A double fermentation process converts apples into cider vinegar. Initially, the yeast added to crushed apples converts the sugar in them to alcohol, or cider. The second fermentation process uses acetic acid to change the sugar alcohol into vinegar. Although yeast is a safe, friendly bacterial organism used for centuries, the vinegar-making process has the potential for growth of unfriendly bacteria, such as E. coli. Bacteria that survive the fermentation process can thrive in unpasteurized apple cider vinegar.
Vinegar Fermentation
Vinegar creation requires an interaction between friendly bacteria and a carbohydrate source. During apple cider vinegar fermentation, yeast and acetic acid create the sour taste associated with vinegar. In some cases, organic producers start the vinegar-making process with a vinegar mother, a jelly-like substance from a previous batch of raw vinegar. Normally, the vinegar mother contains harmless bacteria and nutrients.
Apple Cider Vinegar Bacteria
Contact with insects, birds, dust and fertilizers made with cow manure are common ways that E. coli bacteria get on apples. Inadequate culling of bruised apples also introduces bacteria, and improperly cleaned apples can have bacterial residues. Poor sanitation that results in cross contamination between apples and raw vinegar also fosters the development of E. coli during the vinegar-making process, according to the FDA.
Vinegar Acidity
The level of acidity in apple cider vinegar plays an important role in the survival of E. coli. The U.S. government has established national standards for the acidity of commercially produced vinegar. All vinegar sold in the U.S. must have a minimum acidity of 4 percent, according to The Vinegar Institute. The acidity level for white vinegar ranges from 4 to 7 percent. Generally, for fruit vinegars, such as apple cider vinegar, the acidity level falls between 5 and 6 percent. According to the U.S. Food and Drug Administration, E. coli has survived in unpasteurized apple cider vinegar that has acidity levels between 3.6 and 4 percent. Treating unpasteurized apple cider vinegar with sodium benzoate reduces E. coli contamination.
Pasteurization
To kill bacteria that developed during fermentation, it is necessary to heat the cider used for vinegar to 180 degrees Fahrenheit for 15 seconds or 155 degrees Fahrenheit for 30 minutes, according to the FDA. Pasteurization of apple cider vinegar is effective for E. coli and other strains of bacteria commonly found in food products. Pasteurizing apple cider vinegar destroys some beneficial trace nutrients and reduces the characteristic cloudiness of apple cider vinegar.
References
- U.S. Food and Drug Administration: Guide to Inspections of Manufacturers of Miscellaneous Food Products - Volume 1
- The Vinegar Institute: Today's Vinegar
- The Vinegar Institute: Frequently Asked Questions
- U.S. Food and Drug Administration: Potential for Infiltration, Survival and Growth of Human Pathogens Within Fruits and Vegetables
- Columbia University, Go Ask Alice: Apple Cider Vinegar
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