1. MAJOR CHEMICAL PROCESSES1
The chemical processes in the food chemistry and food technology could be classified in the following groups:
Carbonyl – amine interactions (Maillard reaction);
Thermal transformations of -aminoacids, proteins, vitamins, carbohydrates (caramelization) etc.;
Thermal – oxidative destruction and autoxidation of food lipids;
Polyphenol coloring of the foodstuffs;
Changes of the food components by food irradiation and other treatments.

2. OBJECTIVES 1. Importance of Maillard reaction for food chemistry;2
OBJECTIVES
1. Importance of Maillard reaction for food chemistry;
2. Major steps and some reactions;
3. Study the kinetics and parameters influencing the Maillard reaction;
4. Control and inhibition of
Maillard reaction.

3. Maillard reaction – color and flavor formation2
Maillard reaction – color and flavor formation

4. Maillard reaction - history3
Maillard reaction - history
1912г. Louis Camille Maillard a French physician and chemist
- 3 scientific papers: C.R. Acad. Sci., France, 54, , 1912; C.R. Soc. Biol., 72, , 1912; Ann. Chem., 9 (5), , 1916.
Major conclusions:
All reducing sugars (aldoses, ketoses; penthoses and hexoses) could react with amino acids;
Reaction takes place in broad temperature range – оС;
Reaction has autocatalytic character and the color is changed with accelerating speed and finally reach dark brown color;
During the reaction the amino acid undergo decarboxylation (lost of CO2) – a sign that Strecker degradation takes place;
The participating in the reaction carbohydrates and amino acids can not be hydrolyzed (i.e. restored) by the known methods;
The melanoidins and the humic acids (building the humus) have similar nature;

5. Maillard reaction - significance4
Maillard reaction - significance
- important (major) in the food chemistry and technology;
- formation of humus (decay of the wastes, biomaterials etc.);
- in the medicine – formation of cataracts, cancerogenic compounds; mutagens – aromatic amines; acrylamide, etc.)
heterocyclic aromatic amines (HAAs) - >20
acrylamide
2-Amino-3,4-dimethylimidazo[4,5-f] quinoline
M. Nagao, M. Honda, Y. Seino, T. Yahagi, and T. Sugimura, Mutagenicities of smoke condensates and the charred surface of fish and meat, Cancer Lett., 1977, 2, 221–226.
T. Sugimura, T. Kawachi, M. Nagao, T. Yahagi, Y. Seino, T. Okamoto, K. Shudo, T. Kosuge, K. Tsuji, K. Wakabayashi, Y. Iitaka, and A. Itai, Mutagenic principle(s) in tryptophan and phenylalanine pyrolysis products, Proc. Japan Acad., 1977, 53, 58–61.

6. Maillard reaction - significance
Content of four HCAs in ground beef
HCA
Amount, ng/g
Maximum amount in 3 ounces of ground beef (in ng) IQ
n.d.-1.6
136
MeIQ
n.d.-1.7
145
MeIQx
n.d.-16.4
1395
PhIP
n.d.-68
5783
 Lifetime average weighted intake of four HCAs by men and women in the U.S.
HCA type
Lifetime average intake - All, ng/day
Lifetime average intake - All men, ng/kg/day
PhIP
6.0
6.2
MeIQ
1.1
1.2
DiMeQx
0.20
0.21 IQ
0.23
0.18

7. MAILLARD REACTION 5 AGEs – advanced glycation end-products
N-(carboxymethyl)
lysine - CML
Pentosidine
Pyraline
Crosslines
Det. in protein
+ (chem.)
+ (immun.)
Fluores. + -
Cross.mol.
Acc with age ?
Diabets
The Maillard reaction (Ed. R.Ikan), John Wiley & Sons Ltd. Chichester, 1996, p.62.

8. MAILLARD REACTION 6 Maillard reaction – general schema
Preconditions and participating compounds
complexity:
glucose-glycine – more than 24 products found;
xylose-glycine – more than 50 products found.
According to:
J. E. Hodge, Chemistry of browning reactions in model systems, J. Agric. Food Chem.,1953, 1, 928–943.

9. Maillard reaction - stages! 7
Maillard reaction - stages

10. Maillard reaction - mechanism! 8
Maillard reaction - mechanism
1. Formation of imines and N-glycosides
N-glycosides :
In the medicine – as substances with pharmaco-logical and biological activity.
In the textile industry – as softeners and detergents.
For production of rubber (caoutchouc) – as antioxidants.
N-glycosilation takes place in the human constitution and is among the most resent investigations of the field of the Maillard reaction.

11. Maillard reaction - mechanism9
Maillard reaction - mechanism
2. Amadori’s rearrangement

12. Maillard reaction - mechanism10
Maillard reaction - mechanism
3. Lobri’s rearrangement

13. Maillard reaction - mechanism11
Maillard reaction - mechanism
4. Haynes rearrangement

14. Maillard reaction - mechanism12
Maillard reaction - mechanism
5. Enolisation – obtaining of osones and reductones

15. Maillard reaction - mechanism13
Maillard reaction - mechanism
5. Enolisation – obtaining of osones and their dehydration

16. Maillard reaction - mechanism14
Maillard reaction - mechanism
6. Heterocyclisation processes
The pyrazines are used as artificial flavorings – some have potato, pineapple odor; some have ‘green’ odor
R. Scarpellino and R. J. Soukup, Key flavors from heat reactions of food ingredients, in Flavor Science: Sensible Principles and Techniques, T. E. Acree and R. Teranishi (eds), American Chemical Society, Washington, DC, 1993, 309–335.

17. Maillard reaction - mechanism15
Maillard reaction - mechanism
6. Heterocyclisation processes
isomaltol
Obtaining of maltol from 1-deoxydiketose

18. Maillard reaction - mechanism16
Maillard reaction - mechanism
7. Retro aldol and aldol reactions
aldol R = H
ketol R = alkyl, aryl

19. Maillard reaction - mechanism17
Maillard reaction - mechanism
7. Retro aldol and aldol reactions

20. Maillard reaction - mechanism18
Maillard reaction - mechanism
8. Free radical reactions
Takes place when green coffee seeds are roasted

21. Maillard reaction - mechanism19
Maillard reaction - mechanism
9. Strecker degradation
alloxane
1862 – reaction of alanine with alloxane !

22. Maillard reaction - mechanism20
Maillard reaction - mechanism
9. Strecker degradation
Of cysteine and methionine
dimethyl disulphide
methanethiol
acrolein

23. Maillard reaction - mechanism21
Maillard reaction - mechanism
9. Strecker degradation
Of methionine – various
volatile products formed

24. Maillard reaction - mechanism22
Maillard reaction - mechanism
Premelanoidins formation

25. MAILLARD REACTION 23 Premelanoidins formation
The structures of some low-molecular-mass coloured compounds formed in model Maillard systems

26. MAILLARD REACTION 24 Premelanoidins formation
The structures of some low-molecular-mass coloured compounds formed in model Maillard systems

27. MAILLARD REACTION 25 Melanoidins formation
Melanoidins – gives the color of thermally treated products, fluorescence, flavor; serve as matrix for low-molecular substances; do not fermented in the stomach; have foam forming properties – important for making coffee

28. Maillard reaction - mechanism26
Maillard reaction - mechanism
Melanoidins formation
melanoidins

29. Maillard reaction - mechanism27
Maillard reaction - mechanism
Melanoidins formation
(E)-4,5-bis-[(S)-2-carboxy-1-
pyrrolidynil]-2-cyclopenten-1-on
5-(S)-(2-carboxy-1-pyrrolydinyl)-2
hydroxy-(E,E)-2,4-pentadienal-(S)
(2-carboxypyrrolydin)-imin
(S)-N-(1-carboxyethyl)-2-(Z)-
(2-furylmethylen)-4-(E)-(1-formyl-2-furyl-
1-ethenyl)-5-(2-furyl)-3(2H) pyrolynon)
melanoidins obtained from
2-furfural and lysine residues

30. Maillard reaction – analysis and isolation of melanoidins28
Maillard reaction – analysis and isolation of melanoidins
Model systems and standard melanoidins
• Glucose (Sigma; min 99.5%, Cat. No. G8270)
• Glycine (Sigma; min 99%, Cat. No. G7126)
0.05 mol from each in 100ml H2O;
2 hrs / 125 ºС.
Dialysis of the mixture – 24 h, 4°С; lyophilization

31. Maillard reaction – analysis and isolation of melanoidins29
Maillard reaction – analysis and isolation of melanoidins
Meat
Roasting, grinding
Grinded brown meat
extraction (methanol:
chloroform=1:2)
filtration
filtrate
solid residue
extraction water
filtration
dialysis
Ion-exchange
chromatography
brown filtrate
solution
solid residue
brown
eluate
colorless
eluate
Neutralization;
Dialysis;
Concentration
Melanoidins

32. Maillard reaction – analysis and isolation of melanoidins30
Maillard reaction – analysis and isolation of melanoidins
Coffee (instant or roasted)
Sequential extraction (ether, acetone, CCl3H, ethanol),
Time – 3 h each)
extract
solid residue
Concentration –
distilation
Flavor substances
for instant coffee
for roasted coffee
Gas
chromatography
Water extraction
Evaporation (< 30 °C)
Evaporation (< 30 °C)
Crude extract
Melanoidins
GFC
Evaporation (< 30 °C)
Melanoidins

33. MAILLARD REACTION 31
Kinetics and influence of different parameters on the reaction
C. M. Brands and M. A. J. S. van Boekel, Kinetic modelling of Maillard reaction browning: effect of heating temperature, in Melanoidins in Food and Health, Vol. 2, J. M. Ames (ed), European Communities, Luxembourg, 2001, 143–144.

34. MAILLARD REACTION 32
Kinetics and influence of different parameters on the reaction
1. Type of the carbohydrate
pentoses > hexoses
ribose – the most reactive sugar (pentoses)
galactose – the most reactive sugar (hexoses)
ribose : xylose: galactose = 100 : 6 : 1
lactose – the most reactive disaccharides
2. Type of the amino compound !
Lysine – the most reactive amino acid

35. MAILLARD REACTION 33
Kinetics and influence of different parameters on the reaction
Determination of the nutritionally blocked lysine

36. MAILLARD REACTION 34
Kinetics and influence of different parameters on the reaction
Determination of the nutritionally blocked lysine

37. MAILLARD REACTION 35
Kinetics and influence of different parameters on the reaction
3. Molar ratio
Model system
Molar ratio
Temperature, ° C
Time ,h
Optimum theoretical yield, g
Optimum experimental yield, g
Glucose – glycine
1 : 0.68
110 7
7.718
7.639
Glucose – glutamic acid
1 : 5
100 12
2.640
2.610
Glucose – alanine
1.6 : 1
106 39
9.478
9.150
Fructose – glycine
1: 1.26 35
10.410
10.240
4. pH – optimal is 6.5-7
2-furaldehyde
furanone

38. MAILLARD REACTION 36
Kinetics and influence of different parameters on the reaction
5. Water and water activity – during the reaction water is produced
(according to T.P. Labuza, Sorption phenomena in foods: Theoretical and practical aspects. In “Theory, determination and
control of physical properties of food materials”, C. K. RHA ed., p.197, Riedel, Dordreht, 1975)

39. MAILLARD REACTION 37
Kinetics and influence of different parameters on the reaction
6. Temperature ºС
7. Metal cations – Cu, Fe – catalyzers (speeding); Mn, Sn – inhitors;
8. Other compounds – lipids, chitosan, phospholipids

40. MAILLARD REACTION 38
Kinetics and influence of different parameters on the reaction
9. Pressure – influencing the flavor compounds

41. MAILLARD REACTION ! 39
Kinetics and influence of different parameters on the reaction
10. Inhibition of Maillard reaction
10.1. Storage at lower temperatures – most foodstuffs do not brown at
-10ºС (when stored one year)
10.2. Addition of SO2 (E220; sulphites – Е , )
- allowed limits (EU / mg.kg-1, mg.L-1)

42. MAILLARD REACTION ! 40
Kinetics and influence of different parameters on the reaction
10. Inhibition of Maillard reaction
10.2. Addition of SO2 (E220; sulphites – Е , )

43. MAILLARD REACTION ! 41
Kinetics and influence of different parameters on the reaction
10. Inhibition of Maillard reaction
3. Lowering the рН
4. Dehydration – example: fruit juices (with combination with addition of SO2
5. Removal of some of the foods’ components
5.1. Carbohydrates
dried Chinese egg white – removal of glucose by fermentation (! Microbial contamination)
potato chips – dipping in the solution with glucose oxidase
removal of lactose from milk

44. MAILLARD REACTION ! 42
Kinetics and influence of different parameters on the reaction
10. Inhibition of Maillard reaction
5. Removal of some of the foods’ components
5.2. Amino acids
- precipitation by thermal treatment and filtration
- adsorption
5.3. Changes of the amino acids (mainly lysine)

45. MAILLARD REACTION 43
NO!