Download Browning Reactions

Browning Reactions
FDSC400
Important Types of Browning
• Enzymatic (polyphenoloxidase). Fresh cut
vegetables, non-toxic, no flavor
• Caramelization. Sugars at very high
temperatures.
• Lipid Browning. Polymerization of frying
oils
• Vitamin C Browning. Similar to Maillard
• THE MAILLARD REACTION
Maillard Browning
• “the sequence of events that begins with
reaction of the amino group of amino acids
with a glycosidic hydroxyl group of sugars;
the sequence terminates with the
formation of brown nitrogenous polymers
or melanoidins”
– John deMan
The Maillard Reaction
• Occurs between reducing sugars and
amines at high temperatures
– Produces flavor
– Produces color
– Produces antioxidant products
– Produces toxic products
– Destroys nutrients (lysine)
Addition of an amine to an aldose
The Amadori Rearrangement
DH – A Crucial Intermediate
Amines
Strecker aldehydes
Polymerize
Pyrolytic products
Sugar Pyrolytic Products
O
OH
OH
O
O
O
maltol
CH3
CH3
isomaltol
Strecker Degradation
O
O
-H2O
R
O H2N
-H2O
COOH
H
N
H
amine
dicarbonyl
O
-H2O
ine
N
H
H
OH
R
COOH
NH3
CO2
Stecker
O
R
-H2O
R
COOH
O
R
-H2O
O
-H2O
COOH
O
OH
NH3
CO2
H
Stecker aldehyde
Rich nutty, meaty flavors
Mutagens from the Maillard
Reaction
Asparagine
O
H2N
Strecker aldehyde
CH2
O
C
H
O
H2N
CH
C
H2
Acrylamide
Control Steps
• Rapidly accelerated by temperature
• Significant acceleration at intermediate water
activities
• Sugar type
– Pentose>hexose>disaccharide>>polysaccharide
• protein concentration (free amines)
• Inhibited by acid
– amines are protonated
– and used up, pH drops
• Sulfur dioxide
Inhibition by Sulfite
SO3-
DH
DSH