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Why soda tastes different in a can or bottle

People often have strong opinions about how they drink their soda. Some people prefer it in a can, others prefer a glass or plastic bottle. While soda companies claim that the recipe doesn’t change, there are a few factors that might affect the way you taste a soda depending on the container. Following is a transcript of the video.

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 flavour? 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.

Cans are typically aluminium, 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. –

Rick Sachleben: 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 flavour.

Narrator: This lining protects the taste of the soda and keeps it from being contaminated by the metal.Sachleben: 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?

Sachleben: 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.

Sachleben: 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.

Christy Spackman: 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. Humans taste carbonation using the same taste receptors that recognise sour foods according to a 2009 study by Science Magazine, and we can also detect carbonation from soda in another way.

Sachleben: 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 flavours into your nose as well.

Narrator: So carbonation levels can affect the taste, but how can the CO2 levels change based on the packaging?

Spackman: 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 have both been appropriately filled.

Sachleben: The structure of the glass is pretty tight, ok? 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.

Sachleben: 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.

Spackman: Light can also affect flavour, 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 flavour compounds.

Sachleben: A lot of the flavour compounds are really subtle molecules; they’re the sort of things that can really a little change can change their flavour a lot.

Narrator: So how a soda is stored can prevent any rapid alteration in taste.

Spackman: So something that’s bottled in glass and stored away from light is going to have a flavour 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.

Spackman: So they have a sensory awareness just because their memory is so constantly being refreshed about what sensory experience is like.

Sachleben: 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.

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