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paulraphael

ziplocks for cook-chill sous vide

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Dave Arnold and co. say yes, Nathan Myrhvold and co. say no.

 

Dave makes a good case for it and says that 90% of sous-vide cooking can be done without a vacuum, and that his food saver has been relegated to re-sealing potato chips. Nathan doesn't give a reason.

 

I don't understand why ziplocks couldn't be used for cook-chill applications. Don't we use them to store conventionally cooked food in the fridge?

 

Thoughts? 

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I agree with you and Arnold.

 

Only argument I can think of is that the zip loc might open in the fridge.

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Where does Myhrvold say no? From what I remember, he says you eliminate oxidation using vacuum bags which can increase keeping quality of cook chill foods. When you have a bajillion chamber vacuums like him, this is a no-brainer and he does stuff like chamber vac beans and water to hydrate them instead of just putting them in a bowl like a normal person.

 

For everyone else, just use ziplocks and don't think about it.

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I cook with sous vide bags, un-sealed.

 

It is very nice that I can taste test while the food is being cooked and adjust seasoning if required. For large piece of meat I can even probe temperature once in a while.

 

After cooking, I rinse the bags, turn them inside out and store them. After I have lots of them, I throw them in the clothes washer and they come out totally clean and good for the next round of cooking.

 

Bags are not cheap, and it take time to seal/unseal.

 

dcarch.

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Have a picture of the way you do it, Dcarch?

 

I'm trying to visualize an unsealed vacuum bag that isn't filled with air.

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I've been using zip locks for years with no problems - even with cook chill.  That being said, here and there I've had a problem once in a while with doing high temp stuff in a ziplock - like a confit at 176 for several hours - here and there one bag would leak.  But for most things, especially below say 150degF I've had no problems, and it's much more convenient.

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Where does Myhrvold say no? From what I remember, he says you eliminate oxidation using vacuum bags which can increase keeping quality of cook chill foods. When you have a bajillion chamber vacuums like him, this is a no-brainer and he does stuff like chamber vac beans and water to hydrate them instead of just putting them in a bowl like a normal person.

 

For everyone else, just use ziplocks and don't think about it.

 

I agree with you based on what I know. But Myhrvold does say otherwise.

 

 

“Strictly speaking, vacuum packing is only required (as a safety measure and to prevent oxidation) for cook-chill sous vide, in which the food is stored after cooking.”
 
and
 
“Zip closure bags are inexpensive and available at any corner store. Althought not suitable for cook-chill sous-vide, they can work well in a pinch for improvising sous-vide packaging”
 
I'm curious if there's any substance behind this. Might be that as you suggest, life without a vacuum machine is hust not a life he's ever imagined.

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I'd suggest it hinges on how reliable the seal is.  With a chamber/FoodSaver, sealing involves essentially melting teh two sides of the bag into a single layer.  Ziplocs are good, but can potentially come unsealed under conditions where the temperature, and thus 'direction' of any pressure differential, are changing rapidly.  As when you put a hot bag in a bowl of ice and water.

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I cook with sous vide bags, un-sealed.

 

It is very nice that I can taste test while the food is being cooked and adjust seasoning if required. For large piece of meat I can even probe temperature once in a while.

 

After cooking, I rinse the bags, turn them inside out and store them. After I have lots of them, I throw them in the clothes washer and they come out totally clean and good for the next round of cooking.

 

Bags are not cheap, and it take time to seal/unseal.

 

dcarch.

 

I can't see doing this.  Bags seal in well less than a minute, and take seconds to cut open.  It costs $2.00, in quarters, for me to do a load of wash.  New bags are 20 cents a piece, and I don't have to go out in the snow.

 

If I had a washing machine in my kitchen rather than a chamber vacuum sealer I might feel differently.

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Notice that Dave Arnold says, towards the bottom of the linked article, that one of the disadvantages of ziplocs is that they don't permit the same extended storage as vacuum bags.  Frustratingly, he never says how long he thinks ziplocs are okay for cook-chill, so the advice isn't very useful.  Personally I'd hesitate to rely on ziplocs for holding any longer than open leftovers (three days to a week, depending on fridge temp).  My experience with ziplocs when used for general storage (don't do cook-chill) is that they allow in air rather easily over a period of days even without the seal failing.

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Notice that Dave Arnold says, towards the bottom of the linked article, that one of the disadvantages of ziplocs is that they don't permit the same extended storage as vacuum bags.  Frustratingly, he never says how long he thinks ziplocs are okay for cook-chill, so the advice isn't very useful.  Personally I'd hesitate to rely on ziplocs for holding any longer than open leftovers (three days to a week, depending on fridge temp).  My experience with ziplocs when used for general storage (don't do cook-chill) is that they allow in air rather easily over a period of days even without the seal failing.

 

Isn't a week as long as you'd ever do cook-chill?

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Am.Test Kitchen did a 'study' of plastic storage bags for the freezer.  zip-loc's, zip-loc's w the extraction hole if you will, regular plastic

 

Food saver and the Weston ( 400 $$ ) system.

 

they found that after  ( paraphrasing here ) 1 - 2 months in the freezer ice crystals in the bag penetrated the plastic and the contents were t

 

then subjected to 'freezer burn'

 

the Weston system w the thicker 3.5 MIL bags did not do this and lasted .....

 

I got the Weston system 3 years ago or so to begin my SV studies.  none of these bags have failed me after I understood how clean and 

 

dry  the bags needed to be at the seal.

 

Ive had stuff SV in my freezer thats over a year old:  seal good, tastes fine.

 

so   cooking and saving for a brief period of time is one thing, freezing for a long time is another.

 

i also store my green coffee beans this way, but not in the freezer:  just a very cold basement.

 

so the thickness of the bag will determine who long the contents might keep,   + / -

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I can't see doing this.  Bags seal in well less than a minute, and take seconds to cut open.  It costs $2.00, in quarters, for me to do a load of wash.  New bags are 20 cents a piece, and I don't have to go out in the snow.

 

If I had a washing machine in my kitchen rather than a chamber vacuum sealer I might feel differently.

 

As I said in the above post, there are more reason than just $. In any case, I use boil-able heavy duty bags which are $0.40 each. And recycling means a lot to me.

 

Shopping, buying takes time too.

 

dcarch

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Have a picture of the way you do it, Dcarch?

 

I'm trying to visualize an unsealed vacuum bag that isn't filled with air.

 

Sure. Also someone had asked about how I weigh my bags down.

 

dcarch

 

bagweight_zps24a71d54.jpg

 

bagweight2_zpsbe4f4fc9.jpg

 

bagweight3_zpsc9417034.jpg

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Looks like a lot of air in the bag.

 

How do you deal with that? Fill the bag with fluid?

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Looks like a lot of air in the bag.

 

How do you deal with that? Fill the bag with fluid?

 

There will be very little, if any, air inside.

 

The bag will have some marinade, seasoning, or sauce. The meat will give out some juice once heated. The hot water softens the plastic bag, and the heavy weigh holds down the bag to allow hydro-static pressure to squeeze out the air.

 

dcarch

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Isn't a week as long as you'd ever do cook-chill?

Baldwin gives cook-chill times up to 90 days for very cold storage, presumably for vacuum bags though it's not expressly stated.  Indeed, in my understanding, this was one of the main advantages of sous vide when first developed as a commercial process.  Anyhoo, circling back to the OP, if you're only looking to hold for a week, I think even Nathan would agree ziplocs are okay.

 

And, gfweb, as for your question to dcarch, bear in mind that pressure from the water will evacuate the air, just as when loading ziplocs.  So long as the food stays below the water line, there's no way for the air above to get at it.

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As I said in the above post, there are more reason than just $. In any case, I use boil-able heavy duty bags which are $0.40 each. And recycling means a lot to me.

 

Shopping, buying takes time too.

 

dcarch

 

If you are going to wash the bags I don't see why you could not reseal and reuse the same bag several times.  The 20 cent bags are boilable.  If your bags are retort bags that could be used in a pressure cooker I would probably be interested to buy some.

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I've done a lot of experiments with sealing in Ziploc bags.....they're not dependable in terms of staying sealed and some folks consider them quite permeable.

If you want to cook-chill foods with confidence....use better bags.

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Frustratingly, he never says how long he thinks ziplocs are okay for cook-chill, so the advice isn't very useful.  

 

Some Ziplocs stay sealed well for an extended period of time and some don't so it's impossible to honestly estimate how long they'll stay sealed.

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If you are going to wash the bags I don't see why you could not reseal and reuse the same bag several times.  The 20 cent bags are boilable.  If your bags are retort bags that could be used in a pressure cooker I would probably be interested to buy some.

I guess you are still missing part of what I said above"----It is very nice that I can taste test while the food is being cooked and adjust seasoning if required. For large piece of meat I can even probe temperature once in a while.---"

 

Each time you cut and seal, the bags get smaller, soon I will have close to a hundred bags of various sizes to manage. I have found that the cheaper bags have the problem of the "quilted" layer delaminating after a few cooks.

 

darch

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I'd love to see some experimental evidence on foods cooked to pasteurization in ziplock freezer bags and stored at a range of standard fridge temperatures. 

Not really a home experiment. You'd want lots of samples, a few different types of food, and a range of fridge temperatures. Real life fridges add a lot of variables with their temperature swings.

And you'd need a biology lab, and some agreed-upon standards.

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Maybe I am missing something else, but if you are not using an edge sealer, why use quilted bags at all?

 

A very good question.

 

1. I do, very seldom, vacuum and seal. Although I don't remember when was the last time.

 

2. I trust more the plastic used for boil-able  bags specifically designed for high temperature sous vide water baths. I made clotted cream yeaterday, at 180F for 10 hours.

 

3. And this unique use I came up with. As I said, I am interested in recycling and re-purposing materials.

 

 

dcarch

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I'd love to see some experimental evidence on foods cooked to pasteurization in ziplock freezer bags and stored at a range of standard fridge temperatures. 

Not really a home experiment. You'd want lots of samples, a few different types of food, and a range of fridge temperatures. Real life fridges add a lot of variables with their temperature swings.

And you'd need a biology lab, and some agreed-upon standards.

 

To my knowledge, no such study has been done, which may expain why Dave Arnold was so vague.  But, again, if you're only looking to hold for a week, existing food handling protocols say that's okay, so long as the temp stays below 41F.  See FDA Food Code, § 3‑501.17(A)(1) (scroll down the page about two-thirds of the way).  Whether your fridge actually holds this temp is the bigger issue.  I monitor mine with a thermometer.

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