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.



         Normal native starches consist of a mixture of 15-30% amylose and
    70-85% amylopectin. Amylose structurally is a linear polymer of
    anhydroglucose units, of molecular weight approximately between 40 000
    and 340 000, the chains containing 250 to 2000 anhydroglucose units.
    Amylopectin is considered to be composed of anhydroglucose chains with
    many branch points; the molecular weight may reach as high as
    80 000 000.

         One hundred per cent. amylopectin or "waxy" starches are
    commercially available having been extracted from special mutants of
    the parent plant e.g. waxy corn or waxy rice. Starches with a very
    high amylose content have also been produced, but on a limited scale
    for special application. The granules of native starches are extracted
    from the plant source by purely physical means, washed and dried. Even
    in this way a certain small amount of modification takes place so that
    the raw starch is strictly speaking not the same as it existed in the
    plant. The changes which have taken place are, however, only of
    academic interest. From the nutritional point of view it is important
    to realize that the human gastrointestinal tract digests very
    efficiently raw cereal and root starches such as wheat, maize, rice
    and cassava but is not able to digest easily raw potato, arrowroot and
    canna starches (Booher et al., 1951).

         Digestibility of starches may be assessed by studying the action
    of pancreatin or other sources of amylase (Leach & Schoch, 1961;
    Sandstedt et al., 1962) or of taka-diastase (Kihara & Kawase, 1949)
    in vitro on the raw granular starch, or by feeding the raw starch to
    animals such as rats and chicks. But from the standpoint of use in the
    human diet it is the gelatinized (cooked) form that requires
    evaluation. From the work of Sanstedt et al. (1962) and Borchers
    (1962) it is clear that both in vitro studies and animal feeding
    establish the resistant character of some high amylose corn starches
    to amylolytic attack.

         Nevertheless it does not appear likely that in practice high
    amylose corn starches in gelatinized form will present any problem of
    digestibility to man, who has no difficulty with gelatinized potato
    starch. The digestibility of raw granular potato starch in vitro was
    15.98% under conditions where corn starch yielded a value of 65.64%
    (Kihara & Kawase, 1949). In the studies by Sandstedt et al. (1962) the
    susceptibility of potato starch in vitro to pancreatic digestion was
    far lower than that of the most resistant high-amylose corn starch.
    Although in vivo digestibility invariably exceeds the in vitro
    value, it is unlikely that potato starch would prove more digestible
    than high-amylose corn starch, either raw or gelatinized.


         These native starches should be regarded as food rather than food


    Estimate of acceptable daily intake for man

         Not limited.*


    Booher, L. E., Behan, I. & McMeans, E. (1951) J. Nutr., 45, 75

    Borchers, R. (1962) Cereal Chem., 39, 145

    Kihara, Y. & Kawase, Z. (1949) Rept. Food Res. Inst. (Japan), 2, 25

    Leach, H. W. & Schoch, T. J. (1961) Cereal Chem., 38, 34

    Sandstedt, R. M. et al. (1962) Cereal Chem., 39, 123


    *    See relevant paragraph in the seventeenth report, pages 10-11.

    See Also:
       Toxicological Abbreviations
       Amylose and amylopectin (FAO Nutrition Meetings Report Series 46a)