Toxicological evaluation of some food
additives including anticaking agents,
antimicrobials, antioxidants, emulsifiers
and thickening agents
WHO FOOD ADDITIVES SERIES NO. 5
The evaluations contained in this publication
were prepared by the Joint FAO/WHO Expert
Committee on Food Additives which met in Geneva,
25 June - 4 July 19731
World Health Organization
Geneva
1974
1 Seventeenth Report of the Joint FAO/WHO Expert Committee on
Food Additives, Wld Hlth Org. techn. Rep. Ser., 1974, No. 539;
FAO Nutrition Meetings Report Series, 1974, No. 53.
OXIDIZED STARCHES
Explanation
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% w/w of carboxyl (-COOH) or
0.5% 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.
BIOLOGICAL DATA
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% less digestible by
pancreatin than unmodified starch but there was no obvious difference
as regards salivary digestion (Shuman & Mertz, 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% (dry
basis) of the diet. The degree of assimilation by and the general
effects on groups of six rats over a feeding period of 28 days were
assessed from consideration of body weight changes, faecal residues,
digestibility coefficients for starch and postmortem 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 postmortem 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 postmortem examination (Booher et al.,
1951).
Other studies, in three groups of three rats each, used corn
starch oxidized with 3.9, 4.5, or 5.5% hypochlorite calculated as
chlorine. This corresponds to the introduction of 0.57%, (2.04 COOH
groups per 100 glucopyranose units), 0.8%, (2.86 COOH groups per 100
glucopyranose units) and 0.9% (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, 6 and
43.2% calculated as chlorine, equivalent to a carboxyl content of
0.32% (1.15 COOH per 100 glucopyranose units), 0.9% (3.81 COOH per
100 glucopyranose units) or 1.46% (5.23 COOH per 100 glucopyranose
units), was studied in groups of six male and six female rats. The
animals were kept for seven 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).
TOXICOLOGICAL STUDIES
Rat
Starch treated at a level of 0.375% chlorine was fed to weanling
albino rats at 70% 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 1944-1945, were available (Garton Sons & Co. Ltd.,
1967).
A corn starch oxidized with 5.5% chlorine using sodium
hypochlorite (carboxyl content 0.90) was fed to groups of 15 male and
15 female rats at dietary levels of 0, 5, 10 or 25% for 90 days.
No adverse effects were noted regarding general health, growth, food
intake and efficiency, haematology, serum chemistry and urine
analyses. Diarrhoea was not observed. The amount of faeces dry
matter/unit food consumed was slightly increased at 25% of the
oxidized starch in both sexes. In this group the relative weight of
the caecum was slightly increased, the effect being significant in
females only. The other organ-to-body weight ratios showed slightly
increased adrenal weights of females on the test diets, but the
differences with the controls were not dose-related. No other gross
changes were observed at autopsy. The histopathological examination
has not yet been completed (Til et al., 1973).
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% or more carboxyl groups)
are not applicable because these products are not acceptable for food
additive use. 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
Estimate of acceptable daily intake for man
Temporarily not limited.*
FURTHER WORK OR INFORMATION
Required
Results of histopathological studies by 1974.
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
Til, H. P. et al. (1973) Unpublished report No. R 4081 by Centraal
Instituut voor Voedingsonderzoek TNO
Tremolières, J., Bernier, J. J. & Lowy, R. (1959) Nutritio et Dieta,
1, 100
Whistler, R. L. & Belfort, A. M. (1961) Science, 133, 1599
White, T. A. (1963) Cereal Science Today, 8, 48
* See relevant paragraph in the seventeenth report, pages 10-11.