What do strawberries, roses and apples have in common? They’re red. They’re pretty. Yeah, but they also belong to the same family, Rosaceae. Look around, apples have taken over the world. Literally Steve Job’s gadgets are selling like hotcakes. Heck, we wouldn’t have gravity without apple, a falling apple. Thanks, Newton. But one thing that sucks about them is that they turn brown sometime after cutting. How this happens is one reason to continue reading!
Back at the store, a truckload of apples is piled on top of one another. Red Delicious to the right, Granny Smith to the left and Fuji and Gala neatly stacked together in the center, all set for sale in bright pink foam nets. As the sun sets down, people drop by, bag them home and stuff them in the fridge. Now, they are fated for countless possibilities. These apples could be squeesed into juice, baked into pies, cut for salad or just eaten raw. But almost all of them have one prerequisite-- slicing or dicing. This action fires a series of chemical reactions. Upon cutting, oxygen is introduced to the bruised apple tissue. In its presence, polyphenol oxidase PPO or tyrosinase converts naturally-occurring phenols to a kind of compound known as o-quinone. Quinone goes on to react with amino acids or proteins (also found within the apple) to ultimately produce ‘melanin’. It is said the browning helps to produce an antibacterial effect that would prevent the apple from further damage. This is the same brownish pigment found in our hair and skin. So it shouldn’t come as a surprise that PPO is also found in humans.
Enzymatic browning can most certainly be prevented. The key is to stop the reaction from taking place. Thus, tamper with either the enzyme or its substrate. Toss the slices in a bowl of water-cuts off oxygen supply. If one does not mind a slight tangy/sugary taste alongside, coat the pieces with lemon juice or sugary syrup. Lemon or pineapple juice is acidic in nature therefore reduce the pH affecting enzymatic activity. Apples can be blanched in boiling water for about five minutes as well. A word of caution is in order here. The heat will affect the texture of the fruit and may not be suited for your desired dish.
Hiya Islam is a student of BRAC University.
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