Packaging of fresh and processed meat

BY NIKHIL KULKARNI

SHRIRAJ THATTEHARAN GP

Purpose of packaging

• The basic purpose : protect meat and its derivatives from undesirable impacts

• It protects during processing, storage and distribution from:

1. contamination by dirt (by contact with surfaces and hands)

2. contamination by micro-organisms (bacteria, molds, yeasts)

3. contamination by parasites (mainly insects)

4. contamination by toxic substances (chemicals)

5. influences affecting color, smell and taste (off-odour, light, oxygen)

6. loss or uptake of moisture (evaporation or water absorption)

requirements for packaging

The basic structure :

• Contains inner package (which is in direct contact with the product)• In some cases outer package is also present (cardboard box, metal containers etc.) • For inner packaging many types of synthetic films are available.• Packaging films must be/have:

Flexible Mechanical strength Light weight Odorless Hygienic (clean and toxicologically harmless) Easy recycling Resistance to hot and cold temperatures Resistance to oil and fats Good barrier properties against gases and light Sealing capability Low-cost

Barrier against gases

Good barrier properties against oxygen and evaporation/moisture is important.

Exclusion of oxygen:

Oxygen causes rancidity/oxidation of meat that results in off-flavor/color(red meat to grey or green)

Prevention can be taken by vacuum packaging and by using oxygen-impermeable/oxygen-proof films. e.g. polyvinylidenchloride (PVDC), polyester (PETP), polyamide (PA) and cellulose film (ZG) are almost non-permeable to oxygen.

An exception is the ready-to-sell meat portions in self-service outlets. Here oxygen-permeable foils produces a desirable bright red meat color. e.g. polyvinylchloride (PVC), polyethylene (PE) or polypropylene (PP) have a relatively high oxygen permeability.

Prevention of evaporation of product moisture:

Fresh meat or fresh sausages, cooked ham have a relatively high moisture content

suffer weight and quality losses by evaporation and drying during storage if unpacked

packaging material must therefore be sufficiently water/vapor-proof

Barrier against light

• Prolonged light exposure causes off-color, rancidity/oxidation

• Transparent packaging films allow attractive product presentation as the packaged product is visible.

• Such films provide no protection against light impact. And those products are sufficiently protected when stored in the dark

• Colored or opaque packaging films can be used for light sensitive product. e.g. Films laminated with aluminium foil

Opaque and printed films as light barrier Aluminium foil bag

Sealing capability

• Thermoplastic properties are important as for sealing capability.

• Seal Making : Two of the films, put closely in contact to each other under slight pressure and with simultaneous high temperature application, will melt or seal together along the heated area.

• The packaging material must be sustainable to such temperature and pressure

Sterilization or Pressure Canning

Meat must be processed in a pressure canner for the full time specified to destroy food-poisoning bacteria such as C.botulinum spores that might be present.To destroy C.Botulinum spores, low-acid foods , must be processed at temperatures higher than the boiling point of water. This can only be achieved by surrounding the jars of food with pure steam under pressure, using a steam pressure canner with atleast 15-20 liters capacity.

Pressure Canner

A pressure canner has a dial gauge or weighed gauge. Pressure is created as water boils and is converted to steam in a closed vessel. Pressure : 10 psi Temperature: 115.5 degree Celsius

Packaging Methods

Meat can be packed either hot or raw. The hot pack method is recommended for most meats, as it consistently yeilds a safe, high quality product. The raw pack method is an option for only larger pieces of meat.To pack hot, prepare broth and cook meat to 66 degree celcius. Pack hot into clean, hot canning jars, and cover with boiling broth leaving proper headspace.To pack raw, place larger pieces of meat loosely into jars, leaving proper headspace. No liquid is added, since juices form during processing.

Containers for heat-preserved food must be hermetically sealed and airtight to avoid recontamination from environmental microflora. Most of the thermally preserved products are in metal containers (cans). Others are packed in glass jars or plastic or aluminum/plastic laminated pouches. Most metal containers are cans or “tins” produced from tinplate. They are usually cylindrical. However, other shapes such as rectangular or pear-shaped cans also exist.

Tinplate consists of steel plate which is electrolytically coated with tin on both sides. The steel body is usually 0.22 to 0.28mm in thickness. The tin layer is very thin (from 0.38 to 3.08 µm). In addition, the interior of the cans is lined with asynthetic compound to prevent any chemical reaction of the tinplate with the enclosed food.

Tin cans consist of two or three elements. In the case of three-piece steel cans, they are composed of the body and two ends (bottom and lid). The body is made of a thin steel strip, the smaller ends of which are soldered together to a cylindrical shape. Modern cans are induction-soldered and the soldering area is covered inside with a side-strip coating for protection and coverage of the seam. The use of lead soldered food cans was stopped decades ago. Hence the risk of poisonous lead entering canned food no longer exists.

Two-piece steel cans have a lid similar to the three-piece cans but the bottom and body consist of one piece, which is moulded from a circular flat piece of metal into a cup. These cup-shaped parts may be shallow-drawn (with short side wall) or deep-drawn (with longer side walls) (Fig. 369, 371). However, the length of the side walls is limited through the low moulding ability of steel (example: tuna tins 42/85mm, i.e. side wall: diameter =1:2)Aluminium is frequently used for smaller and easy-to-open cans,. Aluminium cans are usually deep-drawn two-piece cans, i.e. the body and the bottom end are formed out of one piece and only the top end is seamed on after the filling operation. The advantages of aluminium cans compared to tin cans are their better deep-drawing capability, low weight, resistance to corrosion, good thermal conductivity and easy recycability. They are less rigid but more expensive than steel plate cans.

Synthetic materials used for meat packaging

Polyethylene (PE) (oxygen + , water vapour -)

Polypropylene (PP) (oxygen + , water vapour -)

Polyvinylchloride (PVC) (soft) (oxygen + , water vapour -)

Polyester (PET) (oxygen ± , water vapour -)

Polyamide (PA) (oxygen - , water vapour +)

+ = relatively permeable

- = relatively impermeable

For the various purposes in the meat industry packaging films can be divided into•Single-layer films or•Multi-layer films

Single-layer filmsOne common use of single-layer films (Fig. 338, 339) is the wrapping of meat pieces, processed meat products, bone-in or boneless meat cuts or even entire carcasses. These films are usually self-adhesive, i.e. they cling together -“cling film”- in the overlapping areas. Hence they provide good protection from external contamination and to some extend from evaporation, but no protection from oxygen, as they are not hermetically closed or sealed packages. Foils with good self-adhesive properties are PE, PA, PVC and PP.

Multi-layer filmsPractically all the other films used for meat packaging are designed as strong oxygen and water-vapour barriers. In order to fully achieve these requirements, films with good barrier properties for oxygen and water vapour respectively are combined.

Layer A: Outside layer (mechanically strong, gas barrier to oxygen)Layer B: Middle layer (barrier to oxygen)Layer C: Inside layer = sealant layer (capable of being melted and welded under pressure to the sealant layer of the opposite sheet of the bag/pouch, serves also as barrier to water vapour)

Vacuum bags, used for vacuum packaging machines (Fig. 343, 344, 350) are composed of two or more sheets of multi-layer films. By drawing the vacuum and sealing of such bags, the air is excluded from the package and the damaging effects of oxygen such as rancidity or discoloration of the packed products will be significantly slowed down or not develop at all. However, exposure to strong light may cause discoloration even under vacuum.

Sausage slices placed in vacuum bag prior to sealing

Faulty sealing seam: risk of air penetrating inside the package because of film overlapping

Vacuum packed beef cuts / rump, tenderloin, roast beef,

The latest development in this sector is the “form-shrink” packaging technology. Products e.g. meat cuts, chicken carcasses, entire sausages, smaller portions of meat products, are placed between two shrinkable films, which are moulded without wrinkles around the goods. Sealing seams can be kept extremely small. This technology is very cost-effective in terms of usage of packaging films but requires high-tech equipment and is only of relevance for large-scale industries.

A packaging method commonly used in larger meat industries is skin packaging. For this method the products are placed in the packaging machine, usually on a rigid film, which serves as the bottom layer of the final package. Another flexible film (top layer, which is heated for increased flexibility) drapes itself from above around the product, resembling a tight “skin” on the product surface avoiding wrinkles and purges. The skin-like coverage of the product takes place in a sealing station in the packaging machine, where the top and bottom film are sealed around the edges. Individual packages are separated by cutting around the bottom seal perimeter (Fig. 353, 354).

Manual vacuum packaging machine – Phases of operation