Page 42 - FoodFocusThailand No.199 October 2022

SPECIAL FOCUS

Table 1. Factors affecting shelf-life of foods (Modified from Bell, 2001) (-2 to 5°C). At a storage temperature of around
Intrinsic factor Extrinsic factor -1°C, the expected storage lives of pork or chicken
(Product-related) Packaging Environment packed in VP and CO -MAP are ~4 and 9 weeks,
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respectively. While beef can last up to ~10 and 16
Temperature Insulation Temperature weeks. However, since this normally prevents
Opacity Light interaction between oxygen and myoglobin, raw
Water activity; a w Vapor barrier Relative humidity meat products usually display purple-red color
pH Gas barrier Air during storage.
Composition Headspace composition While increasing numbers of consumers have
Initial microflora Integrity Contaminants come to accept the purple-red color of meat packed
in VP and VSP, red meats are often re-packaged
Unlike many processed meat products where colors are produced for retail display in retail-ready packaging systems,
by nitrite cure or other food additives, the color of raw meats is determined i.e., aerobic packaging or high-oxygen MAP (HiO -
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by the oxidation state of muscle pigment, myoglobin. Myoglobin in its MAP) with 20-30% CO , 60-80% O , ≤20% N .
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oxygen-free form (Deoxymyoglobin) is purple red. Meat surface with Elevated carbon dioxide level inhibits the growth
oxygenated myoglobin (Oxymyoglobin) has appealing, bringing red of aerobic microorganisms, and high oxygen
color that the consumers prefer. Deoxymyoglobin or Oxymyoglobin content ensures that myoglobin at the meat surface
reaction is reversible and occurs in response to changes in oxygen is oxygenated. This technique can extend the
content surrounding the meat. product’s shelf-life to 5-10 days.
Shelf life is a function of product, packaging, and the surrounding Additionally, some retail-ready packs for red
environment (Table 1). Due to their high moisture, water activity, fat, and meats use a high-oxygen MAP system with
other nutrients, meat and poultry are extremely perishable. Typical ~25% CO or ~70% O or ≤20% N . Elevated
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deterioration modes of meat and poultry products include microbial carbon dioxide level inhibits the growth of aerobic
spoilage, oxidation (Pigment oxidation and rancidity), and desiccation microorganisms, and high oxygen content ensures
(Moisture loss), resulting in off-odors, slime formation, darkening of that myoglobin at the meat surface is oxygenated.
meat, and nutrient loss. The two-phase or double-phase packaging
system is designed to slow down deteriorative
Packaging system: changes of the product and to allow the meat to
The packaging system for perishable meat and poultry products can be bloom when displayed on a shelf by changing the
categorized into 3 groups, i.e., non-preservative-, preservative-, and gaseous environment surrounding the meat
two-phase packaging system. between the storage period and display phase.
Non-preservative- or aerobic packaging systems like cling film This can be achieved by gaseous exchange or by
overwrap (with or without tray) or loose-fitting, sealed plastic pouches removal of the outer preservative layer (typically
are designed to prevent contamination from the environment. Still, they called mother bag or master pack) or specific part
offer a minimal barrier to vapors and gasses. Thus, contact with oxygen of the packaging to allow air to replace carbon
allows meat to bloom (Deoxymyoglobin changes to oxymyoglobin) but dioxide, turning meat color from purple-red to bright
also accelerates fat oxidation and encourages the growth of aerobic red for retail display.
microorganisms. Typically, at display temperature (~4°C shelf-life of Note: Selection and maintaining distribution
meat and poultry packed in this type of packaging system is up to 5 and storage temperature are crucial in meeting the
days, depending on meat type, packaging used, and other storage product’s expected shelf-life. Increasing chilled
condition. storage temperature by 1°C can reduce the
A Preservative packaging system offers better protection to the product’s storage life by 10%, while rising
products. Packaging materials used are high-barrier polymers or temperature during retail display by 5°C can double
multi-layer materials with a metal layer, limiting transfers of vapors, the rate of color change in meat.
gasses, and odors. Packaging technologies applied include modified
atmosphere packaging (MAP), active packaging with an oxygen What’s NEW:
absorber or antimicrobial agent, vacuum packaging (VP), and vacuum Intelligent packaging: While the objective of
skin packaging (VSP). intelligent- or smart packaging is not to improve
The key is eliminating (or at least reducing) oxygen in the headspace the protection of the product but, rather, the
to minimize oxidation and slow down microbial spoilage. Suppose communication between packaging and its end
antimicrobial packaging (considered a subset of active packaging) is user(s), its applications relate to the product’s
used appropriately. quality and safety. There are 3 major indicators
VP and CO -MAP (with or without an oxygen removal system) are that are often incorporated into the packaging
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often used as a packaging system for meats during chilled storage system for meat and poultry products, such as

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