The intestines are first separated from the adherent mesentery. The small intestine, which consists of various layers of tissue, is rolled by machine in order to empty it and to free it of fat and mucus. Then it is rinsed with water. Only the middle layer of tissue remains.
After the extensive cleaning, the natural casings must be quickly cooled down with ice or ice water. Then you put them in rich brine to effectively prevent the growth of unwanted bacteria.
In order to preserve the high quality of the freshly slaughtered natural casing, the following criteria must be observed in particular: full salt concentration, low temperature and low oxygen partial pressure on the product. Failure to observe even one of these factors causes a significant decrease in quality.
The intestines, which have been cleaned and soaked in brine, are packed in tight plastic containers. They are then cooled and transported to the sorting plants. There they are freed from the salt and brought to the slaughter-warm state with warm water.
Now the actual sorting and calibration begins. This is done traditionally by hand, because the evaluation and recording of the different quality features can only be done by the human eye in a single step. Attention must be paid to mechanical damage and quality defects.
For this purpose, small-calibre natural casings such as the narrow pig intestine and the Saitling of the sheep are filled with water and periodically extended under pressure. In the case of large-calibre natural casings such as pork ruffs, cow’s wreath intestines and appendix, this is done with air.
The division into different quality classes is subject to the following criteria: A casing of quality A must not contain any holes or weak points, for example in sheep. It is suitable for the finest fillings, such as frankfurter sausages. Quality B casings are of acceptable strength and quality. They are suitable for coarse fillings like those used in pork sausages. Then the intestines are measured and packaged.
The measurement method must be very precise, because the unit of measurement forms the basis for the sales price. Sheep intestines are trimmed in hanks (1 hank = 91.44 m = 100 yards). In the case of the wreath casing, the packaging units are bundles between 16 and 100 m, depending on the customer’s requirements.
The casings are prepared in 3 different ways for transport to the sausage manufacturers:
Salted dry: the excess liquid is removed to achieve a semi-dry state. This is necessary in order to survive long distances and / or different storage temperatures.
Ready to fill: the sheep casings are placed in a solution that keeps them swollen and supple. After a short rinse and soaking in warm water (up to max. + 40 ° C), these can be used for filling.
Tubed: Each string of the casing is pulled onto a tube and can thus be placed directly on the nozzle of the filling machine in one step.
Casings should be stored in a controlled cold environment. Extreme heat must be avoided at all costs. A neutral temperature of 4-10 ° C is ideal. The storage temperature should not fall below 0 ° C.