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FPH-31306-Advanced mol. gastronomy > Sweet and savory > Flashcards

Sweet and savory Flashcards

1
Q

what are the 4 types of sugar replacement categories we saw in class ?

A

-low-calorie sweeteners (obesity) -non-glucose-based sweeteners (diabetes) -more natural sweeteners (i.e. stevia) -high-potency sweeteners

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2
Q

T or F : the sweet and umami are taste with T2R

A

flase, both taste are tasted with dimers of T1R2, T1R1 or T1R3

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3
Q

T or F : mGluRs also recognize the umami compound L-Glu

A

true and so the mGluR1 is used in 3D modeling of the receptor to study the response of certain ligands

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4
Q

T or F: 3D structure of mGluR1 has been used to model the structure of other T1Rs (i.e. T1R1)

A

true

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5
Q

how is the L-glutamate bound by the T1R ?

A

it is bound due to its 2 carboxylic groups

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6
Q
A
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7
Q

Sweet perception is due to the dimerisation of __ and ___

A

T1R2 / T1R3

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8
Q

umami perception is due to the dimerisation of __ and ___

A

T1R1 / T1R3

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9
Q

T or F : the sweet and bitter taste can’t be tasted by the same cells

A

true, the expression of T1R and T2R do not overlapp in cells

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10
Q

What is the role of IMP in the taste perception of umami?

A

it is a taste enhancer of umami ; it reduces the EC50 of umami perception. IT is a allosteric modulator and on its own it doesn’t produce a response

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11
Q

What are the two regions of the T1R

A

The TMD : terminal trans-membrane domain with 7 trans-membrane helices
The VTD : venus flytrap domain with its upper and lower lobes

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12
Q

T or F : the sweet/umami receptor is one protein with two domains (1 gene) while bitter receptor is only a protein with one domain (1 gene)

A

true

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13
Q

on which domain is located the hinge region of the T1R

A

in the VFTD

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14
Q

L-glutamate binds in the ___ region of the VFTD

A

hinge

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15
Q

The conformation of the VFTD is ___ when the ligand is bound

A

closed

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16
Q

How does the IMP has an enahncement acitivity ?

A

it binds the VFTD and stabilize the closed form (active form)

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17
Q

What is bonito bushi made from ?

A

either from dired kombu and bonito or from mushroom and dried kombu

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18
Q

** exams : what are the steps involved in making the bonito bushi ?

A

-1 Boiling : musculature cut from body and gently boiled for 1 hour
-2 Smoking : hot smoking above hardwood (oak) fire for 10-20 days
-3 Fermentation : after inoculation with Aspergillus, Eurotium, Penicilliumsurface fermentation for ~2 weeks
-4 Sun drying : sun-drying for 2 days, after which mold is scraped off
The molding process repeated 3-4 times and after a total of 3-5 months, meat is light brown and dense, and sounds like a resonant piece of wood

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19
Q

Lactoyl GMP has an extra ___ group on the NH2

A

lactic acid

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20
Q

Acetyl GMP has an extra ___ group on the NH2

A

acetyl group

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21
Q

___ also enhances salty while ___ only enhances umami

A

salty+umami : lactoyl GMP
umami only : Acetyl GMP

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22
Q

This molecule is the main contributor to the scallop taste :

A

R-strombine

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23
Q

R-strombine is formed naturally from a.a ____ and ____

A

glycine and pyruvic acid

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24
Q

what are the synthetic and bio-synthetic route of making R-strombine?

A
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25
Q

What is the differences between R-strombine and S-strombine

A

R-strombine : The methyl of the chiral carbon is pointing backwards
S-strombine : methyl group of the chiral carbon is pointing forward, methalic taste

26
Q

using synthetic route, what are the two buildiing blocks of R-strombine ?

A

glycoxylic acid and R-alanine

27
Q

Why does the flavour industry doesn’t want the s-strombine in their food ?

A

becaus the s-strombine has a metalic taste

28
Q

alapyridaine is a Maillard reaction product formed upon heating of ___ and ____

A

alanine and hexose

29
Q

what is a multi-modal taste enhancer ?

A

will change the taste perception (often enhancement) multiple other tastes. For example pyridaine with the sweet, umami and salty taste enhancing effect

30
Q

in the case of alapyridaine, the ___ form is not active

A

r-form not active while the s form is active. So the stereochemistry matters for the tast enhancement effect.

31
Q

What is the reason that pyridaine is not used in the industry

A

the reason that pyridaine was not used by companies is that it needs to be added in the same amount than the molecule it is enhancing (for example if sucrose than it would mean that you add a lot and so it is too expensive)

32
Q

The relative sweetness RS is a way to compare sweet molecules to ____

A

sucrose

33
Q

What are the steps involved in the processing of bitter neohesperidin from citrus peel into the sweet version

A

1- C-ring opening by strong alakali environment
2- stabilization of the chalcone by hydrogenation

34
Q

____ seem to underlie inter-individual variation in taste perception

A

the haplotypes

35
Q

Most AA sequence variation T1Rs in first _____, implicated in ligand recognition

A

extracellular domain

36
Q

T2Rs carry AA variation in_____ , where they bind the bitter tastants

A

trans-membrane domains

37
Q

what could explain the large inter-individual variance observed in tasting sweetness

A

there is a lot of variant of the T1R2 (haplotype)

38
Q

True of False : an haplotype automatically leads to an inter-individual variation in taste perception

A

false, it doens’t necessaly lead to a different specificity pf te receptor. Haplotype only means that there is a a.a changed in the seqeuence of the receptor

39
Q

why was it thought that the histidine of neoculin were involved in the taste modifying property of neoculin ?

A

because the sweetness response curve of neoculin ressemble the protonation curve of histidine

40
Q

how does the pH of neoculin influences the conformation of the protein ?

A

the protein is active in the open conformation. At Acidic pH, the majority of the a.a in the subunits (histidine, arginine and lysine) are positive and so there is repulsion between the two sub-unit keeping the protein in its active configuration

41
Q

T or F : removing the histidine for an alanine keeps the protein in its active configuration and the neoculin will be active at neutral pH

A

true

42
Q

____ can only bind small sweeteners while ____ has larger cavity and can bind a larger collection of non-proteic sweeteners

A

T1R2 : small sweetners
T1R3: larger cavity and can bind non-proteic bigger and proteic molecules

43
Q

What is the name of the broad sweet blocker seen in class

A

lactisole

44
Q

T or F : lactisole has an effect on all sweetners known

A

true

45
Q

how does the lactisole blocks the sweet taste perception

A

binds with the histidine of the c-terminal of the Rc and forms a salt bridge. Also, the CH3 of the lactisole binds with the alanine fo the receptir and keep it in the locked position (open/inactive)

46
Q

where does each of the ligand binds on the T1R2/T1R3 receptor

A
47
Q

____ binds : e.g. sucrose, aspartame, neotame

___ binds : e.g. sucrose

___ binds : cyclamate, NHDC

___ binds : sweet proteins

A

Site I (T1R2): e.g. sucrose, aspartame, neotame

Site II (T1R3): e.g. sucrose

Site III (TMD of T1R3): cyclamate, NHDC

Site IV (T1R3): sweet proteins

48
Q

T or F : you could have synergy of two large sweetners

A

false, synergy is only observed between two small sweetners or a small and a large sweetner

49
Q

how does lactisole blocks (physically) the receptor

A

Lactisole(sweet blocker) might lock T1R3 in resting state, preventing conformational changes of heterodimer leading to signal transduction

50
Q

what is the effect of lactisole on the cyclamate response and on the aspartame response

A

cyclamate (binding to the TMD of T1R3 like lactisole)
aspartame (binding to the site I of the T1R2)

51
Q

lactisole inhibits cyclamate by :
lactisole inhibits aspartame by :

A

inbitition of cyclamate by : competitive
inhibition of aspartame by : allosteric modulation / negative cooperativity

52
Q

in cometitive inhibition what happens to the following :

  • EC50 :
  • signal amplitude
A
  1. EC50 shift to the left
  2. No reduction of the signal amplitude
53
Q

in allosteric inhibition what happens to the following :

  • EC50 :
  • signal amplitude
A

No shift in the EC50
reductiion in the amplitude of the signal

54
Q

Can NHDC and cyclamate boost the response to sucrose ?

A

yes, by allosteric modulation since they both bind the site III of the T1R3 and sucrose also binds the site I (like aspartame and lactisole).

55
Q

Synergy between sucrose and NHDC or cyclamate is an example of ___ modulation of sweet response

A

positive allosteric

56
Q

why can’t the synergy be used in the case of zero-calorie sweetners ?

A

synergy is often only observed at lower sweetner levels

57
Q

__ is a PAM that binds the VFTD of T1R2, away from the hinge region

A

SE-2 (indified by high throughput screening)

58
Q

what is the effect of SE-2 on the sucralose response ?

A

lowers the sucralose sweetness even when sucralose is present in sub-optimal concentrations

59
Q

t or f : SE-2 produces a sweet response on its own by binding the VFTD of the T1R2

A

false, it does not produce a sweet response on its own although it is right that is binds the T1R2 region close to the hinge in the receptor

60
Q
A

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

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