Further processing of meat

CASINGS

Casings are special cylindrical containers used to protect sausages and various meat products. Since sausages are comminuted products they must be placed in some type of forming device to give them shape, to hold them together during further processing and for protection. Casings may be natural or artificial.

Natural casings

These are derived almost exclusively from the gastro-intestinal tracts of swine, cattle, sheep, goats and horses. Hog casings are prepared from stomach, small intestine (smalls), large intestine (middles) and terminal end (colon) of the large intestine (bung). Beef casings may be from the oesophagus (weasands), small intestine (rounds), large intestine (middles), bung and bladder (Fig. 172). The intestines of sheep and goats are used to produce casings primarily for fresh sausages, frankfurters, hot dogs etc. Natural casings can be classified as narrow, medium and wide.

172. Natural casings: oesophagus (1), small (2) and large (3) intestine, bung (4), caecum (5), bladder (6) of pig; small (7), and large (8) beef intestine	173. Treatment of pork small intestines (calibration)

TABLE 13
Different diameters of small intestines

Treatment and storage. Intestines intended for use as casings for sausages must be immediately processed after evisceration. First they are emptied and well flushed. Pig, sheep and goat small intestines are scraped thoroughly without inversion to remove the exterior (serous) and interior parts (mucous membrane), preserving the middle elastic muscle (Fig. 173). The same method is applied to the large intestines of all animals.

Well-scraped, flushed and drained intestines are well sprinkled with common salt (dry salting) or saturated salt solution (wet salting), spun and tied into intestine completes. They are arranged into plastic casks. The top of the intestines is pressed down and salted again in order to eliminate air contact. These casks must be firmly closed and stored in a dark cooler. If intestines are prepared for long storage (more than three months), they must be salted with a mixture of salt and 0.2 percent antioxidant.

Large intestines and bladders can be preserved by means of air-drying. In this case, after scraping, flushing and a short draining intestines are blown up in order to eliminate the remaining water and tied at both ends in hanks, for quicker air-drying. They should be hung in a sunny, draughty place. When well dried they are sorted according to diameter and packed. Such dry casings do not require storage in a cooler.

Application. All salted natural casings should be thoroughly flushed inside with running water the morning before use. They are then dipped into warm water to regenerate their elasticity (small intestines 10–20 minutes and large intestines 30–60 minutes) and drained for a short time before use.

Artificial casings

The advantages of these are uniform cylindrical shape, a range of specific diameters, suitable tensile strength, resistance to damage, ease of use, variety of sizes and low microbial level. They can be filled uniformly and linked either by hand or machine into regular lengths.

Four types of artificial casings are available (Fig. 174):

Cellulose casings are prepared from cotton linters in sizes ranging from 1.5 to 15 cm. They are easy to handle and fill, possess a high degree of resistance and are permeable to smoke when moist. The degree of permeability decreases as the casing dries during processing. Small cellulose casings are used for skinless frankfurters or wieners, skinless smoked link sausages and many other small sausage products (cocktail sausages). Small cellulose casings are also available in shirred form.

Large cellulose casings are available in three types: regular, highstretched and large. They are used in making all types of sausages and smoked meat. Cellulose casings are inedible and must be removed before consumption.

Inedible and edible collagen casings are regenerated from collagen extracted from skins and hides. The inedible collagen casings combine some of the advantages of both natural and artificial casings, especially their strength, uniformity and shrink characteristics. They must be removed prior to consumption. Edible collagen casings are mostly used for fresh pork sausages and frankfurters.

174. Different artificial casings prepared in shirred (above) and flat form (below) for sausage manufacturing

Synthetic casings and bags are impermeable to smoke and moisture. They are used with unsmoked products such as liver sausages or products which are heat-processed in water or a retort.

Tying of casings

Artificial casings are delivered either tied at one end with loops prepared in the factory or in hanks. As casings in hanks can be easily stored and their length and the method of tying can be chosen at will, they are well suited to small-scale production. One end of the casing is submerged in cold water (one to two minutes), then tied either in a “doll” or “bow” knot (Figs 175 and 176). To make a “doll” knot, place a string on the casing and twist around, slip the thumb and forefinger on the string 1 cm toward the end of the casing, pass the string through the bight and set the knot, tighten the string, and prepare the loop and tighten with a double knot.

When tying a “bow” knot, casings need not be submerged except the end of every dry casing. The method is to place string on casing and tighten by means of a simple knot, fan-shape casing end with knot in the middle, and tie knot underneath the wing (the tied casing has no loop). This method of tying prevents slipping off.

175. Manually tied casings in strings (left); first step of manual tying (right)	176. Manual tying of casings, with loop (left), and string of tied casings