Download Maillard browning

Nonenzymatic Browning
w/ sugar
w/o sugar
Two major types of
non-enzymatic browning reactions
• Caramelization
• Maillard browning
Louis Camille Maillard (1878-1936)
Reactions during caramelization
• Anomeric equilibration (alpha, beta)
• Pyran, furan equilibration
• Sucrose inversion
– Hydrolysis
•
•
•
•
•
Aldose, ketose interconversions
Inter- and intramolecular condensation
Dehydration
Skeletal fragmentation
Browning
Caramelization
• Flavoring caramelization
buffer
Sucrose syrup
heat
Inversion, fragmentation
(maltol, etc.)
Caramelization
• Caramel pigments
Glucose
syrups
Partially
neutralized
pH 4
heat
Caramel
Colloids
Used to color colas. They are not naturally brown but have
these pigments added to color them.
Clear colas
• See the Wikipedia
entry on Pepsi
Crystal here
http://en.wikipedia
.org/wiki/Crystal_
Pepsi
• A disaster-see the
marketing section
of the Wikipedia
entry
Amadori rearrangement
Maillard reaction (slide 161)
Glycosylamine formation
Glycosylamine Formation
Go to Slide Show mode and click to begin
Amadori rearrangement
Amadori Rearrangement
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Decomposition of the Amadori
compound (slide 162)
Control point
Strecker degradation
Requires dicarbonyls and amino acids
Nutritional loss of amino acids (especially L-lysine)
Pyrazines -- flavor compounds
Maillard browning
reaction variables
• Temperature
– Generally, the higher the temperature, the
greater the browning
• pH
– As pH goes down, so does browning. Due to
protonation of the reactive amino group,
making it unreactive.
Under near neutral conditions
..
NH2
O CH
+
Under acidic conditions
H+
..
NH2
OCH
+
No reaction is possible with the nitrogen lone pair
as it is already reacting with the hydrogen ion
Maillard browning
reaction variables
• Water
0%, min
30%, max
%water
100%, min
Maillard browning
reaction variables
• Oxygen
– Seems to have little effect
• Metal ions
– Cu(I), Cu(II) and Fe(II), Fe(III) speed up the
reaction. Other metals seems to have little
effect. Can control the with metal chelators
(e.g., EDTA).
Maillard browning
reaction variables
Sugar
Glucose
Fructose
Galactose
Xylose
Arabinose
Ribose
Open chain Melanoidin
1
1
-1.2
3.4
2.0
7.1
5.5
7.1
6.7
354
Very high
A practical example of the effect of
Maillard browning in cookies
Image courtesy of Oreg. St. Univ. (www.orst.edu/food-resource/
information/maillard/nancy.html)
Control of browning
• Create unfavorable conditions for the
reactions to take place
– Water--low or high
– pH--lower, decreases browning
– Temperature-- the lower the temperature,
the less the browning
Control of browning
• Removal of substrates
– Glucose oxidase--removes the open chain
form by converting it to gluconic acid. This
technology is used in preserving dried egg
whites.
– Ribose oxidase--This enzyme activity occurs
in Lactobaccilus pentoaceticum and is used to
prevent fish from browning.
Sulfite browning inhibitors
• Principally sulfur dioxide or bisulfite.
These sulfur compounds react with HMF
near the end of the decomposition of the
Amadori compound and divert it to a
non-reactive product, that is one that
cannot be converted into melanoidin
pigments
Sulfite inhibitor reaction
O
R
O
H
HMF
HSO 3
H
m e la n o id in
p ig m e n ts
R
O
O
SO3
-
H
sta b le -w ill n o t p ro ce e d
to fo rm p ig m e n ts
Maillard overview (page 169)
Control point
Pigment
Aromas
Why worry about
Maillard browning?
• Aesthetics
– Overly browned foods are not aesthetically
attractive and may not be accepted
– Also, due to the pyrazines produced by the
Strecker degradation, these highly browned
foods may have odd, off flavors and also not
be accepted
Why worry about
Maillard browning?
• Nutritional effects
– Amino acids that participate in the Maillard
reactions are lost from a nutritional point of
view. This may be especially important
where the amino acid is very reactive and in
foods where it is already in very low
concentration. This would be the case for Llysine in cereals.
Reason for the
reactivity of L-lysine
O
Reactive epsilon amino
O
H3C
OH
H2N
OH
NH2
L-alanine
Alpha amino
NH2
L-lysine
Glucose and lysine
Why worry about
Maillard browning?
• Mutagenicity
– This is not yet settled in the literature. Some
researchers find mutagenic products in
browned model systems, others do not. But
there is still the possibility that highly
browned food may contain potential
mutagens.