Toxicological evaluation of some food
    additives including anticaking agents,
    antimicrobials, antioxidants, emulsifiers
    and thickening agents


    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


    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.



         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.



         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).


    Acute toxicity

    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


         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).


         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.


         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.


    Estimate of acceptable daily intake for man

         Not limited.*


    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

    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)