I whipped some cream with soft peaks and put it in the fridge. A few days most of it has collapsed and is liquid. Can I re-whip it effectively without adding more cream?
If you try to re-whip the cream now, it'll likely turn into butter, not whipped cream. The initial whipping process has already caused the fat in the cream to coalesce; further whipping now will complete that process, similar to if you had over-whipped the cream in the first place.
I wonder what would be the outcome of using a whipping siphon with collapsed cream– AgosDec 5, 2019 at 14:29
2@Agos I would expect better results from a siphon, since much less mechanical agitation (which would squeeze fat globules together) is occurring. In fact, the mechanism of a whipping siphon is not hugely different from that of a milk homogenizer.– SneftelDec 5, 2019 at 15:47
Sneftel answered the question you asked, but to answer a corollary question: you can prevent this from happening by using a stabilizer (also called a cream stiffener). One you can get is by Dr. Oetker and is called Whip It (or Sahnesteif). There are a few other alternatives as well.
1Another way to prevent the cream from collapsing is to store it in a manner that limits air contact. For instance, I store whipped cream in a Tupperware container, but before putting the lid on, I smooth a piece of plastic wrap down right against the surface of the whipped cream, then put the lid on.– dwizumDec 5, 2019 at 20:00