Coke war -- Plastic bottles vs. Aluminium cans

Over lunch one day at 100plus' lab, somehow the topic of canned vs. plastic-bottled sodas was raised. It was noted that Coca-cola in cans tasted better than Coca-cola in plastic bottles. This observation was concurred by a few others, although as usual there were the outliers who insisted that Pepsi tasted better. Anyway, I decided to do a little investigation into this matter...


The reason why some of us think that Soda (or Pop) (or Coke) tastes better in cans is because of difference in the degree of fizziness we experience. Canned soda in general tastes more fizzy than the plastic-bottled soda. Plastic soda bottles are made of PET -- polyethylene terephthalate -- and they were patented in 1973 by the inventor Nathaniel Wyeth. Before the PET bottles were invented, plastic was never an option for storing soda because it was not strong enough and would explode under pressure due to the release of carbon dioxide from soda. Wyeth invented PET (details of the chemical properties of PET will not be included here) which had superior elastic properties.

So what's the deal with plastic soda bottles? They are permeable to gas. Not only does the carbon dioxide in the soda diffuse out of the bottle, the carbonated beverage may end up taking in oxygen as well. The structure of PET also enables it to absorb flavor from the beverage, as the polymer molecules that make up the polyester function as a sponge for flavor absorption. These factors work together to decrease the shelf-life of PET bottled sodas.

I just spent 20 min reading about PET and its gas permeability properties. I am now going home, but not before stopping by the convenience store for a bottle of Sprite. Hehehe