The Steps in Preparation of Casings

THE STEPS IN PREPARATION OF CASINGS

  • The essential steps in prepartion of casings are associated with the removal of the intestinal tract at the slaughtering plant are pulling, running, chilling, stripping, fat removal, fermenting, turning sliming, measuring and inspection.
  • Removal
    • The intestinal tract should be removed carefully to avoid damage due to cuts.
    • A ligature is made to check the escape of contents.
  • Pulling
    • Pulling is a term applied to the process of separating the mesentery and fat from the sheep and goats or pigs intestinal tract and dividing into parts, which require different treatment.
    • It is done by hand without using any instruments as intestines from these animals being very thin and fragile or easily removed.
  • Running
    • Running is the same process (of pulling) but, performed with a knife, which cuts the intestines from the mesenteries and fat.
    • The operator holds the knife vertically in his right hand pulls the intestines with his left hand so that, the sharp edges of the knife cuts off the fat and mesentery from the intestines itself.
    • Running is done only on cattle intestine, which are much thicker and stronger.
  • Chilling
    • Whenever it is impossible to process casings at once the intestine should be chilled (10oC) to as low temperature as possible to reduce changes due to bacterial fermentation process.
    • There are certain merits by chilling.
    • Chilling is essential were casings are not manufactured at the abattoir but are purchased as green intestines and removed elsewhere for processing.
    • Chilling is desirable as a routine after casings are finished and ready for inspection, grading, salting and curing so that, all bacterial or fermentation process are arrested and any excess of made visible and Chilling greatly facilitates further handling.
  • Stripping
    • The intestinal contents are stripped from the intestines either by hand or by machine under a spray of water, which washes away the contents as they are expressed.
    • The water spray also serves to clean the casing.
  • Flushing
    • Flushing is done by forcing tap water is through the gut in order to remove the remaining intestinal contents.
    • All the operations up to this stage can be undertaken in the slaughterhouse itself.
  • Fat removal or fatting
    • There are varying amounts of fat associated with the mesentery and its attachment to the gut depending upon the nutritional status as well as the species of the animals.
    • Removal of the fat is usually by a manual knife operation and it is also termed running.
    • The fat must be removed as completely as possible because fatty residues left on the casing will become rancid after a time and render them unfit for human use.
    • Greatest care should be taken that the casings should not be damaged during this operation.
    • Sheep and hog small intestines, which are called as runners, are generally removed from the fat by hand pulling as opposed to using a knife.
  • Fermenting
    • In this process, the intestines are immersed in warm water, where enzymatic and bacterial action will loosen the different layers so that the undesirable parts can be removed easily.
    • This is done only with sheep, goat or pig intestines, which have a very thin muscular layer, which cannot otherwise be removed by knife.
    • Cattle intestine having stronger muscular layer can be cleaned without fermenting.
    • Fermentation time depends on weather; sheep, goat and hog casings are ready after one or two days.
    • The ideal temperature for fermentation is 21°C (70°F).
    • Temperature much higher than this may lead to “blown casings” due to over fermentation, which is easily toned and have objectionable odour where temperatures are below 21°C (70°F), the water should be warmed.
    • Soda has been claimed to accelerate fermentation in these conditions.
  • Turning
    • It means turning the casings inside out, generally applied to beef casings only.
    • Sheep goat, and pig casings being thin can be cleaned adequately during the process of stripping and sliming, without turning.
    • While beef casings and hog bung having a hard muscular tissue must first be turned before efficient sliming can take place.
    • Turning is done in a tank of warm water.
  • Sliming
    • Sliming is the removal of the mucosa and the technique used depends on the size and origin of the casing.
    • Small hog and sheep runners are first crushed between rollers and then are passed between successive rollers or strippers, which remove not only the mucosa, but also the smooth muscle layers and the serosa associated with the mucosa, leaving only the submucosa.
    • A sliming stick or plastic knife or shell or wooden knife can also do the process of sliming.
    • The knife is placed at an angle of about 30o with mild scrapping movements.
    • If the casings are dipped in a sliming solution consisting of 0.2% sodium pyrophosphate and 1% sodium chloride for 10-15 minutes the process becomes easier.
    • The final cleaned casings are white and nearly transparent.
  • Measuring
    • The width is measured by letting the inflated (cattle) or water filled (sheep and goat) casings rest against the walls of a calibrated casing gauge, which is divided into compartments of different widths.
    • The length is measured in hank.
  • Inspection and grading
    • Casings are inspected for cleanliness, odor, colour, parasites, blood spots, ulcers, holes, scores and generally speaking or any defects which would either prevent the casing from being used as an imperforated container or make it objectionable to the consumer.
    • Then the casings are graded in their respective calibrations.
  • Salting and curing (Preservation)
    • After inspection and measuring, casings are ready for salting and curing.
    • Clean fresh salt of medium fineness should be used for this operation, which is carried out by merely embedding the coiled casings in salt where they are turned several times and then rubbed evenly by hand.
    • Rock salt or coarse, crystalline salt should never be used in salting, as it would damage the whole of the casing, even to such an extent as to perforate it in many places.
    • During the process of curing, the casings will loose moisture, thus absorbing salt and improving in keeping quality.
    • During the initial stages of curing, substantial amount of brine is formed.
    • For this reason, curing is done in curing bins, which has a slatted bottom for easy drainage.
    • Containers such as barrels or boxes preferably of hard wood should be used with recommended insecticide for dried cattle casings.
    • They should be leak-proof, so that brine, which may have accumulated, is kept inside the container.
    • For wet salted sheep casings metal tins, which are completely lined from inside with food grade polyethylene are used for storage and transport.
  • Resalting
    • Properly prepared casings, well packed and kept under refrigerated conditions will not deteriorate quickly.
    • However, casings stored under tropical conditions or in transit from small producers to the main exporters, often undergo deteriorative changes.
    • Sometimes, they become too dry, but often too much of moisture is absorbed and they start to decompose.
    • To prevent deterioration, such consignments must be treated periodically.
    • If they are too dry, sprinkling with a little brine is often sufficient.
    • It is preferable, however, to take out the casings, check each bundle and soak them for a brief period in strong brine, then hang to drain, re-salt and replace in the barrel. 
Last modified: Thursday, 16 September 2010, 10:20 AM