I accidentally left the lid off a completed 21 ltr fermentation bin of white Pinot (from kit). I'd added the last stage of process (finings etc) - phone went and I forgot to go back and replace lid - it was open for 5 days ish - it seems slightly darker than previous batches but tastes ok - is it ok to bottle? Any advice much appreciated - many thanks
It will be more oxidized, for sure. That's a flaw, but if it still tastes acceptable, then nothing to worry about. Hopefully %ABV was large enough to stop any unwanted microorganisms from setting in. Bottle as usual, but if you will start to get unusual haze, any off-flavors etc, be prepared to discard it. And drink it on the fresher side, don't wait too much for it to mature. I don't expect you will have a problem.
Its always difficult to give particular advice on brewing errors as it depends entirely on the circumstances - many of which are often omitted or forgotten. However wine is quite a hardy thing and has been made for centuries in less than "perfectly sterile" conditions. So leaving the lid off the fermented grape juice is not as fatal as it might first appear. I would most definitely recommend bottling the young wine but my inclination would be to leave it for a longer time rather than a shorted time. A lot of errors can be corrected by just conditioning a brew (be it beer or wine) for a sufficient time. It is fair to say that many if not most kit wines are made to be drunk sooner than later, but they often improve greatly with standing - a year is not a long time in wine making! I would bottle, leave it to stand/lay and get on with the next brew.