Marie Kitchen, age 13, of Williamsport, Pennsylvania, for her question:

What is the mother in vinegar?

The slimy stuff that sometimes appears in a bottle of vinegar has no business being there at all. It is known to the manufacturers of vinegars as bacterium xylinum. From this you may suspect that the slimy, feathery scum is caused by in¬vading bacteria. This is correct. As a rule, the so called "mother" attacks the vinegars made from fermented fruits. Cider vinegar is very likely to be attacked. The bacterium, along with countless other types of bacteria, were present on the apples as they grew in the orchards. Usually they do not begin their slimy acti¬vities until the fermentation process of converting the apples into vinegar.

Vinegar manufacturers detest these bacteria. When present, they often scum up the fermenting brew in the vats and clog the machinery. Sometimes they remain quiet until later. The scummy material may not be noticed until a bottle of vinegar has been sitting quietly on a shelf for some time. It seems to come from nowhere  ¬though the bacteria that cause it were actually there all the time.