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 andthe 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

Packaging materials

Fish

Gas mixtures

Gas/fish ratios

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

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

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

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 microbialcell 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 Development of aerobicmicroorganism

Darkening Loss of aroma

Discoloration

Reduced freshness

Loss of organoleptic qualities

Unpleasantflavor

Appearance of mould

Bacterial degradation

Products becomes unfit for consumption with passage of time

Reduced nutritional value

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 spoilageRecommendation 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

Figure 1 Total viable counts (cfu/ml) in sardine stored in air, in VP and in MAP at 4oC.

Total viable count (cfu/ml)

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14 16Storage time (days)

Lo

g 1

0 (c

fu/g

)

4ºC VP MAP

(Ozogul et al, 2004)

Potential problems of MAP and VP

Pack collapsePack 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

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 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

TMA production

TMA content in herring (mg/100g)

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16

Storage time (days)

Con

cent

ratio

n (m

g/10

0g)

NO ICE ICE MAP VP

TMA content in sardine (mg/100g)

0

5

10

15

20

25

30

0 2 4 6 8 10 12 14 16

Storage time (days)

Conc

entra

tion

(mg/

100g

)

4ºC MAP VP

(Ozogul et al, 2002)

Figure 4 TMA content of herring stored in ice,in VP and in MAP at 4oC

(Ozogul et al, 2004)

Figure 5 TMA content of sardines stored in air, in VP and in MAP at 4oC

Histamine production

(Ozogul et al, 2002)

Histamine content in herring

0

10

20

30

40

50

0 2 4 6 8 10 12 14 16Storage time (days)

Con

cent

ratio

n (m

g/10

0g)

NO ICE ICE MAP VP

(Ozogul et al, 2004)

Histamine content in sardine

0

5

10

15

20

25

0 2 4 6 8 10 12 14 16Storage time (days)

Con

cent

ratio

n (m

g/10

0g)

4ºC MAP VP

Figure 3 Histamine content of sardines stored in air, in VP and in MAP at 4oC

Figure 2 Histamine content of herring stored in ice, in VP and in MAP at 4oC

0

1

2

3

4

5

0 2 4 6 8 10 12 14 16

IMP ATPADPAMPHx INO

0

1

2

3

4

5

0 2 4 6 8 10 12 14 16

IMPATPADPAMPHxINO

Nucleotide degradation in sardine in MAP Nucleotide degradation in sardine at 4oC

Storage time (days) Storage time (days)

Co

nce

ntr

atio

n o

f A

TP

an

d r

elat

ed

com

po

un

ds

(mm

ole

s/g

)

ATP and breakdown products

(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 indistribution 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

ConclusionsStorage of fish under modified atmosphere conditions;

•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