Dear Clare
A question not possible to answer easily. The effect of MAP is condition primary by the amount of available carbon dioxide, that again is dependent of initial gas mixture, gas to product ratio, water and salt content of your product, the barrier properties of your packaging and of course temperature. The solubility of CO2 follows Henrys law and hence given same gas to product ratio going from 50% to 30% CO2 initially would reduce problem with top film snug down, but also decrease the bacteriostatic effect of MAP ie. shorten shelf-life. A better solution would be to increase gas to products volume ratio. We recently published a paper regarding this problem and also combining MAP with CO2 pretreatment to avoid package collapse even at low gas to product ratios;
Sivertsvik, M. & Birkeland, S (2006) Effects of soluble gas stabilization (SGS), modified atmosphere packaging (MAP), gas to product volume ratio and storage time on the microbiological and sensory characteristics of ready-to-eat deep-water shrimp (Pandalus borealis). Food Science and Technology International 12(5):445-454
Hope this is some help.
Morten Sivertsvik
Norconserv
Seafood Processing Research
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Fra: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] På vegne av Clare Winkel
Sendt: 30. juli 2007 02:55
Til: 'Pamela Tom'; seafood@ucdavis.edu
Emne: Question on MAP prawns
Dear All,
Just a question from a friend who is not on the list, she is a QA Manager in a prawn processing factory and asks the following questions:
What Gas mixtures (which gases and at what ratio ?) should you use in a 8 x 5 x 40 tray for MAP fish fillets and prawns.
"We had a few issues with the tops sinking on the prawns. We had the gas at 50 / 50 mixture then the gas people told us to go 30 CO2 and 70 N2."
Thanks everyone in advance.
Clare Winkel
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