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Sausage casing - also known as "sausage skin" or simply "casing", its main purpose is to wrap the sausage stuffing. There are natural and artificial casings. Natural casings are made from the intestines or skin of animals; artificial casings, which began to appear in the early 20th century, are made of collagen and cellulose.
There are different types of natural casings, of which the 4 most common types are: cattle, pigs, lambs and sheep.
Natural casings are made from the submucosa of the small intestine of meat animals and are a natural collagen casing. In most Western European and Chinese dishes, they use pig casings, but sheep, cow, and even horse intestines are used elsewhere.
In the process of making natural casings, you repeatedly rinse, scrape, and wash the intestines with water and salt, either by hand or by machine. During processing, the outer layer of fat and inner mucous membrane are removed from the gut, and the casing is salted to reduce water activity (inhibits microbial growth) and preserve the casing.
Natural casings have been used for centuries to produce meat specialties such as sausages, hot dogs and more. Food safety regulations in some countries (US and EU) allow only natural casings, but most of which do not come from the intestines of organically raised animals. Because there is no slaughterhouse that only handles and processes the intestines of organic animals and sells their casings as certified organic casings. So all the big natural casing companies collect casings from all over the world and send them to their processing plants for grading and packaging.
The biggest difference between natural casings and collagen or cellulose casings is their irregularities, although high quality sheep and lamb casings are almost indistinguishable from collagen casings as they are all collagen and have no visible blemishes. The main difference is the way they are twisted and joined, which will affect the appearance of the final product, making it easily distinguishable from a collagen-casing-wrapped hot dog.
The size and purpose of natural casings is influenced by the animal they come from, with lamb casings being the narrowest, sheep casings next, pig casings and finally cattle casings. The diameter of lamb casing is 14-28mm, sheep casing is 16-32mm, pig casing is 28-58mm, and the size range of cattle casing is 43-65mm.
Basic processing starts at the slaughterhouse, where the intestines are removed from the animals and they are cleaned, including breaking down the lining of the intestines, often using machines to do this step. You can also use hand cleaning, which may be relatively clean, but will waste a lot of time.
Its cleaning process is very water-intensive, as the casings need to be rinsed vigorously with cold water to remove residual blood from the mucous membranes. If the initial cleaning is not done properly, it can cause the casing to stain and thus turn pink. After the washing process is completed, the casings are tied up in bundles, packed into plastic buckets, and filled with saturated brine for storage. These are sold to other companies that grade and package the natural casings into finished casings.
Sheep, lamb and pig casings are often 'tubed' for larger sausage makers, with each strand of casing packed in a plastic tube length so that the sausage makers can easily place the casings on the stuffing machine.
Of course they are also available in bulk in brine in 'vacuum packs', mainly the choice of small to medium sausage manufacturers as they need to use no more than 100 strands of casing per month. The advantage of vacuum packaging is that it is easy to use, and the length of the casing is shorter, which is very convenient for stuffing sausages by hand, and the shelf life is also longer. Only need to open the package at the time of use, so manufacturers don't have to worry about not being able to use the opened casing before the quality deteriorates.
Sheep casings and pig casings are also "packed in net bags". Mainly for medium to large sausage makers who don't want to pay extra for tube casings, which come in a variety of diameters and lengths over 2 metres.
Cattle casings are mainly salted and brine, and they are in sets. The length of beef round sausage and beef midgut is about 32 meters, while the length of beef plug cap is only about 1 meter.
From：https://www.sciencedirect.com/topics/food-science/sausage-casing
Hog casings are the most widely used and are the traditional choice for making various link sausages such as salami and kielbasa. This natural casing is also commonly used to make smoked Polish sausages, small diameter ring sausages and bratwursts.
From：https://www.sciencedirect.com/topics/food-science/sausage-casing
Sheep sausage casings are the softest natural casings available, so they produce sausages that don't have the "clicking" sound of pork casings when you chew on them. Because of its small diameter, sheep casings are ideal for making small sausages such as breakfast sausages and hot dogs. The most common types of sheep casings are lamb casings and sheep casings.
From：https://www.sciencedirect.com/topics/food-science/sausage-casing
Cattle casings are taken from different parts of the intestines of cattle, and can be divided into beef rounds, beef middle and beef bung caps, all of which are natural casings with large diameters.
Beef rounds is named for its characteristic round shape. Because they are extremely low in fat, they are perfect for fresh, cooked or smoked sausages and are generally used for ring sausages - such as ring bologna, Polish sausage, blood sausage, etc. In order to preserve these casings, the salt content is very high, so when processing, it is necessary to rinse the outer layer of salt with cold water, and then soak in warm water for a period of time. From the point of view of palatability, beef rounds may be the largest diameter casing that can be eaten, with a diameter ranging from 35-46mm.
Beef middle is a rectal casing that is heavy and has some fat in its lining. It is commonly used to make various dry and semi-dry sausages such as salami, liverwurst or summer sausage. It comes in diameters between 45-65mm and is sold by the root.
Beef bung caps are taken from the end of the large intestine. Its diameter is about 75-125mm. It is often used to make some cooked sausages, dry sausages and semi-dry sausages, and is usually sold by the root.
Artificial casings are made of collagen, cellulose, or plastic and are generally edible, but some are not.
Collagen casings were invented by scientists using cowhide or pigskin, which added a lot of chemicals - ammonium sulfate, ammonium hydroxide, etc. It is therefore usually softer than natural casings and not as rattling as natural casings. Since it cannot pass water or smoke like a natural sausage, the flavor of the sausage comes entirely from the seasoning that was previously put in. Most collagen casings are edible, except for a special form of thicker collagen casing, which is used to make salami and large-gauge sausages, where consumers typically peel the casing off the sausage.
It is cheaper to make and less labor intensive than natural casings, making it less expensive to use and easier to handle.
An innovative process creates 100% plant-based vegetarian casings that are vegan-friendly and ideal for halal or kosher production.
Casings made of cellulose and plastic will not be eaten when removed from food.
Cellulose, usually from cotton linters or wood pulp, is processed into viscose, which is then extruded into clear, tough casings, mainly used to make bratwurst and frankfurters.
Plastic casings are inedible. It can be flat or serrated in appearance. Because neither smoke nor water can pass through the casing, it is used to produce non-smoked products with higher expected yields. The inner surface of the casing can be compounded or coextruded with a polymer that has an affinity for meat proteins and thus allows the meat to stick to the film. Although there is some loss when the casing is stripped, it also has a higher overall yield due to better moisture control.
Plastic casings are usually made of polyamide, polypropylene or polyethylene. This polyamide casing is commonly used in the production of cooked sausages and hams such as luncheon meat and salami.
After knowing the different kinds of casings, you should have a clear idea of their characteristics, which will help you use them to make different kinds of sausages for all consumers.
