Vinegar is an important by-product on many Iowa farms, utilizing a considerable part of the apple crop which would otherwise be wasted by spoiling, often on account of difficulty in marketing. The apple crop of Iowa amounts to between three and four million dollars per year and a more efficient home production of vinegar from culls and windfalls would result in a large saving.

Many inquiries are received by the Iowa Agricultural Experiment Station regarding difficulties or failure in vinegar making. In many cases the vinegar never reaches the legal standard of strength for marketable vinegar, which is 4 percent of acetic acid. This is gene rally due to contamination of the fermenting vinegar with bacteria or other micro-organisms which cause what are called "foreign” or unfavorable fermentations, thus changing the sugars to something else than the acetic acid which is desired. These contaminating bacteria also sometimes impart an unfavorable or disagreeable flavor to the vinegar, as well as preventing the development of the proper amount of acidity, which is necessary for proper preservation as well as to meet the legal standard if the vinegar is to be offered for sale. In a few cases the low acidity produced is due to the use of apples too low in sugar content, or to dilution of the cider with water. The cause and prevention of these difficulties is to be discussed in this bulletin.