complex of enzymatic and nonenzymatic reactions

carbonyl, anomers OH, primary OH, secondary OH

nonenzymatic browning reactions

reaction of saccharides

Maillard reaction

(reaction with proteins, amino acids)

caramelisation

Reactions of saccharides

reactants

reducing mono- and oligosaccharides

non-reducing oligo- and polysaccharides after hydrolysis

main reactions of monosaccharides

Reaction of saccharides themselves

cukerné alkoholy

anhydrocukryoligosacharidy

cukerné

kyselinyisomery

nižší cukry,

reduktony,

jiné fragmenty

ulosy

monosacharidmonosaccharides

oligosaccharides anhydrosugars

isomers sugar acids

uloses

sugar alcohols

reductons fragments

acid-basic catalysed reactions

in acid medium in alcali medium

(further factors: temperature, time)

mutarotation

formation (hydrolysis) of glycosides isomeration

dehydration rearrangement

reductone formation fragmentation

oxidation

formation and hydrolysis of glycosides

reaction of poloacetals OH

hydrolysis (inversion)

production of starch syrups

invert sugar

galactose

preferably (16) bonds, less (14) and other bonds

RR OH

HH2O-

monosacharid

O

OH

OH

HO

CH2OH

OH

O

OH

OH

HO

CH2OHO

OH

OH

HO

CH2OH

O H

H

glykosid (hetero- nebo homoglykosid)

karbeniový kation

O

OH

OH

HO

CH2OHO

OH

OH

HO

CH2OH

O

H

R

-HO

OH

OH

HO

CH2OH

O

+

+

+

+

++

formation (reverse, Fischer reaction)

side products of inversion (starch syrup: 5-6%)

side products of caramelisation

monosaccharide carbenium cation

glycoside (hetero- or homo glycoside)

mechanism of hydrolysis of saccharose

pH (5.2-5.8)

enzymatic hydrolysis, hydrolases, inactivation 80 oC

chemical hydrolysis, losses 0.5% /h

CH2OH

+

+

+

+

sacharosa

D-fruktosa D-glukosa

O

OH

OH

HO

CH2OH

OH

H

H-

H2O

O

OH

O

CH2OH

HO

OH

OH

O CH2

HOHO

O

OH

O

CH2OH

HO

OH

OH

O CH2

HO

CH2OH

HO

O

OH

CH2

CH2OHHO

HO

HOO

OH

CH2

CH2OH

HO

HO

H

pH 8.4

Ca(OH)2

Maillard reaction

saccharose

D-fructose D-glucose

glucose isomaltose -D-Glcp-(16)-D-Glcp 68-70%

(disaccharides) genciobiose -D-Glcp-(16)-D-Glcp 17-18%

maltose -D-Glcp-(14)-D-Glcp

cellobiose -D-Glcp-(14)-D-Glcp

saccharose kestose -D-Fruf-(26)--D-Fruf-(21)--D-Glcp

(trisaccharides) kelose -D-Fruf-(26)--D-Fruf-(21)--D-Glcp

low energy foods

indicators of adulteration

HO6

levanbiosa

1

2

1

2

CH2

OH

OO

CH2OH

CH2

OH

O

CH2OH

O

CH2OH

OH

HO

O

HO HO

HOsacharosa

kestose

saccharose

levanbiose

dehydration reaction

reaction of semiacetal OH and other OH

semiacetal OH / and other OH anhydrosugars (glycosans)

other OH / other OH deoxysugars

anhydrosugars

-D-Glcp 1,6-anhydro--D-Glcp (-glucosan)

-D-Manp 1,6-anhydro--D-Manp (-mannosan)

-D-Galp 1,6-anhydro--D-Galp (-galactosan)

ketoses dimeric anhydrides (tricyclic compounds)

formation

byproducts of inversion (glucose: 1%)

by-products of caramelization (higher amount)

1

6

HO

O

O H

O H

CH2O

2

1

O

O

HO

OH

CH2OHO

HO

CH2OH

OH

O

,1

,2

deoxysugars

1,2-enolisation (series of isomeration and dehydratation)

o

H2O-

C O

CH2

H

H OH

OH

CH2OH

C

C

CH O

3-deoxy-D-erythro-hexos-2-ulosa

3,4-dideoxy-D-glycero-hex-3-enos-2-ulosa

C

C

C

C

CH2OH

OH

H

H

O

H

CH O

H2O-

H2O-

O CHCH2HO O

5-hydroxymethylfuran-2-karbaldehyd

OHH

H

H

H

HO

OH

OH

OH

CH2OH

C

C

C

C

CC

C

C

C

C

CH2OH

O

OH

OH

OH

HO

H

H

H

H

H

D-glukosa 1-en-1,2-diolD-glucose

5-hydroxymethylfuran-2-carbaldehyde (HMF)

O CHCH2HO O

5-hydroxymethylfuran-2-karbaldehyd

D-glukosa

D-fruktosa

pentosy, L-askorbová kyselina

6-deoxyhexosy (methylpentosy)

2-hydroxyacetylfuran

O

CH2OHO

O CH O

5-methylfuran-2-karbaldehyd

furan-2-karbaldehyd

OCH3 CHO

o

D-glucose

D-fructose

pentoses, L-ascorbic acid

6-deoxyhexoses (methylpentoses)

5-hydroxymethylfuran-2-carbaldehyde (HMF)

2-hydroxyacetylfuran

furan-2-carbaldehyde

5-hydroxymethylfuran-2-carbaldehyde (HMF)

5-methylfuran-2-carbaldehyde

2,3-enolisation

C

C

C

C

CH2OH

O

OH

O

H

H

CH2

H

OHH2O-

1-deoxy-D-erythro-hexo-2,3-diulosa2-en-2,3-diol

C

C

C

C

CH2OH

OHH

H

CH2 OH

OH

OH

OH

D-fruktosa

C

C

C

C

CH2OH

CH2OH

O

OH

OH

HO H

H

H

CH3

C

C

O

O

C

C

CH2OH

OHH

OHH

C

C

C

C

CH3

CH2OH

O

OH

O

H

C

C

C

C

CH3

CH2OH

O

OH

O

H

H

O H

H2O- H2O-

O COCH3

OH

isomaltol

O

O

OH

CH3

maltolcaramel aroma

D-fructose

o

o

pentosy

hexosy

6-deoxyhexosy

(methylpentosy)

C

C

C

C

CH3

CH2OH

OH

OH

O

O

H

H

furaneol

CH=OH

O

OHO

CH2HO CH3

4-hydroxy-5-hydroxymethyl-2-methyl-(2 H)-furan-3-on

O

OHO

H3C

4-hydroxy-5-methyl-(2 H)-furan-3-on

O

OHO

CH3H3C

4-hydroxy-2,5-dimethyl-(2 H)-furan-3-on

o

norfuraneol

hexoses

pentoses

6-deoxyheoses (methylpentoses)

reductone formation

antioxidants

reduction of organic substances, metal ions

pH 6 monoanions

pH 6 dianions

1

2

1

2

C

C

C

R

R

OH

OH

O C

C

C

R

R

O

O

O

2 H

2 H

-

redukton triulosareductone triulose

isomeration

aldose ketose

aldose aldose (epimeration)

CH

C

C

C

C

CH2OH

O

OH

OH

OH

HO

H

H

H

H

D-glukosa

CH

C

C

C

C

CH2OH

O

OH

OH

HO

HO H

H

H

H

D-mannosa

D-fruktosa

HO

C

C

C

C

CH2OH

OH

OH

H

H

H

O

CH2OH

CH

C

C

C

C

CH2OH

OH

OH

OH

HO H

H

H

OH

1-en-1,2-diol

D-fructose

D-glucose D-mannose 1-en-1,2-diol

example

Glc / pH 10 /35 oC Glc 64%

Fru 31%

Man 3%

further isomerization - other aldoses and ketoses

disaccharides isomeration

lactose lactulose epilactose

-D-Galp-(14)-D-Glcp -D-Galp-(14)-D-Fruf -D-Galp-(14)-D-Manp

trioses isomerisation

C

CH O

CH2OH

HO H

L-glyceraldehyd

CH2OH

C

CH2OH

O

1,3-dihydroxyaceton

C

CH O

CH2OH

H OH

D-glyceraldehyd 1-en-1,2-diolát

C

CH

CH2OH

OH

OH

1-en-1,2-diolate

1,3-dihydroxyacetone

D-glyceraldehyde L-glyceraldehyde

rearrangement to acids

1-en-1,2-diol, Cannizzaro reaction, benzyl rearrengement

CH

C

C

C

C

CH2OH

O

OH

OH

OH

HO

H

H

H

H

D-glukosa

CH

C

C

C

C

CH2OH

OH

OH

OH

HO H

H

H

OH

1-en-1,2-diol

COOH

CHOH

CH2

C

C

CH2OH

H

H

OH

OH

CH2

C

C

CH2OH

H

H

OH

OH

COH(CH2OH)

COOH

CH2

C

C

CH2OH

H

H

OH

OH

COH(CH3)

COOH

metacukrové isocukrové cukrové

kyseliny

D-glucose 1-en-1,2-diol

meta sugar acids

sugar acids

iso sugar acids

+

+

C

CH O

OH

CH2

Cannizzarova

reakce

CH2OH

C

CH2OH

O

1,3-dihydroxyaceton

H

C

CH O

O

CH3

methylglyoxal

C

CH3

COOH

HHO

L-mléčná kyselina

C

CH3

COOH

OHH

D-mléčná kyselina

-

-

-eliminace

C

CH O

CH2OH

OHH

D-glyceraldehyd

H-

1-en-1,2-diolát

C

CH O

CH2OH

OH C

CH

CH2OH

OH

O

D-glyceraldehyde 1-en-1,2-diolate

1,3-dihydroxyacetone methylglyoxal

L-lactic acid D-lactic acid

Cannizzaro reaction

β-elimination

fragmentation

formation of reactive componds

retroaldolisation

R CH

OH

CH=O R CH CH C

R

CH=O

OH OH OH

aldolizace

retroaldolizace

aldolisation

retroaldolisation

glyoxal 2C hydroxyacetone 3C methylglyoxal 3C

1,3-dihydroxyacetone 3C laktaldehyde 3C hydroxymethylglyoxal 3C

CH

C

C

C

C

CH2OH

O

OH

OH

OH

HO

H

H

H

H

D-glukosa

C

C

C

C

CH2OH

OH

OH

HO

H

H

O

H

CH2OH

D-fruktosa1-en-1,2-diol

CH

C

C

C

C

CH2OH

OH

OH

HO

H

H

OH

H

OH

2-en-2,3-diol

C

C

C

C

CH2OH

OH

OH

HO

H

H

CH2OH

OH

CH2OH

CH O

glykolaldehyd

CH OH

formaldehydCH2OH

C

C

OH

OH

H

H

CH O

D-erythrosaCH2OH

C

C

C

OH

OH

H

H

HO H

CH O

D-arabinosa

CH O

C

CH2OH

OHH

D-glyceraldehyd D-glyceraldehyd

CH O

C

CH2OH

OHH C

CH2OH

CH2OH

O

1,3-dihydroxyaceton

CH O

C

CH2OH

OHH

D-glyceraldehyd

oxidadation (after isomeration, dehydration)

D-glyceraldehyde D-glyceraldehyde 1,3-dihydroxyacetone D-glyceraldehyde

D-glucose D-fructose

formaldehyde glycolaldehyde

D-erythrose D-arabinose

non-enzymatic browning reaction

reactants

sugars (carbonyl compounds)

monosaccharides and reducing oligosaccharides

(nonreducing oligosaccharides, polysaccharides, glycosides)

triose …. pentose hexose (acyclic form)

aldose ketose

-dikarbonyls aldehydes ketones saccharides

proteins (aminocompounds)

-NH2 Lys, N-ending NH2, guanidyl Arg, SH Cys

free amino acids, amines, ammonia

-NH2 …. -NH2 -NH2

NH3 R-NH2 aminoacid (reactivity is related to their basicity)

Maillard reaction

French pronunciation : [majaʁ], Engl.: /maɪˈjɑr/

Réaction générale des acides aminés sur les sucres. Journal de Physiologie, 1912 tome 14 page 813

reaction conditions

water activity (aw 0,3-0,7)

pH (5-9)

others (temperature, time of reaction, other components)

formation of cations

HX

HXX

-

X-

+

+

+

+

+

NH3 NH4

amoniak amonná sůl

R NH2 R NH3

primární amin sůl aminu

1 1 1

R

C O

R

R

C O H

R

R

C OH

R

H

karbonylová sloučenina

protonation of the carboxyl group increases its reactivity

protonation of the amino group reduces its reactivity

carbonyl compound

ammonia ammonium salt

primary amine salt of amine

concequences

positive, negative

• formation of aroma compounds

• formation of yelow, brown, black pigments melanoidins

+ bread crust, coffee, fried products

- dried foods (milk), fruits

• decrease of nutritive value reaction with Lys

• formation of potentially toxic products

reaction in vivo (glykosylation of proteins)

mechanism of reactions

3 stages

initial stage

formation of glykosylamines (Amadori rearrangement) and formation of aminodeoxysugars (Amadori products)

middle stage

decomposition of saccharides, glycosylamines, aminodeoxysugars (dehydratation, fragmentation)

decomposition of amino acids (Strecker degradation)

final stage

reaction of degradation products, formation of aroma, taste and colour products (melanoidins)

glycosylamines and aminodeoxysugars

totally utilisable form non-utilisable form

aldose aldosylamine ketosamine(1-amino-1-deoxyketose) Amadori rearrangement

ketose ketosylamine aldosamine (2-amino-2-deoxyaldose) Heyns rearrangement

O

CH2OH

OH

OH

HO

OH

O

CH2OH

OH

OH

HO

NH R

OH

CH2 NH RO

HO

OH

HO

D-glukosylamin D-fruktosamin

(1-amino-1-deoxy- D-fruktosa)

D-glukosa

adice

dehydratace

cyklizace

isomerace

(Amadoriho p.)

D-glucose D-glucosylamine D-fructosamine 1-amino-1-deoxy-D-fructose

addition dehydration cyclisation

isomeration (Amadori rearrangement)

mechanisms (reaction of acyclic forms)

H2O-R NH2

CH

C

C

C

C

CH2OH

OH

OH

OH

HO

H

H

H

H

O

D-glukosa karbinolamin

C

C

C

C

CH2OH

OH

OH

OH

HO

H

H

H

H

CHOH

NH R

imin (Schiffova báze)

C

C

C

C

CH2OH

OH

OH

OH

HO

H

H

H

H

CH

N R

O

CH2OH

OH

OH

HO

NH R

D-glukosylamin

O

CH2OH

OH

OH

HO

NH R

D-glukosylamin kation Schiffovy

báze

+

+

-C

C

C

C

CH2OH

OH

OH

OH

HO

H

H

H

H

CH

NH R

+

-

NH R

CH2

H

H

H

HO

OH

OH

CH2OH

C

C

C

C O

NH

CH

H

H

H

HO

OH

OH

OH

CH2OH

C

C

C

C

R

enolforma cyklická forma

H H

oxoformaD-fruktosamin (1-amino-1-deoxy- D-fruktosa)

OH

CH2 NH RO

HO

OH

HO

D-glucose D-glucosylamine

D-glucosylamine D-fructosamine (1-amino-1-deoxy-D-fructose) enol form oxo form cyclic form

carbinolamine imine (Schiff´s base)

cation of Schiff´s base

decomposition of aminodeoxysugars

1,2-enolisation acidic medium

2,3-enolisation neutral and alkaline medium

formation of glycosuloses and glycodiuloses (aldoketoses and diketoses)

o

1,2-enolisace

2,3-enolisace

produktyH H2O- H2O

H-

-R NH2

+

+

+ +

enaminol

C

CH

O

O

CH2

3-deoxy-D-erythro-hexos-2-ulosa

produktyH

+

+

+H-

-R NH2

1-deoxy-D-erythro-2,3-hexo-2,3-diulosa

CHO H

C OH

CH NHR

C H

C

CH

OH

NR

C

C

O

O

CH3

D-fruktosamin

CHO H

C

CH2

O

NHR

C H

C

CH NHR

OH

H2O

C

C OH

O

CH2

C

C OH

OH

CH2 NH2R

endiol

CHO

C OH

CH NHRR

R R R R

R R R R

(HMF,…)

(HMF,…)

2,3-enolisation

1,2-enolisation

D-fructosamine

products (HMF, …)

products (HMF, …)

3-deoxy-D-erythro-hexos-2-ulose

1-deoxy-D-erythro-2,3-hexo-2,3-diulose

analogy with the reactions of sugars themselves

lower activation energy

unlike reactions of carbohydrates themselves these are running already at ambient temperatures and pH 4-7

products contain N and S

qualitatively and quantitatively more products

in parallel - decomposition of sugars and aminoacids themselves

examples

formation of methylglyoxal and 2,5-dimethylpyrazine

from fructosamine

NH R

CH2

H

H

H

HO

OH

OH

CH2OH

C

C

C

C O

D-fruktosamin

CH2OH

NH R

CH2

C O

CH=O

H OH

CH2OH

C

aminoanalog

1,3-dihydroxyacetonu

D-glyceraldehyd

CH=O

C O

CH3

methylglyoxal

CH

C O

CH3

N R

H2O

H2O

R NH2

imin

methylglyoxalu

retroaldolizaceretroaldolisation

D-fructosamine 1-amino-1-deoxy-D-fructose

D-glyceraldehyde methylglyoxal

imine of methylglyoxal

amino analogue of 1,3-dihydroxyacetone

R = H

(Strecker´s degradation of amino acids)

formation of 2,5-dimethylpyrazine

aroma of roasted nuts, potato chips

CH

C O

CH3

NH

C

CH3

OH

CH NH2

C

CH3

OH

CH NH2 C

CH3

HO

CHNH2

+

N

N

H

H

CH3

CH3- 2 H2O

oxidace

N

N

CH3

CH3

2,5-dimethylpyrazino

2,5-dimethylpyrazine

important heterocyclic products

isomaltol furaneol furfurylthiol caramel strawberries, pineapple coffee

maltol 2,4-dimethylthiophene 2-acetyl-1-pyrroline 2,6-dimethylpyrazine caramel fried onion bread chocolate, roasted nuts

O

OH

CH3

O

O

HO

CH3 CH3

O

O CH2 SH

O

O

OH

CH3 S

CH3

CH3 NCH3

O

N

N

CH3CH3

Maillard reaction in important food commodities

positive and negative consequences

desirable and undesirable reactions

technology (aroma, taste, colour, nutritive value)

roasting

cooking, baking, frying

drying

extrusion, microvawe heating

milk, milk products

Lys losses: 10-30% traditional drying, 3% sprey drying

cereals, cereal products

Lys losses: 70% bread crust, 10% total

meat, meat products

mutagenes (heterocyclic amines)

fruits, vegetables

coffee, cocoa, nuts

reactions in the processing of milk unavailable (blocked) Lys

isomeration lactose lactulose + epilactose

lysinoalanin

-N-deoxylaktulosyllysin)

R

H2O2+

HOH2C

NH

CH

C

HN

O

HCl

NH

CH

C

HN

CH

CO

O

protein

furosin

OO

C CH2 NH

CH3

HO

pyridosin

NO

[CH2]4 CH COOH

NH2

NHCH2

C

C

CH2

C

CH2OH

OHH

O

O

[CH2]4 CH COOH

NH2

[CH2]4 CH COOH

NH2

[CH2]4

O

OH

OH

OH

NHCH2

OC

OH

H

H

H

HO C

C

C

CH2OH

O

[CH2]4

laktosa

OH

O

OH

OH

CH2OH

O

OH

OH

OHO

CH2OH

NH2

1-lysino-1-deoxylaktulosalactose

inhibition of Maillard reaction

creating unfavorable conditions

water content (activity), lower temperature, regulation of pH

removal of one reaction partner

use of inhibitors

SO2 + H2O H2SO3 H+ + HSO3-

CH=O

CH OH

HSO3- CHOH

CH OH

SO3-

sulfonová kyselinaaldehyd

o

aldehyde sulfonic acid

sugars

sugars (saccharose, glucose, fructose, starch sirup, invert sugar

temperature

150-190 oC (240 oC)

reaction time

5-10 h

catalysts

caramel = solid product

couler = liquid product

Caramelisation

class name of couler additives matter utilisation

I CP caustic Na2CO3, K2CO3, NaOH, KOH, H2SO4, acetic acid, citric acid

alcoholic beverages (high content of alcohol)

II CCS caustic sulphite SO2, H2SO4, Na2SO3, K2SO3, NaOH, KOH,

vinegar, beer, alcoholic beverages, aromatised wine

III AC ammonium NH3, (NH4)2SO4, Na2CO3, H2SO4, NaOH, KOH

beer, alcoholic beverages, acid food

IV SAC ammonium-sulphite

NH3, SO2, (NH4)2SO3, Na2SO3, K2SO3, Na2CO3, K2CO3, NaOH, KOH, H2SO4,

acid food, non-alcoholic beverages