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.
DISTARCH PHOSPHATE
Explanation
Native starches are known to contain phosphoric acid esters
equivalent to 0.004% P and some potato starches up to 0.1%. Distarch
phosphate is made by the use of sodium trimetaphosphate which cross-
links starch chains at an approximate rate of one phosphate link per
620 glucopyranose units. The amounts of phosphate introduced are at
the most 0.04% P (Graefe, 1964).
Cross-linking of starch chains may be produced also by the use of
phosphorus oxychloride. Although theoretically likely, there is no
relevant chemical evidence to show that modification by phosphorus
oxychloride in fact produces distarch phosphate. Although the addition
of phosphorus oxychloride to dry material will cause chlorination, the
processes involved in starch modification always proceed in the
presence of water and/or alkali. Under these circumstances phosphorus
oxychloride hydrolyzes rapidly with the production of phosphoric and
hydrochloric acid and the formation of other products than phosphate
cross-linkages is very unlikely (Hudson & Moss, 1962; Grunze, 1959).
The maximum number of phosphate bridges could reach one per 100
glucopyranose units.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
In vitro digestion of a distarch phosphate using
trimetaphosphate by salivary, pancreatic and intestinal amylase was
measured by the production rate of reducing sugar. No deleterious
effect was shown on enzymic depolymerization (Rosner, 1960).
Caloric value and digestibility of a distarch phosphate using
trimetaphosphate were tested in groups of 10 rats fed for seven days
on 4 g basal diet with either 0.9 g or 3.6 g starch supplement by
observing the gain in body weight and the organ weights of liver,
kidney, heart and spleen after the feeding period. No significant
differences were noted between the modified and the unmodified
starches (Hixson, 1960). Distarch phosphate using trimetaphosphate was
fed to groups of male and female rats on 5 g diets as 1 g or 2 g
supplements over 21 days. Weight gains were comparable for modified
and unmodified starches tested. Animals appeared normal at autopsy
(Whistler & Belfort, 1961).
The in vitro digestibility of trimetaphosphate modified starch
by pancreatic amylase was somewhat reduced compared with normal
unmodified starch (Kohn & Kay, 1963). In vivo digestibility was
examined in groups of 10 male rats fed for 10 days 5 g basal diet
supplemented by 1 g, 2 g or 4 g unmodified or trimetaphosphate
modified starch. Weight gains were identical for both types tested at
all three levels of supplementation. No unusual behavioural reactions
were observed (Kohn & Kay, 1963).
In vitro digestibility by pancreatin of corn or potato starch
modified with 0.05 or 0.1% phosphorus oxychloride was found to be
similar to the unmodified starch. When 0.5 or 1.5% of phosphorus
oxychloride was used, the resulting cross-linkage considerably
inhibited digestibility in vitro in a manner related to the
concentration of cross-linking agent used (Janzen, 1969). Caloric
value was determined for starch treated with 0.06% phosphorus
oxychloride in groups of six male and six female rats receiving 52% of
distarch phosphate for six weeks as sole carbohydrate source in their
diet. No differences were noted between modified and unmodified
starches (Oser, 1954). The in vitro digestibility by
amyloglucosidase of starch modified with 0.035, 0.07 or 0.1%
phosphorus oxychloride varied between 96.4 and 98.3% (Kruger, 1970).
TOXICOLOGICAL STUDIES
Acute toxicity
LD50
Animal Route mg/kg bw Reference
Mouse, female Oral > 24 000 Hodge, 1954
> 19 000 Hodge, 1956
Rat, female Oral > 20 000 Hodge, 1954
> 35 000 Hodge, 1956
Guinea-pig Oral > 8 800 Hodge, 1954
> 18 000 Hodge, 1956
Rabbit Oral > 7 000 Hodge, 1954
> 10 000 Hodge, 1956
Cat Oral > 6 800 Hodge, 1954
> 9 000 Hodge, 1956
Only small numbers of animals were used but no deaths occurred
from the quantities administered. Livers and kidneys of guinea-pigs,
rabbits and cats showed no histological abnormalities related to the
administration of the modified starch (Hodge, 1954; Hodge, 1956).
Short-term studies
Rat
Groups of 10 male and 10 female rats were fed on a diet
containing 10% rising to 35% of phosphated distarch phosphate
(trimetaphosphate) for a total of 60 days. Female rats showed a
consistent reduced rate of weight gain throughout the test. Although
four test and two control animals died during the test these incidents
were regarded as unrelated to the test substance. All animals behaved
normally. Haematological examination and urinalysis were normal and
comparable in the various groups. The liver weights of male rats were
lower for the test group than for controls and the kidney weights were
lower for both sexes but these findings were not associated with any
gross or histopathological changes (Kohn et al., 1964).
Groups of 25 male and 25 female rats were fed diets containing
0.2, 1.0 and 5.0% trimetaphosphate modified or unmodified starch for
90 days. Eleven controls and three test animals died from intercurrent
disease. There were no obvious gross or histopathological changes
attributable to the test substance. Organ weights and haematological
examination (days 45 and 90) were normal in both groups. Pooled
urinalysis was comparable for all groups (Kohn et al., 1964).
Groups of 10 male and 10 female rats received 0, 5, 15 and 45% of
two types of distarch phosphate (0.085% esterified and 0.128%
esterified phosphate) in their diet for 90 days. No abnormalities
compared with controls were seen as regards general appearance,
behaviour, mortality, food consumption, haematology, serum chemistry
and urinalysis which could be ascribed to the action of either of the
test substances. No diarrhoea or increased caecal weights were
observed. Gross and histopathology revealed no abnormalities
attributable to the test substances (Til et al., 1970).
Pig
Groups of eight Pitman-Moore miniature pigs were weaned at three
days of age, and were fed formula diets containing 5.4% unmodified
starch or 5.6% distarch phosphate for 25 days. Growth was normal
during the test period. At termination of the study, biochemical
analyses of blood (haemoglobin) and serum (cholesterol, triglyceride,
calcium, phosphorus, alkaline phosphatase, urea nitrogen, total
protein, albumin and globulin) were similar for test and control
animals. Relative organ weight as well as carcass composition (water,
fat, protein, ash, Ca, PO4, Na, Mg) and liver composition (water,
fat, protein and ash), were similar for test and control animals
(Anderson et al., 1973).
Long-term studies
None available.
Comments:
Although direct chemical evidence is lacking, it is very likely
that phosphorus oxychloride modification will produce distarch
phosphates similar to those formed from trimetaphosphate. The extent
of phosphate cross-linkage using trimetaphosphate is very small. The
metabolic behaviour of the phosphate bridges has not been studied.
However, the available short-term studies reveal no adverse changes
with either type of modified starch even at high levels in the diet.
As these modified starches represent preliminary stages in the
manufacture of the more highly modified phosphated distarch phosphates
it is appropriate to use the results of the long-term and reproduction
studies in rats relating to phosphated distarch phosphate to evaluate
all phosphate-modified starches.
EVALUATION
Estimate of acceptable daily intake for man
Not limited.*
REFERENCES
Anderson, T. A. et al. (1973) Unpublished data submitted by Corn
Refiners Ass., Inc.
Graefe, G. (1964) "Die Stärke", 16, 158
Grunze, H. (1969) Z. Amorg. Allg. Chemie, 298, 152
Hixson, O. F. (1960) Unpublished report H-1004 by Rosner-Hixson
Laboratories, 3 February
Hodge, H. C. (1954) Unpublished report from University of Rochester,
Division of Pharmacology & Toxicology, 8 October
Hodge, H. C. (1956) Unpublished report from University of Rochester,
Division of Pharmacology & Toxicology, 26 May
* See relevant paragraph in the seventeenth report, pages 10-11.
Hudson, R. F. & Moss, G. (1962) J. Chem. Soc., 3599
Janzen, G. J. (1969) Unpublished report submitted by Association des
Amidonneries de Mais
Kohn, F. E. & Kay, J. H. (1963) Unpublished report submitted by Corn
Products Co.
Kohn, F. E., Kay, J. H. & Calandra, J. C. (1964) Unpublished report C
submitted by Corn Products Co.
Kruger, L. (1970) Unpublished reports Nos 405 & 406 submitted by
National Starch and Chemical Co.
Oser, B. L. (1954) Unpublished report No. 69190 a-i by Food and Drug
Laboratories submitted by American Maize Products Co.
Rosner, L. (1960) Unpublished report H-1004-1 of Rosner-Hixson
Laboratories
Til, H. P., Van der Meulen, Harriet C. & De Greet, A. P. (1970)
Unpublished report No. R 3303 by Centraal Instituut voor
Voedingsonderzoek TNO
Whistler, R. L. & Belfort, A. M. (1961) Science, 133, 1599
See Also:
Toxicological Abbreviations
Distarch phosphate (WHO Food Additives Series 1)
DISTARCH PHOSPHATE (JECFA Evaluation)