Browning reactions in foods Some foods are naturally brown

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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
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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 nitrogenous compounds
are involved -Dehydration reaction resulting in
polymerization -Used to produce caramel colors
and flavors
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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
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• 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 color Some bitter flavors
developing
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4) Heat at 200C for an additional 55 min - Loose
about 14 of original weight Form pigment named
caramelen C36H50O25 - More bitter flavors,
darker color
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5) Heat at 200C for an additional 55
min Formation of very dark and very bitter
insoluble compounds Form 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
• 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 browning i.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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• 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
critical 2-3X faster for each 10C rise in
storage temperature
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Involves a complex series of reactions Figure
reaction sequence 3 major steps
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• 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
• Keep product cool
• 2) Limit reducing sugars
• 3) Optimize pH and moisture
• 4) Add inhibitors- sulfur dioxide
• reacts with intermediate
• products to prevent polymerization

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