Cucumbers in pickling brine often develop a removable layer of scum.
When you make your own pickles, you may be concerned when the mixture of cucumbers and spiced brine develops a layer of scum. This scum is a normal part of the pickling process and is nothing to worry about.
Pickling
Pickling involves fermenting and curing vegetables like cucumbers by soaking them in a solution of brine -- highly salted water -- and various spices. Bacteria consume the natural sugars in the vegetables and produce lactic acid, which kills the bacteria that cause food to spoil.
Significance
Scum forms on the vegetables or on top of the brine as molds and yeasts in the air settle on the surface and begin to feed on the acid. Because these airborne molds and yeasts can dilute the strength of the brine, you should completely remove them each day. You can inhibit the formation of this scum by ensuring that the pickling container is well-sealed and that the vegetables are completely submerged in the brine.
Warning
The scum is not dangerous as long as the vegetables themselves do not become slimy. If the vegetables do become soft or slimy, they should be discarded, as they have spoiled and are no longer safe to eat.
Tags: layer scum, molds yeasts