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FPH-31306-Advanced mol. gastronomy > Astringency > Flashcards

Astringency Flashcards

1
Q

T or F : there is a receptor associated with astringency

A

False, it is a mouth feeling that results from the interaction between saliary proteins and polyphenols

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2
Q

Why is tea less astringent when you add milk?

A

Because of the interaction between the milk proteins and the tannins of tea

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3
Q

What at the two types of tannins seen in class and what is the difference between them?

A
  1. Hydrolysable - ester linkage
  2. Condensed - no esther linkage
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4
Q

Is this a condensed hydrolysable tannin ?

A

condensed because there is a c-c covalent linkage between the multiring phenols and because there is no esther linkage in the structure.

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5
Q

Is this a condensed or a hydrolysable tannin ?

A

Hyrolysable because there are some esther linkage in the strucutre

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6
Q

What is the structure of galllic acid

A
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7
Q

What do you get after the hydrolysis of this condensed tannin

A

1 glucose molecule, a dimer of gallic acid and a tetramer of gallic acid

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8
Q

What is the major difference between the bitterness and the astringency

A

bitterness is receptor mediated

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9
Q

What is the molecular weight of epi-catechin and catechin

A

290

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10
Q

What are the building blocks of flavan-3-ol

A

Catechin and epi-catechin

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11
Q

Catechin and epicatechin are part of the ____ family

A

Flavan-3-ols (sometimes referred to as flavanols)

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12
Q

What is the difference between flavanols and flavonols

A

flavonol contains a ketone group.
In the picture we can see the major classes of flavonoids

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13
Q

What are the different classes of proanthocyanidins ?

A

Propelargonidins: R1=R2=H

Procyanidins: R1=H, R2=OH

Prodelphinidins: R1=R2=OH

They depends on the R1 and R2 groups

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14
Q

When cathecins polymerise, they can form _____

A

proanthocyanidins

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15
Q

What is this molecule ?

A

Proanthocyanidins

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16
Q

The hydrolysable tannins can be hydrolysed by ___ enzyme or a ___ environment

A

tannase
alkali

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17
Q

What are the two types of proanthocyanidins seen in class and what is the difference between them?

A
  1. A-type : two links between the cathecins subunits
  2. B-type : one links between the cathecin subunits
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18
Q

what information can you get in the normal phase chromatography?

A

info on the molecular weight (time eluted) and on the concentration (height of peak)

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19
Q

in normal phase chromatography, ___ molecules elutes first

A

small

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20
Q

In normal phase chromatography, the ____ (polar/apolar) compounds elutes first because the column solvent gradient goes from ___ to ____

A

apolar ellutes first
apolar to polar

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21
Q

In the reversed-phase chromatography, the first compounds to ellute are ____ (polar/apola)

A

polar

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22
Q

In reverse phase chromatography, the column goes from ___ to ___

A

polar to apolar

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23
Q

in the case of reverse phase chromatography your column is ___ while in normal phase the column is ____

A

reversed phase : apolar
normal phase: polar

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24
Q

When there is a peak at 575 on your MS spectrum, you have a ___ in your mixture

A

dimeric proanthocyanidins with A type linkage

25
If you have a peak at 577 on your MS spectrum you have a type ___ proanthocyanidins
B
26
What are the two types of complexation we saw in class
1. Monodentate 2. Multidentate
27
in the case of monomeric polyphenol, you will have a ___ complexation
monodentate
28
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
29
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
30
Which a.a does the polyphenol need in order to bind the salivary proteins
proline
31
What are the two hypothesis of the interaction between polyphenols and proline residues
1. Stalking interaction (hydrophobic) between the A-ring of the polyphenol and the pyrrolidine ring of the proline 2. Hydrogen bonding between the B ring of the polyphenol and the hydrogens of the pyrrolidine ring
32
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
33
What are the three functions of saliva
1. protective: tissue coating, lubri-cation, remineralizationof teeth 2. host-defense: immunological activity, anti-viral, anti-microbial 3. digestion: digestive enzymes, bolus
34
T or F : the composition of the saliva depends on the gland it originate from
true
35
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
36
What are the three types of proteins in the saliva
1. Mucins 2. PRP (proline rich proteins) 3. Histadins
37
\_\_\_\_ is a family of proline-rich proteins, with MUC7 as most important representative in saliva
mucins
38
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
39
\_\_\_\_ is a family of proteins that are rich in histidine
Histatins
40
What do the three classes of salivary proteins have in common?
They are rich in proline and histadine and also flexible (random coils).
41
Which family is the most abundant in salivary proteins?
The proline rich proteins
42
What are the three types of PRP ?
1. acidic 2. basic 3. Glycosylated
43
\_\_\_ and ____ PRPs are related and have a higher proline content than the acidic PRPs
Basic and glycosylated
44
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.
45
What are the way used to reduce the astringency in wine processing?
1. Adding gelatins (rich in proteins) 2. Adding laccase that convert the B type (1 link) into the A type (2+ links)
46
T or F : A type bonds are more common in peanut skins
true
47
\_\_\_\_ 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)
48
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
49
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
50
what are the physical properties of B-type proanthocyanidins
1. linkage are easier to break 2. Less compact 3. higher astringency
51
What are the physical properties of A-type proanthocyanidins?
1. compact structure that doesn't faciliate the interaction with proteins 2. lower astringency 3. can be converted by laccase to reduce the astringency
52
What are the three important factor for the affinity of the polyphenol for salivary proteins?
1. size 2. flexibility 3. Conformation
53
The presence of ___ residue in proteins and the ____ of these residues will promote binding with tannis
proline residues repeats
54
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
55
What is the primary interaction responsible for the binding of the polyphenol ?
The primary interaction is the stalking interaction
56
T or F : the most astringent compounds are the one that are the most efficient precipitating proteins
57
T or F : the glycosylation pattern of the molecule will determine if the molecule is perceived very astringent of moderatly astringent.
true
58
T or F : Compounds with high affinity for salivary proteins show relatively low astringency scores
true
59

FPH-31306-Advanced mol. gastronomy (10 decks)

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