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Presentation on theme: "BROWNING IN THERMALLY PROCESSED FOODS: THE MAILLARD REACTION."— Presentation transcript:


2 Food modifications during thermal treatment (1) Protein denaturation Physical changes (starch gelatinization, structural alterations of cell wall, depolymerization of dietary fibre) Lipid oxidation Degradation of some bioactive components

3 Food modifications during thermal treatment (2) Reaction between different components generate new compounds. Proteins-sugar: Maillard reaction formation of Advanced Glycosilation End-products (AGEs) Lipid-protein: Advanced lipoxidation end products (ALEs)

4 The same chemistry The reaction is in both cases (sugars or oxidised lipids) between a carbonyl moiety and an amino group The same products The final product of both reaction patways (AGEs and ALEs) are polymeric brown macromolecules

5 The Maillard Reaction in Foods Produces aromas in heated foods Responsible for colour formation (non-enzymatic browning) Maillard products have antioxidant properties Can cause loss of nutrients Some products may be toxic

6 LATTE UHT LATTE STERILIZZATO BIRRA CHIARA PASTA PRODOTTI DA FORNO BIRRA SCURA CACAO CARNE ARROSTITA CAFFE Stadi iniziali Stadi intermedi Stadi avanzati Temperatura e tempo di trattamento termico Diminuzione dellattività dellacqua

7 Louis-Camille Maillard ( ) Photographed in his laboratory ca – 1916: He published 8 papers on his observations of colour changes on mixing amino acids and sugars. No one else took much interest in the reaction until 1950s

8 Maillard- Hodge Reaction? John Hodge: Chemist at USDA in Illinois (1941 – 1980) His proposed mechanism for the chemistry of non-enzymic browning is largely unchanged after 60 years. Citations since 1970 PaperCitations Hodge, J. E. Chemistry of browning reactions in model systems. J. Agric. Food Chem. 1953, 1: Maillard, L. C. Action des acides amines sur les sucres: formation des melanoidines par voie methodique. Compt. Rend. 1912, 154:

9 Hodge Scheme Hodge J E. Dehydrated foods: chemistry of browning reactions in model systems. J. Agric. Food Chem. 1:928-43, 1953.

10 First step: formation of Amadori product PRODOTTO DI AMADORI

11 slow fast

12 Formation of Carbonyl through Maillard Reaction slow fast

13 Strecker Degradation Free amino acids with dicarbonyl compounds R-CHO Aldeide di Strecker

14 Flavour and Colour in the Maillard Reaction Amino acid or proteins

15 General scheme of MR browning Amine Ammonia Phospholipids Amino acids Proteins Carbonyl Aldehydes Ketones Reducing sugars Polysaccharides Oxidised lipids Amino Carbonyl Interaction (Amadori product) HEAT Melanoidins Brown colour Amides Acrylamide Furans, Pyrroles, Thiopenes, Thiazoles, Oxazoles, Imidazoles, Pyridines, Pyrazines

16 N R CHO R O R N HO O OOH CH 3 N HO OH CH 3 O R N N + H 2 N N NN O R H Protein A Protein B Lysine Food melanoproteins

17 Pronyl-lysine This compound is formed on the lateral chain of Lysine residues Pronyl-lysine has a high antioxidant activity

18 Possible toxicants Acrylamide Furan Heterocyclic amines 3-MPCD (Mono Chloro Propan Diol) 3-Methyl Imidazolone Development of mitigation strategies to reduce their concentration

19 A network of many reactions giving thousands of products Products formed depends on: Chemical nature of the reactants Time and temperature of heating Technological conditions Water activity, pH

20 Practice Effects of reactants: Sodium Carbonate (pH effects) Protein and carbohydrates Water activity (fibre addition) Butter clarification Control Added with sodium bicarbonate


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