Dear AnswerLine, I found several jugs of unused vinegar in my pantry with old “Best By” dates on them. Can I safely use them for canning, pickling, and other general cooking? Does vinegar spoil or become less acidic over time? Are they still good for cleaning? Should old vinegar be disposed of?
Almost Indefinite Shelf Life
Vinegar is a fermented product and has an “almost indefinite” shelf life according to the Vinegar Institute . “Because of its acid nature, vinegar is self-preserving and does not need refrigeration. White distilled vinegar will remain virtually unchanged over an extended period of time. And while changes can be observed in other types of vinegars, such as color or the development of a haze or sediment, this is only an aesthetic change. The product can still be used and enjoyed with confidence.” The main component of vinegar, acetic acid, is relatively stable under the right conditions.
Because there are few organic compounds to cause random reactions affecting the quality of white distilled vinegar, StillTasty  concurs that commercially prepared white distilled vinegar keeps indefinitely. Like white vinegar, commercially prepared cider, malt, balsamic, rice, wine, and flavored vinegars are also safe indefinitely. However, over time, the appearance and flavor of non-white vinegars may start to change. Most of these changes are harmless if the vinegar has been stored properly. Due to the changes that may take place, StillTasty recommends that these non-white vinegars are of best quality if used within 2-3 years of purchase. The “Best By” date is not a safety date, but rather the manufacturer’s estimate of how long the vinegar will remain at peak quality. The “Best By” date, by convention, for most manufacturers is two years from the production date.
To maximize the shelf life of all vinegars, store them in a cool, dark cupboard away from direct heat or sunlight. Vinegar should only be stored in glass, plastic, or non-reactive containers. It is important that the lid is secured and replaced immediately after use to reduce the amount of oxygen coming in contact with the vinegar. The acidity of vinegar does not change unless moisture or water gets into the container.
Common and Harmless Changes in Vinegar
Cloudiness – Once opened and exposed to air, harmless “vinegar bacteria” may start to grow. This bacteria causes the vinegar to cloud. Cloudiness does not affect the quality of the vinegar or its flavor. Straining cloudy vinegar through a coffee filter may clear it.
Color – Red wine vinegar may become a pale red if sulfites are not added in the manufacturing processes. Other vinegars can change color by a process known as the Maillard reaction. Residual sugars and amino acids in many fruit vinegars may cause a browning over time similar to the browning of baked food. This reaction is long time (likely years) in coming. A change in color likely indicates a change in taste as well.
Sediment – Vinegars are usually filtered to make them clear. Those that are less filtered can form sediment over time as the particles settle. To deal with sediment, simply strain the vinegar through a coffee filter set inside a fine-mesh strainer before using it.
Mother – Most vinegars are pasteurized unless stated otherwise. When pasteurization is incomplete or the vinegar is re-inoculated with vinegar bacteria from the air after opening, a slimy, amorphous blob or substance will form and float near the bottom. This is a vinegar mother and is just bacteria that feeds on alcoholic liquids. If one develops, it simply means that there were some sugars or alcohol that weren’t completely fermented in the vinegar process. Mother can be strained out using a coffee filter. Some look on a mother as something beneficial to health or to restart their own batch of vinegar.
Canning and Pickling
When considering vinegar for canning and pickling, it is always best to use fresh ingredients as they are very important to the process. If you start with good ingredients, your product will likely be successful. As previously stated, acetic acid, is relatively stable so any vinegar with 5% acidity is safe to use regardless of age for canning and pickling. However, non-white vinegars may lose flavor so for that reason, fresh vinegar may be advisable. Also, if any vinegar is showing any of the harmless changes mentioned, it would be best to not use the vinegar for canning or pickling as such changes may cause unwanted darkening, cloudiness, off flavor, or sediment in the product. Further, should there be any sign of condensation in the container or the container was left open for a period of time, the vinegar could possibly be less than 5% acidic and therefore, should not be used for canning or pickling.
Past Its Prime – No Need to Toss
Contrary to “when in doubt, toss it out,” there is no need to toss out older vinegars. They are safe to use but may change over time. If the change is too bothersome for food preparation, vinegar past its prime can still be used for cleaning, weed control, fabric softening, and dying to name a few. There are a plethora of websites touting the many uses of vinegar. You may wish to begin with tips from the Vinegar Institute .