By Eben van Tonder and Christa Berger, 7 January 2025
For the Complete work on the Hallstatt Curing reaction, see The Hallstatt Curing Method. All subsequent updates and relevant articles are listed there.
Abstract
This paper provides an update on our work to uncover the most likely curing process and underlying reaction sequence for the meat curing practices in Hallstatt during the Late Bronze Age, emphasizing the large-scale industrial nature of these operations. Drawing upon archaeological findings, historical records, and scientific analyses, we explore the methods employed, the role of lysine in the curing process, the prevention of putrefaction, and the microbial dynamics involved. Special attention is given to the use of natural additives, such as urine, and their biochemical implications. The study culminates in a detailed reconstruction of the most effective and plausible ancient industrial meat curing process, reflecting the technological sophistication of the period.
Introduction
The Hallstatt region of Austria is renowned for its prehistoric salt mines and associated meat curing industry, particularly during the Late Bronze Age (13th–12th centuries BCE). Archaeological excavations have uncovered substantial evidence of large-scale meat processing facilities, including wooden curing vats capable of holding up to 200 pork carcasses each. These findings suggest a highly organized and industrialized approach to meat preservation, essential for sustaining the local population and facilitating trade.
This study aims to reconstruct the Hallstatt meat curing process, examining the materials and methods used, the biochemical reactions involved, and the strategies employed to prevent spoilage. We also assess the role of lysine, a key amino acid, in enhancing the curing process and explore the potential use of natural additives, such as urine, in facilitating biochemical reactions.
Materials and Methods
1. Archaeological Evidence
Excavations in the Hallstatt region have revealed:
-> Wooden Curing Vats: Large wooden structures, interpreted as curing vats, were discovered, each with the capacity to hold between 150 and 200 pork carcasses. These vats were constructed using timber and sealed with clay to ensure they were watertight.
-> Animal Remains: Analyses of animal bones found near these vats indicate a predominance of pig remains, suggesting that pork was the primary meat processed.
-> Stirring Tools: Implements resembling wooden paddles were found near the curing vats, indicating that stirring was an integral part of the curing process.
2. Role of Lysine in the Curing Process
The new insight comes from examining possible sources for ammonia which would be essential in nitrite production. Lysine emerged as the most likely candidate. It is an essential amino acid, that will plays a significant role in the proposed system by:
-> Enhancing Deamination: Lysine undergoes deamination, producing ammonia, which nitrifying bacteria can convert into nitrites and nitrates.
-> Preventing Oxidation: Studies have shown that lysine can inhibit the oxidation of lipids and proteins in meat products by scavenging free radicals and chelating metal ions .
3. Natural Sources of Lysine
In the Late Bronze Age Hallstatt region, lysine could have been sourced from:
-> Animal Skins (Collagen): Collagen-rich pork skins, when boiled, release gelatin containing lysine.
-> Grains and Legumes: Barley, wheat, lentils, and peas were prevalent in the region and are known to contain lysine.
4. Prevention of Putrefaction
The biggest challenge facing Richard Bosman in Cape Town who is working to reproduce our proposed method was to prevent purification which he has been unable to achieve till now. We propose to address the challenge by (preventing spoilage during the curing process) in the following ways which are all “seamless/ natural” for the late Bronze Age Hallstatt environment:
-> Salt Concentration: High salt levels create an inhospitable environment for spoilage bacteria.
-> pH Control: Maintaining an alkaline environment through the addition of ammonia-rich substances, such as urine, can inhibit the growth of putrefactive microorganisms.
-> Aeration: Regular stirring introduces oxygen, promoting the growth of aerobic bacteria that outcompete anaerobic spoilage organisms.
5. Microbial Dynamics
Key bacteria involved in the curing process include:
a. Nitrifying Bacteria: Nitrosomonas spp. and Nitrobacter spp. convert ammonia into nitrites and nitrates, essential for meat preservation.
b. Spoilage Bacteria: Clostridium perfringens and Fusobacterium nucleatum are anaerobic bacteria that can cause putrefaction if not controlled.
Proposed Curing Process
Based on the available evidence, the following is a reconstruction of the Hallstatt meat curing process:
1. Preparation of Curing Mixture
-> Salt Extraction: Salt was obtained from the local mines, likely in the form of a mixture known as Haselgebirge, which contains salt, clay, and anhydrite.
-> Lysine Enrichment: To enhance the curing process, lysine could have been introduced by:
a. Boiling Pork Skins: Pork skins were boiled to extract gelatin rich in lysine.
b. Fermenting Grains/Legumes: Barley, wheat, lentils, or peas were soaked, ground into a paste, and fermented for several days to release lysine.
2. Meat Preparation
-> Butchering: Pigs were slaughtered, and the carcasses were partially deboned using techniques similar to those still employed in the Alps today.
-> Application of Curing Mixture: The meat was coated with the salt and lysine-enriched mixture, ensuring thorough coverage.
3. Curing in Vats
In the vats, the following is proposed to have taken place.
a. Placement in Vats: The prepared meat was placed in large wooden vats, layered with the additional curing mixture as discussed above.
b. Addition of Urine (Optional): Small amounts of urine may have been added to introduce urea, which breaks down into ammonia, aiding in pH control and providing a substrate for nitrifying bacteria.
c. Aeration through Stirring: Wooden paddles, discovered at the site, were likely used to stir the curing mixture. This aeration encouraged the growth of aerobic bacteria (Nitrosomonas and Nitrobacter) while inhibiting anaerobic spoilage organisms like Clostridium perfringens.
d. Temperature and Time Control: The vats were placed in cool, shaded areas where temperatures ranged from 5–15°C. This environment slowed spoilage and promoted enzymatic reactions over 10–14 days.
Biochemical Reaction Sequence
Phase 1: Early Reactions (Days 1–3)
Deamination:
Proteins and lysine undergo enzymatic deamination, producing ammonia:
Ammonia Accumulation:
Ammonia creates an alkaline environment that inhibits spoilage bacteria and provides a substrate for nitrification.
Phase 2: Nitrification (Days 4–10)
Nitrosomonas Activity:
Ammonia (NH3) is oxidized to nitrite (NO2-):
Nitrobacter Activity:
Nitrite is further oxidized to nitrate (NO3-):
Meat Stabilization:
Nitrites react with myoglobin in the meat, forming nitric oxide myoglobin, which stabilizes colour and flavour.
Phase 3: Completion of Curing (Days 11–14)
Nitrite and Salt Diffusion:
Salt and nitrite penetrate deeper into the meat, preventing microbial growth and ensuring preservation.
Enzymatic Reactions:
Residual enzymes break down fats and proteins, contributing to flavour development.
Phase 4: Drying (Weeks 1–6)
Moisture Reduction:
After curing, the meat is rinsed and hung in the salt mines, where controlled humidity (70–80%) and temperature (10–15°C) promote gradual drying.
Chemical Concentration:
As water evaporates, salt, nitrites, and nitrates concentrate on the surface, further enhancing preservation and flavour.
Prevention of Putrefaction
1. Salt Levels
High salt concentration (3–5% by weight) inhibits the growth of spoilage bacteria, particularly Clostridium perfringens.
2. pH Control
Ammonia from deamination or added urine maintains an alkaline environment, suppressing anaerobic bacteria.
3. Aerobic Conditions
Stirring introduces oxygen, which supports the activity of aerobic nitrifying bacteria while limiting the proliferation of anaerobes.
Late Bronze Age Scaling Practices
Archaeological evidence indicates that the Hallstatt curing process was already scaled to industrial levels:
-> Large Wooden Vats:
Capable of holding 150–200 carcasses, these vats demonstrate advanced planning and resource allocation.
-> Efficient Workflows:
The integration of curing vats, stirring tools, and drying facilities suggests a well-organized system capable of processing large quantities of meat.
-> Regional Trade Networks:
Preserved meat was likely a key trade commodity, with Hallstatt functioning as a hub for distribution.
Evaluation of Urine Addition
If lysine from collagen or legumes was sufficiently available, the addition of urine would not be strictly necessary. However, its inclusion would:
1. Provide a reliable source of ammonia for pH control and nitrification.
2. Accelerate the curing process by supplementing natural enzymatic reactions.
Without urine, achieving the same level of ammonium availability would depend heavily on lysine deamination, potentially extending the curing time.
We add the work we have done on the use of Urine in ancient cultures under the reference section.
Conclusion
The Hallstatt meat curing method represents a sophisticated integration of biochemical knowledge and industrial practices during the Late Bronze Age. By combining salt from local mines, lysine-rich additives, and careful environmental control, the Hallstatt community preserved meat on a scale unparalleled in the ancient world. This process demonstrates an advanced understanding of microbial dynamics, chemical reactions, and spoilage prevention.
References
Animbiosci.org. “Role of Lysine in Curing Processes and Oxidation Prevention.”
EarthwormExpress.com. “Bay Salt in Seventeenth-Century Meat Preservation.”
NHM Wien. “Hallstatt and Its Meat Processing Industry.”
Onlinebiologynotes.com. “Microbial Spoilage of Meat and Methods of Preservation.”
Preusser, F., et al. “Salt Production in Hallstatt During the Late Bronze Age.”
Salzbergwerke.at. “Historical Salt Mining in Austria.”
Our Work on Eurine in Ancient and Pre-History
- The Role of Urine as a Filtration System for Amanita Muscaria and Other Uses Across Eurasia.
This article explores how ancient Siberians utilized urine, particularly reindeer urine, to safely consume Amanita muscaria mushrooms by reducing their toxicity while preserving psychoactive effects. It also delves into urine’s applications in traditional medicine and preservation methods across Eurasia. Earthworm Express - The Ancient Use of Urine as a Filter for Amanita Muscaria Consumption: Ritual and Medicinal Practices Across Eurasia. This piece examines the historical practice of using urine as a metabolic filter in the consumption of Amanita muscaria mushrooms, focusing on spiritual traditions in Siberia, Arctic shamanism, and European cultures. Earthworm Express
- A Newspaper’s Record and Old Chemistry Textbooks References on Use of Urine and Dung in Antiquity with Traces in Old but More Recent Usages. This article provides historical references on the use of urine and dung in ancient times, highlighting their applications in agriculture and other industries. Earthworm Express
- Ammonia from Urine and Horse Sweat: An Ancient Pathway to Curing. This chapter discusses the role of ammonia derived from urine and horse sweat in ancient meat curing practices, shedding light on historical preservation techniques. Earthworm Express