Fresh Apple Slices

Ever wonder why some foods turn brown moments after slicing them? If only you had that magical ingredient the food industry has to keep those apple slices looking fresh long after cutting them.

Well you're in luck because that secret ingredient in right in your kitchen!

What causes fruits and vegetables to turn brown?
Plants (fruits & vegetables) contain an enzyme called polyphenol oxidase in their cells. If the fruit or vegetable becomes bruised or comes in contact with oxygen, a reaction occurs causing it to turn brown. This enzyme is believed to act as a defense mechanism for plants. When other insects see this discoloration they believe it is unsafe to consume and find food elsewhere.

* NOTE: This browning is safe for human consumption, it's just not visually appealing.

What foods are susceptible to this type of reaction?
The following are some foods susceptible to this type of reaction:

  • Potatoes
  • Apples
  • Bananas
  • Tea leaves
  • Pears, etc.

How do lemons affect browning?
Since the pH of lemons is extremely low, about 2.0, it prevents oxygen from reacting with the enzyme, polyphenol oxidase. When an acidic environment is present, oxygen first reacts with acid. This delays the brown spots you see, for example, on your apples. Once the acid is depleted, oxygen will then react with the enzyme.

Is lemon the only thing I can use to prevent this enzymatic browning?
Lemons are not the only foods you can use to delay browning. Anything with a pH of 4 or less will inhibit the enzymatic reaction. The following are some examples:

  • Lemons
  • Cream of tartar
  • Vinegar 
  • Orange Juice
This post is simply on the use of acidic foods to delay enzymatic browning, this is not the only method used in prevention. Blanching, refrigeration, dehydration, high pressure treatments and so forth are used by the food industry as well. These methods are not limited to fruits and vegetables, but other foods as well. 

Have a STACKed day!


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