
true
Why is saliva good for binding polyphenols although it has less proteins per /l than serum?
Because there are more random coil proteins and protein rich in proline in the saliva than in the serum
What are the three types of proteins in the saliva
- Mucins
- PRP (proline rich proteins)
- Histadins
____ is a family of proline-rich proteins, with MUC7 as most important representative in saliva
mucins
Which protein family are we talking about here :
-most abundant salivary proteins
- at least 6 family members, in 3 subclasses
- between 6 and 66 kDa
The proline rich proteins
____ is a family of proteins that are rich in histidine
Histatins
What do the three classes of salivary proteins have in common?
They are rich in proline and histadine and also flexible (random coils).
Which family is the most abundant in salivary proteins?
The proline rich proteins
What are the three types of PRP ?
- acidic
- basic
- Glycosylated
___ and ____ PRPs are related and have a higher proline content than the acidic PRPs
Basic and glycosylated
Why is gelatin used in fining of wine
gelatin is used to reduce the astringency because it is rich in proline and can interact with the tannins.
What are the way used to reduce the astringency in wine processing?
- Adding gelatins (rich in proteins)
- Adding laccase that convert the B type (1 link) into the A type (2+ links)
T or F : A type bonds are more common in peanut skins
true
____ is cleaved into ___ to study the salivary-polyphenol interactions because it is a flexible C-terminal part of the pro-protein
PRB4S is cleaved into IB-5 (the C terminal part of the protein)
Which of these molecules would have the highest affinity to the salivary proteins?
It would be the pentagalloyl glucose and the proanthocyanidin because they are more flexible because there is free rotation around the ester bond and between the phenolic rings
T or F : the affinity of a tannins to proteins measured by the BSA precipitation test can predict its astringency in senosry analysis
false because grandinin has the less afinity for the salivary proteins but it is the one that is perceived as the most astringent
what are the physical properties of B-type proanthocyanidins
- linkage are easier to break
- Less compact
- higher astringency
What are the physical properties of A-type proanthocyanidins?
- compact structure that doesn’t faciliate the interaction with proteins
- lower astringency
- can be converted by laccase to reduce the astringency
What are the three important factor for the affinity of the polyphenol for salivary proteins?
- size
- flexibility
- Conformation
The presence of ___ residue in proteins and the ____ of these residues will promote binding with tannis
proline residues
repeats
In the case of tannins, the presence of ___ in the molecule will promote the binding to the protein
presence of gallic acid because they are not connected by c-c bonds and so they give some flexibility to the tannins
What is the primary interaction responsible for the binding of the polyphenol ?
The primary interaction is the stalking interaction
T or F : the most astringent compounds are the one that are the most efficient precipitating proteins
T or F : the glycosylation pattern of the molecule will determine if the molecule is perceived very astringent of moderatly astringent.
true
T or F : Compounds with high affinity for salivary proteins show relatively low astringency scores
true
