LPT 321: Meat Science (1+1)

PACKAGING OF MEAT AND MEAT PRODUCTS

Packaging materials used for fresh meat

• Trays-made of polystyrene
• Transparent films-cellophane, LDPE (most commonly used for fresh meat ), PVC
• Shrink films-PVC, cellophane, rubber hydrochloride, polypropylene, irradiated PE and PVDC are used in shrink wrapping of meat.

Advanced and emerging systems of packaging of meat and meat products

Vacuum packaging

• It is the placing of 'primal or sub primal cuts of meat into plastic bags or pouches and extracting air from them by means of a nozzle type vacuumizing machine or a vacuumizing chamber.
• The bags are then sealed to effect closure with either metal clips or heat- impulse sealing of the sides of the bags.
• The most commonly used film for fresh meat vacuum packages is PVDC.

Modified atmosphere packaging

• It is a technology where in foods are packaged in high barrier packages in which air has been replaced with an artificial (modified) atmosphere.
• Commonly used gases are oxygen, carbon dioxide and nitrogen.
• For red meats, high-oxygen MAP systems utilize atmospheres containing approximately 20% to 30% carbon dioxide, 60% to 80% oxygen, and up to 20% nitrogen. The elevated oxygen concentration enhances the bright red meat color and the elevated carbon dioxide concentration inhibits the growth of aerobic spoilage microorganisms. High oxygen concentrations in display packs enhance meat color by increasing the thickness of the oxymyoglobin surface layer. At the same time the metmyoglobin layer lies deeper in the meat.
• The time taken for that layer to reach the surface is increased, so display life is extended. Unlike overwrapped trays, high oxygen display packs use a film with high gas barrier properties, to prevent the gases equilibrating with the ambient atmosphere. The modified atmosphere display packs consist of deep high barrier trays that are gas flushed before an upper high barrier film or lid is sealed in place. However, the pack atmosphere tends to change during display because the oxygen is lost to respiration and carbon dioxide is highly soluble in meat.
• The absorption of carbon dioxide can lead to pack collapse. The pack atmosphere remains reasonably stable and the pack shape is maintained when the ratio of pack volume to meat volume exceeds approximately 3 to 1. The use of high oxygen with high carbon dioxide effectively doubles the color stability and time to spoilage over that achieved using ambient atmosphere overwrapped packs
• High-oxygen MAP, which provides a chilled product life of only 5 to 10 days, is not suitable for prolonged storage of meat. Its suitability for display packaging is determined as much by commercial merchandising strategies as by the preservative capability of the packaging.
• The excessive space occupied by deep tray packs, compared to net weight of meat sold, tends to restrict MAP packaging to high value products catering to the upper end of the market. As discussed previously, the rate of discoloration is inversely related to temperature, so the importance of display cabinet temperature management cannot be overemphasised.

Mother bag concept in MAP

• These are the simplest two-phase packaging systems, consisting of retail-ready packs inside an outer preservative pack. The retail-ready packs may be overwrapped trays or lidded packs. In both cases, retail films must be highly gas permeable, first, to allow the meat contact with the carbon dioxide preservative atmosphere and later, on removal from the mother pack, to allow atmospheric oxygen to bloom the meat.
• While a simple outer bag could be used to contain the carbon dioxide atmosphere, the inner packs would be free to move within the pack. Such movement could damage both inner and outer packs. Consequently, most proprietary mother pack systems employ a semi-rigid outer container to protect and restrain the inner packs.