Blood in the bottle?

[Lady Of The Pensieve]

No: HPFGUIDX 82352

 Hi,
this is a sentence which make me think.

" an ornate crystal bottle with a large opal set into the stopper,
full of what Harry was quite sure was blood." OoP page 99, UK edition

I highly doubt it was blood. I suppose it could be have been red wine,
red liqueure or something like that. Is it an alcoholic drink instead?

What do you think about it?

I really wonder.

Chrissi