Understanding Enzymic Browning
Picture this: You buy fresh green apples from the market,
You come home and wash them,
Slice them into bits and relax on the couch facing your TV getting set to nourish your body,
You suddenly realize that the apple slices have turned brown.
You're filled with so many questions; what, how, when did this happen?
That is Enzymic Browning in action!
Enzymic browning is an oxidation reaction that occurs in certain raw foods causing them to turn brown in colour upon exposure to oxygen. It occurs in foods such as fruits, vegetables, yams, potatoes, etc.
What simply happens is that upon exposure to air, oxygen in the air reacts with enzymes in the food. Exposure can be in the form of slicing/ cutting, squashing or deterioration of the fruit as a result of age/ ripening.
Using our apple illustration, slicing the apple exposes it to oxygen in the air. Next the enzyme phenolase in the apple reacts with oxygen in the air which causes phenols in the apple to be transformed to melanin which has a brown colour. Yes, that melanin!
Studies have shown that enzymic browning has an effect on nutrients say vitamin C level meaning that the longer a sliced fruit is exposed to oxygen, the less vitamin C it'll have.
Enzymic browning can be slowed down by inactivating enzymes responsible for the browning reaction. This inactivation can be done by simply providing an unfavourable environment for the enzyme to act because enzymes are known to work under certain conditions like temperature and pH.
Here are some ways to achieve this:
- Decrease in pH reduces enzymic browning. This can be achieved by dipping the food/ fruit in water containing containing acids such as lime/ lemon juice, vinegar or citric acid.
- Temperature increase or decrease reduces enzymic. Temperature increase can be achieved by blanching or mild heating. Conversely, temperature can be reduced by dipping in cold water.
For example:
To prevent yam slices from turning brown before boiling or frying, dipping in warm water is recommended.
Cold water reduces browning in peeled potatoes.
About the Author
Chidinma Ezinne Ochulor is a certified Food Technologist, a quality assurance professional with over 3 years' experience. She is a professional member of the Nigerian Institute of Food Science and Technology (NIFST). Reach her on LinkedIn, here.
