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What is the science of drying meat?

This is a cross-topic question, but I think it's best suited here. Let me know if it should be elsewhere...

I am South African and one of our traditional snacks is 'biltong' which is essentially air-dried meat (beef most commonly). I know there are many different types of dried meat from different parts of the world, which are significant in different societies and cultures, which is facinating. Biltong is traditionally very simply seasoned and air-dried in the South African climate but is made in driers nowadays, particularly in climates outside of SA.

I no longer live in SA (live in UK) and make my biltong in a homemade drier. It essentially comprises of a wooden box, with a small fan and a very small heater. Beef is hung until it's dried to my liking. Drying of meat is an (inexact) art and there are a number of factors that influence the final product, which means drying times change and each batch can be different. When drying, you also dont want to dry too fast, as this can result in 'case hardening', where the outside is hard and the inside still raw and very soft, the best is to slowly dry, so you get a consistent dryness and texture throughout the meat.

The factors I am aware of are: temperature and humidity of the air outside drying chamber, temperature and humidity of air inside drying chamber, airflow through drying chamber, thickness of cut of meat and size of meat, amount of meat hung in chamber, fat content of meat and the moisture content of the meat.

I am a physicist and interested in the science behind meat drying and have the following questions:

  1. Is there a recognised relationship between drying time (of beef), relative humidity, airflow and temperature?
  2. Is there a recommended temperature, humidity and airflow for drying beef?
  3. Which environmental condition(s) is most important for drying beef, and why? For example, should i only be concerned about controlling RH or RH and temperature combined etc?
  4. My understanding of the driers is that the heater is there to increase the temperature of the air and reduce its density and thus RH of the air. I assume the fans only function is to remove the air that has taken on some of the moisture from the meat - is this correct or does this serve another function?

I am interested in the above, so that I can write an algorithm to control the fan and heater. I am also potentially interested in sharing data that I collect on drying and relationships with different environmental variables, see below.

I have constructed a complex drying chamber, which measures all environmental variables inside and outside of the chamber (using a Raspberry Pi) and has a controllable fan and heater. I am also looking to upgrade with a weighing facility, so I can measure the temporal variation in temp, RH and weight and to relate these variables to drying times.

Any ideas/observations or recommended reading would be gratefully received.

Edit 9.8.21

Some photos of the drying chamber and the web dashboard I have created. All work in progress...ignore the data on the dashboard - i am exploring different configurations and fan speeds. I will also add the fan speed (RPM and frequency) and heater status to the dashboard. Note that there are some spare (intentional) relays, so i can add a second heater, UVC light etc... The box is completely yacht varnished so it can be hygienically cleaned after each use.

View inside the drying box

View of the electrics and electronics at the rear

BBox dashboard

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  • That sounds so cool! I would love to see a photo or two of the setup!
    – Stephie
    Aug 9 at 14:19
  • @Stephie just added in some photos and a bit more of an explanation of the box/drying chamber i have built. Aug 9 at 14:57
  • Excellent set up. While it isn't the same, you might want to check out Meathead Goldwyn's site for (american style) BBQ, particularly the science tab.
    – bob1
    Aug 9 at 21:30
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Humidity needs to be controlled to avoid mold growth. In the Highveldt where biltong originated from humidity was never much of a problem because of the arid, dry winters. You would be better served to control the humidity. Certain hams are dried for well over a year and dry in both winter and summer, but are hanged in areas where humidity is naturally low.

Meat drying is often done to cured meats. Not all cured meats are dried, but some are. Curing of meat dehydrates the meat to the point were spoilage bacteria cannot thrive. This is usually done with salt or sugar. This was traditionally done as a preservation technique, but these days it is done for taste. Charcuterie is the term in French for these meat crafts.

And just btw when you cure meat it stops being raw, cured meat may not be cooked, but it is not raw. You can have the wettest piece of biltong ever but if it is cured properly it is not raw.

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  • Thanks. If cured meat is not raw, what is the technical definition of raw and cured meat? At what point does raw meat become cured and no longer raw? Does this definition apply to raw & dried meat (biltong) or is the biochemical transition different? I was (incorrectly) under the impression that beef only transitioned from raw when it was dried. There is the issue for both curing and drying meat - about how deep this penetrates the substrate. In particular, for biltong, drying too quickly leads to case hardening, which I dislike and you end up with wet beef inside a very hard outer case. Aug 9 at 15:05
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    @CairanVanRooyen, the salts used in curing essentially denature and precipitate the proteins in a process known to biochemists as salting out
    – bob1
    Aug 9 at 21:32
  • Its interesting that the recipe i have developed over many years only contains a very small amount of salt. It is also very common to use vinegar in biltong making, which i have read was for controlling bacteria. Aug 10 at 7:16

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