Key facets of tea preservation include reduction of: oxygen (O2) levels, moisture, light exposure, and temperature. Many vendors approach this through use of aluminized mylar packaging, which has good O2 and moisture barrier properties. Shelf life is further enhanced through use of modified atmosphere packaging (MAP) via O2 scavengers and desiccants. Vacuum sealing is sometimes used. Some vendors do inert gas flushing for sensitive teas (typically nitrogen flushing with Japanese greens from what I’ve seen). Also, inventory is sometimes refrigerated.
I’m kind of tired of having to burn through 100g of sencha in a month (neglecting other teas) to avoid wastage. Seeking to free myself from this burden, I decided to play around with MAP at home.
My system consists of an argon (Ar) tank with an adjustable flowmeter connected to flexible tubing terminated with a hypodermic needle to pierce the tea packaging for flushing.
The flowmeter is fitted with a brass hose barb, and a short length of tubing (polyethylene, 0.5”/12.7mm OD, 0.375”/9.5mm ID) is jammed onto it to act as a semi-flexible coupler. A bit of electrical tape makes it a snug fit, and it’s secured with a hose clamp. A 3cc syringe with Luer lock (with the finger flange sliced off) is then snugly jammed into the tubing. A compressed wad of “poly-fil” polyester fiber fill is stuffed into the syringe to act as a filter just in case. It will be interesting to examine the appearance of the filter after some usage – hopefully it’ll be spotless.
A medical “monitoring line” (PVC, 72”/182.9cm, male-to-female Luer lock terminated) is then attached to the syringe and fitted with an 18 gauge needle.
Tea packaging is modified by applying blobs of silicone sealant which, when cured, act as self-healing injector ports. One port is the Ar inlet, and the other is the outlet.
These things (adhesive-backed ports) might be a nice alternative, but I haven’t shopped for them. Silicone sealant works fine.
With the packaging impulse sealed, a bare needle is inserted into one port as the outlet, and the Argon line needle is inserted into the other port. I’m flushing the packaging for a couple of minutes with occasional shaking. I also deflate the bag by squeezing it and flush it once more at the end. I should get some of those oxygen indicator tablets or something to see how long it’s really necessary to flush for.
If someone has other indicator suggestions, please let me know.
When shincha is upon us, I’ll take a packet, drink some, and then experiment with the unused portion by dividing it into 4 sealed packs and subjecting them to: room temp without flushing (control), refrigeration without flushing, room temp with flushing, and refrigeration with flushing. I’ll open them some months later and compare them blind.
Of course, this can be used to extend the shelf life of any sensitive tea.
A note about the argon: it is industrial grade (reported >= 95%) that I have for TIG welding, but I’m working under the assumption that the contaminants are basically other atmospheric components (N2, O2, H2O, etc.). The likely contaminants I’m interested in are O2 and H2O. Even if the tank is 5% H2O, after poking around in a thermo textbook, it looks like that would be under 4% RH @ STP, which seems pretty dry. The other worst-case scenario is that it’s 5% O2. Atmosphere contains about 21% O2, so even 5% would be a significant reduction. Those are worst-case scenarios though. High purity gasses (>99.9%) are available, and I may get a new N2 or Ar tank if I can find a reasonable supplier. My current supplier informed me that they only do rentals for high-purity gasses, so I’ll have to shop around. I’d appreciate any hints here (especially for a smaller size tank). However, if my test results are good, then I might not bother with a new one.
Why not just use O2 scavengers instead? Arguably a more sane solution. A main reason is that I haven’t found small ones individually sealed. I think it would be great if someone sold them like that for a reasonable price.