ACETYLATED DISTARCH ADIPATE
Explanation
This substance was evaluated for acceptable daily intake for man
(ADI) by the Joint FAO/WHO Expert Committee on Food Additives in 1969
and 1971 (see Annex I, Refs. 20 and 27). A toxicological monograph was
issued in 1974 (see Annex I, Ref. 33).
Since the previous evaluation, additional data have become
available and are summarized and discussed in the following monograph.
The previously published monograph has been expanded and is reproduced
in its entirety below.
Introduction
Modification is carried out by the use of 8% acetic anhydride and
a maximum of 0.12% adipic acid, the latter acting as cross-linking
agent. The maximum number of acetyl groups introduced is 2.5%. The
number of adipic cross-links does not exceed more than 1 in about 1000
glucopyranose units, or not more than 0.09% adipyl groups introduced
in the starch.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
In vitro studies with pancreatin have shown that only the
acetate ester bond splits easily while the adipic acid ester linkages
are not attacked. No free adipic acid could be demonstrated in the
hydrolysate (Morgareidge, 1959a). In vitro digestion with
amyloglucosidase of acetylated distarch adipate showed a digestibility
of 98.3% (Kruger, 1970). The metabolic fate of adipate-modified
starches was investigated in male rats in vivo using adipic acid
labelled at Cl and C6 with C14. The rate of appearance of 14CO2 was
compared between labelled adipic acid and starch modified with 1,6-
C14 adipic acid. Starch adipate is absorbed and/or metabolized more
slowly than adipic acid, as evidenced by the delayed appearance of
14CO2 in the respired air. 99.3% of the C14 activity of the free
adipic acid was recovered in the respired air; 5.8% appeared in the
urine while none was detected in the faeces in the gastrointestinal
tract or in the carcass. 70.5% of the C14 activity of the esterified
adipic acid appeared in the respired air and 7.2% in the urine; 24.5%
was found in the faeces. No activity appeared in the carcass
(Morgareidge, 1959b). The caloric equivalent of the modified starch
was determined in groups of 10 male rats fed for 28 days on a basal
diet containing either 1.5 or 3.0 g of starch supplements. The
modified starch had been treated with 0.2% adipic anhydride and 5.5%
acetic anhydride. Native starch was used as control. Caloric values
were determined from a dose/response curve obtained by the use of 0,
0.75, 1.5, 3.0 and 4.5 g of sucrose supplements equivalent to 0, 3, 6,
12 and 18 calories per day. There was no difference in caloric value
between the modified and unmodified starches (Oser, 1961).
TOXICOLOGICAL STUDIES
Special studies on kidney lesions associated with dietary
modified starch
Hamster
Groups of 10 male and 10 female Syrian golden hamsters, weighing
30-40 g, were fed a diet containing either 30% acetylated distarch
adipate or 30% untreated starch for 30 days. Hamsters fed the test
diet exhibited a reduction in average daily weight gain, compared to
control animals, but the average daily test diet intake was also
reduced. Comparison of feed consumption to corresponding weight gain
did not indicate a significant difference in efficiency of utilization
of the test and control diets. No treatment-related differences were
noted in haematology, clinical chemistry or urinalysis data. No
treatment-related lesions were evident in histological sections from
liver and kidney (Newberne & Buttolph, 1977).
Groups of 8 male and 12 female Syrian golden hamsters (weanlings)
were fed a diet containing either 30% acetylated distarch adipate or
30% untreated starch for periods of either 30 or 60 days. The diets
contained Ca, 0.51%, P, 0.4% and Mg levels ranging from 0.017% to
0.210% (0.6% is the normal requirement). Ten animals/group (6 female,
4 male) were sacrificed at day 30 and the remaining animals at day 60.
At autopsy, animals on test diet showed increased caecal weight. No
weight difference was observed for liver and kidney. Haematological
studies showed no compound-related effects. Histological sections from
kidney demonstrated an increased incidence of lesions (cortical
scarring and tubular dilatation) associated with consumption of the
test diet for 30 or 60 days. These kidney lesions did not appear if
the test diet was supplemented with magnesium. Kidneys from hamsters
fed acetylated distarch adipate were analysed for calcium and
magnesium content by neutron activation analysis. No correlation was
evident between kidney magnesium levels and either dietary magnesium
levels or severity of renal lesions. However, a suggestive correlation
existed between kidney calcium levels and severity of lesions
(Newberne & Buttolph, 1979a).
Rat
Weanling Sprague-Dawley rats were distributed into groups of 6 or
12 males or females and fed a test diet containing 30% acetylated
distarch adipate + 10% unmodified starch or a control diet, consisting
of 40% unmodified starch, for 30 days. The mineral mix in the diet was
held constant, but Ca, P and Mg were varied according to design,
which permitted manipulating the Ca/P content and ratios from
1.5/1.36-0.5/0.56 to 0.1/0.76-1.6/0.26. The level of magnesium was
0.06% (the required intake), but in 1 group with Ca/P Ca/P ratio of
1.5/1.36 was lowered to 0.02% and in another group raised to 0.2%. One
control group of Ca/P ratio of 0.5/0.56 had a magnesium level of
0.04%. A total of 9 different groups were used in the study. Serum
biochemistry and urinalysis were carried out on the test animals. At
low dietary calcium/phosphate ratios, females on test diet experienced
slightly elevated serum calcium. Serum magnesium tended to be
depressed by low dietary calcium/phosphate ratios and by low dietary
magnesium levels (0.02%), but was not affected by the test diet.
Urinary magnesium levels tended to be increased in animals on the test
diet. Fluctuations in other urinary electrolytes were affected by
dietary calcium/phosphate ratios and magnesium content, but not by the
test diet. Significant fluctuations occurred in urinary creatinine
levels, but these fluctuations did not appear to be treatment related.
At autopsy, organ weights showed no treatment-related effects except
for the caecum, which was enlarged. Histopathological evaluation of
kidney sections from control and test animals revealed a
characteristic lesion consisting of mineral deposits in tubules at the
corticomedullary junction. This lesion was not considered to be
morphologically comparable to the "pelvic nephrocalcinosis" lesions
previously reported in other laboratories. It was more common in
females than in males. A high calcium/phosphorus ratio (5.8/1) and low
phosphorus level (0.26%) in the diet prevented mineralization in
kidneys of animals on test diet and significantly reduced this lesion
in controls. There were no other compound-related effects.
Histological examination of bone tissue and parathyroid glands showed
no effect even with relatively severely imbalanced Ca/P ratios
(Newberne & Buttloph, 1980).
Groups of 25 female Sprague-Dawley rats were fed diets containing
either 30% acetylated distarch phosphate or 30% unmodified starch
(control) in a 1-year study with weanling rats (Experiment I) and a
separate 9-month study utilizing 9-month-old rats (Experiment II). The
calcium concentration in the diet was ca. 1%, phosphorus ca. 0.8% and
magnesium ca. 0.15%. Urinary calcium concentration and total daily
output were significantly increased in animals on the test diet
(Experiments I and II), but only minor differences were seen in
phosphorus, oxalate, magnesium and creatinine excretion. No
significant effects were observed on body weight, food consumption,
urine volume, urine pH and crystal content or faecal mineral content
in animals on the test diet. At autopsy, caecal enlargement was
present in treated animals, but no other treatment-related effects on
relative organ weights were observed. No treatment-related
histopathological effects were observed in the uterus or lower urinary
tract, liver, parathyroid, caecum or ovaries in either experiment.
Histological examination of kidney sections demonstrated the presence
of treatment-related pelvic nephrocalcinosis. An apparent correlation
was observed between the increased incidence of pelvic
nephrocalcinosis, increased accumulation of calcium in the kidney, and
increased urinary excretion of calcium. Residues of calcium in kidney
tissue were significantly higher in test groups than in controls
(Hodgkinson et al., 1981).
Roe (1979) has conducted an extensive review of mineral
deposition in the renal pelvis of rats and concluded that pelvic
nephrocalcinosis, corticomedullary nephrocalcinosis, acute tubular
nephropathy, and calculus formation are manifestations of mineral
imbalance and are of relatively common occurrence in untreated
laboratory rats (particularly older animals).
Special studies on reproduction
Rat
Groups of 10 male and 10 female rats, Sprague-Dawley-derived,
were selected at random from a concurrent 2-year chronic toxicity
study and, 6 weeks after weaning, mated to produce F1a and F1b
litters. Test animals were maintained on a diet of 62% acetylated
distarch adipate, while controls received 62% unmodified starch in
their diet. After breeding was complete, parents were returned to the
chronic study while 10 male and 10 female rats from the F1b litter
were bred to produce F2a and F2b litters. A similar process was used
to obtain F3a and F3b litters. In each generation, litters from the
first mating were sacrificed at weaning and, from the second mating, 6
weeks after weaning, except for the 10 males and 10 females selected
for breeding. Pre-weaning deaths were significantly elevated in
offspring from F2b litters for both control and test animals compared
to the previous generation, but were within normal limits for the
strain. The remaining test parameters (litter size, incidence of
stillbirths, sex ratio at weaning and pre-weaning growth) were similar
in treated and control animals. Histological sections taken from
principal organs of F3b rats reportedly did not reveal evidence of
anomalies. No detailed information from the histopathological
examinations was provided (Truhaut et al., 1979).
Short-term studies
Rat
A 90-day feeding study was carried out in groups of 15 male and
10 female rats at a dietary level of 50% modified or unmodified
starch. The growth rate of males was significantly lower in the test
group and the full and empty caecal weights of both sexes were
significantly greater in rats fed the treated starch. All rats
survived the test period and no differences were observed between the
groups with respect to liver and kidney weights, haematology, blood
chemistry, urinalysis, gross and histopathology. The modified starch
used had been treated with 0.12% adipic acid and 10.5% acetic
anhydride resulting in 3.1% of acetyl groups being present (Oser,
1964).
Groups of 15 male and 15 female weanling albino rats, FDRL
strain, were fed diets containing either 50% acetylated distarch
adipate or, for control diet, 50% thin-boiling starch for 90 days.
Treated males suffered a significantly reduced growth rate, which was
paralleled by reductions in food intake and efficiency of utilization.
Relative weights of caeca, empty or full, were higher in both sexes of
the test group compared to control weights. No treatment-related
changes were observed in relative weights of liver and kidneys, or in
haematology or blood chemistry analyses. However, female rats on the
test diet experienced alkaline urine relative to control at week 6 of
the study. Histological sections of liver, spleen, stomach, small and
large intestine, caecum, pancreas, kidneys, bladder, adrenals, gonads,
thyroid, thymus, salivary gland, lymph nodes, heart, lungs, bone
marrow and muscle were taken from 5 female and 5 male animals of
control and test groups, and liver and kidney sections from all
animals. No treatment-related adverse effects were observed, but 6
control females and 3 test females had calcification at the
corticomedullary junction (Oser, 1964).
Long-term studies
Rat
Rats, Sprague-Dawley derived, 4-5 weeks old, were distributed in
groups of 30 males and 30 females and fed a cooked test diet
containing 62% acetylated distarch adipate and a control diet of 62%
unmodified starch for 2 years. Significant reductions in growth
occurred in treated animals, particularly in females. These
differences could not be attributed to reduced food intake, because
consumption of modified starch and control diets was comparable. The
2-year survival rate in treated animals (60%) was slightly higher than
in control animals (52%). Haematology and serum clinical chemistry
tests from treated and control animals were within normal range, with
the exception of SGOT which was elevated in test animals. At autopsy,
adipose deposits were much less extensive in treated rats than in
controls, which could account for the reduced weights of the test
animals. Skeletal growth, as demonstrated by femur measurements, was
similar in test and control animals. Statistically significant
treatment-related variations occurred in absolute organ weights
relative to controls. However, relative to body weight, significant
treatment-related differences in organ weights were rare. Because no
treatment-related changes could be detected microscopically, the
variations in organ weight were considered to be incidental.
Histological examination of tissues from test and control animals
showed no significant differences between the groups for either non-
tumorous lesions or tumours. In the case of the kidney, hyperplasia of
the kidney urothelium, sometimes accompanied by calcification, was
observed in both control and test groups, but neither the incidence
nor severity of these effects were considered by the authors to be
treatment related. However, independent reviewers of the data
concluded that in female rats, the incidence of epithelial hyperplasia
was greater in the rats fed modified starch (Truhaut et al., 1979).
Comments
A study of 14C-labelled starch adipate in the rat showed that
the adipic acid moiety entered the metabolic pool more slowly but
followed the normal pathways for free adipic acid. No retention of
label was found in the carcass. The previous short-term feeding
studies with rats at a high dietary level showed no significant
pathological changes with the exception of measured caecal weight. The
available evidence for modified starches as a group suggests that
caecal enlargement without associated histopathological changes is
without toxicological significance. The observed decrease in growth
rate with a high dietary level was considered to be due to nutritional
imbalance. However, recent studies with the rat and hamster have shown
that high dietary levels (30%) of acetylated distarch adipate result
in an increased incidence of renal lesions under various dietary
conditions. The occurrence of renal mineralization has been the
subject of special studies on the rate of mineral imbalance in the
development of this lesion. These lesions were associated with the
Ca/P ratio in the diet, as well as the presence of adequate magnesium.
Changing the Ca/P ratio (particularly lowering the phosphate level),
and raising the level of Mg in the diet resulted in a marked decrease
or elimination of the lesion. A multigeneration reproduction study in
the rat did not show any significant effect on reproductive
performance. In the lifetime study in the rat, in which the diet
contained 62% cooked acetylated distarch adipate, the only significant
compound-related effects were a decrease in body weight and the
occurrence of renal lesions (epithelial hyperplasia).
EVALUATION
Estimate of acceptable daily intake for man
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 an acceptable daily intake (ADI) in mg/kg bw is not deemed
necessary.
REFERENCES
Hodgkinson, A. et al. (1981) A comparison of the effects on mineral
metabolism of diets containing waxy maize starch, either of two
chemically-modified waxy maize starches, or lactose. Unpublished
report from the General Infirmary, Leeds, and from the Medical
School, University of Leeds
Kruger, L. (1970) Unpublished reports Nos. 405 & 406, submitted by
National Starch and Chemical Corporation
Morgareidge, K. (1959a) Unpublished report No. 78522 of Food and Drug
Research Laboratories, Inc., submitted by National Starch and
Chemical Corporation
Morgareidge, K. (1959b) Unpublished report No. 79408 of Food and Drug
Research Laboratories, Inc., submitted by National Starch and
Chemical Corporation
Newberne, P. M. & Buttolph, M. L. (1977) A preliminary report of a
thirty-day study in hamsters fed modified starch. Unpublished
report from Massachusetts Institute of Technology, submitted to
the World Health Organization by the US Food and Drug
Administration, 1982
Newberne, P. M. & Buttolph, M. L. (1979a) Final report. Review and
conclusions of hamster studies with modified food starch. Study
No. 78-4. Unpublished report from Massachusetts Institute of
Technology, submitted to the World Health Organization by the US
Food and Drug Administration, 1982
Newberne, P. M. & Buttolph, M. L. (1979b, rev. 1980) Final report on
study No. 79-2. Metabolism studies in rats fed modified food
starch. Unpublished report from Massachusetts Institute of
Technology, submitted to the World Health Organization by the US
Food and Drug Administration, 1982
Oser, M. (1961) Report No. 81776 of Food and Drug Research
Laboratories, Inc., submitted by National Starch and Chemical
Corporation
Oser, B. L. (1964) Subacute (90-day) feeding studies with Amioca
treated with adipic acid and acetic anhydride. Report No. 85555.
Food & Drug Research Laboratories, Inc., Maspeth, NY, submitted
to the World Health Organization by the US Food and Drug
Administration, 1982
Roe, F. J. C. (1979) Mineral deposition in the renal pelvis of rats:
A brief review. Unpublished report submitted to the World Health
Organization
Truhaut, R., Coquet, B., Fouillet, X., Galland, D., Guyot, D. & Long,
D. (1979) Two-year oral toxicity and multigeneration studies in
rats on two chemically modified maize starches, Fd. Cosmet.
Toxicol., 17, 11-17