Introduction to Fresh Meat Packaging Solutions

一， Packaging of fresh meat

The quality of fresh meat generally refers to meat color, flavor, juiciness, tenderness, muscle tissue, etc., among which meat color is the simplest and most important indicator for judging quality.

Meat color is mainly based on the natural changes of three types of myoglobin in the atmosphere: myoglobin, oxymyoglobin and metmyoglobin. Under high oxygen partial pressure, oxygen permeates and surrounds myoglobin molecules, combines with iron ions in protohemoglobin to form oxymyoglobin, producing bright red meat color, while oxygen continues to combine and dissociate with protohemoglobin. Under lower oxygen partial pressure, myoglobin and oxymyoglobin turn into brown metmyoglobin.

Therefore, the packaging of fresh meat should choose packaging materials with good oxygen permeability, but this packaging material is only used for short-term storage of fresh meat, because fresh meat will turn brown if left in the atmosphere for too long, and it will also increase the growth of microorganisms and the oxidation and rancidity of fat. The following are some common ways to package fresh meat in actual production.

1. Trays

Most frozen meat sold in supermarkets is placed on polystyrene trays. The bottom of the tray is padded with absorbent paper to absorb the meat juice, making the meat extra bright red and stimulating consumers' desire to buy.

2. Transparent film

Common transparent film materials include the following:

(1) Cellophane, one side of which is coated with nitrocellulose. When this side is in contact with meat, it can absorb moisture from the surface of the meat and make it saturated, thereby promoting oxygen penetration to maintain excellent color and reduce weight loss. However, cellophane coated with nitrocellulose on both sides is not suitable.

(2) Polyethylene: PE for short, which can be divided into three types: low-density PE, medium-density PE and high-density PE. It has high permeability to oxygen, especially low-density PE. In addition, it is also resistant to acids and alkalis, oils and water vapor, and is very suitable for packaging fresh meat. The only disadvantage of this material is its poor tensile strength and abrasion resistance.

3. Vacuum packaging

Vacuum packaging refers to extracting all the air in the package and using packaging materials with extremely low oxygen permeability, so that external oxygen cannot penetrate into the package, reducing the rate of oxidation and rancidity of fresh meat to ensure the freshness of fresh meat. Vacuum-packed fresh meat can be stored for 14 to 20 days at 0±1℃. The shelf life of vacuum packaging itself is 5 to 7 days longer than that of pallet packaging, but after vacuum packaging, due to the blocking of oxygen, the meat will generally be dark red, which will damage the appearance. However, if the packaging is removed, the cooled meat will return to bright red when it encounters oxygen. Therefore, vacuum packaging is generally used in hotels and some large supermarkets that require a long storage time and high quality.

In addition to polyvinylidene chloride (PVDC) with good oxygen permeability and shrinkage, the materials used for vacuum packaging include polyester, polyamide; or nylon, polyester film and polyethylene multilayer materials. Among them, polyvinylidene chloride has the best oxygen and water vapor permeability among various film materials, but its biggest disadvantage is that it cannot resist heat sealing. Polyester has strong tensile strength and softness; nylon has a good oxygen permeability, good heat and cold resistance, and strong mechanical properties, but it has a high water vapor permeability and is expensive, so it is often used as a multi-layer composite material for fresh meat vacuum packaging.

4. Modified atmosphere packaging

Modified atmosphere packaging is also called inflation packaging. It is to remove the air from the packaging bag and then fill it with a certain proportion of nitrogen, carbon dioxide and oxygen to minimize the possibility of oxygen penetration, so as to inhibit the growth and reproduction of microorganisms and extend the shelf life of the product. The use of modified atmosphere packaging for cold fresh meat can also maintain the color of the meat. This packaging form is currently in the experimental research stage in my country.

5. Vacuum shrink packaging

Large pieces of meat can also be packaged in vacuum shrink packaging. The advantage of this packaging form is that it can effectively reduce the bag breakage rate and eliminate the juice leakage phenomenon of vacuum packaging. The vacuum shrink treatment not only inhibits the growth of aerobic bacteria on the surface of chilled meat, but also prevents secondary contamination of chilled meat, effectively extending the shelf life. Compared with modified atmosphere packaging, it is convenient to transport and has low packaging costs. Vacuum shrink packaging is widely used in developed countries in Europe and the United States, and is a packaging method worth learning from for chilled meat packaging in my country.


二. Packaging of frozen meat

In addition to preventing oxygen and water vapor from penetrating to avoid oxidation and rancidity of fat, packaging materials for frozen meat must also be able to adapt to rapid temperature changes and shrink or expand with freezing or thawing operations.

1. Aluminum foil

It can be combined with other materials to form a soft packaging material for packaging frozen food. It can also be processed into semi-rigid packaging containers of various shapes to package meat or ready-to-eat food. It has excellent water vapor permeability and gas permeability, but poor shrinkage and heat sealing properties.

2. Plastic film composite materials

Multi-layer composite packaging materials such as nylon and polyethylene, polyethylene and polyester film, low-density polyethylene, polyvinylidene chloride-coated polypropylene, etc. are often used to package hamburgers, steaks, etc., and then put into waxed cartons for frozen storage.

三. Packaging of processed meat products

In order to maintain the quality of processed meat products, the selection of packaging materials for meat products should take into account the characteristics of their production, processing, storage and consumption. There are many packaging materials for meat products, and commonly used packaging materials can be divided into natural casings, artificial casings and other packaging materials.

1. Natural casings

Natural casings are mainly made from the small intestines, large intestines, and bladders of pigs, cattle, and sheep. Pig casings and sheep casings are the most commonly used. The choice can be based on product quality and size characteristics. The processed natural casings are divided into salted and dried. Before using the salted casings, they should be rinsed repeatedly in clean water to fully wash away the salt and dirt on the surface of the casings; the dried casings should be soaked in warm water to soften them before use. The advantages of natural casings are good toughness and firmness, ability to withstand tension and heat treatment during processing, and the ability to shrink and expand. The disadvantages are uneven thickness, high cost, limited sources, and unsuitable for large-scale automated production.

2. Artificial casings

Artificial casings include collagen casings, cellulose casings, and plastic casings. The advantages of artificial casings are uniform specifications, easy processing, and suitable for large-scale production. At the same time, they can preserve the flavor of the product, extend the shelf life, and reduce dry consumption. At present, artificial casings have been widely used worldwide. In addition to the import of some artificial casings, my country has begun to mass-produce artificial collagen casings and plastic casings.

(I) Collagen casings

Made from animal glue, it has the characteristics of good air permeability, smokeability, uniform specifications, hygiene, stronger than natural casings, and mass production. Collagen casings can be divided into edible and inedible types. Edible ones are suitable for making smoked and boiled sausage products, while inedible ones are mainly used for air-dried sausages.

(II) Cellulose casings

Cellulose casings are seamless tubular films made of short cotton wool and pulp as raw materials. They have toughness, shrinkage and colorability, uniform specifications, hygiene, air permeability, smokeability, and surface printing. This type of casing with a small diameter is mainly used for smoking and roasting sausages without casings and small sausages. After smoking and boiling, it is cooled by cold water spraying, and the casing is removed and sold after secondary packaging; large-diameter cellulose casings can be used to produce and process smoked ham. After smoking and cooling, the casing does not need to be removed and can be directly secondary packaged.

(III) Plastic casings

Plastic casings are single-layer or multi-layer composite cylindrical or sheet casings made of polyethylene, polypropylene, polyvinylidene chloride, polyester plastic, polyamide, etc. It is characterized by being tasteless and odorless, having very high oxygen and water barrier properties, having certain heat shrinkage, being able to meet different thermal processing requirements, having good mechanical filling properties, and being safe and hygienic. This type of casing is widely used in the packaging of high-temperature steamed ham sausages and low-temperature ham products.

Other packaging materials

(i) Aluminum foil is suitable for high-temperature sterilization packaging of traditional meat products and has a long shelf life.

(ii) Shrink bags use multi-layer composite materials with relatively high oxygen and water barrier properties, heat sealing, shrinkage and printing properties. They are vacuum packaged to increase the shelf life of the product. They are used for secondary packaging of low-temperature meat products.

(iii) Stretch film packaging materials have the following characteristics: high tensile strength, high longitudinal and transverse elongation, good puncture resistance and tear resistance, strong fastening, and high degree of mechanization of stretch film, which is particularly suitable for secondary packaging of meat products. The packaged products are beautiful and elegant, safe and hygienic in circulation, and have been widely used in Western countries. In recent years, they have also been widely used in the world's largest meat product companies.