Because I object to dietary restrictions that are unnecessary and that further limit an already restricted diet, I have tried to learn something about the manufacturing process. The following summary is for others who might like to know how white vinegar comes into being and what the level of gluten contamination, if any, is likely to be. My sources of information have been the biotechnology literature and telephone contacts with knowledgable people in the industry. I personally have had no hands-on experience in vinegar making. In most of the world, molasses, which can be fermented directly by yeast, is the major source of alcohol.
Starches are mixtures of large straight and branched chain polymers of the simple sugar, glucose.
Since yeast is incapable of fermenting starches, whether from corn, wheat, potatoes or any other source, the grain starches must be pre-digested with amylases, enzymes that are capable of splitting the starch molecules into smaller fragments. In the brewing industry, the source of the amylases is usually barley malt, barley that has been allowed to sprout until the amylases and proteases needed to digest the nutrient stores in the seed have developed and then heated enough to stop the sprouting without inactivating the enzymes. Glucose is then converted by fermentation to ethanol and carbon dioxide, releasing energy in the process which is used by the yeast for growth. These volatile contaminants which vary with the yeast strains used and with the bacterial contaminants in the fermentation mixture contribute significantly to the flavors of alcoholic beverages but must be removed in the production of purified neutral spirits. The problem for the distiller is not the relatively simple task of avoiding carry over of the non-volatile material in the distilling pot, but rather the separation of the various volatile products from one another.