Best Sausage Casings
Casings are crucial components for successfully manufacturing fresh and processed sausages. Not only do they hold a meat batter or mixture together while simultaneously forming the final product; they also come in a variety that makes a wide assortment of products possible.
The casings commonly used today fall under the general classification of natural and artificial casings, the latter which comprise regenerated collagen, cellulose (skinless), fibrous and cloth or plastic.
Natural casings have changed very little since their early development while others have been spectacularly improved thanks to better raw materials, improved casing manufacturing procedures or the advent of new casing technologies such as pre-coating/pre-treatments.
Natural casings are more expensive than many other casing types, but then, their association with premium products is well known.
Natural casings are derived from the gastrointestinal tract of meat animals such as sheep, pigs and cattle, with sheep casings being the smallest (16 mm to 28 mm), most tender and best used for dried fresh sausage (dry wors) and small-diameter smoked and cooked sausage.
Hog casings are somewhat larger (30 mm to 42 mm) and less tender, whereas beef casings are the largest (35 mm to 125 mm), toughest and best suited for larger-diameter products in which more strength is needed. Large-diameter casings are sometimes tied with string loops or netting to provide the added strength needed to allow hanging stuffed product in a smokehouse.
Natural casings, which require proper processing treatments for tenderness and permeability, are essentially all collagen because the inner mucosa and outer fat/muscle layer of unprocessed casings are removed, leaving the middle collagen layer to be used as a casing.
Manufactured or regenerated collagen is animal collagen –from beef or hog hides, and the bones and tendons – that is first solubilised. It is then re-formed into a uniform collagen tube of various sizes. These casings also need proper processing treatments for tenderness and permeability, but have an advantage over natural casings in terms of greater uniformity and consistency.
Collagen casings are also not susceptible to potential microbial loads and the occasional rancid surface fat residues that sometimes occur with natural casings. Collagen casings are permeable to smoke and moisture, are less expensive to use, give better weight and size control, and are easier to run when compared to natural casings.
What’s more, they can be designed for specific product applications such as cooked, dry or semi-dry products, and a special form of thicker collagen casing used for salami and large-calibre sausages where the consumer peels off the casing before eating the sausage.
As the sausage is stuffed through a stuffing horn, collagen may also be co-extruded on the surface of a sausage mixture. Subsequent treatment hardens the coating around the sausage to form a casing very similar to manufactured collagen casings.
A major advantage of this approach is that the process of formulation, blending, mixing and stuffing becomes a continuous, inline process. This approach also minimises human contact with product to smooth the progress of improved sanitary control.
One form of cellulose casings that is widely used is the small-diameter, peelable casing, for example, those used for skinless frankfurters. These casings are precisely sized and highly uniform to facilitate use of high-speed stuffing and linking equipment. During ensuing smoking and cooking of the product, a meat protein “skin” is formed that permits removal of the casing and production of “skinless” sausage.
The protein surface skin formation is a critical step and some form of acid, either in natural smoke or liquid smoke form, must be applied. It is also important that these casings are stuffed to their recommended diameter because overstuffing can result in poor peelability. Casing moisture is also important to facilitating peelability, and a final cooking step with steam or high humidity may be helpful.
Another form of cellulose casing for large-diameter products is the fibrous casing, which consists of cellulose with paper fibres that increase the strength of the casing. As with cellulose, fibrous casings are very uniform and compatible with high-speed machine stuffing. These casings are typically soaked in water prior to use to improve flexibility and provide a small degree of expansion during stuffing.
Some specialised applications for fibrous casings include the use of an internal coating that adheres to dry and semi-dry products as they dry. However, if the product is to be sliced, such as pepperoni, a peelable fibrous casing is preferable.
Fibrous casings are also available with tiny holes in the surface or larger holes in the end, which are added to allow air to escape during stuffing. These fibrous casings are designed for use with chunked or whole muscle products such as sectioned and formed hams or boneless hams.
Moisture-impermeable casings are made from materials such as polyethylene, nylon and several others, which are used to manufacture a moisture-proof casing that is frequently used for water-cooked or steam-cooked products.
These casings are typically impermeable to both moisture and smoke, so smoke flavouring such as liquid smoke must be incorporated with the meat mixture.
Advantages include minimal cooking shrink for the product and a finished product that is thoroughly protected from external contamination as long as the casing is intact.
Cellulose and regenerated collagen technologies were developed in late 1920s. But although casings have been utilised in the meat industry for decades, the practice of pre-treating casings with a coating containing ingredients such as flavourings and colourings or antimicrobial ingredients is a technology with widespread application occurring in the last 30 years only.
Pre-coating or treating is technology in which a manufactured casing is treated, adjusted or even newly developed to result in a characteristic or benefit which can lead to improvements in performance or functionally.
These casings can offer a number of advantages to processors including increased product throughput, improved finished product quality and uniformity, expansion of an existing product line, and even improved shelf-life and food safety.
Pre-coating or treating applies to the casing type being coated or treated (i.e. collagen, fibrous, cloth), casing configuration (i.e. tubed, flat stock) and the specific ingredient or substance added to the casing, as an array of different ingredients can be impregnated or coated in or on the casings themselves.
Natural smoke condensate, also known as liquid smoke, impregnation is one of the most common types of casing treatment, but other ingredients such as flavourings and spices are also readily used in casing treatments.
Today’s high demands for ham manufacturing processes make smoke condensates one of the most useful applications for pre-coated or treated casings. By saturating the manufactured fibrous casing with a liquid solution of smoke condensate, the length of thermal processing time can be significantly reduced while improved external colour and flavour uniformity can be achieved.
A pre-treated casing, having a uniform concentration of smoke condensate applied throughout the casing, helps result in less smoke-related variation and problems due to smokehouse or operator inconsistencies.
Depending on the specific application (cured, uncured, whole muscle, chopped, minced) and the desired final appearance, a variety of smoke condensates can be used. However, special consideration must be taken during thermal processing to ensure optimum application parameters are met, similar to those required for drenching, showering or atomising smoke condensate applications.
Multi-layer casings composed of fibrous material laminated with moisture impermeable plastic such as nylon or polyethylene offer the ability to combine the benefits of a smoke-infused fibrous material with a moisture impermeable environment.
Further, the moisture-resistant casings create a cook-in-bag product environment, which offers significant improvements for food safety as well as shelf life, as the product is not exposed to a post-processing environment. A variety of flavouring applications can also be included in casing treatments. Flavours ranging from oil-fried to a vast number of herbs and aromatics can be added via coating or impregnating, which makes possible an immediate product line expansion.
Spices coated on the inside of cloth, fibrous or plastic casings in a number of mixtures, seasoning profiles and grind sizes offer a exclusive and striking product appearance with new and unique flavour profiles.
Adhered to the casing walls by starch or sugar molecules, spice particles are released and transferred to the product surface upon moisture absorption and heating during thermal processing, which dissolves and breaks the particle-to-casing bond.