vanilla chemistry

7/24/2019 Vanilla Chemistry

1/22

Chemistry and Physics of Vanillin

Chaim Frenkel, Professor

Department of Plant Biology and PathologyRutgers-the State University of New Jersey

New Brunswick, NJ 08901-8520

(732) 932-9711 x 365

(732) 932-9441 fax


2/22

Cross section of vanilla bean showing a dark central cavity(seeds) surrounded by vanillin forming cells.


3/22

C H

OH

OCH3

O

C H

OH

OCH3

O

Hydrophobicity Hydrogen bonds (intra and intermolecular)of the aromatic ring

C H

OH

OCH3

O

Reactivityof a carbonyl group (Maillard Reaction)

Molecular features of vanillin, including hydrophobicity, efficacy

for forming hydrogen bonds and reactive carbonyl group, whichcould influence the fate of vanillin during various handling stages.


4/22

- stacking of aromatic rings. This phenomenon, stemming

from the hydrophobicity of aromatic compounds contributesto the tendency of vanillin to form aggregates.


5/22

C

O

O

O

C

O

H

OH

O

CH3

CH3

C

O

H

OH

O

CH3

H

H

* Adapted from: Aihara A (1973) A study of hydrogen bonds in Vanillin I.

Denki Tsaushin Daigaku 24:71-75

Inter and Intra Hydrogen Bonds in Crystalline Vanillin


6/22

0 10 20 30 40 50

80O

C

50OC

60OC

40OC

20O

C

100

80

60

40

20

0

PercentVanillin

Days

Rate of disappearance of dry vanillin held at atmosphericpressure and at different temperatures.


7/22

Time (days)

PercentVa

nillin

40O

C

60

O

C

0 2 4 6 8 10 12 14

60OC

0OC, 20

OC

40O

C

50OC

80OC

100

80

60

40

20

0

Rate of disappearance of dry vanillin held at 0.1 atmosphericpressure and at different temperatures.


8/22

Pe

rcen

tVan

illin

Temperature (O

C)

100

80

60

40

20

0

20 30 40 50 60 70 80

0.1 atmospheric pressure

1.0 atmospheric pressure

Disappearance of vanillin held at 1.0 or 0.1 atmospheric pressure.

Vanillin was held for 18 and 4 days at 1.0 or 0.1 atmospheric pressure,respectively. The data shows that vanillin disappearance is greatly

accelerated above 40o C.


9/22

0 10 20 30 40 50 600

2

4

6

8

10vanillin

methanol

Temperature (O

C)

M

van

illin

mlMe

thano

laft

er

24hours

290

280

270

260

250

Vanillin content solubilized in 100% methanol

and held for 24 hours at different temperatures.The data shows that while methanol is volatilized

vanillin remains in solution.


10/22

0 10 20 30 40 50 60 70 80

0

2

4

6

8

10310

270

230

190

150

Temperature (OC)

Van

illinCon

ten

t(M)

vanillin

water

mlWa

ter

Vanillin content solubilized in water and held for

48 hours at different temperatures. The data showsThat disappearance of vanillin is correlated to the

rate of water disappearance.


11/22

0 10 20 30 40 50 60 70

0

2

4

6

8

10

vanillin

methanol (40%)

MVan

illin

Rema

ining

Vo

lumeo

fLiquid(40%me

thano

l)

Temperature (OC)

340

320

310

300

Vanillin content solubilized in 40% methanol-water

solution and held for 2 days at different temperatures.The data shows that presence of water caused some

disa earance of vanillin.


12/22

C

O

O

H

O

CH3

H

C

O

OO

C

O

H

OH

O

CH3

CH3

H

H

WATER

C

O

O

H

O

CH3

H

HEAT

C

O

O

H

O

CH3

H

A hypothetical scheme indicating that hydration of vanillin,

due to vanillin-water hydrogen bonding, leads to thevolatilization of vanillin-water complex.


13/22

0 1000 2000 3000 4000 5000 6000

3

4

5

6

7

8

9

10

11

pH

mole KOH or NaOH

KOH

NaOH

Titration curve of vanillin in water.

The data shows that native vanillin is acidic and,moreover, exhibits a substantial buffering capacity.


14/22

0 10 20 30 40 50 60 70 80

0

2

4

6

8

10

water

vanillin pH 8.0

vanillin pH 6.5

3.0

2.6

2.2

1.8

1.4

VanillinContent(

mole)

Temperature (OC)

mlWater

Vanillin content in water, adjusted to pH 6.5 or 8.0 and held

for 48 hours at different temperatures. Disappearance of vanillinis function of solubility (greater at pH 8.0 that 6.5, above 40o C).


15/22

0 10 20 30 40 50 60 700

2

4

6

8

10

Van

illinCon

ten

t(

mo

le)

Temperature (OC)

3.4

3.0

2.6

2.2

water

vanillin pH 2.0

vanillin pH 3.0

mlW

ater

Vanillin content in water, adjusted to pH 3.0 or 2.0 and held

for 48 hours at different temperatures. Disappearance of vanillin

is function of solubility (greater at pH 3.0 that 2.0, above 30o C).Lower levels of vanillin at pH 3.0, below 30o C, reflect precipitation

of the compound in the aggregate state.


16/22

A schematic view of water structure showing a tight inter-

molecular arrangement created by hydrogen bonding ofneighboring water molecules.


17/22

Solute cavity in water showing disengagement of water

structure to accommodate a guest molecule (middle) *

* Martnez JM, Pappalardo RR., Marcos ES, Mennucci B, Tomasi J (2002) Analysis of the Opposite Solvent Effects Causedby Different Solute Cavities on the Metal-Water Distance of Monoatomic Cation Hydrates. J Phys Chem B 106:1118-1123


18/22

Maillard Reaction

Inhibitors Promoters

F Cl Br I ClO4 SCN

Li

+

Na

+

K

+

Rb

+

Cs

+

NH4+

Water Structure Water Structure Breakers

Makers (Chaotropes)

(Kosmotropes)

Some ions, which enhance or diminish the structure of water.

Water structure-breaking ions are presumed to enhance the

solubility and, thereby, the chemical reactivity of vanillin.

Schiff's base formation


19/22

C=O + H2NR

HO C N R

Carbinolamine Schiff's base

C=O + H2NR

H

C OH

C H

H

HO

C OH

C H

H

HO

HO C N RH

C OH

C H

H

HO

C N R+ HOHH

H

H

C N R + HOH

Carbinolamine Schiff's base Aldose

C OH

C H

H

HO

C N RH

C OH

C HHO

HC N R

H

C O

C HHO

HC N R

HH

Schiff's base 1-amino-2-keto sugar

Amadori Rearrangement

C N R + HOH + HC O RNH3

Sciff's base Hydrolysis

In acid medium Schiff's base will undergo hydrolysis

+

H

A generalized scheme of Maillard Reaction showing Schiff baseformation followed by Amadori Rearrangement, leading to further

de radation includin formation of brown color.


20/22

0 20 40 60 80 1000.1

0.2

0.3

0.4

0.5

OD

420nm

Concentration of CsCl or LiCl (mM)

CsCl

LiCl

Rate of Maillard reaction occurring between vanillin and

lysine in presence of varying concentrations of water structure-

breaking ions (CsCl) or water structure-maker ion (LiCl).Solutions containing 5 mM vanillin and lysine adjusted to pH 6.5, held at

65o C for 2 days. Brown pigment formation estimated by spectroscopy.


21/22

Visualization of Maillard reaction for vanillin and lysine occurring

in absence or presence of varying concentrations of water structure-

breaking ions (CsCl) or water structure-maker ion (LiCl).


22/22

Summary

Conditions, which increase the water solubility of vanillin

(alkalinity or chaotropic agents) enhance water co-volatility

and chemical reactivity of the compound.

vanilla chemistry

Documents