I recently crushed and strained about thirty pounds of wild grapes to ferment into wine. About a month in, I did a visual inspection of the wine under microscope to try and identify some yeast and bacteria species. However I was more taken by the sight of many sharp, needle-shaped crystals in the wine (along with microbes). Pictures are below:
My best guess is that they are raphides (crystals of calcium oxalate/carbonate), a supposed defense mechanism of some plants. These seem to be complicit in causing acridity in certain plants, and indeed the grapes (and resultant wine) were extremely tart. I've not, however, heard of any wild grape species having known toxicity.
My question is, then: are any wild grape species known to produce such crystals and, if so, are they known to be harmful in any way? Is there another explanation?