Whey vinegar

What it is

Whey vinegar is a vinegar made from the liquid left when milk is curdled for cheese. That liquid, whey, petit-lait in French and Molke in German, holds water, lactose, whey proteins, minerals and a little of the other milk constituents. A suitable whey is first fermented to alcohol, and acetic acid bacteria then oxidise that alcohol to acetic acid. It is a true fermentation vinegar and not ordinary vinegar mixed with whey.

The sugar in whey is lactose, a disaccharide of glucose and galactose. That is what separates it from apple, grape or malt vinegar. Most brewing strains of Saccharomyces cerevisiae cannot ferment lactose, so a whey vinegar needs a lactose-using microbe, a prior enzyme treatment, or a process designed for the job. Published work generally uses Kluyveromyces yeasts for the alcohol and Acetobacter for the acid.

Whey differs by cheese. Sweet whey comes mainly from rennet cheeses and starts at a higher pH. Acid whey comes from acid-curdled products such as some fresh cheeses and strained yoghurt and carries more lactic acid. Whey permeate is whey with most of the protein removed by membrane. Swiss law separates Molkenessig, from whey, from Milchserumessig, from milk serum or permeate.

Swiss shops sold such a vinegar in the 1950s under the name Lactavinaigre, made by Bourgeois Frères & Cie of Ballaigues from concentrated whey. It should not be mixed up with the later Japanese lacto-vinegar, which uses koji and Zymomonas mobilis. Flavour depends on the whey, the cultures and the method: a Japanese study described a yellow, slightly green vinegar with a faint milky smell and a mellow sourness, and a South Tyrolean producer describes a mild vinegar made by a first fermentation followed by vinegar cultures.

It stays a dairy product. Fermentation lowers lactose but does not guarantee that milk protein is gone, so whey vinegar is not vegan, not dairy-free and not automatically suitable for milk allergy. Swiss law treats it as its own vinegar type, with acetic acid present in greater quantity than lactic.

History

People have used whey for food, drink and feed for centuries, but eating whey is not the history of acetic whey vinegar. Older European texts sometimes call spontaneously soured whey Molkenessig even when the souring was mostly lactic. An 1860 German encyclopedia describes making a weak whey vinegar by adding vinegar mother to whey. That shows the name and the idea, not that the result met a modern definition of fermentation vinegar.

A more specific trail is Swiss. A pharmaceutical-history article of 2018 credits the first Lactavinaigre to I. Bourgeois in 1914, citing a 2003 presentation by J. F. Bourgeois, so it is a retrospective claim and the 1914 record has not been seen. The article also describes a medicinal Lactavinaigre tied to Paris laboratories and pharmaceutical advertising of the 1930s and 1940s. Its claims of benefit against digestive and metabolic illness were marketing and are not repeated as fact.

The commercial product is better documented. A 1968 Ontario industrial-waste conference report says Lacta-Vinegar had been marketed in Western Europe since 1952, citing a Bourgeois Frères & Cie brochure from Ballaigues, and that it made up about five percent of Swiss vinegar consumption. Those are secondary figures that have not been checked against the brochure.

Swiss newspapers give direct evidence from the late 1950s. An advertisement of 21 May 1958 describes a vinegar from concentrated whey through successive fermentations, names Bourgeois Frères & Cie SA of Ballaigues, and recommends it as mild for salads. One of 3 September 1959 names the same firm, describes the conversion of milk sugar by successive fermentations and gives a price of 1.70 Swiss francs per litre. The product was advertised as 4½ degrees, and what that figure measured is unclear.

Belgian archives add a case dated 1953 to 1959 about whey vinegar made by Dumont Frères & Cie at Chassart, with an official opinion of 4 February 1959 involving sulphuric acid. It shows a whey vinegar under food-regulatory scrutiny and does not show that the Belgian and Swiss products were the same.

Scientific work then built controlled processes: a Japanese study in 2000, a Spanish one in 2003, Italian laboratory and pilot work including a 2,000-litre system, a Brazilian study of whey permeate in 2021, and a Turkish study of kaşar whey in 2023. Whether the original Swiss brand is still sold is unclear, and a separately made whey vinegar is sold from South Tyrol.

How it works: yeast, bacteria and lactose

Lactose is glucose joined to galactose by a beta-1,4 bond. Before its carbon can enter ordinary alcoholic fermentation the sugar has to be taken into a suitable microbe and hydrolysed, or broken down by an enzyme outside the cell. Standard winemaking and brewing strains of S. cerevisiae cannot use lactose even though they ferment glucose freely.

Kluyveromyces yeasts can. In K. lactis the LAC12 gene encodes a lactose transporter and LAC4 encodes beta-galactosidase, which splits lactose into glucose and galactose. Related lactose-using K. marxianus strains do the same overall job. The sugars become ethanol and carbon dioxide, and galactose goes through the Leloir pathway before glycolysis. Alcohol dehydrogenase regenerates the NAD+ the cell needs to keep going.

The experimental strains vary. A 2003 Spanish study fermented lactose-enriched whey with a yeast identified as Kluyveromyces fragilis and acetified it with Acetobacter pasteurianus. A 2023 Turkish study used K. marxianus CECT 1442 and Acetobacter aceti CECT 298, and Italian researchers used K. marxianus Y102 and A. aceti DSM-G3508. They are experimental strains, not proof of what commercial makers use, and K. fragilis is an older name linked to K. marxianus.

Acetic acid bacteria then oxidise ethanol to acetaldehyde with membrane-bound alcohol dehydrogenase and on to acetic acid with aldehyde dehydrogenase, passing electrons to oxygen: C2H5OH + O2 giving CH3COOH + H2O. The rate of oxygen transfer limits productivity, and rising acidity eventually checks the bacteria.

Whey can also hold lactic acid from cheesemaking or from lactic bacteria. Lactic and acetic acid are different compounds, and lactic fermentation alone does not make an acetic whey vinegar. Swiss law requires whey vinegar to contain mainly acetic and lactic acid, acetic being the larger. Proteins, peptides, minerals, residual sugar and yeast by-products shape the final composition, and studies have found ethyl acetate and higher alcohols.

How it is made, and why each step matters

Production starts with suitable whey from cheesemaking, which supplies lactose, minerals and nitrogen for the microbes. Sweet whey carries less lactic acid than acid whey. Residual fat and suspended solids complicate processing, so whey may be clarified, separated or filtered, and experimental work often heats or sterilises the medium to reduce competing organisms.

The next question is whether there is enough lactose. Fresh whey is mostly water, so its alcohol potential is small. A Swiss Agroscope presentation notes that many yeasts cannot ferment lactose and that fresh whey may not hold enough milk sugar for the required vinegar strength, and suggests adjusting with whey powder. Researchers have used concentrated whey, added lactose or lactose-enriched permeate.

A Japanese study of 2000 concentrated whey threefold and fermented it with a Kluyveromyces yeast from kefir, giving about 8 percent ethanol. It diluted this twofold for acetification with Acetobacter pasteurianus IFO 14814, adding another 4 percent ethanol after three days, and ended with 5.2 percent acetic acid. Adding ethanol directly may be incompatible with current Swiss rules for fermentation vinegar.

The 2003 Spanish study supplemented whey with lactose, used Kluyveromyces fragilis and then Acetobacter pasteurianus, and reported 5 to 6 percent acetic acid and an ethanol-to-acetic-acid efficiency of 84 percent. The Turkish experiment used 500 mL batches of kaşar cheese whey with additional treatments of 5, 10 or 15 percent added lactose by weight per volume, inoculated at 1 percent by volume with K. marxianus CECT 1442 before A. aceti CECT 298.

A Brazilian study of 2021 gives clear parameters: whey permeate with 88 g/L lactose at 29 degrees C and pH 4.5 gave 47.18 g/L ethanol after 45 hours, which was acetified with Acetobacter aceti. Of the methods compared, the Orleans surface method gave 42.30 g/L acetic acid after 21 days. These belong to that substrate and cannot be assumed for ordinary unconcentrated whey.

The South Tyrolean producer Fischerauer describes an alpine dairy in Algund with about two weeks of first fermentation, separation from the yeast, a rest and conversion by vinegar cultures. It does not publish starting lactose, inoculum, acetification time or analysis. After fermentation a whey vinegar may be clarified and bottled, with verified acidity and compliance with local rules.

Regional and historical variations

There is no single historical recipe. The term has covered different products, and some older whey vinegars were probably soured whey, not vinegar made through ethanol and acetic fermentation. The nineteenth-century German reference adds vinegar mother to whey without enough detail to confirm the strength or the degree of alcoholic fermentation, so a recipe cannot be rebuilt from the name alone.

The best-documented historical product is Swiss Lactavinaigre of Bourgeois Frères & Cie in Ballaigues, Vaud. The 1958 and 1959 advertisements describe concentrated whey changed by successive fermentations into a mild condiment of 4½ degrees for salads, and a 1968 report says Swiss sales began in 1952. The business records and the full specification have not been found, so the process cannot be reconstructed from advertising.

Switzerland still recognises two legal products: Molkenessig, fermentation vinegar from whey, and Milchserumessig, from milk serum or ultrafiltration permeate. Both must meet requirements for total acidity, residual alcohol and lactose. The split follows the raw material and not the sweet and acid whey division, and Swiss law forbids adding ethanol to the raw materials for fermentation vinegar.

Japan has explored whey vinegar as a use for Hokkaido cheese whey, concentrating before alcoholic fermentation, and a separate 2021 Japanese development made lacto-vinegar using rapeseed-meal or wheat-bran koji, Zymomonas mobilis and Acetobacter pasteurianus. That is a different technology from the Kluyveromyces methods and not the Swiss Lacta trade name.

Spain developed a lactose-enriched whey process, Italy tested laboratory and pilot scale including use in dairy-cow feeding trials, Brazil studied whey permeate, and Turkey used kaşar whey from Göle in Ardahan province. These are experimental places and formulations and not household traditions. Algund in South Tyrol shows that whey vinegar is also a current product, and nothing links it in an unbroken line to the Swiss brand.

How it is eaten and used

Whey vinegar is used as a sour seasoning like other culinary vinegars, perhaps milder or more dairy-toned depending on substrate and method. The best evidence of use is the Swiss advertising: the 1958 and 1959 advertisements recommend it for salads and raw vegetables, and one calls it less sharply acid than ordinary vinegar. Those are promotional claims and not measured comparisons.

The 1959 advertisement priced it at 1.70 Swiss francs per litre and claimed that a litre could season about fifty salads for two or three people. It marks a table vinegar for salad and not an industrial preserving ingredient, and gives no full vinaigrette recipe or use in cooked Swiss dishes.

Fischerauer recommends its South Tyrolean whey vinegar with grapeseed, olive or walnut oil, where the oil moderates the acid and the vinegar adds sourness and a fermentation aroma. The producer calls it mildly acidic. Food-science literature also mentions whey vinegar as a possible ingredient in salad dressings, mayonnaise and other acidified foods, which shows technical plausibility and not a regional tradition.

It should not replace a specified commercial wine or cider vinegar in shelf-stable canning. A finished product may meet the acidity rules of its market, but experimental batches vary widely in residual lactose and total acidity. For preserving, follow the whole tested recipe and its acidification requirements.

Being a dairy product it has dietary consequences that fruit and grain vinegars lack. Residual lactose may remain and measurable milk protein has been reported in experimental products, so people with cow's milk allergy should not assume it is safe because the liquid is fermented or sharp. It is not vegan, and a label should disclose milk-derived ingredients and allergens.

Reading results and problems

The first problem is too little sugar. Fresh whey holds far less than grape must or fruit juice, and its lactose is not fermented efficiently by ordinary brewing yeast. With the wrong yeast the liquid may make little ethanol while lactose remains. Agroscope guidance names the need for a lactose-fermenting yeast and notes that concentrating the whey or adding whey powder may be needed for enough strength.

Judge the alcoholic stage by residual lactose, ethanol and acidity, not by sourness. A pH fall does not show lactose became ethanol, because lactic bacteria sour whey without making alcohol. Strains differ: work comparing sweet cheddar whey, acid whey from cream cheese and yoghurt whey found large differences in ethanol between strains and substrates, so a culture that suits one whey may not suit another.

Acetification needs an established acetic culture, ethanol and oxygen, and the oxygen transfer rate matters most in submerged systems. The 2003 study's 84 percent efficiency shows conversion is incomplete, and rising acid can stop the bacteria. A sour taste or a surface film does not identify the culture, the acetic acid produced or the safety of the product.

Swiss law supplies reference points. In the provisions checked for 2026, fermentation vinegar needs total acidity of at least 45 g/L as acetic acid and residual ethanol of no more than 0.5 percent by volume, apart from the separate wine-vinegar allowance. Whey and milk-serum vinegar must contain mainly acetic and lactic acids with acetic predominant, and residual lactose must not exceed 5 g/L. These are legal requirements in that jurisdiction, not an international standard or a home safety protocol.

The 2023 kaşar-whey study shows why measurement matters. Titratable acidity across its four formulations ran from 5.92 to 14.97 percent by weight per volume. Residual lactose varied: the highest lactose supplement left 50.798 g/L, while the unsupplemented whey vinegar held 0.540 g/L, which would break the Swiss lactose limit even though it was a properly made vinegar. Acidity, residual sugar and legal identity are separate questions.

Safety begins with the whey. Whey is rich in nutrients and raw or badly stored whey supports unwanted growth. The US regulation defining whey for food use requires pasteurised-milk origin or equivalent treatment, and industrial experiments sterilise the starting medium. Fermentation may lower pH but does not remove toxin already formed, eliminate every pathogen or make unhygienic material safe.

Milk allergy is a separate matter: the Turkish study measured protein in its vinegars, so fermentation did not remove it. UK allergen guidance lists milk products, including lactose, as regulated allergens, and an exemption does not generally apply to whey vinegar. Laboratory reports of antioxidant or antibacterial activity do not show clinical benefit.

Record the whey origin, any concentration or lactose added, the starter, fermentation conditions, ethanol, titratable acidity, residual lactose and storage. A vinegar of unknown acidity should not go into shelf-stable pickling. The original Lactavinaigre is too thinly documented to copy, so a modern process should be called a reconstruction or adaptation and not the authentic Swiss recipe.