Biltong Case Hardening: What Is It & How To Fix It?

Biltong, the savoury dried meat delicacy, is delicious and seemingly straightforward. But as enthusiasts and your regular producers will tell you, it has its challenges. One such predicament people often encounter is “biltong case hardening.”

Biltong Case hardening occurs when the exterior of the biltong dries too quickly, causing the outer layer to harden while leaving the inside raw. The hardened shell creates a ‘case’, which prevents moisture from leaving the centre of the meat. This is an undesirable predicament as no matter how long you leave the biltong, the inside of the meat will not dry.

The preparation of biltong involves air drying, a process where moisture gradually moves outwards from the centre of the meat and is extracted through airflow (evaporating from the surface). In order for the moisture to be drawn out, the surface of the meat must remain permeable, allowing the liquid to escape. Otherwise, the moisture will be trapped inside.

The key to successfully drying biltong and preventing case hardening is ensuring the drying process is slow and gradual. The main culprit for causing this undesirable situation is too much airflow, followed by too much heat in your biltong box.

Let’s delve deeper into how you can prevent case hardening and troubleshoot so we can save your lovingly prepared biltong.

An ideal gradient of colour in ‘Dry’ biltong

Table of Contents

What Is Biltong Case Hardening?

If you are in the biltong or dry-curing world, you’ve most likely heard of ‘case hardening’ (it’s an unpleasant situation), but what is it exactly?

Biltong ‘Case-hardening’ means that the meat surface is dry and hard, but the inside is still moist or raw. The hardened surface or dried crust forms a ‘case’ which prevents the moisture from leaving the centre.

Case hardening prevents the typical colour gradation of dark brown to red/pink on the inside of the biltong. Typically Biltong with case hardening will have a defined dark ring on the outside and a very pink/red centre.

For biltong to dry correctly its outside needs to remain permeable for the inner moisture to evaporate and leave the meat. This drying process requires airflow to prevent mould formation, but not too much to cause the outer surface to dry rapidly. If the surface dries too quickly, the moisture will be sealed in, much like searing a steak.

What Causes Biltong Case Hardening?

Now if you potentially have a case of case hardening or are simply trying to avoid it at all costs, you need to know what causes it.

Biltong case hardening can be caused by several situations such as too much airflow, too much heat and the problem of cutting the meat too thickly.

Too much airflow is the most common culprit for causing case hardening. Too much airflow is undesirable because it dries the outside hastily, rather than slowly, trapping the moisture inside (as it has formed a hard sealed case). While airflow is essential for drying biltong (the moisture needs to leave the surface of the meat), too much air will keep this process from happening.

The next most common situation for case hardening is having too much heat around or in your biltong box. Biltong requires a moderately cool temperature of around 22-24 degrees Celsius (71-75 Fahrenheit). If biltong is dried at higher temps, it will begin to cook, (This is more a jerky-making thing) and will cause a very hard outer casing.

Cutting your biltong slices too thick (more than 3 cm wide) is another cause of case hardening. For thicker meat, the drying process takes much longer and often results in a well-dried outside and a raw centre. Leaving the meat longer can also result in the inside going bad before you get to eat it.

Does My Biltong Have Case Hardening?

So we know what Biltong case hardening is, it’s indeed undesirable, but how do you know if you have it? Or if your biltong is just how it’s supposed to be?

The most common situation indicating biltong case hardening is when the biltong doesn’t appear to be drying internally after several days. By cutting through a piece of your biltong you can view the interior and determine if case hardening is occurring. What you are ideally looking for is a gradation of colour from a dark exterior to a pinkish/red interior.

If it appears that you have a dark ring around the outside and no gradation of colour on the inside, you most likely have some amount of case hardening.

It is important to remember that Biltong should have some degree of outer hardening, this is a natural part of the slow drying process in a dry climate. This is unlike other charcuterie which are dried slowly in a humid climate where mould is actually beneficial and desired.

So let’s get into the troubleshooting so we can solve the mystery behind why your biltong has developed an undesirable outer casing.

Here the interior has remained raw after 4 days of drying

Trouble Shooting

Reduce Airflow

Airflow is the most important aspect of biltong drying, without good airflow, you will experience issues with humidity and mould growth. While airflow is crucial, it is equally detrimental to your biltong if you have too much air being extracted or blown directly on your meat.

Air should always be pulled out of your biltong box rather than the air blowing directly on the meat. In the same respect, air should not be extracted from the box too rapidly as it will draw in large volumes of air. Too much Airflow causes the outside of the biltong to dry too quickly creating a dried crust around the meat.

To ensure you have the right amount of airflow firstly consider having no fan but good ventilation in the sides and top of the drying box. If you don’t have a humid climate, it is usually efficient enough to allow your biltong to dry naturally. Also, remember not to overcrowd your drying space to ensure air can flow around your biltong.

Secondly, if you are using a fan, make sure it is extracting air from the top of your biltong box. If air is blowing into the biltong box it will simply dry the outside and not effectively draw moisture from the centre of the meat and away.

Here is a useful article I wrote on the topic that explains how biltong dries, All The Ways To Dry Biltong: Budget-Friendly To Lavish.

Lastly, make sure your fan is not pulling too much air. This can be the case if you have a powerful fan or you have it on a high speed. Small Low-wattage computer fans, or ones with variable speeds, are a cheap and effective option. You can easily place one in the top of your biltong box which will extract air perfectly. Remember to ensure the fan is placed so that air is flowing out, not in.

This is the fan I use in my DIY biltong box which I also wrote an article on why it’s worth it to make biltong at home.

Decrease Temperature

Too much heat in your biltong box will cause the outside of your meat to cook slightly, thus creating a cooked outside that prevents moisture from escaping. The most common reason for having too much heat is using a lightbulb in your biltong box.

Using a light bulb is usually not necessary if you don’t live in a humid or very cold climate. The first option to solve most issues is to add in an extractor fan. This article will explain more deeply if you want to know more about whether biltong needs heat to dry.

If you live in a very cold or humid climate a lightbulb may be beneficial, though it is crucial to always use a low-wattage bulb 40 watts. Avoid LED light bulbs and look for the old-school incandescent bulbs that you can find in your grocery or hardware stores.

If you live in a very hot but dry climate, like Australia, you may want to dry your biltong in a cool room with aircon and use an extractor fan to pull air over your meat.

Cut Meat 3cm Or Less

When you have very thick slices of biltong, the drying process needs to happen slowly over a longer period of time. If the meat is dried too quickly, the centre will remain raw and leave you with a hard crust and an inedible mess. But if the process takes too long you will have the chance of your meat going off or rancid before you get a chance to eat it.

For best practice it is best to keep the thickness of your meat within 1-3 cm, some long-time makers will go up to 4 cm. I have written an article on the ideal thickness to cut biltong here to help you.

Perfectly dried biltong – sliced 3 cm thickness

Can You Fix Biltong Case Hardening?

Biltong case hardening is undesirable but fortunately, it can often be rectified before it’s too late. Here are some tried and trusted methods to stop case hardening in its tracks.

Try It And See If You Like It

Firstly if you like wet biltong, case hardening may not be too much of an issue for you, cut open your biltong and give it a taste. Biltong is safe to eat even when very wet, as the vinegar and salt marination kill the harmful bacteria on the surface. But if you don’t like wet biltong, keep reading.

Slice Your Biltong and Leave In The Fridge

The quickest and simplest option is to slice up your biltong into bite-size pieces (how you usually slice your biltong when you want to eat it) and place them in a paper bag.

Keep the paper bag in the fridge for a few days and shake it around a couple of times a day. Shaking around is important to prevent mould formation (Here is an article on mould if you are curious).

This will continue to dry your biltong and should even out the colour gradient. Try the biltong after a couple of days to see if it is to the level of dryness that you like.

Vacuum Seal Your Biltong

Your next option is to vacuum seal your biltong in whole slabs and put them in the fridge for a few days to a week. By vacuum sealing the whole slabs, the moisture is locked in and will work through the hardened crust.

After a week, slice into one of your biltong slabs to see if the gradient has evened out. At this stage, your pieces will be tender all the way through, if you like you can slice up the biltong and leave it to dry in a paper bag for a couple of days (As per the step above).

Vacuum seal biltong food saver — Vacuum sealed biltong

Re-soak In Vinegar

If you have the time and would like to experiment with an uncommon technique, you can (I promise this works), soak your biltong and rehang it to dry again.

You will need to dilute some vinegar with equal parts vinegar to water ratio, then dip your entire slab of biltong into the vinegar mix. Leave this to soak for a couple of minutes, then vacuum seal it while it’s still wet.

After leaving it for a few hours in the fridge to rehydrate, remove the biltong from the bag and re-hang it to dry. You can pat the biltong dry with a paper towel and press on some more spices before hanging.

Hopefully, after these steps, your biltong will have a second chance at life and you can say good bye to any worrisome cases of case hardening. Remember, case hardening is not the end of the world and most often can be easily remedied.