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Week: 12
Modified atmosphere packaging
(MAP) and vacuum packaging (VP)
to seafood safety
Definitions and Terminology
Modified Atmosphere Packaging (MAP)
“ It is a form of packaging involving the removal of air from the pack and
the replacement with single gas or mixture of gases” (Parry, 1993).
Vacuum Packaging (VP)
VP is also a type of MAP system because air is evacuated from a pack and
not replaced and then the package sealed
Modified atmosphere packaging components
for seafood
Fish
Gas mixtures
Gas/fish ratios
Packaging materials
Modified atmosphere packaging components
for seafood
Fish
• biological structure
• chemical composition
• extremely perishable and generally spoil
faster
Gas mixtures
• carbon dioxide (CO2), oxygen (O2) and nitrogen (N2)
• for white fish and shellfish 40/30/30:CO2/N2/O2
• for fatty and smoked fish 60/40: CO2/N2
Modified atmosphere packaging components
for seafood
Gas/fish ratios
• gas/products ratio 2:1 to 5:1 for MA packed fish while the CO2
concentration 20% and 100%
• recommended product ratio 3:1 with a minimum concentration of
20% CO2
Packaging materials
• good visual display, low water vapour transmission, high gas barrier
• mechanical strength to withstand machine handling and
subsequent storage
• polyvinyl chloride (PVC), polyethylene terephthalate (PET),
• polypropylene (PP) and polyethylene (PE)
• tray with an impermeable film
Gases used in modified atmosphere packaging
Oxygen (O2)
• stimulates the growth of aerobic bacteria and inhibits the growth
of the strictly anaerobic bacteria
• presence of oxygen can cause oxidative rancidity in fatty fish
• low levels might induce browning reactions
• low level oxygen inhibit the growth of pathogenic anaerobic bacteria
such as C. botulinum, Clostridium perfringens
Carbon dioxide (CO2)
• not inert and can bring about chemical changes in the microbial
cell and its environment
• highly soluble in both water and lipids
• 25% CO2 is recommended to control bacterial and mould growth
• most effective in reducing the growth of aerobic and
Gram-negative psychrotrophic bacteria
• negative effects of CO2 on the colour of fish, the texture of fish
and drip loss
• high concentrations of CO2 cause excessive drip, metallic and sour
off-odors and off-flavors
Gases used in modified atmosphere packaging
Nitrogen (N2)
• an inert and tasteless gas with a low solubility in both water and lipid
• delaying oxidative rancidity and inhibiting the growth of aerobic
microorganisms
• filler gas to prevent pack collapse due to its low solubility
Carbon monoxide (CO)
• highly toxic gas and is not approved by the regulatory authorities
• heath hazard for packaging machine operatives as well
The other gases
Potential gases: chlorine, ethylene oxide, nitrogen dioxide, ozone
and sulphur dioxide
•unlikely to meet regulatory authorities approval due to safety concerns
Noble gases: xenon, argon and helium
•permitted as food grade gases by EC legislation
Effect of oxygen on seafood
Oxygen (O2)
Oxidation
Darkening Discoloration Loss of
aroma
Reduced freshness
Loss of organoleptic
qualities
Development of aerobic
microorganism
Appearance
Unpleasant Bacterial
flavor
degradation of mould
Reduced nutritional
value
Products becomes
unfit for consumption
with passage of time
Oxygen requirement of some common food microorganisms
Aerobes- require atmospheric oxygen for growth
Spoilage organism
Pseudomonas species
Acinetobacter / Moraxella
Micrococcus
Pathogens
Bacillus cereus, Yersinia enterolitica
Vibrio parahaemolyticus
Microaerophiles- require low levels of oxygen
Spoilage organism
Lactobacillus
Pathogens
Camplylobacter jejuni
Listeria monocytogens
Facultative organism - grow in presence or absence
of oxygen
Spoilage organism
Brocothrix thermosphacta
Shewanella putrifaciens
Bacillus species, Enterobacteriaceae
Pathogens
Salmonella, Staphylococcus
Anaerobes- inhibited / killed by oxygen
Pathogens
Clostridium perfringens
Clostridium botulinum
(Parry,1993)
Effects of MAP on some common microorganisms
Pathogenic microorganism Spoilage microorganism
Clostridium botulinum
Lactobacillus species
Listeria monocytogenes
Pseudomonas
Salmonella
Acinetobacter / Moraxella
Staphylococcus aureus
Yersinia enterolitica
Aeromonas hydrophila
Campylobacter jejuni
Escherichia coli
Vibrio parahaemolyticus
Effects of MAP on Clostridium botulinum
Clostridium botulinum
• the single most important concern for MAP
• potential for the outgrowth and toxin production
• non-proteolytic, psychrotrophic (grow at a low as 3.3oC)
• grow and produce toxin without producing over sign of spoilage
Recommendation for controlling the growth of Clostridium botulinum
(Betts, 1995)
•
•
•
•
•
a heat treatment of 90oC for 10 min or equivalent
a pH value of 5 or less
a minimum salt level of 3.5% NaCl in the aqueous phase
an water activity of 0.97 or less throughout all parts of food
a combination of heat and preservative factor or components
Potassium sorbate, sodium chloride, nisin and irradiation in combination
with MAP are shown to be effective
Bacteriological changes
Total viable count (cfu/ml)
12
Log 10 (cfu/g)
10
8
6
4
2
4ºC
VP
MAP
0
0
2
4
6
8
10
12
14
16
Storage time (days)
Figure 1 Total viable counts (cfu/ml) in sardine stored in air, in VP and in MAP at 4oC.
(Ozogul et al, 2004)
Potential problems of MAP and VP
Pack collapse
Pack collapse occurs
• CO2 permeates through packing films up to 30 times faster than N2
• fat and water-soluble
• solubility increases when temperature decreases
To minimise pack collapse
• reducing CO2 content,
• increasing the product to gas ratio,
• injecting gas with a slight overpressure,
• pre-treating products with CO2 saturated water or bicarbonate
solutions
• pack in air
Increased exudates/drip loss
• Fish loses about 1-3 % drip during normal storage
• Drip levels up to 14 % have been found for prawns
• decrease in water holding capacity of proteins due to a decrease in
pH
Potential problems of MAP and VP
Discoloration
• the precipitation of sarcoplasmic proteins at low pH
• fading and browning have been attributed to packing in 100 % CO2
TMA production
• TMA is produced only in fish in which contain adequate amounts of
TMAO
• TMA production has been shown to be inhibited by MAP
• released when the consumer opens the pack
Histamine production
• produced by microbial decarboxylation of histidine
• numerous different bacterial species to possess histidine
decarboxylase activity
• Vibrio, Proteus, Morganella morganii, Klebsiella pneumoniae,
Hafnia alvei, etc.
• FDA legal limit: 5mg/100g fish (1996)
• EEC limit for histamine:10mg/100g fish (1991)
TMA production
TMA content in herring (mg/100g)
TMA content in sardine (mg/100g)
30
NO ICE
ICE
MAP
VP
Concentration (mg/100g)
Concentration (mg/100g)
35
30
25
20
15
10
5
4ºC
MAP
VP
25
20
15
10
5
0
0
0
2
4
6
8
10
12
14
16
0
2
4
6
8
10
12
14
16
Storage time (days)
Storage time (days)
Figure 4 TMA content of herring stored in ice,
in VP and in MAP at 4oC
(Ozogul et al, 2002)
Figure 5 TMA content of sardines stored in
air, in VP and in MAP at 4oC
(Ozogul et al, 2004)
Histamine production
Histamine content in herring
NO ICE
ICE
MAP
VP
40
30
20
10
Concentration (mg/100g)
25
50
Concentration (mg/100g)
Histamine content in sardine
4ºC
MAP
VP
20
15
10
5
0
0
0
2
4
6
8 10 12 14 16
Storage time (days)
Figure 2 Histamine content of herring
stored in ice, in VP and in MAP at 4oC
(Ozogul et al, 2002)
0
2
4
6
8 10 12 14 16
Storage time (days)
Figure 3 Histamine content of sardines
stored in air, in VP and in MAP at 4oC
(Ozogul et al, 2004)
ATP and breakdown products
Concentration of ATP and related
compounds (mmoles/g)
Nucleotide degradation in sardine in MAP Nucleotide degradation in sardine at 4oC
5
5
IMP
ATP
ADP
AMP
Hx
INO
4
3
4
3
2
2
1
1
0
0
0
2
4
6
8
10
Storage time (days)
12
14
IMP
ATP
ADP
AMP
Hx
INO
16
0
2
4
6
8
10
12
14
16
Storage time (days)
(Ozogul et al, 2004)
Advantages and disadvantages of MAP
Advantages of MAP
• Increased shelf life of products
• High quality products and reduced economic loss
• Products can be distributed longer distances, resulting in a decrease in
distribution cost
• Clear view of products
• Hygienic stackable pack, sealed and free from product drip
Disadvantages of MAP
• Visible added cost, for example; cost of gases and packing materials
• Temperature control required
• Specialized training and equipment are necessary
• Different gas formulation required for each product type
• Potential growth of food-borne pathogens such as C. botulinum
• Benefits of MAP are lost once the pack is opened
Conclusions
Storage of fish under modified atmosphere conditions;
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•
•
•
decrease the production of ATP and its degradation products,
inhibit bacterial growth,
reduce the formation biogenic amine (histamine, cadaverine etc.),
decrease the concentrations of TMA and TVB-N,
extend sensory rejection,
prolong self-life and maintained quality
In general, depending on raw materials, temperature, gas mixtures and
packaging materials, the percentage of increase in shelf life in MAP
ranges from 0% to 280% compared with aerobic storage
Addopt from:
Dr. Fatih ÖZOĞUL
Çukurova University, Faculty of Fisheries