Cold Conversion Does not Work

[Dieser Artikel liegt auch auf deutsch vor.]


Martin Zarnkow proposed the certainly plausibel theory that beer was produced in Northern Syria (Tall Bazi) during the Bronce Age without heating the mash.

Same Experiment – Different Measures

Again we mixed

  • 50 g Munich malt (EBC 17 – 22)
  • 400 ml water at 24 °C

and added

  • 0,63 g dry yeast

After 2 days a mildly alcoholic drink developed that smelled distinctivly of beer. To make sure we fermented the drink for a total of 3 days at 24 °C.

Starch Measurement

The iodine test at the preceding experiments was negative. But that was a measurement error. Starch colloides, it agglutinates to little clumps. You can see it in the iodine test with a magnifying glass as tiny little black spots. But over all the iodine test does not appear as black as we are used to from heated, stirred mash.

Look like the innocent flour
But be the starch under it.

In addition the starch clumps sink down and settle under the spelts. If you take off clear wort from the top for the test you miss the starch.

This time we mixed the mash including the spelts with a hand blender. That smashed the starch clumps to fine flour and spread it evenly within the emulsion.

Now the iodine test was positive. This provided evidence of the existence of starch. Even after 3 days the enzymes have not converted the starch completely to sugars.


Alcohol Measurement

We determined the alcohol content in two different ways (more on this in a later blog entry).

Result: The alcohol content lies in a range of 0.5 Vol.% to 2 Vol.%. That is far from what you’d expect considering the malt-water ratio employed. It is much closer to the 1.6 Vol.% Martin Zarnkow stated for his experiment.

Before any conversion of starch malt contains 1 – 5 % sugar. Even if all amylases remain completely inactive we would still have this amount of sugar to ferment into alcohol. And that matches quite well with the measurement amount of alcohol in the final drink.

Conclusion: Cold Conversion Does not Work

At least in our temperate zones starch does not convert to sugar at 24 °C room temperature. You have to heat the mash to achieve a conventional alcohol content. If you are happy with the below-2-vol.% alcohol content of unconverted starch you might as well skip any mashing period. Then you could add the yeast right away to the steeped malt and within hours you have a low-alc drink.

Possible variation:

You might try to save cooking stones and try to find the minimal mash temperature that would lead to a complete starch conversion.
Possibly the mash reached 40 °C in Northern Syria on a hot summer day which might have led to active amylases converting the starch. Yet this is rather unlikely as e. g. the thesis of Torsten Dickel shows.


Same Experiment – But more Thoroughly

In the thesis

Torsten Dickel: „Untersuchungen zu enzymatischen Abbauprodukten beim Maischen“ (Examinations of Enzymatic Metabolites During Mashing);
TU München, June 17th 2003

some further experiments are documented. According to it the conversion starts only at temperatures above 55 °C. Only in the temperature range between 70 and 80 °C noteworthy amounts of glucose, maltose and maltotriose developed. Below 55 °C the total share of sugars is 2 %. This is most probably the initial amount of sugar being always contained in dry malt.

Tall-Bazi Theory of Martin Zarnkow

Martin Zarnkow described his experiment for example in

Martin Zarnkow, Adelheid Otto, Berthold Einwag: „Interdisciplinary Investigations into the Brewing Technology of the Ancient Near East and the Potential of the Cold Mashing Process“; in „Liquid Bread: Beer and Brewing in Cross-Cultural Perspective“ (Editor Wulf Schiefenhövel, Helen Macbeth); Berghahn Books, 2011, New York

For fermentation he employed apart from the regular Sacchoromyces cerevisiae also Schizosaccharomyces and Lactobacillus . That appears unnecessary.

  • Fermentation by lactobacilli happens anyways. He might have aimed at an improved conservation by lowering the pH quickly.
  • We do not know of any additional fermentation powers of the yeast Schizosaccharomyces (pombe?). For that reason this administration appears superfluous.

In one article Martin Zarnkow mentions an initial warming of the mash to 40 °C. According to the conversion charts of Torsten Dickel we do not expect any positive effect on the enzyme activity by that.

Apart from that we have to consider the lower diastatic powers of the grain varieties in those days.

Tall-Bazi Brewing reconsidered

Tall_Bazi rekonstruiert

Tall Bazi (Reconstruction: Adelheid Otto and Berthold Einwag, Visualisation: Valentina Hinz and Stefan Franz)
[Mit freundlicher Abdruckgenehmigung des Instituts für Vorderasiatische Archäologie der LMU München und des Büros für Bauforschung und Visualisierung ‚Hinz & Franz‘]


According to Zarnkow et al. oxalates were found inside some ceramics of Tall-Bazi from 1,400 to 1,200 b. c. That indicates some form of brewing.

Virginia Badler has examined oxalates for beer evidence in

Rudolph Michel, Patrick McGovern, Virginia Badler: The First Wine & Beer – Chemical Detection of Ancient Fermented Beverages. Analytical Chemistry, Vol. 65, No. 8; April 15 1993; pp 408 ff.

Beerstone is calcium oxalate – a sparingly soluble salt that adheres to the inside of containers used to ferment or store beer. In sour environment the calcium oxalate reacts with other substances and the resulting agent shows a typical pink-purble colour. Mrs Badler was able to detect calcium oxalate in modern containers as well as ancient egyptian ceramics marked explicitly as beer jugs. This way she was able to prove that a jug of Godin Tepe in the Zagros mountains in Iraq of 3,500-3,100 b. c.  has been used to store beer.

Malting on Location?

Possible the brewing procedure started in Tall-Bazi with grain. Grain was found in jugs – but it may have been used for other purposes.

If not the village must have bought malt or dried malt cakes from outside. Malting and/or pre-mashing would have happened in other places then.

Possible Brewing Process with Hot Conversion

An alternative theory for brewing at Tall-Bazi would be therefore:

  • The inhabitants desired maximum alcohol from their precious malt. Therefore they heated the mash to 70 °C.
  • If no wooden mash tuns were used, they employed ceramic containers. In fact suitable containers were found apparently. They could have been used this way:
  • Put a 100-liter container on top of a 200-liter storage/fermentation jar.
    [A filled mashing pot is very heavy. We sometimes here the theory that these pots were suspended from the ceiling. This appears questionable: The construction would be complex, stiring is obstructed, and it bears the risk of a torn string without any benefit.]
    The 100-liter container has a hole in the bottom which is closed by a long stick.
    The bottom is cushioned with brushwood. [In case the mash has to be heated hot cooking stones can be thrown into the pot without crushing it.]
    In this container malt and hot water are mashed.
    The mash converts while it slowly cools down. The mash is stirred with a long spoon in the meanwhile (without touching the brushwood).
    After about an hour the stick is raised to have the wart rinse – filtered by spelts and brushwood – into the storage/fermentation jar below. [Filtering cold wart is tedious. Certainly a drawback of this method.]
    The 100-liter container is lifted and cleaned.
    [This process resembles the Carinthian and Nordic brewing methods of course. The found ceramic pots with holes in the bottom simply suggests this process.]
  • In the storage/fermentation jar yeast is added (for example being preserved on a piece of wood from the last brewing).
    It would be no surprise if there were family or village yeasts. Once a brewer comes across a mutation resulting in a better beer this yeast certainly found its way quickly to other brewers.

As long as chemists do not find a way to determine the mashing temperatures afterwards it will be close to impossible to decide if the folks at Tall-Bazi actually brewed that way.

All we know is: They brewed. And they did not cold-convert the mash’s starch.

[I would like to thank Graham und Merryn Dineley for the valuable input in this discussion.]


3 Gedanken zu “Cold Conversion Does not Work

  1. I might add that the fermentation temperature in this case was 24 °C. Martin Zarnkow uses a warmer temperature with his experiments as it is warmer in Syria (we prefer to call his method rather „warm conversion“ therefore). In his experiments the conversion to sugar apparently works. We will now try to find the exact minimum temperature needed for a successful saccharification. Either way: For the cooler middle european climate extra heating is required. „Cold conversion“ is not a suitable method here.


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