> We most certainly
>know the temperature when yeasts are killed.  Any wine maker is familiar with
>the temperature 100F.  We also know the temperature many other contents of
>honey are ruined (Honey  -  E. Crane).

        The processes in question are chemical reactions.  The extent to
which they proceed  -  how much of the reactants get converted to how much
products  -  depends on not only the T but also the t.  Even the crudest
rule of thumb for how much a chemical reaction is promoted by heating must
include an indication of both temp AND time.  In order to begin thinking
about such matters one must form some concept of a T-t combination.
        Taking the matter even further away from simple rules-of-thumb is
the fact that in nearly all actual cases these two influences are not
simply reciprocal so you can't use anything like "double the temp and
that'll let me halve the time".  Few of the responses are linear, so that
doubled time may give, say, quadrupled extent of reaction; dependences on
temp are exponential, but the steepness of the graph differs from one
reaction to another; etc.   This is an area of physical chemistry &
biochemistry in which rules of thumb are very hard to come by.
        What you end up with, where possible, is empirical rules based on a
lot of actual measurements and a margin for safety  e.g. 'all microbes are
killed by steam at 121 C for 20min.' (a common rule of thumb for
autoclaving).  More delicate matters, which are the main interest in
processing honey, are more tricky.

R

-
Robt Mann
consultant ecologist
P O Box 28878   Remuera, Auckland 1005, New Zealand
                (9) 524 2949