Plastic bag storage


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Plastic bag storage

Postby needaTEAcher » Nov 14th, '12, 15:16

This has been bugging me for a while. Once upon a time, years and years ago when I was first delving into tea, I bought a teapot at a moving sale, and she threw in some tea. It was super fragrant-type tea, but it was all in ziplocks, and the smell was completely gone.

Paid notice for a while and figure out that ziplocks, and other plastics, kill the smell and flavor, sometimes replacing it with a plastic smell.

But in the last year or two I have been noticing lots of tea shops dolling out tea in plastic bags, which I pass off as just temp housing til we get our goods home, but also a lot of puerh shops keep their sample cakes in plastic bags, even ziplocks. Legit dealers even. I got a sample of some 98 sheng today in a bag with a thick plastic front.

So what's up with all that? Some plastic ok, others not? Any ideas?

Thanks!
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Re: Plastic bag storage

Postby Neist » Nov 14th, '12, 15:29

Unfortunately, plastic bags of the ziplock variety are not air-tight as I understand it. Maybe the essences of what makes the tea fragrant manages to slip out of the bags?

I've seen the practice, too, and I don't really understand it. I'm personally considering investing in an impulse sealer and just going that way. They are cheap and relatively easy to use.
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Re: Plastic bag storage

Postby wyardley » Nov 14th, '12, 15:36

I think the major issue is with bags which are either too thin, or have an off odor. Obviously, if the tea is going to spend much time in direct light of any kind, clear is also bad. But, I think a heavy duty bag with a good seal and no strong smell can be a good way to store tea for medium or long periods of time. Also, in the case where you have a large bag with a large amount of tea in it will have relatively little contact with most of the tea.

One good thing about bags is that it typically makes it a little easier to control the amount of extra air in the bag, even as the amount of tea in the bag may change. This is more difficult to accomplish with jars, tins, cans, etc.
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Re: Plastic bag storage

Postby Chip » Nov 14th, '12, 15:56

Also clear plastic is actually semi permeable meaning air can pass through the plastic.

Not to mention light transmission ...

Plastic bags are very accessible, good foil (food grade) bags are not so easy to get and must often be purchased in very large lots. So it is understandable why the practice occurs ... to a degree.

Usually these are zip close as heat sealing is yet another time comsuming expense.

I also just ran into a situation where the zips failed on tea sample bags for OTTI 16. They simply would not zip, period. Obviously a failed run at the factory level.

There are also a lot of topics on the subject on the forum.
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Re: Plastic bag storage

Postby blairswhitaker » Nov 14th, '12, 16:10

polyethylene ziplock bags do not really off-gas at a lower temperature, off-gassing will increases with an increase in temperature. This means you are not really being exposed to anything toxic, I however have noticed the plastic smell myself thus something IS off-gassing but I do no know what. The bags themselves are very poor at retaining scent and they also are not airtight at al,l so they have a rather heavy exchange of oxygen thus oxidation is happening. aluminum foil poly bags are the best alternative as they protect against all the major problems we face when storing tea, light, heat, and oxygen. I highly recommend getting your tea out of those plastic bags and keeping it in a better container. It's fine for short term storage but It's a real shame the dealers who should know better aren't taking the time to investigate this issue.
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Re: Plastic bag storage

Postby jayinhk » Nov 14th, '12, 21:24

I believe the aluminum bags are still lined with HDPE, so there may still be some off-gassing. Ziplocks are definitely a no-no for long term storage, although I find Saran does seriously slow down the loss of volatile compounds responsible for aroma to oxidation and evaporation.
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Re: Plastic bag storage

Postby Neist » Nov 14th, '12, 22:02

Guess you could always pack the tea into a good tin, then put the entire thing into a large food sample bag. :)

Overkill? Perhaps..
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Re: Plastic bag storage

Postby jayinhk » Nov 14th, '12, 23:12

Glass jars are the way to go for optimal preservation IMO. :)
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Re: Plastic bag storage

Postby pgho » Nov 15th, '12, 06:56

Best to use plastic bags for short term storage, most of the plastic material used in these bags contain some amount of plasticiser otherwise the bags will be too stiff. With time and temperature outgassing and decomposition will occur thus releasing the plasticiser or their decomposed compounds. That is why if coins especially copper coins are left in plastic bags for a period of time, a greenish compound is formed on the coin surface. Attacked by the compounds released from the plastic material.

Best to use stiff plastic bags made of OPP or PP, both are basically polypropylene. Common to see these used to shrink wrap puerh tea beengs in Malaysian tea shops. For other teas, tins are still the best.
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Re: Plastic bag storage

Postby jayinhk » Nov 15th, '12, 08:38

Tins are also plastic-lined, no?
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Re: Plastic bag storage

Postby needaTEAcher » Nov 15th, '12, 09:26

I've got this great little travel tea infuser, Taiwanese, and it is plastic. Piao I Travel Buddy. Some sort of recent technology? It says min temp is -30c, max is 137c. I use it all the time on the road, boiling water. Doesn't mess with the flavor that I have noticed. Plastic, plastic everywhere!
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Re: Plastic bag storage

Postby jayinhk » Nov 15th, '12, 09:40

Polycarbonate tea infuser?
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Re: Plastic bag storage

Postby needaTEAcher » Nov 15th, '12, 10:39

Next to the temp range says "PC". I take it that doesn't stand for "Politically Correct"? :lol:
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Re: Plastic bag storage

Postby JRS22 » Nov 15th, '12, 16:52

jayinhk wrote:Tins are also plastic-lined, no?


None of my tins are. I have a few less expensive tins that have a plastic inner lid, but all my good, yet moderately priced tins, have inner metal lids.
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Re: Plastic bag storage

Postby jayinhk » Nov 15th, '12, 21:17

Hot water and PC = BPA

I meant the actual inside of the can: they are commonly lined with plastic
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