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discoloration of fruit and vegetables, Like - Coggle Diagram
discoloration of fruit and vegetables
Fruits and vegetables that discolou
r
Apples:
Commonly affected by enzymatic browning, leading to a brown coloration.
Pears:
Similar to apples, they also experience browning due to enzymatic reactions.
Bananas:
Enzymatic browning is a significant factor in the discoloration of bananas.
Avocados:
Enzymatic browning can cause avocados to turn brown upon cutting.
Mushrooms
: They also experience browning due to enzymatic reactions.
Lettuce:
This vegetable can discolor due to enzymatic browning as well.
What is enzymic browning?
Enzymic browning
is a chemical reaction in fruits and vegetables where enzymes convert phenolic compounds into brown pigments upon exposure to oxygen.
What is
oxidation
on fruits/ vegetables during enzymic browning
Oxidation
is a related process that can lead to the loss of nutrients, particularly vitamin C, when fruits and vegetables are exposed to air or cooked.
Methods to stop enzymic browning on fruits and vegetables
Lower the pH (acid treatments)
Lemon, lime, pineapple juice:
Common and effective
Vinegar:
Works but may alter flavor.
Ascorbic acid
(Vitamin C): Strong antioxidant that reacts with oxygen before PPO can.
Remove or Block Oxygen
Water immersion
: Temporary barrier.
Sugar syrups or brines:
Create a physical barrier.
Vacuum sealing:
Removes oxygen from packaging.
Reduce Temperature :
colder temperatures slow enzyme activity. Refrigeration helps maintain color longer.
Heat Treatment (Blanching)
Blanch in boiling water for a short time, then cool in an ice bath.
Salt Solutions
:
Light salt-water brines inhibit PPO activity through chloride ions.
Why does it turn brown?
The phenolase changes the phenols into melanin, which has a
brown colour
. To stop the oxidative reaction, the phenolase enzymes need to be denatured
What is melanin?
Melanin
is the pigment that gives human hair, skin and eyes their colour. Its also the pigment that gives the fruit and vegetables that brown colour.
What enzymes causes enzymic browning?
primary enzyme
responsible for enzymic browning is polyphenol oxidase
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