corn vs arrowroot starch: pure amylose?

BruceRat brucerat at
Sat Mar 23 12:09:19 EST 1996

I have been doing photometric studies of amylase degradation of amylose,
and gotten just OK results using cornstarch (Kingsford's).   By "OK"
results I refer to fact that my data curve does only an OK job of holding
to the theoretical Michaelis Menten curve.  (The data seems to keep
drifting up.)
When I switched to using arrowroot starch, the  match between data and
theory is excellent!     Since cornstarch is actually a mixture of amylose
and amylopectin, the amylase has two different substrates.  Hence, I
assume my curve is actually the sum of two curves, amylose degrading two
my question:  Why should arrowroot starch give results that are so much
better?  Is arrowroot starch pure amylase?
Bruce Ratcliffe, a puzzled high school science teacher in Fresno
(BruceRat at AOL.COM)

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