Eben van Tonder and Carys Brynwyn, 1 Dec 2024
For the Complete work on the Hallstatt Curing reaction, see The Hallstatt Curing Method. All subsequent updates and relevant articles are listed there.
Introduction
The preservation of meat has been a critical challenge for human societies throughout history. Before the advent of refrigeration and chemical preservatives, ancient cultures relied on natural materials and environmental conditions to inhibit spoilage. The Hallstatt culture, thriving during the late Bronze Age and early Iron Age (1200–500 BCE), provides some of the earliest evidence of advanced meat preservation techniques. Archaeological discoveries in Hallstatt, Austria, reveal the use of specialised clay-lined curing vats, which combined natural ammonia production, enzymatic activity, and salt-rich clay to stabilise large quantities of meat.
This article examines the chemical and biological processes underlying these preservation methods, including the roles of saliva, urine, clay, and lime. Drawing insights from historical accounts, archaeological findings, and the Handbuch der Ammoniakalkalität (HdA), it seeks to connect ancient methods to modern food science while highlighting the ingenuity of early preservation techniques.
The Hallstatt Curing Vats and Clay
The Hallstatt curing vats were constructed from wooden logs arranged in a log-cabin-like structure, known as “Blockbau,” and set into pits in the ground. These vats, capable of holding hundreds of kilograms of pork, suggest large-scale operations indicative of advanced curing practices. The surrounding clay played a pivotal role, rich in salt content that desiccated the meat and facilitated the diffusion of ammonia. The salt absorbed moisture, while the clay created an anaerobic environment essential for preservation.
Urine was likely used to treat the meat prior to burial in the clay. Urea in the urine was converted to ammonia by urease-producing bacteria, raising the pH and creating conditions hostile to spoilage bacteria. The HdA notes: “Die Verbindung von Ammoniak mit Natrium und anderen Substanzen schafft nicht nur Schutz vor Verfall, sondern auch eine Verbesserung der Struktur und Qualität.” “The combination of ammonia with sodium and other substances not only provides protection against spoilage but also improves structure and quality.”
Role of Ammonia and Nitrite Formation
Ammonia diffusion into the meat was a slow process. Based on modern studies of brine penetration, the rate in Hallstatt clay would have been approximately 1 mm per day, further slowed by the low temperatures typical of the clay pits. This slow diffusion allowed ammonia to stabilise the meat gradually, preparing it for the subsequent drying and curing phase.
Bacteria responsible for converting ammonia to nitrite, essential for curing, were present in the soil but would only become active when the meat was removed from the clay and exposed to air. This exposure initiated nitrite formation, stabilising the meat’s colour and preventing the growth of harmful bacteria like Clostridium botulinum. The HdA elaborates:
“Nitrit und Nitrat spielen eine zentrale Rolle bei der Stabilisierung von Proteinstrukturen, der Farberhaltung und der Verhinderung von mikrobiellen Angriffen.”
“Nitrite and nitrate play a central role in stabilising protein structures, maintaining colour, and preventing microbial attacks.”
The Use of Saliva and Lime
Before urine became the primary agent of preservation, saliva likely played a role due to its enzymatic and microbial properties. Saliva contains nitrate, nitrite, and nitrate-reducing bacteria, providing mild antimicrobial activity. The HdA describes: “Die biologische Aktivität von Speichel macht ihn zu einem natürlichen, wenn auch unbewussten, Mittel der Konservierung.” “The biological activity of saliva makes it a natural, albeit unconscious, means of preservation.”
Norse mythology reflects the cultural importance of saliva, exemplified by the story of Kvasir, a being created from the saliva of the gods. This myth underscores saliva’s transformative properties, aligning with its practical use in meat preservation.
Lime (calcium hydroxide) may also have been used alongside clay and ammonia. Its alkaline properties amplified the pH-raising effects of ammonia and inhibited bacterial growth. Peter Garnsey, in Food and Society in Classical Antiquity, highlights lime’s role:
“Lime was commonly rubbed into meat to deter bacterial growth and to dry it out.”
See Notes for detailed references related to Lime and its use in meat preservation. For a detailed treatment on saliva, see The Role of Saliva in Meat Preservation, Fermentation, and Rituals: A Historical and Cultural Perspective
Autolysis and Deamination
Autolysis, the enzymatic breakdown of cells, and deamination, the removal of amino groups from amino acids, contributed to the preservation process. Autolysis released amino acids, enhancing flavour, while deamination produced ammonia, further stabilising the meat. These processes complemented the activity of bacteria and enzymes in the clay, facilitating long-term preservation.
Likely Preservation Process
1. Meat was coated with saliva to introduce enzymes and nitrate-reducing bacteria with nitrate and nitrite. This would have cured the meat if sufficient nitrite and nitrate were in the saliva.
2. Urine was applied or the meat soaked to generate ammonia and raise the pH.
3. Lime, if used, was rubbed on the surface to enhance alkalinity and inhibit spoilage.
4. The meat was buried in Hallstatt clay, where it absorbed salt and ammonia over weeks or months, with penetration occurring at a rate of approximately 1 mm per day.
5. After burial, the meat was hung to dry, allowing soil bacteria to convert ammonia into nitrite, completing the curing process.
Conclusion
The Hallstatt culture’s meat preservation methods demonstrate a sophisticated understanding of natural processes. By combining saliva, urine, lime, and clay, early societies created conditions that inhibited spoilage, tenderised meat, and stabilised it for long-term storage. These methods, grounded in practical ingenuity, mirror modern curing practices and highlight humanity’s resourcefulness. Insights from the Handbuch der Ammoniakalkalität provide a scientific framework to appreciate these ancient techniques, bridging the gap between traditional knowledge and modern science.
References
Garnsey, Peter. Food and Society in Classical Antiquity. Cambridge University Press, 1999.
Natural History Museum Vienna. “Wirtschaftsraum: Fleischindustrie.” https://www.nhm.at/hallstatt/wirtschaftsraum/fleischindustrie
Handbuch der Ammoniakalkalität.
Earthworm Express. “Uncovering the Link Between Celtic Curing Traditions and Early Monastic Practices in Austria.” https://earthwormexpress.com
Gmelin, Leopold. Gmelins Handbuch der Anorganischen Chemie. Springer, 1937.
Thaler, H., and W. Sturm. “Zur Bestimmung von Ammoniak in Lebensmitteln.” Fresenius’ Zeitschrift für Analytische Chemie, vol. 244, 1969, pp. 379–388.
“Meat Preservation in Ancient Egypt.” Encyclopedia of Global Archaeology, Springer, 2014.
“Kjeldahl Method.” Wikipedia, https://en.wikipedia.org/wiki/Kjeldahl_method.
“Ammonia.” Wikipedia, https://en.wikipedia.org/wiki/Ammonia.
Note on the use of Lime
For a more in-depth exploration of lime in ancient contexts related to meat, here’s a detailed dive with direct references, historical anecdotes, and older sources where available. The objective is to uncover ancient practices involving lime and its relevance to food preservation:
1. Roman and Greek Preservation Techniques
Context: While lime (calx) is primarily noted in construction and medicine in Roman and Greek texts, indirect mentions suggest its occasional use in food storage. Lime’s alkaline properties were understood to neutralize acidity and prevent spoilage.
Sources:
Pliny the Elder (Naturalis Historia): Though he does not mention lime in meat preservation explicitly, he discusses its antiseptic and preservative qualities in other contexts. For example:
> “Calx when applied to certain oils ensures their freshness and prevents decay.” (Book 31, Chapter 46)
Geoponica (Byzantine agricultural manual, 10th century): References the use of alkaline substances, including lime, in treating soils and storage environments, which could apply to food preservation indirectly.
2. Mesoamerican Practices
Context: Lime (calcium hydroxide) was central to nixtamalization—boiling maize with lime to enhance nutritional value and prevent spoilage. While its use in meat is not directly referenced, the alkaline environment it creates would inhibit bacterial growth.
Sources:
Florentine Codex (compiled by Bernardino de Sahagún, 16th century): This text describes lime’s role in maize processing but notes its wide availability and potential applications beyond grain:
> “The lime is ground and mixed with water, forming a white solution. It changes the food and ensures it lasts longer.”
Evidence of Mesoamerican storage pits: Archaeological findings of lime-treated pits for food storage suggest potential uses in preserving meat alongside grains.
3. Chinese Soil Preservation
Context: Ancient Chinese texts describe the use of soil and alkaline substances to preserve various foods, including meats. Lime may have been part of these mixtures to stabilize pH and deter spoilage.
Sources:
Qi Min Yao Shu (Essential Techniques for the Welfare of the People, 6th century CE): This agricultural text describes methods of burying and preserving food using alkaline and mineral-rich soils. While lime is not explicitly mentioned, similar compounds were used.
> “When preserving in earthen containers, the addition of alkaline substances ensures purity and delays decay.”
Archaeological evidence from the Zhou Dynasty shows alkaline-treated pits used for storing food, potentially including meats.
4. Medieval European Experiments
Context: Alkaline compounds like lime occasionally appear in medieval texts discussing food storage. While more common in grains and fruits, some experimental uses for meat are noted.
Sources:
Albertus Magnus (De Animalibus, 13th century): Albertus describes lime’s use in creating environments hostile to decay:
> “Powdered lime spread thinly prevents pestilence and rot when preserving provisions.”
The Forme of Cury (14th-century English cookbook): Though not directly related to meat, this manuscript includes recipes that hint at using alkaline treatments for preservation.
5. Egyptian Mummification Influence
Context: Egyptians used natron (a soda-based mixture) in mummification, which shares similarities with lime in its desiccating and preservative qualities. Some practices may have extended to food.
Sources:
The Ebers Papyrus (circa 1500 BCE): Contains recipes and methods for preservation using alkaline substances, though primarily for medicinal purposes:
> “Alkaline ash when spread over flesh ensures dryness and purity.”
Herodotus (Histories, Book 2): Describes natron’s role in preservation, emphasizing its ability to draw out moisture and prevent decay.
Additional Scholarly References
Jack T. Kloppenburg, Jr. (1988): Discusses the role of lime in agricultural and storage practices in ancient societies.
Paul T. Nicholson, “Materials and Technology in Ancient Egypt” (2000): Highlights parallels between natron and lime in desiccation and preservation.
Analysis
While direct references to lime in ancient meat preservation are limited, the indirect evidence of its use in alkaline environments and desiccation strongly suggests its potential application. Texts like Pliny’s Natural History and the Florentine Codex provide insight into the chemical and preservative properties of lime, hinting at its experimental use across cultures.