Lecture VI Dehydration/Browning Reactions Caramelization Maillard Rx Lecture #6 - CHO Dehydration/Browning Reactions Will cover mainly ...Caramelization, and ...Maillard Rx

Reactions of Carbohydrates VII Dehydration/Degradation Carbonyl group (only) Hydroxyl groups Anomeric hydroxyl group Both carbonyl & hydroxyl groups Hydrolysis Dehydration/degradation

Reactions of Carbohydrates VII Dehydration/Degradation In Strong Acid HO C H CHO OH 4 3 O CHO Furfural 4 3 2 12% HCl - 3 H2O 2 5 5 1 1 a pentose

Reactions of Carbohydrates VII Dehydration/Degradation In Strong Acid HMF O CHO HOH2C 4 3 12% HCl - 3 H2O + a hexose 2 5 6 1 O C CH2OH O= O CHO CH2 OHC + hydroxyacetylfuran

Reactions of Carbohydrates VII Types of Browning Rxs in Foods Ascorbic acid Enzymatic Caramelizaton Non-enzymatic - Malliard

Reactions of Carbohydrates VII Types of Browning Rxs in Foods I Type of Browning Ascorbic Acid Enzymatic Caramelization Maillard Starting Material (Precursors) Ascorbic Acid Phenols Sugars Amino groups & carbonyls from sugars, oxidized lipids, etc.

Reactions of Carbohydrates VII Types of Browning Rxs in Foods II Type of Browning Ascorbic Acid (AA) Enzymatic Caramelization Maillard General Rx types oxidation of AA and multiple condensations Enzymatic ox, followed by multiple condensations Heat induced ox and multiple condensations Substitution and multiple condensations

Reactions of Carbohydrates VII Browning Rxs - Similarities Starting Materials (or precursors) Polyhydroxy compounds Furfural-type intermediates** Except for enzymatic browning Colored end-pdts; all polymers Pathways to polymers Some similarities Some distinct differences

Reactions of Carbohydrates VII Ascorbic Acid Browning 6 C HO O 5 4 3 2 1 C O O C OH O CHO OH O C OH O2 O C C OH HF HO HO HO C CH2OH CH2OH CH2OH Polymers AA L-DHAA L-DKA Anaerobic O *COOH *HCOH *O CHO + CO2 Furfural

Reactions of Carbohydrates VII Dehydration/Degradation Caramelization I CH2OH O CH2 OH O Heat OH OH - H2O OH OH 1,6-Anhydro-b-D-glucopranose (Levoglucosan) D-glucose

O 1st Stage 2nd Stage 3rd Stage Polymers hydroxyacetylfuran 1st Stage O enediol 3-deoxyosone 2nd Stage 3rd Stage Polymers hydroxymethylfurfural (HMF) 3,4-dideoxyosone Formation of hydroxymethylfurfural by dehydration of a hexose enediol

Reactions of Carbohydrates VII Caramelization Third Stage of the Rx, Polymerization O CH HOCH2 OH + O CH HOCH2 : + HMF -H+ O CH HMF O C HOCH2 OH CH OCH2 H HOH2C O

Reactions of Carbohydrates VII Dehydration/Degradation Caramelization II Polymeric, colloidal particles Types of Caramel particles Strongly negative (pH 2 – 4.5) Positive (pH 4.2 – 4.8) Weakly negative (pH 3 – 4)

Reactions of Carbohydrates VII Dehydration/Degradation CH2CH3 OH Caramelization III 1 3 4 2 6 5 O OH CH3 C O= O O= CH3 OH 1 3 4 2 5 1 3 4 2 6 5 O O= HO CH3 Ethyl maltol 1 3 4 2 5 Isomaltol Maltol 2H-4-Hydroxy-5- methylfuran-3-one

Reactions of Carbohydrates VII Dehydration/Degradation Browning Reactions - non-enzymatic Caramelization Maillard reaction General observations I

KITCHEN CHEMISTRY Grilled meats. Crusty bread. Dark beer KITCHEN CHEMISTRY Grilled meats. Crusty bread. Dark beer. The Maillard reaction gives our favorite foods their taste and aroma.

Reactions of Carbohydrates VII Dehydration/Degradation Browning Reactions - non-enzymatic Caramelization Maillard reaction General observations II Positive vs negative effects + bread crust, soy sauce, cake color, flavor development - browning of evap milk, “skunky” beer flavor, nutritional destruction of aa’s Controlling the Rx pH, RH, Trace minerals

Reactions of Carbohydrates VII Dehydration/Degradation Browning Reactions - non-enzymatic Caramelization Maillard reaction (Non-enzymic glycation) General observations III Positive vs negative effects Controlling the Rx Medical consequenses

Reactions of Carbohydrates VII Dehydration/Degradation Browning Reactions - non-enzymatic Caramelization Maillard reaction Requirements for Rx Amino groups Reducing sugar Water “Nonacidic” environment

Reactions of Carbohydrates VII Dehydration/Degradation Browning Reactions - non-enzymatic Caramelization Maillard reaction Initial Stage of the Rx Color development (none) Reactions Properties

Schiff base

Reactions of Carbohydrates VII Maillard reaction Innital Stage Cpds, Schiff Base Formation RNH 2 -H2O O R2C R2CNHR NR R2C OH + Schiff base HCOOH H R2CNHR CO2 H:CO2 - R2CNHR + + +

Reactions of Carbohydrates VII Maillard reaction CH2OH C OH C(H)(OH) R N H Initial Stage, Compounds O CH2OH OH CH2OH C OH HC O : +RNH2 D-Glucopyranose NR CH2OH C OH HC O CH2OH OH NHR -H2O mild a glycosylamine Schiff Base

Reactions of Carbohydrates VII Dehydration/Degradation Amadori Rearrangement - R’ C HC NR OH H R’ C HC NR OH -: R’ C HC OH NR : -H+ Schiff Base : O R’ C HC NHR - O R’ C CH2NHR R’ C HC NHR O- -H+ +H+ Amadori product

Reactions of Carbohydrates VII Maillard reaction Initial Stage, Compounds 6 O CH2OH OH HO NHR O CH2OH OH HO + H2O 6 5 2 +RNH2 4 5 2 1 3 4 3 1 O CH2OH OH NHR 6 Heyns rearrangement a ketose 5 1 4 2 3 a 2-amino aldose

Reactions of Carbohydrates VII Maillard reaction Initial Stage, Reaction Rate(s) Pentoses > hexoses (aldoses>ketoses) >disaccharides

Reactions of Carbohydrates VII Dehydration/Degradation Browning Reactions - non-enzymatic Caramelization Maillard reaction Intermediate Stage of the Rx Color development(buff yellow) Reactions Properties

Reactions of Carbohydrates VII Maillard reaction Intermediate Stage, Compounds (Path 1) + O C CHOH H2CN OH C CHOH HCN HC=N -OH- C OH Amadori product CH -RNH2 1,2-ene-aminol CHOH +H2O O CHO HOH2C O C CH HC O C CH2 HC CHOH -H2O HMF -H2O -H2O 3-deoxy-hexosone +amine +amine Melanoidin pigments

Reactions of Carbohydrates VII Maillard reaction Intermediate Stage, Compounds (Path 2) O C CHOH H2CN C H2CN CHOH OH O C CH2 CHOH OH -Amine Amadori product 1-amino- 2,3-enediol O C CH3 CHOH OH O C CH3 Methyl reductones, a-dicarbonyls Methyl a-dicarbonyl cpd -H2O +amine +Amine Melanoidin pigments

Reactions of Carbohydrates VII Dehydration/Degradation Browning Reactions - non-enzymatic Caramelization Maillard reaction Final Stages of the Rx Color development (brown) Reactions Properties

Reactions of Carbohydrates VII Maillard reaction Final Stages of the Rx, Aldol Condensation CH3CHCH2CHO OH H O C CH3 + H. CH2CHO a - aldol b CH2OH C OH HC H CHO b a CH2OH C OH HC O H + a OH -

Reactions of Carbohydrates VII Maillard reaction Final Stages of the Rx, Strecker Degradation O + H2N COOH O NH2 + H -CO2 2,3-butanedione L-valine 3-amino-2-butanone methylpropanal N O NH2 H2N + + O2 tetramethylpyrazine 3-amino-2-butanone (X2)

Reactions of Carbohydrates VII Maillard reaction Controlling the Rx - I Inhibiting techniques Decrease moisture Labuza, IFT, 1970, p 618, from Crit Reviews, CRC Press, 1991

Reactions of Carbohydrates VII Maillard reaction Controlling the Rx - II Inhibiting techniques Decrease moisture Liquid systems -- Increase dilution Lower pH and/or temp Remove heavy metal ions

Reactions of Carbohydrates VII Maillard reaction CH2OH C OH C(H)(OH) R N H Initial Stage, Compounds O CH2OH OH CH2OH C OH HC O + X +RNH3 D-Glucopyranose NR CH2OH C OH HC O CH2OH OH NHR -H2O mild a glycosylamine Schiff Base

Reactions of Carbohydrates VII Maillard reaction Controlling the Rx - III Inhibiting techniques Decrease moisture Liquid systems -- Increase dilution Lower pH and/or temp Remove heavy metal ions Remove one substrate (sugar) Add sulfur compound(s)

Reactions of Carbohydrates VII Maillard reaction Controlling the Rx O CHO R a furan derivative HSO3- O CSO3- R OH H Melanoidin pigments

Reactions of Carbohydrates VII Maillard reaction Controlling the Rx - IV Importance of control ….. Loss of nutritive value Adverse contribution to flavor/odor Potential toxicity

Reactions of Carbohydrates VII Maillard reaction

Reactions of Carbohydrates VII Maillard reaction Controlling the Rx - V Practical applications I Cooking http://www.finecooking.com/

Reactions of Carbohydrates VII Maillard reaction Controlling the Rx - VI Practical applications II Cooking For less browning….