Investigations on wood starches
dc.contributor.author
Frahn, John Leslie
en
dc.date.accessioned
2018-09-13T15:55:21Z
dc.date.available
2018-09-13T15:55:21Z
dc.date.issued
1950
dc.description.abstract
en
dc.description.abstract
The difficulties encountered in preliminary
investigations on wood starches are described. The
presence of gallotannin, aToarently strongly adsorbe'
on the granules, was found to be responsible for
serious interference, particularly with the results
of potentiometric iodine titration for the determina
tion of amylose and with the results of periodate
oxidation for the determination of the number of
glucose residues in the starches per non -reducing
end -group. The reactivity of gallotannin with
iodine has been shown to be responsible for erroneouvalues of molecular weight determination of the starch
samples by means of alkaline hypoiodite oxidation.
en
dc.description.abstract
A technique for overcoming the interference of
the impurities with potentiometric iodine titrations
was developed and the amylose contents of the wood
starches were shown to vary between 14. and 20 ¡0
en
dc.description.abstract
Attempts to remove the impurities from the wood
starch samples are described. Solvent extraction of
the granules with boiling 8* aqueous methanol was
found to be the most effective method of removing the
reactive gallotannin without simultaneous degradation
of the polysaccharides.
en
dc.description.abstract
Samples of amylose were isolated by fractionation of elm and oak sapwood starches by slow cooling
of hot dispersions of the starches in 15% aqueous
pyridine. The crude amyloses obtained from the
initial fractionations were each repreoipitated thre
times from butanol- saturated water. The amylosebutanol complexes were isolated in typical spherocrystalline form. The recovered amyloses were
shown to adsorb iodine to the extent of 19-20% of
their own weight.
en
dc.description.abstract
Acetylation of wood starches yielded products
the general properties of which were characteristic
of other similarly acetylated starches.
en
dc.description.abstract
Methylation of elm sapwood starch yielded a
product which closely resembled other similarly
methylated starches. The material possessed relatively
high specific viscosity in m-cresol indicating a
molecular weight of the order of 5 x 10⁵. Hydrolysis
of methylated elm starch and chromatographic separation of the products on a cellulose column yielded a
quantity of 2:3:4:6- tetramethyl glucose consistent
with a repeating -unit chain- length for the amylopectin component of 20± 1 glucose residues on the
basis of the Haworth-Hirst 'laminated' formula for
atnylopectin.
en
dc.identifier.uri
http://hdl.handle.net/1842/32211
dc.publisher
The University of Edinburgh
en
dc.relation.ispartof
Annexe Thesis Digitisation Project 2018 Block 20
en
dc.relation.isreferencedby
Already catalogued
en
dc.title
Investigations on wood starches
en
dc.type
Thesis or Dissertation
en
dc.type.qualificationlevel
Doctoral
en
dc.type.qualificationname
PhD Doctor of Philosophy
en
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