WORLD HEALTH ORGANIZATION
WORLD HEALTH ORGANIZATION
Toxicological evaluation of some food colours, thickening
agents, and certain other substancse
WHO FOOD ADDITIVES SERIES NO. 8
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
THICKENING AGENTS
CAROB BEAN GUM
Explanation
This substance was evaluated for acceptable daily intake for man
by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
Refs No. 20 and No. 33) in 1969 and 1973.
Since the previous evaluation, additional data have become
available and are summarized and discussed in the following monograph.
The previously published monographs have been expanded and are
reproduced in their entirety below.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
The principal component of this gum is a galactomannan with
a linear chain of (1 -> 4) linked ß-D-mannopyranose units with
alpha-D-galactopyranose units attached by (1 -> 6) linkages to every
fourth or fifth mannose. In a bioavailable calorie assay groups of
10 male weanling rats (Sprague-Dawley) were given 5 g basal diet or
plus 0.5, 1, 2 g sucrose or 0.5, 1, 2 g gum for 10 days. Comparison of
the carcass weight gain showed that carob bean gum was not a source of
bioavailable calories (Robaislek, 1974). Fifteen controls and 18 male
test rats, after three days on normal diet followed by a 12 hour fast,
received two-and-one-half days in their diet either 67% cocoa butter
with wheat flour or 67% cocoa butter with 33% carob bean gum. Glycogen
accumulated in the liver but far less efficiently than with wheat
flour (Krantz et al., 1948). A digestibility study in groups of five
male and five female rats (Purdue strain) on a mannose-free diet
showed that 85-100% of mannose fed as 1% carob bean 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 carob
bean gum in vitro (Towle & Schranz, 1975) after conditioning to
1% carob bean gum in the diet for three weeks. Groups each of eight
male Holtzman rats were maintained on a purified synthetic diet, or
the diet plus 1% cholesterol, or the diet + 1% cholesterol + 10% carob
bean gum for 28 days. The increased liver cholesterol and liver total
lipid induced by cholesterol feeding was largely counteracted by
concurrent feeding of carob bean gum (Ershoff & Wells, 1962).
TOXICOLOGICAL STUDIES
Special studies on teratogenicity
Teratological experiments with four species of animals (rats,
mice, hamsters and rabbits) did not indicate that the test material
was a teratogen to mice at 280 mg/kg body weight and 1300 mg/kg
although 5/21 dams died at the latter dose. Up to 1300 mg/kg in rats,
up to 1000 mg/kg in hamsters and at 196 mg/kg in rabbits no
teratological effects were seen. At 910 mg/kg in rabbits most of the
pregnant dams died (Morgareidge, 1972).
Special studies on mutagenicity
Mutagenic tests on rats and mice using three different methods
gave negative results. There was no measurable mutagenic response in
recombination frequency for Sacch. cerev. in host-mediated assay at
5 g/kg or in vitro. No adverse effects were seen on chromosomes in
rat bone marrow or human lung cell cultures. The dominant lethal test
in rats was negative (Maxwell & Newell, 1972).
Acute toxicity
LD50 Reference
Species Route mg/kg body weight
Rat Oral >5 000 Maxwell & Newell, 1972
Short-term studies
Rat
Groups of 10 males and 10 females were fed in their diet carob
bean gum at levels of 0%, 1%, 2% or 5% for 90 days. General condition,
behaviour, survival, growth, food intake, haematology, blood
biochemistry and urinalysis showed no treatment-related differences
between test and control groups at any dietary level except that the
blood glucose level was slightly increased in the 5% group. Gross and
microscopic examination did not reveal any pathological changes
attributable to ingestion of the gum. The increase in the relative
weight of the caecum at the 2% and 5% levels is not considered to be
of toxicological importance (Til et al., 1974).
Chicken
Groups of 20-day-old chicks were fed diets containing 0.25%,
0.5%, 1% and 2% carob bean grain for three weeks. Growth depression
was dose related and marked at the 2% level of intake (Kratzer et al.,
1967; Vohra & Kratzer, 1964).
Dog
Four groups of five male and five female beagles were fed 0%,
1%, 5% or 10% of a precooked mixture of carob bean and guar gum
(proportions unknown) for 30 weeks. Only at the 10% level were
hypermotility and soft, bulky stools observed, probably of no
toxicological significance. Also at the 10% level digestibility
was reduced. No adverse haematological, urinary, gross and
histopathological and ophthalmological findings were noted (Cox
et al., 1974).
OBSERVATIONS IN MAN
A clinical study of a commercial preparation of carob bean grain
as a laxative in doses of "two heaping teaspoonfuls" in 56 patients,
some of whom took the preparation regularly for two years, resulted in
no untoward effects related to the gastro-intestinal tract, and no
allergenic reaction (Holbrook, 1951).
Eight infants between the ages of 2.5-5 months were fed meals of
sugared milk or sugared milk plus a 1% powder extracted from carob
bean. Addition of the carob supplement did not alter the duration of
the gastro-intestinal transit time of the meal. Physiological
aerophagy was markedly suppressed by the supplement (Rivier, 1952).
Comments:
In vitro tests with human enzyme preparations show little
utilization by the gut. The available short-term studies in the rat
and dog showed no evidence of adverse effects at the 5% level. Carob
bean gum is used in pharmaceutical preparations. No long-term or
reproduction studies are available but no teratogenic or mutagenic
potential has been found.
EVALUATION
Estimate of acceptable daily intake for man
Acceptable daily intake not specified.1*
FURTHER WORK OR INFORMATION
Required by 1980.
(1) An adequate long-term study in a rodent species.
(2) Reproduction studies.
REFERENCES
Cox, G. E., Baily, D. E. & Morgareidge, K. (1974) Subacute feeding in
dogs with a pre-cooked gum blend. Unpublished report from the
Food and Drugs Labs, Inc. submitted to the World Health
Organization by Hercules BV
Ershoff, B. H. & Wells, A. F. (1962) Effects of Gum Guar, Locust Bean
Gum and Carrageenan on Liver Cholesterol of Cholesterol-Fed Rats,
Proc. Soc. exp. biol. med., 110, (3), 580-582
Holbrook, A. A. (1951) The behaviour of carob bean in the
gastrointestinal tract of man, A. J. Dig. Dis., 18, 24-28
Krantz, J. C., jr, Carr, C. J. and de Farson, C. B. (1948) Guar poly
saccharide as a precursor of glycogen, J. Amer. diet Ass.,
24, 212
Kretzev, F. H., Rajaguru, R. W. A. S. B. & Vohra, P. (1967) The effect
of polysaccharides on energy utilization, nitrogen retention and
fat absorption in chickens, Poultry Sci., 48, 1489-1493
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/kg bw is not deemed necessary.
* Temporary.
Maxwell, W. A. & Newell, G. W. (1972) Study of the mutagenic effects
of FDA-71-14 (Locust bean gum). Unpublished report from the
Stanford Research Institute submitted to the World Health
Organization by Hercules BV
Morgareidge, K. (1972) Teratological evaluation of FDA-71-14 (Carob
bean gum). Unpublished report from the Food and Drug Research
Labs, Inc. submitted to the World Health Organization by Hercules
BV
Rivier, C. (1952) Recherches sur le mode d'action du Nestargel,
Schweiz. Mediz. Wchsch., 82, 256
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 locust bean gum in rats. Unpublished report
from Centraal Instituut voor Voedingsonderzoek TNO submitted to
the World Health Organization by Hercules BV 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
Tsay, 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
Vohra, P. & Kratzer, F. H. (1964) Growth inhibitory effect of certain
polysaccharides for chickens, Poultry Sci., 43, 1164-1170