INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
WORLD HEALTH ORGANIZATION
TOXICOLOGICAL EVALUATION OF SOME
FOOD COLOURS, ENZYMES, FLAVOUR
ENHANCERS, THICKENING AGENTS, AND
CERTAIN FOOD ADDITIVES
WHO FOOD ADDITIVES SERIES 6
The evaluations contained in this publication were prepared by the
Joint FAO/WHO Expert Committee on Food Additives which met in Rome,
4-13 June 19741
World Health Organization Geneva 1975
1 Eighteenth Report of the Joint FAO/WHO Expert Committee on
Food Additives, Wld Hlth Org. techn. Rep. Ser., 1974, No. 557.
FAO Nutrition Meetings Report Series, 1974, No. 54.
OXIDIZED STARCHES*
Explanation
These compounds have been evaluated for acceptable daily intake
by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
Refs Nos 20, 27 and 34) in 1969, 1971 and 1973.
Since the previous evaluation additional data have become
available and are summarized and discussed in the following monograph.
The previously published monographs have been expanded and are
reproduced in their entirety below.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
Early comparative experiments pointed to inhibition of amylolysis
(Tremolieres 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 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, 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% (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 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).
* 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 carbozyl 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.
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 dilation 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
Short-term 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. No compound related effects were
observed. Haematologic studies at week 13 showed no distinct or
significant differences between tests and control groups (Til et al.,
1973; Til et al., 1974).
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 extends over 90 days and
showed no serious toxic effects at the 25% dietary level, the highest
level-tested. The full results of this study have now been reported.
Studies with highly oxidized starches (14% or more carboxyl group) are
not applicable because these products are not useful as food
additives. Provided the chemical change is limited to the introduction
of no more than one carboxyl group per 25 anhydroglucose units, the
biological effects of the modified starch do not appear to be
deleterious. The requirements of the Committee have now been met.
EVALUATION
Acceptable daily intake not specified.*
* The statement "ADI not specified" means that, on the basis of the
available data (toxicological, biochemical, and other), the total
daily intake of the substance, arising from its use or uses at the
levels necessary to achieve the desired effect and from its acceptable
background in food, does not, in the opinion of the Committee,
represent a hazard to health. For this reason, and for the reasons,
stated in individual evaluations, the establishment of any acceptable
daily intake (ADI) in mg per kg of body weight is not deemed
necessary.
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 Laboratories Inc. to Corn Industries Research Foundation
Til, H. P. et al. (1973) Unpublished report No. R4081 by Centraal
Instituut voor Voedingsonderzoek TNO
Til, H. P. et al. (1974) Unpublished report NR R4081 by Centraal
Instituut voor Voedingsonderzack, TNO
Tremolieres, J., Bernier, J. J. & Lowy, R. (1959) Nutritio et Dieta,
1, 100
Whistler, R. L. & Belfort, A.M. (1961) Science, 133, 1599
White, R. A. (1963) Cereal Science Today, 8, 48