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CO2 and N flushing of bakery products - effect of freezing/defrosting - (Jan/15/2015 )

Hello all, a quick, probably very easy question for most of you.

 

We gas flush our products with a mixture of CO2 and N (80% : 20 %).  Although there is a residual level of 2% O2 remaining.

 

The baked products generally have a moisture content of about 40%, pH  ~5.0.

 

It has been noted than after the products have been forozen and then defrosted, the products appear 'shrink-wrapped' - the packaging sucks in. I assume the warming process is allowing the diffusion of the gases into the product...?

 

Does anyone know the actual chemistry of what is happening? I've been out of research too long - my brain doesn't work that way anymore!

 

Thanks for any help you can give, much appreciated.

-scoob00-

i'm not sure of the reason but here are some thoughts:

 

gases are more soluble at low temperatures than at high temperatures so your thought that they are being absorbed ("diffusion into the product") when defrosted may not be correct

 

maybe gas shrinkage when freezing can account for the "shrink-wrapped" appearance, the wrapper may not be recovering (may be more plastic than elastic)

 

have you checked moisture content and pH after defrosting? if the co2 is absorbed then the pH should go down

-mdfenko-

Hello,

Thanks for the reply!

 

Apparently the shrinking of the packaging appears to occur as/whilst the product is defrosting - not when it is actually still frozen itself, which is what stumped me a bit.

 

I have just arranged some moisture/pH testing throughout the entire process to see what's going on. There is no effect to the product/packaging when samples are frozen without undergoing the gas-flushing process.

 

Perhaps the source of the infomration was mistaken, I'll check when excatly the 'sucking' effect actually occurs. My company asked me for some chemical reasons for it happening, and I can't think of anything!

-scoob00-