Toxicological evaluation of some food colours, thickening
    agents, and certain other substancse


    The evaluations contained in this publication were prepared
    by the Joint FAO/WHO Expert Committee on Food Additives which
    met in Geneva, 14-23 April 19751

    World Health Organization, Geneva 1975

    1 Nineteenth Report of the Joint FAO/WHO Expert Committee on Food
    Additives, Wld Hlth Org. techn. Rep. Ser., 1975, No. 576;
    FAO Nutrition Meetings Report Series, 1975, No. 55.

    The monographs contained in the present volume are
    also issued by the Food and Agriculture Organization
    of the United Nations, Rome, as
    FAO Nutrition Meetings Report Series, No. 55A

    ISBN 92 4 166008 2

    (C) FAO and WHO 1975




         The principal component of this gum is a galactomannan with a
    linear chain of (1 -> 4) linked ß-D-mannopyranose units with
    alpha-D-glactopyranose units attached by (1 -> 6) linkages to every
    third mannose unit on average. In a bioavailable calorie assay groups
    of 10 male weanling rats (Sprague-Dawley) were given 5 g basal diet
    alone or with 0.5, 1, 2 g sucrose or 0.5, 1, 2 g tara gum for 10 days.
    Comparison of the carcass weight gain showed that tara gum was not a
    source of bioavailable calories (Robaislek, 1974). A digestibility
    study in groups of five male and five female rats (Purdue strain) on a
    mannose-free diet showed that 88-100% of mannose fed as 1% tara gum in
    the diet for 18 hours were excreted in the faeces over a total of 30
    hours. Some decrease in chain length of galactomannan may have
    occurred probably through the action of the microflora as mammals are
    not known to possess mannosidase. Liberation of galactose units was
    not determined (Tsai & Whistler, 1975). Incubation of solutions or
    suspensions with human gastric juice, duodenal juice + bile,
    pancreatic juice and succus entericus with or without added rabbit
    small gut membrane enzymes produced no evidence of hydrolysis
    (Semenza, 1975). Rat large gut microflora partially hydrolyzed tara
    gum in vitro (Towle & Schranz, 1975) after conditioning to 1% tara
    gum in the diet for three weeks.


    Acute toxicity

         No information available.

    Short-term tests


         A 90-day feeding study was carried out in groups of 10 male and
    10 female rats at dietary levels of 0%, 1%, 2% or 5% of the diet. No
    abnormalities were observed in general appearance, behaviour, and
    survival in any of the groups. Growth, food intake and food efficiency
    were slightly decreased at the 5% dietary level in both sexes. A
    relative lowering of the body weight was found in the males in the 2%
    group, but no effect on food intake and efficiency. Haematology and
    urinalysis showed no treatment-related differences. A significant
    increase in blood urea nitrogen was observed in males at the 5%
    dietary level. At the 2% and 5% levels an increase was found in the
    relative weight of the caecum. An increase in the relative weight of

    the thyroids at the 2% and 5% levels and a slight increase in the
    relative weight of the kidneys at the 5% level was observed in males
    only. No lesions were found on gross and histopathological examination
    attributable to the ingestion of the gum (Til et al., 1974).


         Three groups of three male and three female beagles received
    either 0, 1% or 5% tara gum in their diet for 90 days. No
    abnormalities were noted as regards behaviour, mortality, haematology,
    urinalysis, clinical chemistry, organ weights, gross and
    histopathology (Oshita et al., 1975).

    Long-term tests

         None available.


         The studies in rats on the in vivo digestibility and calorie
    bioavailability show that this gum is not digested by mammalian
    intestinal enzymes but is partially attacked by rat gut flora. Human
    gut enzymes do not hydrolyse this gum in vitro. Short-term studies
    in rats and dogs showed no evidence of adverse effects at the 5%
    level. The observed effects on caecal weight were discussed in a
    previous report and were not considered significant for man. The
    effect on thyroid weight without concomitant histopathological changes
    was also considered to be of doubtful significance. No information is
    available on long-term effects in rodents. No studies on reproduction
    and teratogenicity are available.


    Estimate of acceptable daily intake for man

         Acceptable daily intake not specified.1*


    1    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/kw bw is not deemed necessary.

    *    Temporary.


    Required by 1980.

    (1)  Adequate long-term studies in a rodent species.

    (2)  Reproduction and embryotoxicity (including teratogenicity)


    Oshita, G., Burtner, B. R., Kennedy, G. L., jr, Kinoshita, F. K. &
         Keplinger, M. L. (1975) 90-day subacute oral toxicity study with
         tara gum in beagle dogs. Unpublished report from Industrial Bio-
         Test Labs, Inc. submitted to the World Health Organization by
         Hercules Incorporated

    Robaislek, E. (1974) Bioavailable calorie assay of guar gum.
         Unpublished report from WARF Institute, Inc. submitted to the
         World Health Organization by Institut Européen des Industries de
         la Gomme de Caroube

    Semenza, G. (1975) Report on the possible digestion of locust bean gum
         in the stomach and/or in the small intestine in an in vitro
         study. Unpublished report from the Eidgenössische Technische
         Hochschule Zürich submitted to the World Health Organization by
         the Institut Européen des Industries de la Gomme de Caroube

    Til, H. P., Spanjers, M. Th. & de Groot, A. P. (1974) Sub-chronic
         toxicity study with tara gum in rats. Unpublished report from
         Centraal Instituut voor Voedingsonderzoek TNO submitted to the
         World Health Organization by Hercules B.V. and Institut Européen
         des Industries de la Gomme de Caroube

    Towle, G. A. & Schranz, R. E. (1975) The action of rat microflora on
         carob bean gum solutions in vitro. Unpublished report from
         Hercules Research Center submitted to the World Health
         Organization by Hercules Incorporated

    Tsai, L. B. & Whistler, R. L. (1975) Digestibility of galactomannans.
         Unpublished report submitted to the World Health Organization by
         Professor H. Neukom, Chairman of the Technical Committee of Inst.
         Europ. des Industries de la Gomme de Caroube

    See Also:
       Toxicological Abbreviations