Production
The main steps of the production process for natural casings are as follows:
- cleaning;
- fat removal;
- turning;
- mucous removal / rinsing;
- sorting by calibre;
- measurement;
- rolling on tube or funnel (if required);
- salting or drying;
- packaging.
Hog casings
The intestine is cut away from the caul and processed in the cleaning machine. All tissue layers are removed from hog casings in the slaughterhouse. Only the layer of connective tissue, the sub-mucosa, remains.
The cleaning machine has various rollers that press out the contents of the intestine and the mucous membrane. The machine uses lukewarm water to keep the casings supple and easier to process.
Hog casings ultimately consist of a network of collagen and elastic fibres and blood vessels of various sizes. The average thickness of flushed hog casing is 0.32 mm.
The product removed from the casing is used by the pharmaceutical industry as a raw material for medicines.
Sheep casings
The process for sheep casings is slightly different from that for hog casings.
Before flushing, sheep casings are soaked in water. The average thickness of sheep casings is 0.11 mm.
Beef casings
Beef casings consist of smooth muscle cells, sub-mucosa and serosa, and are usually somewhat thicker than hog casings. They contain more fat than hog casings during the cleaning process, the small intestine is turned inside out.
Other processes
After the casings have been cleaned, the salting process begins. There are two methods for this, using brine or dry salt only. Depending on the product, fine, medium or rough food grade salt is added.
Salt is first rubbed into the casings, and they are then left to drain for a night.
If dry salt is used, they are then shaken out and new salt is added.
With the brine method, the casings are packed in brine immediately. The salt content of the brine must be higher than 20° Beaume.
After the casings have been cleaned, they are sorted by calibre and measured.
The length is measured either by machine or manually, when the casings are wet. The casings are then divided into quality categories and immediately afterwards, are salted again and packed.
The different types of packaging are:
ready for stuffing, on plastic tubes or funnels;- in hanks or bundles;
- dry salted in tubs or barrels;
in plastic bags in brine.
Processing in sausage plant
Casings in salt and brine are first rinsed with clean tap water to remove the salt.
They are soaked in water at about 21°C for at least an hour. Some types of casings need to be soaked for longer in order to soften them. Overnight soaking is then an efficient solution.
Excessive temperatures damage the casings. Immediately after soaking, the casings are stuffed (the stuffing machine should be positioned close to the soaking bath). If casings are left for any length of time without salt, this will have microbiological consequences. Pre-soaked natural casings should not be left to stand, but should be used the same day.
