Vacuum sealing hot or cold?

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    Posted: 03 Mar 2014 at 10:47am
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Hi there, I have just got a vacuum sealer and was wondering if I should let the smoke fish cool down before vacuum sealing it or just back it up straight from the smoker while it's still hot?
Thanks
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Post Options Post Options   Likes (0) Likes(0)   Quote Moggy Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2014 at 2:00pm
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You should never seal anything hot.

Apart from anything else it helps to know what materials your bags are made of as the end result may well be a bad and potentially a dangerous product.

A bit of background, whilst these domestic machines are called a Vacuum packer they actually create no vacuum, if they did then when you cut the pack open you would hear a inrush of air, you don’t. So what the machines are doing is removing air from the bags.
Plastic bags are not strong enough to resist pressure at ground level which is about 1,013mbars or say 14.7psi as a result the pressure inside a sealed pouch is equal to the pressure outside.

If you only partly vac a bag say 80% you are also pretty much negating the reason for Vac packing (which is usually to preserve foods) as the amount of oxygen inside the bag will eliminate the gain of the vac packing, the oxygen will ruin the food after all.

In true vac sealers vac packing hot food causes a problem as it speeds the evaporation of water from the food which can actually create that water to boil. That evaporation does a lot of damage to the food, rupturing cells and causing channels to open in the food such that when you finally cook it the food won’t be as it should be – fish particularly.

You can get around this problem by making sure your food is very cold first, even at fridge temps water can evaporate at pressures less than 20mbar/0.3Ppsi, why, as we all know water boils at lower temps the higher we go (as the pressure decreases) so at a typical sealing pressure of say 23mbar/0.3psi the boiling point of water is only 20degC, if you vac pack something that is warmer than this it will boil.

These mainly are the commercial machines you see around but the same problems still apply to domestic sealers main difference is that the vac pump on domestic sealers isn’t anywhere near powerful enough to seal as tightly
There is a good chance that if the food is hot you will also not get a complete seal.
There is also a good chance that the hot food will create a mess in your sealer as the liquid will be much more readily free to be drawn out of the bag.

Warm food can also get a good crop of anaerobic bacterial growth, if it does throw the food away. That can happen when you don’t properly freeze the bag after sealing and the bacteria have produced excess gas.
The sealers we have are properly called edge sealers not vac sealers.
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Post Options Post Options   Likes (0) Likes(0)   Quote Raging Bull Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2014 at 2:58pm
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I think what Moggy is trying to say is, let it cool down.
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Post Options Post Options   Likes (0) Likes(0)   Quote Clifftastic Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2014 at 3:20pm
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Post Options Post Options   Likes (0) Likes(0)   Quote feeder Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2014 at 4:16pm
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Jezz that was a pretty long winded bit of advise, Moggy has too much time on his hands

Cheers
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Post Options Post Options   Likes (0) Likes(0)   Quote Keith C Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2014 at 6:05pm
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I believe that may be the Moggypedia version.
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Post Options Post Options   Likes (0) Likes(0)   Quote muchalls Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2014 at 7:21pm
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I believe the youth of today would say TLDR
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Post Options Post Options   Likes (0) Likes(0)   Quote Moggy Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2014 at 11:04pm
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Originally posted by muchalls muchalls wrote:

I believe the youth of today would say TLDR


I believe you are 100% right as most have the attention span of a gnat

But hey only reason I know is that is its been bugging me why something seal right and some don't for no apparent reason. So I have done some serious research and found all sorts of weird and wonderful things so thought I would share (tui ad I know)


got to say the humour on here is top notch even I got a laugh from you guys posts...
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Post Options Post Options   Likes (0) Likes(0)   Quote Ara Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2014 at 10:55am
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Originally posted by Moggy Moggy wrote:

You should never seal anything hot.

Apart from anything else it helps to know what materials your bags are made of as the end result may well be a bad and potentially a dangerous product.

A bit of background, whilst these domestic machines are called a Vacuum packer they actually create no vacuum, if they did then when you cut the pack open you would hear a inrush of air, you don’t. So what the machines are doing is removing air from the bags.
Plastic bags are not strong enough to resist pressure at ground level which is about 1,013mbars or say 14.7psi as a result the pressure inside a sealed pouch is equal to the pressure outside.

If you only partly vac a bag say 80% you are also pretty much negating the reason for Vac packing (which is usually to preserve foods) as the amount of oxygen inside the bag will eliminate the gain of the vac packing, the oxygen will ruin the food after all.

In true vac sealers vac packing hot food causes a problem as it speeds the evaporation of water from the food which can actually create that water to boil. That evaporation does a lot of damage to the food, rupturing cells and causing channels to open in the food such that when you finally cook it the food won’t be as it should be – fish particularly.

You can get around this problem by making sure your food is very cold first, even at fridge temps water can evaporate at pressures less than 20mbar/0.3Ppsi, why, as we all know water boils at lower temps the higher we go (as the pressure decreases) so at a typical sealing pressure of say 23mbar/0.3psi the boiling point of water is only 20degC, if you vac pack something that is warmer than this it will boil.

These mainly are the commercial machines you see around but the same problems still apply to domestic sealers main difference is that the vac pump on domestic sealers isn’t anywhere near powerful enough to seal as tightly
There is a good chance that if the food is hot you will also not get a complete seal.
There is also a good chance that the hot food will create a mess in your sealer as the liquid will be much more readily free to be drawn out of the bag.

Warm food can also get a good crop of anaerobic bacterial growth, if it does throw the food away. That can happen when you don’t properly freeze the bag after sealing and the bacteria have produced excess gas.
The sealers we have are properly called edge sealers not vac sealers.

Thanks Moggy,
I will vac seal my smoked fish cold next time, the juice did make a bit of a mess.
Cheers
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Post Options Post Options   Likes (0) Likes(0)   Quote Moggy Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2014 at 10:58am
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Originally posted by Ara Ara wrote:

Originally posted by Moggy Moggy wrote:




Thanks Moggy,
I will vac seal my smoked fish cold next time, the juice did make a bit of a mess.
Cheers


Make sure you have cleaned it out properly, even if you have to take the machine apart as that juice will turn bad if left in the machine, most machines are easy to take apart and get the plastic tubes out of.

good luck.
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Post Options Post Options   Likes (0) Likes(0)   Quote feeder Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2014 at 11:54am
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The easy way Ara to avoid the liquid getting sucked into your vac packer is to fold a paper towel and put that between your fish and packer.

Incidently Moggy if -85kpa is not a vacuum, what is it.

Cheers
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Post Options Post Options   Likes (0) Likes(0)   Quote Moggy Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2014 at 5:41pm
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Originally posted by feeder feeder wrote:

The easy way Ara to avoid the liquid getting sucked into your vac packer is to fold a paper towel and put that between your fish and packer.

Incidently Moggy if -85kpa is not a vacuum, what is it.

Cheers

Dennis I assume your meaning the 80%?
if so the point I that at 80% there is enough air left in the bag to turn food to something that grows and glows in the dark.
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Post Options Post Options   Likes (0) Likes(0)   Quote PE Pete Quote  Post ReplyReply Direct Link To This Post Posted: 08 Apr 2014 at 8:02pm
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Moggy absolutely brilliant mate. I have just bought one of these & am wondering what I ever did without one. I figured moisture might be an issue so what I have been doing is drying my fillets with paper towel before vacuuming. Good tip about letting smoked fish to completely cool & firm up a bit before sealing. The model I got has not as yet had any issue with the heat sealing only ever do one seal each end & haven't had one open yet.
Cheers Pete
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Post Options Post Options   Likes (0) Likes(0)   Quote waynorth Quote  Post ReplyReply Direct Link To This Post Posted: 08 Apr 2014 at 8:45pm
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These things remind me of printers that cost $5 but the ink cartridges require a second mortgage on the house. Buying 'genuine' vacuum bag rolls costs about $5/m, & if you don't like the idea of putting a paper towel inside then when the juice screws up the sealing process & you have to do it again with a new bag it starts getting pretty expensive. Has anyone found a supplier of generic bags that can be used ?
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Post Options Post Options   Likes (0) Likes(0)   Quote Clifftastic Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2014 at 11:48am
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I bought 200 generic bags off trademe by mistake, my vac sealer wont work with them. Bought 50 of the textured bags for $25 on trademe and can usually get about 5 uses from each bag when sealing up fillets. So its pretty economic I reckon if you dont have the juice issue.
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Post Options Post Options   Likes (0) Likes(0)   Quote Moggy Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2014 at 5:40pm
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You can seal wet products easy if you use this idea which I am sure what some other people have been referring to.

Basically take a paper towel and fold it in half and half again till you end up with a flat towel about 15 to 20 mm wide, place on vac bag and measure inside width of the bag then snip off excess so it fits exactly across the width inside the bag

Pack bag with wet fish etc - or even liquid and place towel in near the top as you can but outside of the sealer - don't let it get trapped under the sealer lid otherwise you won’t seal well at all.

 

Now grip both sides of the bag with finger of both hands - yep that one hand a side and squeeze tight, practice that first, ok you can let go now

Now your use to it have the towel held by one hand and with other push the vac button and immediately grab and squeeze the sides - this stops any moisture from going around the sides - and it will if you don't do it.

You could of course play boss and have your kids/wife/etc hold the bag whilst you do what any skipper job is and push the button...LOL

The towel will mop the moisture up and your sealed. With liquid as soon as the towel gets close to being wet to about mid-way press the seal switch to stop the vacuum and start sealing.

You should be ok at that point

Works every time, word of caution – make sure you do not contaminate the paper towel make sure your hands are clean and you are folding it an a clean surface, if you do that you won’t have any problems. I have had towels stay in bags for 2 years without any problems.

 

Basically mine look like this

 
Ham that's been brined and cold smoke but uncooked tends to shed moisture so works well with this
 
 
you can see how its tried to go around the towel
 
Brined snapper leak as well.
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Post Options Post Options   Likes (0) Likes(0)   Quote waynorth Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2014 at 6:06pm
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Originally posted by Moggy Moggy wrote:

Works every time, word of caution – make sure you do not contaminate the paper towel make sure your hands are clean and you are folding it an a clean surface, if you do that you won’t have any problems. I have had towels stay in bags for 2 years without any problems.


That's the bit I was concerned about - the paper towel looks pretty disgusting. Good to hear it isn't an issue.
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Post Options Post Options   Likes (0) Likes(0)   Quote Moggy Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2014 at 6:24pm
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Originally posted by waynorth waynorth wrote:

Originally posted by Moggy Moggy wrote:

Works every time, word of caution – make sure you do not contaminate the paper towel make sure your hands are clean and you are folding it an a clean surface, if you do that you won’t have any problems. I have had towels stay in bags for 2 years without any problems.


That's the bit I was concerned about - the paper towel looks pretty disgusting. Good to hear it isn't an issue.
 
Yes it mops up a lot of fluid, good thing is that the fluid all comes from the same item as your vac'ing down so no problem there - There is one other proviso I would also make and that is you get that bag freezed down a quickly as you can again just for safety and don't leave it in direct sun or heat whilst your doing more of them - I put mine straight in the fridge as I do them then transfer when finished to freezer.
 
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Post Options Post Options   Likes (0) Likes(0)   Quote ZeroPak Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2014 at 11:28am
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Some good advice there Moggy. A lot of our customers swear by the paper towel trick, I really like the idea of finger pressure on the outer edges.
There is one thing in your above posts I need to take issue with. You state that in vacuum bags that there is no such thing as a true vacuum and that if there was you would hear an inrush of air when opening the bag.
I could demonstrate negative vacuum in a bag by placing a vacuum gauge inside the bags and then vacuuming it. the gauge will show negative vacuum. The reason there is no in rushing of air is because the film has conformed to the shape of whatever is in the bag and left no space. there is an accessory available for the ZeroPak units which is a vacuum canister, these canisters are attached to the vacuum port on the machine and the air is vacuumed out of the canister. When these canisters are opened there is a very audible in rushing of air as the internal pressure is equalised to the external pressure. Thus demostrating the fact that there was a pressure difference between inside and outside the container.
ZeroPak Vacuum Sealers. Zero air Zero waste. The ultimate vacuum packing machine.
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