HomeRoast Digest


Topic: bean interior devoid of oxygen? (3 msgs / 114 lines)
1) From: Kevin DuPre
While I don't have specifics of coffee beans, "Plants,
an Introduction to Modern Botany, John Wiley & Sons,
1963" (I don't suspect much has changed in basic
botanical principles in 40 years - being relatively
short in the span of evolution)in the chapter "Levels
of Plant Organization" states "The exterior covering
of the bean seed is a tough glossy layer of high
protective value (would this be analagous to the
"cherry"?). This is underlain by a thin membranous
layer (would this be analagous to the "silverskin"?).
When the seed is soaked in water these two layers, the
seed coats may be easily removed (such as in wet
processing?)...Separation of the two fleshy cotyledons
(hence, dicotyledonous) reveals that they are
oppositely attached near the summit of a tapering
axis. The part of the axis above the attachment of the
cotyledons is the epicotyl, consisting chiefly of a
pair of folded miniature leaves enclosing a growing
point. The fleshy cotyledons contain reserve food [for
germination of the epicotyl], chiefly starch...The
seed coats of some species are impermeable to water or
oxygen or are hard and mechanically resistant, thus
bring about seed dormancy that may have considerable
survival value."
This might support why the success rate for
germination of coffee seeds is so poor. Perhaps when
the seeds are processed, what gets left, and what we
roast are actually the cotyledons, the minature leaves
and growing point being largely absent (excepting
peaberry which would technically be called
monocotyledonous).
While it has been said through numerous sources that
the beginning of the roasting process up until and
including first crack liberates moisture from the bean
resulting in weight loss, even if this form were pure
water [which it is not], it still gets liberated as
steam, that is the H2O molecules are not broken. 
While not entirely scientific, O2 in a form that might
be present within the bean must occur as a gas (beans
aren't cold enough to support liquid oxygen). The
density of the seed tissue and its mechanically
resistant structure suggest that the amounts of
gaseous oxygen would be miniscule if not entirely
nonexistent, thereby supporting the premise that
pyrolysis must occur in an oxygen free environment to
be called pyrolysis.
<Snip>
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--
Kevin DuPre
obxwindsurfhttp://profiles.yahoo.com/obxwindsurf"The real voyage of discovery consists not in seeking new landscapes but in having new eyes -- Marcel Proust"
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2) From: Ed Needham
OK...sounds feasible.  Might relate to the coffee bean.  Still not
scientifically proven though.  If true, maybe we can call that 'pyrolysis',
if in fact the interior of the bean is devoid of oxygen.  Now...does
exothermy occur as a result of continued pyrolysis?
Ed Needhamhttp://www.homeroaster.comed
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3) From: Ryuji Suzuki -- JF7WEX
From: "Ed Needham" 
Subject: +Re: bean interior devoid of oxygen?
Date: Sun, 8 Sep 2002 12:23:20 -0400
<Snip>
For one thing, the hard layer covering the seed is removed by the time
you receive the green coffee.
"Pyrolysis" is not a preferred term here because it technically means
heat driven decomposition in general (and somewhat suggests synthesis
of new compounds bigger than the original compounds is not of
interest) and the term is given more specific context in engines and
treatment of wastes today.
--
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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