General Technical Issues In Vinegar Plants

A vinegar plant appears to be a mass of gigantic, non-descript tanks, each one indistinguishable from one another. That’s the first problem that mashgichim face when visiting vinegar companies. Production is hidden within the tanks, and until mashgichim develop an understanding of how the vinegar is made, it is not at all easy to follow the flow of production. But there’s another complication with vinegar that keeps a hashgacha’s policy-makers busy: the halachos of vinegar are unlike the halachos of other prohibited foods. Non-kosher vinegar is typically wine vinegar, which is governed in part by hilchos stam yenam and in part by the laws of other prohibited foods. Furthermore, vinegar is considered a davar charif, a sharp food, which has far-reaching stringencies. Certifying vinegar production, particularly in places that also produce non-kosher vinegar, presents significant challenges.

This article will discuss some basic points about vinegar production to provide some background to the kinds of questions a hashgacha considers, and a mashgiach has to keep in mind, when certifying kosher vinegar.

1. Vinegar production is a fermentation process. Fermentation refers to a natural microbiological process in which bacteria, which are not visible to the eye, eat, and thereby convert, a sugar or alcohol solution to vinegar. A fermentation tank, the heart of a vinegar plant, creates an environment in which this natural process is exploited: as much bacteria as possible get access to as much alcohol as possible, while still having air available for sustenance.

What Types of Solutions are Used in Vinegar Production?

Anything that contains alcohol (i.e., ethanol), or can be converted into alcohol can be a raw material for fermentation into vinegar. It may be helpful to distinguish the following three groups:

  • a. Solutions that contain sugars that have been broken down (also called hydrolyzed) from starch. These include, for example, corn syrup or barley syrup (malt).
  • b. Solutions that contain sugars, such as grape or apple juice; and
  • c. Solutions of dilute distilled ethyl alcohol. Distilled alcohol itself is prepared from fruit juices (apple, grape, etc.), solutions of hydrolyzed starch, or petroleum, which yields synthetic alcohol.

White vinegar, also called white distilled vinegar or distilled vinegar, is made from distilled alcohol, category “c.”. Usually, in this country, distilled alcohol is made from corn, and occasionally from grain (chametz).

The fact that the great majority of alcohol production in the U.S. is from corn, as opposed to wheat, is relevant to decisions people have to make these days, in the wake of Pesach, when determining whether it’s acceptable to buy a vinegar or vinegar-based product that may have been in Jewish hands, and not sold, during Pesach. Since it is highly likely that the product would have been kitniyot, and not chametz, many rabbanim in the U.S. hold that buying vinegar and vinegar-based products in those circumstances is absolutely fine.

Distilled alcohol can theoretically come from grape fermentation (and be a kosher problem) and in Western Europe it frequently does. It is also worthwhile to note that in Europe alcohol is frequently grain-derived, more so than in United States. Vinegar manufacturers in this country purchase domestic alcohol and it is not likely that alcohol from a grape source would be a problem. Nevertheless, when alcohol is used in a vinegar plant it is critical that a hashgacha agency verify that the source of the alcohol is acceptable.

When a mashgiach looks at the list of raw materials he’s expecting to find at a vinegar plant – no mashgiach these days enters a facility without being equipped with such a list – he would find that there are, in addition to the liquids mentioned above, a whole slew of additional ingredients that are approved to be used. Nutrients, for example, are used to supplement the diet of the bacteria in the fermentation of white vinegar and other vinegars. Nutrients are generally made up of yeasts, phosphates, nitrates, and other ingredients. Often nutrients are purchased from a kosher-certified company. But it is also common for companies to supplement the nutrients package with their own additions or to formulate entirely their own nutrients package. Other possible raw materials include enzymes which are used in the conversion of starches – rice, for example, can be hydrolyzed to rice syrup – and yeast is used in the fermentation of sugar to alcohol.

Generally speaking the first tanks used in a vinegar plant are storage tanks for these various raw materials. These tanks may not be the first things a mashgiach runs into, however. He has to find these tanks – they could be nestled among other large tanks — identify them as raw material storage tanks, and then proceed from there. Additional preparatory tanks used in the production of white vinegar, and sometimes for other vinegars, are mash tanks in which materials such as water, alcohol, and nutrients are mixed before being pumped to the fermentation tanks.

2. The fermentation of an alcohol/sugar solution yields acetic acid; vinegar is actually the common name for a dilute water solution of acetic acid. Vinegars, of course, vary in taste and appearance. The difference between malt vinegar and wine vinegar is the example used by the heilige Rava and Abaye (Avodah Zorah, 66a) in their well-known dispute over whether the taste of a food or its name determines the similarity or difference of foods. But all vinegars are dilute solutions of acetic acid.

Two different fermentation tanks are commonly used today. A generator, a wood tank that looks unexceptional, if somewhat imposing, from the outside, houses a quite unusual kind of technology: thousands of wood shavings fill the top three quarters of the tank. The wood shavings provide an extensive amount of surface area for the microorganisms to exist. When alcohol is charged through the top of the generator and drips through the shavings, the microorganisms convert the alcohol to vinegar. Although generators are still commonly found at vinegar facilities, they are being supplanted by acetators, which is actually a brand name for a technology that makes use of something called submerged fermentation, an entirely different technology that provides space for the microorganisms through air chambers in the tank.

Fermentation is, halachically, a cold process. Temperatures in a fermentation tank should not approach even 110ºF. Actually, solutions used to make vinegar are pumped to the fermentation tank considerably less than 110ºF, usually at room temperatures. But the activity of the bacteria in making acetic acid creates considerable heat. In fact, the heat created by the bacteria is more than the bacteria themselves would be able to tolerate. The threshold for their continued survival is below 110ºF. A vinegar plant manager (or a computer, which has assumed many of the responsibilities of a plant manager) has to make certain that the tank’s temperature remains well below the bacteria’s tolerance level. One way of doing this is by removing liquid, cooling it down using a mechanism called a heat exchanger, and sending it back.

The temperature control necessary in a fermentation tank underlines an important aspect of vinegar production: it is a microbiological process. Vinegar production is therefore not perfectly predictable – it is subject to the fickleness of the microscopic bugs on which it relies. In addition, bacteria must be constantly fed in order to perpetuate themselves. The absence of food for even a few seconds can destroy an entire bacterial population. Weeks, and even months, are necessary to restart a bacteria culture. Certain generators have been running for the last sixty years without stopping because stopping could mean months of down time.

Because the bacteria in the fermentation tank must always have something to eat, vinegar (acetic acid) is discharged from the fermentation tanks only in increments. The vinegar is pumped to a discharge tank. The remaining steps in vinegar production involve taking the highly concentrated acetic acid solutions and diluting, mixing, coloring, spicing, clarifying, or otherwise preparing the vinegar for consumption. At a vinegar plant that bottle red wine vinegar, enocianina, a grape skin extract that is almost always not kosher, is used to darken the red vinegar.

Although much of the production of vinegar is cold, liquid can be absorbed into the walls of equipment through kavush. In general, it is critical that plants that manufacture both kosher and nonkosher vinegars have tanks and other equipment dedicated for kosher and nonkosher production. As mentioned, vinegar is a davar charif. One ramification of its charifus is that vinegar revives flavors absorbed in a container (or a tank) even if the prohibited liquid was emptied more than twenty-fours earlier. Other prohibited foods do not revive staling foods absorbed in the walls of a vessel and are not subject to this stringency. Kosher vinegar can be made non-kosher even b’dieved if it sits, cold, in a non-kosher tank for twenty-four hours (if the volume of the non-kosher vinegar in the walls of the container is not nullified by the volume of the kosher vinegar in the container). According to some opinions, even if the kosher vinegar was in a non-kosher tank for just 18 minutes the vinegar could be rendered non-kosher. Converting a tank normally used for non-kosher to kosher, even if liquids in the tank were always cold, would also require a kosherization.

Where dedicated production has been set up, a hashgacha should regularly affirm the separation of lines. In the event that common equipment is used – a circumstance that should be avoided – extra safeguards should be in place that will guarantee that the stringencies relevant to vinegar be observed.

3. Although production of vinegar is a cold process, bottling of vinegar can involve genuine heat. Vinegar, because it is highly acidic, is immune to the decay which microorganisms cause in other foods. Its acidity is what makes vinegar a pickling agent. But vinegar is nevertheless pasteurized – that is, heated – before it is bottled. Bottled vinegar, once opened, can suffer clouding problems or unattractive deposits – a result of the “mother” of vinegar, a bacterial mass, collecting at the bottom of the bottle. Pasteurization seeks to guarantee long-lasting clarity in the final product.

Pasteurization far exceeds yad soledes bo. When a vinegar plant bottles non-kosher vinegar and kosher vinegar on the same equipment, the equipment must be kosherized. The unique halachos applicable to vinegar have implications on how to kosherize the pasteurizer and any other equipment exposed to hot vinegar. At the point of bottling, vinegar may be cooled down and may or may not be yad soledes bo.

Some companies have begun using sulfites to clarify the product, in place of pasteurization. The use of sulfites accomplishes the same goal as pasteurization and is a cold process that poses no kosher problems. It would be helpful, from a kashrus perspective, if the use of sulfites as a clarifier would replace the practice of pasteurization, and it is a smart idea to mention this fact to vinegar companies that have the practice of pasteurizing their vinegar.

A vinegar plant is a kind of metaphor for life. It appears to be a blur of unrelated events. But with time, and some focus, a narrative can be discerned.


This article was written by Rabbi Gavriel Price, a rabbinic coordinator at the Orthodox Union. It is adapted from an article written by Rabbi Price that was originally published in the OU’s publication for Mashgichim, The Daf HaKashrus.