ROAST BEAN STORAGE  - an post I made:

Inspired by Doug Cadmus's earlier posts on bean storage, I put some thought and testing into it.

Then Ukers book (All about Coffee) arrived - and there is a small but significant bit in there which I will try to summarise. For the sake of completeness I will add in a summary of what Illy has to say on the subject

I roasted two types of beans - a colombian to start of second and a kenyan to middle of second and stored a sample of each in an open container (in a glass fronted cupboard indoors), a sealed glass container and a new oneway valve bag. The last two I filled as much as possible before sealing. All sealing was done within an hour of roasting. I then left the colombian for a fortnight and the kenyan for three weeks (it takes AGES for a nonsupertaster like me to cup - and there are more important things than coffee.)

Tasting was done blind (cups marked on the bottom, randomising, sniffing and tasting using Penny - isn't she great!). I repeated with two samples.

The oneway valve sample was fresher on both beans - no contest - easy to spot. Differentiating between the open container and the sealed container took a lot of sniffing and slurping - they were much closer together. The sealed container fortnight colombian was marginally fresher tasting but the three week kenyan was marginally better in the open container - by 3 votes out of the 4. In retrospect I should have done twice as much, opened one lot after a week, another after a fortnight and roasted up a two day old identical bean as a control.

My conclusion at that point was that the sealed glass container - which I had been using - was useless and that I should put oneway valves into my nice collection of glass containers.

Then arrived my copy of Ukers. Written in 1935 there is a bit by a research chap (Punnett pg 299 et seq).

Very, very briefly he states:-

1 He devised a "standard cup" test which I understand as a series of cups each containing different percentages of stale and fresh coffee. Compare these with your sample and you can determine how stale your sample is. Cute.
2 The rate of flavour loss in ground coffee is quite rapid - 60% in the first two weeks and thereafter slowly.
3 About 10 days after roasting a different flavour arises - " the familiar "stale" flavor"
4 Using 15 different types of container - screwtops/glass/fiber/cans. - there was no significant difference in rate of staling - "after the 10th day staleness increased rapidly".
5 The vacuum packed cans lost only 20% of their flavour "because of air left in the container"
6 In 29 inches of vacuum, the loss of flavour is less than 2.5% ("an amount that can only be detected by the most sensitive highly trained palate"). At 27 inches the loss is 10%; 25 in = 30% and at 20 inches we are back to 60% (You coffeevac users - what are you getting?)
7 They concluded with other tests that the staling was due to absorption of the oxygen and that after two months and all the oxygen left in the can has been absorbed - no further staling takes place. Even 7 years...
8 They tackled the objection that comes up whenever vac sealing is raised here - pumping the air out sucks the flavour out - no it doesn't (or at least not after sucking for 6 hours to give 29.5 inches.)
9 They then tackled the "Wilson half baked hypothesis" that I proposed a month or so ago - "yes but it then stales faster when it comes out the can" - no it doesn't.
10 There was no difference in taste between coffee in use in a gasket sealed jar and left just loosely covered.

Which is where I came in.

Struggling around for anything later than this gave me:

K Davids (Home Coffee Roasting) - roast and drink every 3 or 4 days. Store in a cool dry place in a SEALED jar or cannister. Don't refrigerator - damp and odour taint. Freeze if more than 3 or 4 days. (but he says in "Coffee" not to freeze dark roast coffees).

Corby Kummer (Joy of Coffee). Vacuum packed is useless because the vacuum only removes 90% and the remaining 2% of oxygen does the staling. Recommends emptying into opaque, airtight cannister with as little air as possible. "Paper bags lined with a greaseproof coating .. are a decent way to keep coffee but once you get the beans home from the store, its far better to to
store the beans in a tightly sealed ceramic or plastic container"..

Re Freezing - he refers to the Sivetz 1950's research who concluded that freezing removed fewer aromatics and therefore one should do so - but at -20deg....... Again - no fridge.

Rosen, Roden and Stella - three writers who I also like within their spheres - don't mention it.

Go make a cup of coffee - we next do Illy (Espresso Coffee) - the Formula King.
1 "Oxygen uptake is the main cause of deterioration . leading to the characteristic stale smell"

2 The shelf life of coffee beans exposed to air for eight hours prior to packaging is 40% shorter than..within one hour.

3 Moisture level should be kept below 5%

4 Temperature. The deterioration rate increases sevenfold for each 10deg C of temperature rise. And it might be higher for oily espresso blends.

5 Light acts as a catalyst ("it catalyses the prime trigger of autooxidation reactions for unsaturated fatty acids" - there is an "i.e." as well but I didn't understand that either..)

6 Certain low boiling point compounds are the key for fresh smelling coffee. These principally evaporate and the graph also shows loses of around 60% of some of these in 10 days.

7 Water cooling of beans decreases shelf life (all you spray fans!)

8 They analyse packaging methods by a series of criteria (including environmental friendliness - bet Ukers never though of that!) but there is a shelf life table showing
Airtight         1     month                                                                                                                                                                                           With valve                  3 months
Vacuum                      4-6 mnths
Inert atmosphere     6-8 mnths
Pressure             > 18 mnths.
Regretfully, he doesn't define vacuum level nor what % degradation defines "shelf life".

9 "None of the test methods available can yet replace sensory evaluation"

Finally there is an article on the SCAA web which concentrates on packaging material,; defines "stale" as the "point at which coffee is no longer acceptable to a group of tasters" and sets out to optimise a six month shelf life... - different ball game to us lot I fear! But I couldn't see anything else useful on the SCAA refs.

There must be some more up to date articles kicking around which do a proper summary - presumably in the Tea and Coffee Journal archives?

Meanwhile - I shall home roast and tip straight into the hopper after degassing for 2 days; only buy preroast in airtight valves or Illy tins.