citrusfermentation
I am testing out the Buddha hand fruit ferment.
I washed everything well, cut the rind and poured honey water in the jar and sealed it tight. I opened it one day and it bubbled for a few minutes very strongly. I put the top back on and now there is a white film on top of the liquid and I am not sure what or if something went wrong.
Yes, those spots are normal, they form as the nattou ages. They are amino acid crystals, and they are perfectly safe. Here's a picture.
They're a bit crunchy, which you may or may not like. If you don't like the dots, get young nattou and consume it before the crystals form. If you do like them, get more mature nattou. With younger nattou, you should be able to store it opened in the fridge for a few days before the crystals start to form. As you have experienced though, once they start, they grow quickly.
if it tasted extra 'yeasty' you're probably just fermenting too far. try starting with less of the bug per liter of liquid, and stop the fermentation sooner.
Best Answer
First and foremost, you shouldn't seal anything fermenting because it could accumulate too much pressure and fail in a potentially explosive manner (as with this unfortunate accident https://www.homebrewtalk.com/forum/threads/glass-carboy-explosion.517237/).
Also, white films forming on top of fermenting beverages usually means that an infection got hold (and the fermentation vessel, if not made of glass, usually will harbor these bugs from now on and infect the next batches). A good ressource here : https://www.homebrewsupply.com/learn/is-my-batch-infected.html
It's not uncommon in fruit based fermentation if everything isn't frozen then pasterized. Regarding if it's drinkable, it would need a proper identification of the bugs you got in there, but folks over at https://alcohol.stackexchange.com/ might be a better fit to answer this kind of question. Stay safe!