Why is my casing tough, hard or chewy? That is a question that is impossible to answer with any certainty, as each situation can be different and in fact there are many reasons. Below is a compilation of some of the reasons and causes that I gathered from my personal experience, from talking to seasoned sausage makers and from the Polish forum of Wedliny Domowe. Feel free to comment and add to the list. My list concerns itself with standard salted hog casings, but we can also discuss other natural casings here is well
1. To begin with, the casings should be properly prepared. Most manufacturers instructions will advise you to soak the casings for one hour, flush and soak for one more hour. But soaking longer and changing the water more often will never hurt. The key here is not only to re-hydrate the salt preserved intestine, but also to get rid of the salt. So just to make sure that this is accomplished, soak the casing for a couple of hours, flush out the inside, change the water over several hours, and change the water a couple of times more before stuffing. Best is to plan ahead and start soaking in the fridge a couple of days in advance.
2. Hobbyists/amateurs tend to smoke theirs sausages longer than do the commercial processors. The long smoking phase will result in a dryer sausage and a tough casing. Next time you are smoking weigh a few sausages before and after smoking, and you will discover that you can have a weight loss of as much as 10%. Electric smokers are particularly notorious for this. Placing a pan of water in the smoker can help, but also try shortening the smoking time. Once the sausage has achieved good colour, turn up the heat and bring it up to the necessary IT. If you like the flavour of a heavily smoked sausage and will be smoking it heavily for a long time, don't expect the casing to be soft. Instead use a collagen casing and peel before consumption.
3. Poaching the sausage after it has picked up colour will almost always result in a softer casing. But if you keep it in the smoker for an extended period of time, poaching will not help.
4. After stuffing the sausage needs to set. This is usually accomplished at room temp for 1-3 hours, or several hours in a refrigerated environment. Here we have to be careful so that the casings do not dry out too much. They should be dry to the touch but still moist and flexible. If the casing dries to the consistency of paper, the casing will be tough. Hanging in a frost free fridge with air blowing over the sausages is also not recommended.
5. When stuffing, the farce should be packed in firmly with as little air as possible. Loosely stuffed sausage with air between the casing and meat will cause a dry casing. On the other hand, if the sausage is stuffed too tightly, the casing will be stretched out to its maximum and may also become tough.
6. Start smoking with at a lower temp, 52-55C. Once the sausage starts taking on colour increase the temp to 60C. A hot smoker will quickly dry and shrink the natural casing.
7. If cooling with water, after smoking or poaching do not chill thoroughly. There still needs to be some warmth inside the sausage to dry the exterior. There are also claims that ice cold water should not be used but rather room temp water.
8. The addition of a large amount of binders such as soy protein powder, or non fat milk powder (non-instant) may cause excessive adherence of the meat to the casing which will harden when heated, giving the illusion that the casing is tough, when in fact a dry ring is formed on the meat inside. My dad, a Polish trained butcher, claims that it is also more difficult or even impossible, to peel off the casing a sausage with binder will also be harder .
9. And of course one of the main causes of a tough casing is the casing itself. Larger diameter casings and especially those from older pigs will be naturally tough. Casings not prepared properly by the processor may also be faulty and therefore hard. And we have come to terms that natural hog casings are just that, and no two are alike.