- [Narrator] People have strong opinions
about soda containers.
- Cans are significantly better than bottles.
- I think bottled probably tastes the best to me.
- A can keeps it colder.
- I prefer a glass bottled soda.
- [Narrator] But does the container
really affect the flavor?
Soda companies claim to use
the same proportion of ingredients.
A company spokesperson for Coca-Cola told us that
Coca-Cola uses the same recipe
regardless of the package type,
and that it's best enjoyed ice cold.
But there are a few factors that could still affect
the way you taste it.
First, let's take a look at the ingredients
in the containers.
Glass bottles are pretty basic
and contain no other chemical ingredients besides the glass,
so there's nothing in it that could really change the taste.
(soda lid popping)
Cans are typically aluminum,
lined on the inside with a polymer that can contain BPA
or Bishphenol A.
Rick Sachleben, a retired chemist
with the American Chemical Society,
says this has little effect on the taste.
- The amount of that material that would get into
the contents of a container
are so low I don't think it would have any effect
on the flavor.
- [Narrator] This lining protects the taste of the soda
and keeps it from being contaminated by the metal.
- The likelihood of having a break in that lacquer coating,
that plastic coating, and exposing the contents
to the metal are pretty, pretty low.
- [Narrator] Despite protective lining,
some people still think there's a metal taste.
- I actually think it tastes like can.
- Sometimes cans can taste a little bit metallic.
- [Narrator] So where is this sensation coming from?
- Your tongue is very sensitive to metal.
The one time when the product is exposed to the metal itself
is when the can's opened.
You put your tongue on a metal can it's entirely possible,
especially people who are sensitive to it,
there would be just enough to come off
to change the way things tasted on their tongue.
- [Narrator] Plastic bottles are typically made with PET,
or Polyethylene terephthalate.
While both cans and plastic bottles contain chemicals
you probably wouldn't want to consume in large quantities,
they are perfectly safe to drink out of.
- All containers that they use, glass, plastic, metal,
have been extensively tested for what will leech
into the liquid that's put in them.
- [Narrator] The FDA also regulates
the amount of contaminants allowed in drinks
to make sure they're safe.
But humans have been known to detect
even minute amounts of contaminants
according to Christy Spackman,
a researcher at Harvey Mudd College, who studies taste.
- Here too to remember that zero is not always zero.
People can detect certain things at levels
well below instrumental detection;
it depends on the molecule and it depends on the human.
- [Narrator] So while unlikely,
it's possible that even the slightest bit of contamination
might affect the taste for some.
Now let's take a look at carbonation.
(fizzing and popping)
Humans taste carbonation using the same taste receptors
that recognize sour foods
according to a 2009 study by Science Magazine,
and we can also detect carbonation from soda
in another way.
- [Rick] When you drink it you get two things going on:
one is you get that tingly thing from the bubbles,
but you also get that carbon dioxide going up in your nose;
it carries the other flavors into your nose as well.
- [Narrator] So carbonation levels can affect the taste,
but how can the CO2 levels change based on the packaging?
- [Christy] So carbonation can slowly, potentially,
leak out of a plastic bottle in a way it can't
leak out of a glass bottle.
That's assuming they've both been appropriately filled.
- The structure of the glass is pretty tight, okay?
It's like a really tight mesh rather than a loose mesh.
The diffusion rates through glass are really, really slow.
And in metal it's the same thing.
- [Narrator] But most bottles are typically designed
to prevent CO2 from escaping quickly.
- A plastic bottle is a multilayered thing:
Some of them provide rigidity,
some of them provide a barrier to the oxygen
going in and the CO2 coming out,
and then there's a final barrier
that just protects the contents.
- [Narrator] And if the container is warm
more CO2 will be released when you open it
making the soda taste flat.
Light can also affect flavor, assuming the bottle
does not contain any light protective layers.
- [Narrator] Light can cause chemical reactions to occur,
and some of the substances in there may change
some of the flavor compounds.
A lot of the flavor compounds are really subtle molecules;
they're the sort of things that can really
a little change can change their flavor a lot.
- [Narrator] So how a soda is stored can prevent
any rapid alteration in taste.
- So something that's bottled in glass and stored
away from light is going to have a flavor profile
that can last much longer,
and also carbonation levels that will stay
consistent much longer, than something in plastic.
- [Narrator] But there's also more to taste
than what happens on a molecular level.
Spackman says experience can also affect the way we taste.
People who drink Diet Coke a lot, every day for example,
might be able to tell a difference
more than someone else.
- So they have a sensory awareness just because their memory
is so constantly being refreshed about what
sensory experience is like.
- It's really hard to separate the objective
and subjective sides to taste.
What we can taste sometimes is as much affected by
what we expect as what's actually there.
- [Narrator] So soda drinkers aren't likely
to change their habits any time soon.