By Eben van Tonder, 10 August 2025

Introduction to Dr. Eduard Polenske and His Seminal Work

Dr. Eduard (Ed) Polenske (1849–1911) was a German chemist whose career at the Imperial Health Office (Kaiserliches Gesundheitsamt) in Berlin placed him at the centre of late 19th-century developments in food chemistry, public health, and regulatory science. Born on 27 August 1849 in Ratzebuhr, Neustettin, Pommern, to Samuel G. Polenske and Rosina Schultz, he married a woman with the surname Möller and lived in Berlin until his death in 1911.

The Imperial Health Office, where Polenske spent much of his professional career, was established on 16 July 1876 in Berlin to serve both the medical and veterinary sectors of the German Empire. Initially under the Reich Chancellery, it came under the Ministry of the Interior in 1879, in parallel with the adoption of the Law concerning the marketing of food, luxury foods, and commodities. This institution was tasked with ensuring compliance with that law, performing chemical and microbiological analyses, and developing scientific standards for food safety. In 1900, the newly formed Reichsgesundheitsrat began to support its activities, strengthening its role as a national authority. Within this environment, Polenske worked alongside leading chemists, veterinarians, and public health officials, contributing to the scientific foundation of modern food regulation.

Polenske’s research career was marked by his broad interest in food preservatives and their safety. During the 1880s, he became known for critical evaluations of chemical preservatives in meat products. At a convention of chemists in Speyer, Bavaria, on 10 September 1888, he participated in debates on the safety of agents such as boric acid. As reported in The Wichita Daily Eagle (1890), he investigated ten different commercial meat preservatives, identifying substances including sulphurous acid, sulphites, borax, boric acid, alum, arsenious oxide, salicylic acid, phosphoric acid, glycerine, boroglycerine, niter (saltpetre), and common salt — many of which were the subject of public health concerns at the time.

In 1891, Polenske published the work that would make his name a permanent fixture in the history of meat science: Über den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen salpeter-haltiger Pökellaken (“On the loss of nutritional value in beef due to curing, and on the changes in saltpetre-containing curing brines”), in Arbeiten aus dem Kaiserlichen Gesundheitsamte, Band 7. In this study, he reported the presence of nitrite in curing brines where only nitrate (in the form of saltpetre) had been added, almost certainly the first time this finding was documented in a rigorous, published scientific investigation.

This work positioned Polenske as one of the founding figures of modern meat curing. While later research would confirm that nitrite, not nitrate, is the active curing agent responsible for colour development and preservation, through the formation of Nitric Oxide, Polenske’s careful measurements opened the way for these advances. The industrial implications were transformative: by the early 20th century, understanding and managing nitrite formation allowed curing times to drop from weeks to mere days, revolutionising the production of bacon, hams, and other cured meats.

The significance of Polenske’s 1891 paper has long been recognised. For decades, it was accessible only in a few specialised libraries, and although a copy existed on Google Books, it was restricted from public viewing. A successful petition to Google for its release on historical and scientific grounds made it freely available, ensuring that this landmark document in food science is preserved and accessible to scholars and industry professionals alike.

In 1892, Polenske followed up with Untersuchungen über die Gesundheitsschädlichkeit des mit Salpeter gepökelten Fleisches (“Investigations into the Harmfulness to Health of Meat Cured with Saltpetre”), published in the same journal. This second study shifted focus from chemical changes and nutritive losses to potential toxicological risks, marking a logical expansion of his research from the mechanics of curing chemistry to the implications for public health.

Together, these works form a cornerstone in the history of food preservation and safety studies that bridged chemistry, microbiology, and nutrition at a time when these disciplines were only beginning to converge in the service of public health and industry.

Below are the cover of the original journal, the title page and the first page of the actual article.

Introduction to the Work: Über den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen Salpeter-haltiger Pökellaken (On the loss of nutritional value in beef due to curing, and on the changes in saltpetre-containing curing brines)

The present article focuses on one of Polenske’s most important works:

Polenske, Eduard. “Über den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen Salpeter-haltiger Pökellaken”

This paper is held by only a handful of university libraries worldwide. While a copy exists on Google Books, it was originally restricted from public access. Recognising the extraordinary significance of this work, arguably one of the most important papers in the history of food science, I petitioned Google several years ago to make it freely available, outlining its historic and scientific value. Google graciously granted this request, allowing wider access to a document that not only shaped our understanding of meat preservation chemistry but also stands as a cornerstone in the field of food safety.

In the year following the publication of his 1891 study on the loss of nutritional value in beef during curing and the changes occurring in saltpetre-containing brines, Dr. Eduard Polenske produced a follow-up paper that expanded his investigation into the broader question of food safety. This 1892 work, titled Untersuchungen über die Gesundheitsschädlichkeit des mit Salpeter gepökelten Fleisches (Investigations into the Harmfulness to Health of Meat Cured with Saltpetre), was also published in Arbeiten aus dem Kaiserlichen Gesundheitsamte. While the 1891 study was primarily concerned with chemical changes and nutritional implications, the 1892 article shifted the focus to the potential toxicological risks of saltpetre in cured meat, marking a direct progression from compositional and preservation effects to the public health dimension of meat curing practices.

Über den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen Salpeter-haltiger Pökellaken

Arbeiten aus dem Kaiserlichen Gesundheitsamte, Volume 7, 1891

Communications from the Chemical Laboratory of the Imperial Health Office
(Director: Privy Councillor Professor Dr. Sell)

13. On the loss in nutritive value suffered by beef during pickling, as well as on the changes in saltpetre-containing meat products
By Dr. E. Polenske,
Assistant in the Chemical Laboratory of the Imperial Health Office

It was my objective to determine to what extent the nutritive value of beef is diminished by pickling, especially during preservation for extended periods, and also to clarify the chemical changes occurring in saltpetre-containing meat products during storage.

For this purpose, a series of experiments were conducted with beef, in which 120 g portions of lean muscle meat were cured. The composition of the fresh meat was as follows:

Sample	Moisture (%)	Fat (%)	Nitrogenous substances (%)	Ash (%)
I	74.05	1.94	22.11	—
II	“	“	“	—

The curing process was carried out by rubbing the beef thoroughly with a mixture of common salt and saltpetre, then storing it in a cool place. After the specified periods, the salt content was determined in the same way as in salted meat, by extracting with water, filtering, and titrating the chloride content with silver nitrate.

The differences in smell and taste became apparent as early as the first month. High-priced beef samples showed a milder taste. At the same time, the older the animals, the darker the meat generally became. This darker colour could not have been due to spoilage but must be attributed to natural changes in the muscle pigments during curing.

The nitrogen content was found to be lower in older animals, and in addition, an increase in nitrogen-free extractives in the meat could already be expected from the outset. At the same time, due to the advanced age of the cattle, the fat content of the meat was generally higher. This alone could account for the fact that the proportion of total nitrogenous matter was relatively lower.

The weight of the fresh meat varied accordingly; it amounted, including fat and bones, to:

Sample	Fresh meat (g)	Actual meat (g)	Fat percentage (%)
I	1255	1065	15.2
II	1085	1120	3.2
III	1050	1120	6.2

From these weight determinations, which were made after the careful removal of visible fat and careful trimming, the required material for the preservation experiments was prepared.

The determination of the basic composition was carried out monthly, and the average values of water content, total nitrogen, fat, and ash in the different types of meat were as follows:

Sample	Water (%)	Nitrogen (%)	Fat (%)	Ash (%)
I	75.3	3.24	1.50	0.95
II	74.5	3.18	1.60	0.98
III	73.6	3.12	1.65	0.94

The meat samples were then salted with ordinary kitchen salt and saltpetre in the usual way, and the nitrite content was determined by the starch-iodide method.

The nitrite content was as follows:

Sample	Nitrite (%)
I	0.123
II	0.126
III	0.124

The fat content was:

Sample	Fat (g)
I	143.2
II	145.0
III	146.8

Average nitrogen-free extractives (in g):

Sample	N-free extractives (g)
I	11.2
II	11.9
III	12.0

The bones were also examined:

Sample	Ash (%)	Phosphoric acid (%)
I	55.8	26.1
II	55.6	26.2
III	55.4	26.0

After salting, the meat was stored for three days in brine and then smoked.

Storage results:
The salted meat kept for at least six months without any change in taste, smell, or appearance. At the same time, no signs of spoilage were detectable during the entire storage period.

The ammonia formation must therefore be attributed mainly to the breakdown of the extractives already present in the meat, which were dissolved out with water and precipitated with phosphotungstic acid, rather than to the decomposition of muscle proteins or connective tissue proteins.

In order to determine the amount of ammonia formed during storage under the given conditions, fresh meat was treated in the same way, and the ammonia content found was subtracted from the value obtained from the stored meat. The difference represents the ammonia formed during the storage period.

The increase in ammonia, calculated for 100 kg of meat, is:

I — 0.0940 g
II — 0.0022 g
III — 0.0035 g
IV — 0.0030 g
V — 0.0028 g
VI — 0.0025 g
a) — 0.0025 g
b) — 0.0022 g
VIII — 0.0025 g

It is noteworthy that the ammonia content did not rise sharply, despite the presence of a significant quantity of nitrogen-containing extractives in the fresh meat, from which ammonia could have been liberated under the storage conditions. This result suggests that the extent of putrefactive processes during the storage period was relatively small.

The determination of nitric oxide (N₂O₃) shows that the amounts present in the stored meat were minimal and did not change significantly compared to the fresh product. This indicates that nitrate breakdown into nitrite and further into nitric oxide and ammonia was not occurring to a major degree during the storage period under the tested conditions.

Reference: German (original form)

Polenske, E. (1891). Über den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen Salpeter-haltiger Pökellaken. Arbeiten aus dem Kaiserlichen Gesundheitsamte, 7, 467–492.

Polenske, E. (1891). On the loss in nutritive value suffered by beef during pickling, as well as on the changes in saltpetre-containing meat products. Reports from the Imperial Health Office, 7, 467–492.

Reassessing the Origins of the Nitrate-> Bacteria -> Nitrite Hypothesis in Meat Curing

Polenske clearly identified nitrite in the brine when he only added nitrate through saltpetre. It is often stated in later literature that Polenske expressed surprise at finding nitrite in curing brines and speculated that its origin might be microbial fermentation of nitrate (Binkerd & Kolari, 1975; Honikel, 2008). The problem is that the widely reported speculation that bacteria are responsible for the conversion of nitrate to nitrite does not appear in this article. That paper is focused on quantifying nutritive losses in beef during pickling and tracking chemical changes, without any commentary on unexpected nitrite formation (Polenske, 1891).

The next logical question to ask is whether he made the comments in a subsequent work. This is possible, but tracing such a publication is extremely difficult. Despite an intense search, I could not locate even a secondary reference to a later article by Polenske where he made the widely reported remarks. Every secondary source cites Über den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen salpeter-haltiger Pökellaken (Arbeiten aus dem Kaiserlichen Gesundheitsamte, 7, 471–474) of 1891 as the source.

What Ostertag and Contemporaries Actually Say

Robert von Ostertag (1864–1940) was a leading German veterinarian and food hygienist, regarded as a founder of modern meat inspection. He taught at the University of Berlin and served as Director of the Imperial Health Office’s veterinary division. His Handbuch der Fleischbeschau was a foundational reference in meat hygiene, influencing both legislation and scientific practice in Germany and beyond. The 1892 first edition is fully digitised and available via the Internet Archive: Handbuch der Fleischbeschau (1892).

A contemporaneous hygiene summary quoting Ostertag on Nothwang (1892) states plainly that nitrate disappears in cured goods and that Nothwang attributes the conversion to reduction in the meat tissue, not bacteria, with nitrite (salpetrige Säure) as the product:

German:
Die Physiologen schreiben dem Fleische die Fähigkeit der Reduktion bestimmter Substanzen zu. Nach Munk nimmt der überlebende Muskel reichlich Sauerstoff auf und scheidet Kohlensäure ab. Er entzieht Nitraten Sauerstoff und verwandelt dieselben in Nitrite. Nothwang fand, dass der Salpeter in konservierten Waren oft fehlt und dass das Kochsalz im Lakefleisch ständig zunahm, während der Salpeter nach einiger Zeit (acht Tagen) stetig absank. Dieses Verschwinden des Salpeters, das jedoch nicht immer eintrat, führt Nothwang auf Reduktionsvorgänge im Fleische zurück und glaubt an die Bildung von salpetriger Säure (nach Ostertag). (Ostertag, 1892, p. xx)

English translation:
Physiologists attribute to meat the ability to reduce certain substances. According to Munk, living muscle takes up oxygen in large amounts and gives off carbon dioxide. It removes oxygen from nitrates and converts them into nitrites. Nothwang found that saltpetre is often absent in preserved goods, and that common salt in brined meat continually increased while the saltpetre steadily declined after some time (eight days). Nothwang attributes this disappearance of saltpetre to reduction processes in the meat and believes nitrous acid is formed (as reported by Ostertag).

Ostertag’s Handbuch der Fleischbeschau (1892) is the right place to document how he synthesised Nothwang, Polenske, and others. There is no explicit line crediting bacteria to Polenske in this edition; the framing leans toward physiological/tissue reduction when summarising early work (Ostertag, 1892).

Where the “Microbial” Mechanism Shows Up Explicitly

Modern encyclopedic summaries in German state:

German:
1891… Polenske… Nitrat im Fleisch durch Bakterien zu Nitrit umgewandelt. (Wikipedia, 2024)

English translation:
1891… Polenske… nitrate in meat converted to nitrite by bacteria.

These statements do not show a Polenske verbatim line and appear to be retrospective generalisations.

The weight of proof for the bacterial mechanism in the early 20th century shifted to Lehmann & Kisskalt (1899), who identified nitrite as the active colouring agent in curing, and Haldane (1901), who elucidated the nitric oxide–haem chemistry (Lehmann & Kisskalt, 1899; Haldane, 1901). A widely cited German academic overview summarises that understanding and lists Lehmann, Kisskalt, and Haldane as the key proofs that nitrite arises from nitrate and causes the curing colour (MediaTUM, 2020).

Polenske 1891 Location (for Completeness)

The table of contents for Arbeiten aus dem Kaiserlichen Gesundheitsamte confirms Polenske’s article and pagination:

German:
Ueber den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen salpeter-haltiger Pökellaken. Arbeiten aus dem Kaiserlichen Gesundheitsamte, Band 7 (1891), pp. 471–474.

English translation:
On the loss which beef suffers in nutritional value through curing, as well as on the changes in saltpetre-containing curing brines.

The full paper contains valuable data on curing brines and nutritive losses but no explicit bacterial-mechanism claim (Polenske, 1891).

My Assessment

The earliest explicit “bacteria do it” formulation that becomes standard in the field is best attributed to the Lehmann/Kisskalt (1899) circle and the immediate scientific reception, not to a sentence in Polenske 1891. Ostertag’s early treatment (1892) reflects the competing hypothesis of tissue reduction. The later habit of saying “Polenske (1891) concluded bacterial reduction” appears to be a historiographic shortcut that solidified in 20th-century summaries.

Conclusion

Even though Polenske probably did not make the widely reported speculation that nitrite was present in the curing brine (saltpetre and salt-based) in his 1891 investigation, the clear fact remains that he was, in all likelihood, the first person to publish this data after a thorough scientific investigation. That achievement stands without any question and makes him, in a very real sense, the father of meat science. Whether the mechanism for the creation of nitrite — being the microbially driven reduction of nitrate — can be ascribed to him is probably not true. However, as with all matters of historical science, further investigation could still overturn my conclusions here.

The second question that emerges from this enquiry is: if not Polenske, then who first speculated that bacteria were responsible for converting nitrate to nitrite in meat curing? This remains unresolved. Early contemporaries such as Nothwang, as reported by Ostertag, explained the change through reduction processes in the meat tissue itself rather than bacterial action. The shift towards a microbial explanation seems to have taken hold only by the turn of the 20th century, with the work of Lehmann and Kisskalt and their scientific circle. Pinpointing the first printed attribution of the bacterial mechanism to Polenske remains an open challenge — one that may yet be answered through closer reading of veterinary hygiene texts, technical manuals, and institutional reviews from the period immediately following 1891.

References

Binkerd, E. F., & Kolari, O. E. (1975). The history and use of nitrate and nitrite in the curing of meat. Food and Cosmetics Toxicology, 13(6), 655–661.

Haldane, J. S. (1901). The red colour of salted meat. Journal of Hygiene, 1(1), 115–122.

Honikel, K. O. (2008). Principles of curing. In F. Toldrá (Ed.), Handbook of Fermented Meat and Poultry (pp. 17–30). Blackwell.

Lehmann, K. B., & Kisskalt, K. (1899). Über die Umrötung von Fleisch durch salpetrige Säure. Archiv für Hygiene, 35, 137–172.

MediaTUM. (2020). Geschichte der Fleischverarbeitung [Digital archive].

Ostertag, R. (1892). Handbuch der Fleischbeschau. Stuttgart: Enke. Retrieved from https://archive.org/details/ostertag1892

Polenske, E. (1891). Ueber den Verlust, welchen das Rindfleisch an Nährwerth durch das Pökeln erleidet, sowie über die Veränderungen salpeter-haltiger Pökellaken. Arbeiten aus dem Kaiserlichen Gesundheitsamte, 7, 471–474.

Wikipedia. (2024). Pökeln. Retrieved from https://de.wikipedia.org/wiki/P%C3%B6keln

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