A. Textiles
Textile containers have poor gas and moisture barrier properties and have a poorer appearance than plastics. Woven jute sacks, which are chemically treated to prevent rotting and to reduce their flammability, are non-slip, have a high tear resistance, and good durability. They are used to transport a wide variety of bulk foods including grain, flour, sugar and salt
B. Cotton
Calico is usually a closely woven, strong, plain, cotton fabric which is inexpensive and is satisfactory as a wrapper for flour, grains, legumes, coffee beans and powdered or granulated sugar. It can be re-used as many times as the material withstands washing and is easily marked to indicate the contents of the bag.
C. Sisal
Sisal is a fibre that comes from the agave family of plants. Sisal is resistant to salt water and therefore makes an ideal natural material from which to make rope. The nets in which hard fruits are transported are often hand-made from vegetable fibre.
D. Wood
Wooden shipping containers have traditionally been used for a wide range of solid and liquid foods including fruits, vegetables, tea and beer. Wood offers good mechanical protection, good stacking characteristics and a high weight-to-strength ratio.
E. Metal
Metal cans have a number of advantages over other types of container: they provide total protection of the contents, they are convenient for ambient storage and presentation and they are tamperproof. However, they are heavier than other materials, except glass.
F. Glass
Glass containers have the following advantages:
• they are impervious to moisture, gases, odours and micro-organisms
• they are inert and do not react with or migrate into food products
• they are suitable for heat processing when hermetically sealed
• they are re-useable and recyclable
• they are resealable
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• they are transparent to display the contents
• they are rigid, to allow stacking without container damage.
However, they possess some disadvantages which include:
• higher weight which incurs higher transport costs than other types of packaging
• lower resistance than other materials to fractures, scratches and thermal shock
• more variable dimensions than metal or plastic containers
• potentially serious hazards from glass splinters or fragments in foods . G. Casings
Casings have been utilized in the production of sausage and processed meat products. Casings are referred to as the oldest form of packaging materials for sausage. They determine the final size and shape of the sausage product and serve as processing molds and containers during handling and shipping, and as merchandising units for display (INSCA, 2011).
Casings are made of two basic materials, cellulose or collagen. Five specific casings are generally used in the production of sausage products. These include animal, regenerated collagen, cellulose, fibrous and plastic casings.
(i) Natural Casings
Natural casings come from the gastro-intestinal tract (intestine) of animals such as cattle, hogs, and sheep. Natural casings are made from the sub-mucosa, a largely collagen layer of the
intestine, having removed the fat and the inner mucosa lining. It has the advantages of traditional appearance, traditional texture and cooking performance that is expected of sausage. Its
disadvantages include decreased machinability, reduced uniform weight or length and cost (Wenther, 2011).
(ii) Beef Casings
The three most used beef casings are: beef bung caps, beef rounds, and beef middles. The beef casings come in a variety of sizes depending on which type is used (e.g. bung caps, rounds or middles). Beef bung caps are used for large diameter sausage such as bologna and salami, beef rounds have the characteristic ring or round shape that are used in the production of ring bologna and polish sausage while beef middles can be sewn so that the final product will have a uniform diameter and uniform length. Beef bladders can also be used in the production of large diameter
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sausages such as specialty sausage (souse or head cheese) and these are the largest diameter of casings from cattle and are oval in shape.
(iii) Hog Casings
Hog casings are used for smaller diameter (30-44 mm) sausages. These casings can be used for fresh sausage as well as fully cooked smoked sausage. After cleaning, hog casings are measured /sized to ensure a more uniform/size and shape to achieve uniform portion control of the final product. They are transparent and consumer can see the particle definition of the meat and the ingredients used in the sausage.
(iv) Sheep Casings
Sheep casings are the smallest (16-28 mm) of the natural casings that are commercially available. They are the most tender and the most adaptable to fresh pork sausage, which are sold fresh. These casings can also be used in the production of high quality frankfurters.
(v) Regenerated Collagen Casings
Regenerated collagen casings have many of the physical properties of animal casings. Collagen casings are being used to simulate natural casings. Collagen casings are essentially produced from the same material "chemically" and this material being collagen. The collagen originates from the corium layer of the hide of beef animals.
The corium is extracted with alkaline solution to remove the soluble components and washed with potable water. The collagen is then swollen with acid to give a viscous mass of acid collagen that is pushed through an annular die to form a tube. The tube is fixed by moving it through an alkaline bath, and the neutralized collagen returns to its original state. The tube is dried and cut to size. The casings can be shirred into sticks for faster production.
The advantages of utilizing collagen casings relate to the availability of these casings in a variety of sizes (INSCA, 2011). The collagen casings work well when machine-handled because they can produce uniform diameters to reduce the "give-away" of sausage, which in turn affects final profit. Collagen casings are edible which means that the sausage do not need to be peeled after thermal processing.
(vi) Cellulose Casings
Cellulose casings include those made from cotton bags and those derived from processed cotton linters. The cloth bags give a high degree of uniformity to the encased sausage product. Cotton
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linters are a fine fuzz-like material that is removed from cottonseed after the cotton fiber and seed have been separated at the cotton gin.
Cellulose casings are permeable to smoke, which gives the final product good consumer eye appeal. The casings are also permeable to moisture to some extent. Cellulose casings are impermeable to organic molecules such as meat emulsion (INSCA, 2011; Wenther, 2011).
Cellulose casings come in a variety of sizes, but are generally divided into two categories - small diameter and large diameter.
(vii) Fibrous Casings
Fibrous casings, also known as large diameter cellulose casings, are made by impregnating a strong paper like material with cellulose. Fibrous casings have good machinability and uniformity which adapts well to high speed operations. Fibrous casings are manufactured in such a manner that they adhere to the sausage surface, which is important in the production of dry and semi-dry sausage. There are a variety of fibrous casing sizes which give processed meat processors a great number of choices to fit market preferences.
(viii) Plastic Casings
In some processed meat applications, a moisture impermeable casing is best suited. The recognized product made using plastic casings is braunschweiger. The impermeable material used to produce plastic casings is PVDC.
Any casing which is impermeable to moisture is also impermeable to smoke. Therefore, any smoke flavoring must be incorporated directly into the product during manufacturing. Plastic casing can also be produced in a variety of sizes and colors to increase the visual appeal to the consumers (INSCA, 2011; Wenther, 2011).
H. Plastics
The range of plastics and co-polymers used to make rigid plastic food containers is wide. For most small food processors the choice will be restricted to packaging made of polypropylene, polythene and polyvinylchloride (PVC). However, polyethylene tetraphthalate (PET) is rapidly becoming more common. For the food processor, plastic containers have the great advantages of:
low cost, lightness, resistance to impact damage, availability both in clear and colored types.
None the less, plastic containers give less protection than colored glass against light and air. In addition, they are not as strong, in terms of weight bearing and crushing, as glass and are easily
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punctured by sharp objects. In general, they cannot be easily re-used or re-cycled. Example commonly found is Polyethylene.
Polyethylene is divided into high density and low density polyethylene. The difference is that high density polyethylene is stronger, thicker, less flexible and more brittle than low-density polyethylene and has lower permeability to gases and moisture. Polyethylene has a high tear strength, penetration resistance and seal strength. They are waterproof and chemically resistant.
I. Polyamide
Polyamide is a clear glossy film with a low strength and is susceptible to puncture. It has moderate permeability to moisture, gases and odours (Wenther, 2011).