WORLD HEALTH ORGANIZATION
WHO Food Additives Series 1972, No. 1
TOXICOLOGICAL EVALUATION OF SOME
ENZYMES, MODIFIED STARCHES AND
CERTAIN OTHER SUBSTANCES
The evaluations contained in this publication were prepared by the
Joint FAO/WHO Expert Committee on Food Additives which met in Rome,
16-24 June 19711
World Health Organization
Geneva
1972
1 Fifteenth Report of the Joint FAO/WHO Expert Committee on Food
Additives, Wld Hlth Org. techn. Rep. Ser., 1972, No. 488; FAO
Nutrition Meetings Report Series, 1972, No. 50.
The monographs contained in the present volume are also issued by the
Food and Agriculture Organization of the United Nations, Rome, as FAO
Nutrition Meetings Report Series, No. 50A
(c) FAO and WHO 1972
OXIDIZED STARCHES
Biological data
Whatever oxidizing agent is used only minor modifications of the
starch molecule are achieved in normal manufacturing practice. These
are equivalent to the introduction of 1 per cent. w/w of carboxyl
(-COOH) or 0.5 per cent. w/w of keto (-CO) groups or, 3.6 carboxyl and
2.9 carbonyl groups per 100 glucopyranose units. No chlorine is
introduced into the molecule and the final products usually contain
only residues of sodium chloride, sodium sulfate and sulfur dioxide.
Biochemical aspects
Early comparative experiments pointed to inhibition of amylolysis
(Tremolières et al., 1959). In vitro digestibility by pancreatin
or saliva was used to compare slightly and highly oxidized corn starch
with unmodified corn starch and a reference starch. Maltose
production after a fixed interval of enzyme action was taken as a
measure of digestibility. The oxidized starch was 10-15 per cent.
less digestible by pancreatin than unmodified starch but there was no
obvious difference as regards salivary digestion (Shuman, C. C. &
Mertz, E. T., 1959). The digestibility of oxidized wheat starch
(conditions not stated) was examined in rats by matched-feeding
techniques using the modified starch as the sole source of
carbohydrate at a level of 63.7 per cent. (dry basis) of the diet.
The degree of assimilation by and the general effects on groups of 6
rats over a feeding period of 28 days were assessed from consideration
of body-weight changes, faecal residues, digestibility coefficients
for starch and post-mortem appearance of the animals and their
gastrointestinal tracts. The digestibility coefficients were
calculated from the starch content of ingested food and residues found
in faeces and post-mortem gastrointestinal contents. Body-weight gain
and digestibility coefficients were practically indistinguishable from
those obtained for wheat starch or corn starch. Nothing abnormal was
noted on post-mortem examination (Booher et al., 1959).
Other studies, in 3 groups of 3 rats each, used corn starch oxidized
with 3.9 per cent., 4.5 per cent., or 5.5 per cent., hypochlorite
calculated as chlorine. This corresponds to the introduction of 0.57
per cent., (2.04 COOH groups per 100 glucopyranose units), 0.8 per
cent., (2.86 COOH groups per 100 glucopyranose units) and 0.9 per
cent. (3.57 COOH groups per 100 glucopyranose units) carboxyl groups.
To 5 g basal diet were added 1, 2 or 4 g modified or control starch
and this diet was fed to rats for 10 days. Comparison of
digestibilities showed an apparent decrease with increasing oxidation
but no effect on caloric values. No tissue damage was associated with
the diarrhoea and caecal enlargements observed in groups receiving 2 g
or 4 g starch in their feed. Liver, kidney, heart and spleen weights
were normal. Diarrhoea and caecal enlargement are known to occur in
rats fed starches of poor digestibility or other carbohydrates (White,
1963).
The digestibility of oxidized starches at levels of 2.5 per cent., 6
per cent. and 43.2 per cent. calculated as chlorine, equivalent to a
carboxyl content of 0.32 per cent. (1.15 COOH per 100 glucopyranose
units), 0.9 per cent, (3.81 COOH per 100 glucopyranose units) or 1.46
per cent. (5.23 COOH per 100 glucopyranose units), was studied in
groups of 6 male and 6 female rats. The animals were kept for 7 days
on 5 g basal diet and then given either 1 g or 2 g starch supplements
for 21 days. Poor weight gain with diarrhoea were noted only with the
highly oxidized material at both dietary levels. One rat from each of
the high dietary level groups was examined. Marked caecal dilatation
was seen only in animals fed the heavily oxidized starch. It is to be
noted that this very highly oxidized starch is a commercially
unacceptable product (Whistler & Belfort, 1961).
Short-term studies
Rat
Starch treated at a level of 0.375 per cent. chlorine was fed to
weanling albino rats at 70 per cent. of their diet for 10 weeks with
corn starch as control. Feeding was either unrestricted or by
paired-feeding technique. No toxic effects were noted. No details of
this work, carried out in 1944-5, were available (Garton Sons & Co.
Ltd., 1967).
Long-term studies
None supplied.
Comments
The digestibility of hypochlorite-oxidized starch has been
investigated in vivo and found to be similar to that of unmodified
starch. The longest of the short-term studies reported extended only
over 10 weeks and was carried out with an inadequately defined sample.
Studies with highly oxidized starches (1.4 per cent. or more carboxyl
groups) are not applicable because these products are not commercially
acceptable. Provided the chemical change is limited to the
introduction of no more than 1 carboxyl group per 25 anhydro-glucose
units, the biological effects of the modified starch do not appear to
be deleterious.
EVALUATION
Temporarily not limited.*
Further work required by 1973
Ninety-day studies in 2 species.
* Except for good manufacturing practice.
REFERENCES
Booher, L. E., Behan, I., & McMeans, E. (1951) J. Nutr., 45, 75
Garton Sons & Co. Ltd. (1967) Unpublished report
Shuman, A. C. & Mertz, E. T. (1959) Unpublished report No. 4 of Shuman
Chemical Lab. Inc. to Corn Industries Research Foundation
Tremolières, J., Bernier, J. J. and Lowy, R. (1959) Nutritio et Dieta,
1, 100
Whistler, R. L., and Belfort, A. M. (1961) Science, 133, 1599
White, T. A. (1963) Cereal Science Today, 8, 48