Browning Reactions
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Transcript of Browning Reactions
Browning reactions in foods
Some foods are naturally brown
Some foods are expected to be brown
Some are expected not to be brown
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Browning can be
Desirable:Cooking meat, bread crust,
coffee, chocolate
Undesirable:Fruits, vegetables, sauces
Much of the undesirable browning occurs during storage
Lowers quality FSTC 605 MURANO
How do you formulate a food to limit browning?
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3 major types of browning in foods
1.) Caramelization
2.) Enzymatic browning
3.) Non-enzymatic browning (Maillard reaction)
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Caramelization-Formation of melanoidins by
heating sugar to high temperatures in low water conditions
-No protein or nitrogenouscompounds are involved
-Dehydration reaction resulting in polymerization
-Used to produce caramel colors and flavorsFSTC 605 MURANO
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Generic progression of reaction
1.) Sucrose is dispersed in a small amount of water
-Start with disaccharide
C12H22O11 -Subjected to heat
-Crystals melt at 160C
2) Heat to 200C for 25 minutes - Loose 4.5% of original weight - Weight loss is water from the
polymerization reaction- Very light brown color
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3) Heat to 200C for 55 more minutes- Loose 9% of original weight (water)
Form pigment called Caramelan C24H36O18
Light brown colorSome bitter flavors developing
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4) Heat at 200C for an additional 55 min
- Loose about 14% of original weightForm pigment named caramelen
C36H50O25
- More bitter flavors, darker color
5) Heat at 200C for an additional 55 minFormation of very dark and
very bitter insoluble compoundsForm pigment named caramelin
C125H188O80
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Enzymatic browning
Polymerization of phenolic compounds by PPO enzymes
PPO describes all enzymes with the capacity to oxidize phenolic compounds
Figure- PPO action
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Important in plant tissues especially wounded tissues
Detrimental in produce color and bitterness
Potato, apple, banana, avocado- loss of quality
Beneficial in coffee and tea production
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How to limit enzymatic browning
1)Minimize damage to tissues
2) Exclude or remove molecular oxygen
3) High pressure processing
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4) Water soluble antioxidants (ascorbic acid)
5) Blanching- heat treatment to deactivate PPO
6) Metal complexing agents can block active site
7) Sulfites can prevent reactions with enzymes
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Non-enzymatic browningi.e. Maillard reaction
Desirable in cooking and baking
Undesirable browning during storage
Cannot stop it, but can limit / control reaction rate
Reactants are in food
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1) Amino group
-proteins-peptides
-amino acids
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2) Carbonyl group
-aldehydes and keytones
-mostly from reducing sugars
-some can come from oxidized lipids
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3) Time-Control reaction velocity by
manipulating product
-moisture, temperature, pH, concentration of reactants
- Temperature is critical2-3X faster for each 10C
rise in storage temperatureFSTC 605 MURANO
Involves a complex series of reactions
Figure – reaction sequence
3 major steps
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1) Condensation of carbonyl group with free amino group
Carbonyl + Free Glycosamine + water Group amino
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2) Rearrangement of glycosamine to produce flavor and odor compounds
3) Polymerization into larger melanoidin compounds- color development
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Limiting Maillard reaction in foods
1)Keep product cool
2) Limit reducing sugars
3) Optimize pH and moisture
4) Add inhibitors- sulfur dioxide- reacts with intermediate
- products to prevent polymerizationFSTC 605 MURANO