I found this mold in my new vinegar batch. It has grown in the second refill of alcoholic soda when the mother of vinegar was already formed. Does anyone know why this mold has come out in the vinegar? Thank you for your help..
Probably the pH was not low enough and/or the sugar content was too high. The recommended way to make vinegar has 2 steps:
- turning the sugars into alcohol through yeast: this is an anaerobic process, so mold should not be a problem (mold needs oxygen) if you install the airlock properly (note: the link above does not mention the airlock, but I highly recommend it, this video explains why)
- turning the alcohol into vinegar: at this point there should not be any sugar left in the liquid, otherwise at the start when the pH is not low enough, molds can form. This is an aerobic process because the acetic acid bacteria need oxygen
There is one more reason to use this process: if you do not have a separate step for the alcoholic fermentation, you will never know, when it is finished. If you bottle an unfinished batch, the alcoholic fermentation might continue, causing the bottle to explode (you could injure yourself). This should not be the case for unfinished vinegar fermentation, because the AAB run out of oxygen.