Keypoints of Maillard Reaction (MR)
- MR occurs in all foods where reducing carbohydrates and free amino groups are present.
- MR causes browning. In fact it is called non enzymatic browning reaction.
- MR depends of many factors, the main ones are:
- Type of reagents.
- Water activity.
- Time and temperature of the treatment.
Maillard Reaction Products (MRP)
- MR is important because its product MRP are colored and flavoured.
- In many foods MRP is essential to give desired color and flavour, in others they should be avoided.
- Some MRP are potent antioxidant.
- Some MRPs are potentially toxic.
Louis-Camille Maillard
Louis-Camille Maillard (1878 - 1936) Photographed in his laboratory ca 1915.
Maillard-Hodge Reaction?
John Hodge: 1914 -1996
Chemist at USDA in Illinois (1941 – 1980)
His proposed mechanism for the chemistry of non-enzymatic browning is largely unchanged after 60 years.
Maillard-Hodge Reaction?
John Hodge
Hodge Scheme
Hodge J E. Dehydrated foods: chemistry of browning reactions in model systems. J. Agric. Food Chem. 1:928-43, 1953.
Hodge Scheme
Chemistry of MR
At high temperature reducing carbonyl react with free amino groups.
Reducing carbonyl usually belongs to glucose or fructose group, but can also be an oxydised fat.
Free amino group is usually on lateral chain of proteins (Lys or Arg) In a few cases free amino acids or ammonia.
The first step is the formation of a Shiff base followed by a complex sequence of dehydratation and rearrangments leading to the formation of colored and flavoured MRPs.
Amadori products is the first stable intermediate
Final MRP: the melanoidins
Melanoproteins, melanoidins different Maillard polymers in different products
Melanoidins are present in coffee (soluble) bread (crust) and many other products.
In some cases they are made up mainly of polysaccharides in others by proteins.
Loss of free lysine: nutritional implications.
Role in texture, taste and antioxidant activity.
Behave as dietary fibre.
Norwegian brown cheese
Melanoproteins
Dangerous MRPs: Acrylamide
Acrylamide is formed through MR only from free asparagine.
Potato, cereal (particularly bran), cocoa, coffee.
Correlation between acrylamide biomarkers and incidence of cancer.
Dangerous MRPs: Heterocyclic amines
In roasted meat heterocyclic amines can be formed from creatine amino acid and sugar.
Only in the burned region.
Heterocyclic amines are potent carcinogenic agents.
Mutagenic activity of extracts obtained from meat cooked at different time/temperature
Le lezioni del Corso
2. Water and interactions in water solution
3. Amino acids and peptide bond
7. Protein properties and their role in foods
9. Carbohydrate and polysaccharides
10. Sugar properties
