[Tagbert]

Caffeine has no smell so what you are detecting is some other component or effect on the semen taste. Many things can affect the taste of semen.

[calmdownpeople]

He said smell not taste! At least I hope he wasn't tasting the lab samples.

[fnordpiglet]

Just the semen.

[vineyardmike]

“Lab samples”

[e12e]

He didn't specify difference between de-caf coffee vs regular - only coffee vs non-coffee - so might be something other than caffeine that effects smell?

[Tagbert]

Coffee contains a large number of aromatic components that could be transferred to the semen. Just the way methyl mercaptan from asparagus can be transferred to your urine.