Brewtips - Hops

Hop Storage

" The concept of an "oxygen barrier" polymer for long term storage of hops is quite flawed. Polyethylene [e.g. ziplock bags -oliver] has a permeability of between 55 and 0.4 barrers depending on polymer density and crystallinity (a 'barrer' is a unit that represents volume permeation rate per area per pressure driving force and is commonly used in gas permeation literature). Ziplock type bags are at the higher end of this range.

The lowest oxygen permeability I found was for polyvinylidene chloride (Saran ) which was at 0.05. While this will provide up to a 1000 times reduction in permeability, there will still be significant oxygen permeation through this sort of barrier within a fairly short time. With the exception of natural rubber, almost anything is better than PET, but you can certainly do better. In addition, as polymers age, permeability increases. Note: the low temperature will also decrease permeability due to a glass/rubber transition, but I'm not sure about where this happens for commonly used polymers.

The solution? Glass mason jars. The permeability of glass is constant (at zero) and the only opportunity for permeation is at the lid/glass contact point which is a tightly compressed seal. And you don't have to buy special plastic bags either.

No affiliation with the glass people, the masons, or the jar people...."

Source: HBD

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