The importance of multi-layer co-extruded heat-shrinkable casings on sausage packaging was reviewed. The performance of high-quality casings was evaluated and the application was discussed.
With the development of plastics and its superior performance, the application fields of plastic packaging materials are more and more extensive. As a very important member of the packaging material family, plastic film is getting more and more attention from the food packaging industry.
In recent years, with the continuous development of multi-layer coextrusion technology, multi-layer co-extruded composite film is widely used in food and meat for its excellent barrier properties, chemical resistance, high temperature and low temperature resistance and mechanical properties. In the field of seafood, grain and chemical products, multi-layer co-extruded heat-shrinkable casings are applied to the packaging of low-temperature enema products requiring pasteurization due to their unique processing technology and excellent packaging effect.

As a package of low-temperature enema products, multi-layer co-extruded shrinking casing plays a very important role in the production, sales, circulation and storage of filling products.

(1) It must protect the sausage from microbial, chemical, and physical contamination.

(2) Maintain the physical state required for the sausage.

(3) Can tell the purchaser which ingredients are included in the sausage.

(4) It is the advertising medium of the product, and advises customers to buy your product instead of buying a competitor's product.

In view of the above effects, high quality casings should meet the following requirements for sausages:

(1) good oxygen, water vapor and aroma barrier properties;

(2) Good physical and mechanical properties to meet the requirements of the enema process;

(3) Good meat stickiness prevents water and gravy from spilling out of the meat;

(4) Safe and reliable food hygiene;

(5) The retort resistance meets the requirements of the sausage sterilization process;

(6) The brightness of the surface of the casing and the printing effect;

(7) Good specifications performance and price ratio.

As the outer packaging of sausage, the basic function of the casing is to ensure that the sausage does not deteriorate under certain conditions and time to meet the needs of storage and circulation. This function is provided by the barrier properties of the casing, namely: oxygen barrier, moisture barrier, aroma barrier.

The oxidative deterioration of sausages and the loss of nutritional value are caused by the following reasons;

(1) Oxygen enters the inside of the sausage, causing oxidative browning of the sausage. This change is made from the outside to the inside. First, the outer sausage is lightened from pink, whitened, and then gradually turned taupe. Cut the sausage horizontally to see an oxidized ring. The longer the time, the deeper the oxidized ring.

(2) Meat spoilage caused by bacterial reproduction. Under the protective effect of the casing, the bacteria outside the sausage will not enter the inside of the sausage. The bacteria referred to herein refers to the bacteria in the raw meat of the sausage, which cannot be completely killed by the pasteurization treatment at 80-90 ° C after the filling. This sterilization process can only kill most of the pathogenic bacteria, and cannot kill the heat-resistant Bacillus. This part of the bacteria breeds slowly at 0-4 ° C, but if the casing is not well oxidized or prolonged over time, it will spoil the sausage. Thus losing the value of food.

(3) The loss of moisture in the sausage makes the sausage lose its elasticity, the freshness of the sausage is lowered, and the taste is deteriorated, which requires the casing to have very good water resistance.

(4) The smell of the sausage is lost, the aroma of the sausage is lost, and the casing is required to have a very good gas barrier property.

According to foreign research, combined with our actual work experience, it is shown that the pasteurization sausage is packed in multi-layer co-extruded nylon casing. The actual oxygen transmission rate of the casing is less than 40ml/m2, atm, 24h, 23°C, 65%. RH. Thus, the sausage has a shelf life of three months at 0-4 ° C storage conditions. The actual oxygen transmission rate mentioned here refers not only to the data measured before the casing is used, but also to the indicators achieved after the sterilization of the casing. Because nylon resin is a moisture-absorbing material, its oxygen transmission rate varies greatly with temperature and humidity. If the structure of the casing is unreasonable, it may reach less than 40ml/m2, atm, 24h, 23°C, and 65% RH before use, and the gas barrier property after enema declines, which will greatly exceed this index. For the water vapor transmission rate index, it is less than 5g/m2, atm, 24h, 23°C, and 90% RH. In this way, the sausage will not lose too much water during the shelf life of the sausage to ensure its good elasticity and taste. The aroma retention has a lot to do with the choice of casing materials, because the aroma of different materials is very different, because the aroma is different from oxygen. It can be seen that the excellent oxygen, water vapor and aroma barrier properties are very important for sausage packaging, which is the characteristic of high quality casing.

In the determination of the thickness of the casing film, there is still no unified understanding in China. Referring to the foreign large-scale casing processing manufacturers and our own test situation, 50um is a reasonable thickness design in the case of reasonable structure and scientific selection. At this thickness, the barrier properties, mechanical strength, and cost performance of the casing can reach an excellent combination. Too thin a thickness has a certain impact on performance. Too thick will increase the cost of the customer. For example, for a transparent casing with a diameter of 90 mm, if it is designed to a thickness of 50 um, a 1 kg casing can produce 110 m. If it is designed according to the thickness of 60 um, 1 Kilograms of casing can only produce 96m, the difference between the two is 14m. Approximately 12% difference, in other words, a 12% loss in packaging costs. From an economic point of view, it is not economical for the user to analyze the latter.

For the shrinkage rate of the casing, the bigger the better, the foreign generally is 16-17%, then for the user, as long as the equipment allows, choose the casing with a smaller shrinkage as much as possible. Because of the same volume of sausage, the amount of casing used will increase for casings with a higher shrinkage ratio than for casings with a small shrinkage. This is a waste of customer costs.

It is also important that the use and storage methods of the casing are proper for the action of the casing. The storage environment of the casing is generally required to be stored in a dry, ventilated, dark place below 25 °C. How to use it according to the method recommended by the casing factory. Improper use can have a negative impact on the quality of the sausage. 1 The casing is bruised before use or during use. In severe cases, the casing may burst during the enema or during the sterilization process. The lighter may cause the barrier structure to be degraded during the storage or sale of the sausage. Oxidative deterioration or bacteria entering the inside of the sausage causes the sausage to become corrupt and lose its edible value. 2 The storage of the casing under high temperature and humidity conditions will cause the sausage to deform, reduce the shrinkage rate, and change the specifications. 3 Long-term storage of casings, due to incomplete storage conditions, will deform the casing and cause losses. The general recommended shelf life is 3 months.

The evaluation of the quality of the casing is a systematic project. The following "fourteen quality evaluations" can be reasonably used as the basis for the evaluation of poor quality.

1. Barrier of casing: refers to the degree of barrier to oxygen, water vapor and aroma. Good barrier properties can provide sausages with a longer shelf life and shelf life, avoiding the return of sausages due to deterioration during the shelf life, and ensuring that the freshness and aroma of the sausages are not lost.

2, the rationality of the structure of the casing: the reasonable structural design of the casing can provide an ideal packaging for sausages.

3. Intestinal film strength: Good mechanical strength can meet the requirements of various filling and punching machines, thus reducing the loss of casing film during use.

4, stability of shrinkage: refers to the same volume or the same batch of casing shrinkage consistency is good, if the shrinkage rate of the upper and lower floating will cause the same size of sausage length, uneven thickness, will give you boxing and sales Come a lot of trouble.

5, color uniformity: For the color of the casing, the uniform color can give the sausage the appearance quality to glory, so that its appearance is beautiful, can attract the attention of consumers.

6, the opening of the casing: the opening is good for the filling of sausage is very important. If the opening is not good, the casing casing and filling are more difficult, which will directly affect the working efficiency of the operator.

7. Specification accuracy: The deviation of the diameter and thickness of the casing should be controlled within a strict range. If the specification is not allowed, the thickness of the sausage will be uneven. If the thickness deviation is too large, the sausage will be bent and the performance will be degraded. The phenomenon.

8. Transhesive film transparency: For transparent casing film, good transparency is very important for high quality sausages. It enables consumers to clearly see the meat texture of sausages, attract consumers' desire to buy and enhance consumption. The first impression of the product.

9, soft touch: good hand feel will be easy to use, sausage meat after filling is strong, for mold ham, softer casing can make its shape angular and smooth. On the contrary, the edges are hard and easy to make the product effluent.

10, the brightness of the casing film: make the sausage on the shelf is very bright, dazzling, very easy to attract customers.

11. Meat viscosity of the casing film:

(1) refers to the meat viscosity of the casing film, which can reduce the moisture in the sausage and prevent the sausage from getting worse.

(2) refers to the degree of adhesion between the layers of the casing film, so that the casing structure is stable and the performance is stable.

12, the adhesion between the layers: refers to the degree of adhesion between the layers of the casing film, so that the casing structure is stable, stable performance.

13, film roll flatness: reflects the thickness of the casing film uniformity, but can give a comprehensive evaluation of the product.

14, packaging sealing: refers to the outer packaging of the casing should be tightly sealed on the one hand, to prevent the casing from moisture absorption; the box is strong and reliable, to prevent the casing from being destroyed, so that the casing is under good protection.

The casing is probably the last step in the processing of sausages for the processing of sausages, but ignoring its importance may cause a lot of trouble. Then in the choice of casings must be considered comprehensively, on the one hand choose high-quality casings with good value for money, on the other hand, choose casings to be in line with the requirements of the sausages you produce. At the same time, we must pay attention to the use of methods, so that the casings play their due role and bring you considerable economic benefits.