INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
WORLD HEALTH ORGANIZATION
TOXICOLOGICAL EVALUATION OF SOME
FOOD COLOURS, EMULSIFIERS, STABILIZERS,
ANTI-CAKING AGENTS AND CERTAIN
OTHER SUBSTANCES
FAO Nutrition Meetings Report Series
No. 46A WHO/FOOD ADD/70.36
The content of this document is the result of the deliberations of the
Joint FAO/WHO Expert Committee on Food Additives which met in Rome,
27 May - 4 June 19691
Food and Agriculture Organization of the United Nations
World Health Organization
1 Thirteenth report of the Joint FAO/WHO Expert Committee on Food
Additives, FAO Nutrition Meetings Report Series, in press;
Wld Hlth Org. techn. Rep. Ser., in press.
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. Some depolymerization
takes place by rupture of the bonds between glucose units. No chlorine
in introduced into the molecule and the final products usually contain
only residues of sodium chloride, sodium sulfate and sulfur dioxide.
Oxidation with hypochlorite
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 lightly 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 pancreatic than unmodified starch but there was no obvious
difference as regards salivary digestion (Shuman, A. 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 at al., 1951).
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 6.4
(?) per cent. (5.23 COOH per IOD 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 all dietary levels. One rat from each of
the high dietary level groups Showed marked caecal dilation only in
animals fed the heavily oxidized starch (Whistler & Belfort, 1961).
Acute toxicity
None supplied
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
Hypochlorite-oxidized starch has been investigated by digestibility
studies in vitro and in vivo. One Short-term study over 10 weeks
was reported only in outline and referred to one particular commercial
sample. Assimilation difficulties and delayed in vitro enzymic
degradation occur only at high levels of oxidation together with
diarrhoea and caecal dilatation. Hypochlorite oxidation affects the
physical properties of the starch; provided the chemical change is
limited to the introduction of no more than 1 carboxyl group per 28
anhydroglucose units and a carbonyl content which is negligible, the
biological effects of the modified starch do not appear to be
deleterious. Despite the paucity of animal data and lack of any
information in man it would be unwarranted to exclude the use of
oxidized starches (containing no more than 1 carboxyl group per 28
anhydroglucose units) as food additive pending the provision of
metabolic studies preferably in man.
EVALUATION
Temporarily not limited except for good manufacturing practice.
Further work required by June 1972
Metabolic studies in several species.
REFERENCES
Booher, L. E. Behan, I., & McMeans, E. (1951) J. Nutr., 45, 75
Garton Sons & Co. Ltd., (1967) Submission to U.K. authorities
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