WORLD HEALTH ORGANIZATION
WHO Food Additives Series 1972, No. 1
TOXICOLOGICAL EVALUATION OF SOME
ENZYMES, MODIFIED STARCHES AND
CERTAIN OTHER SUBSTANCES
The evaluations contained in this publication were prepared by the
Joint FAO/WHO Expert Committee on Food Additives which met in Rome,
16-24 June 19711
World Health Organization
Geneva
1972
1 Fifteenth Report of the Joint FAO/WHO Expert Committee on Food
Additives, Wld Hlth Org. techn. Rep. Ser., 1972, No. 488; FAO
Nutrition Meetings Report Series, 1972, No. 50.
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. 50A
(c) FAO and WHO 1972
DISTARCH PHOSPHATE
Biological data
Native starches are known to contain phosphoric acid esters equivalent
to 0.004 per cent. P and some potato starches up to 0.1 per cent.
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 per cent. 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 hydrolyses rapidly with the
production of phosphoric and hydrochloric acid and the formation of
other products than phosphate cross-linkages is very unlikely (Hudson
and Moss, 1962; Grunze, 1959). The maximum number of phosphate bridges
could reach one per 100 glucopyranose units.
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 depolymerisation (Rosner, 1960).
Caloric value and digestibility of a distarch phosphate using
trimetaphosphate were tested in groups of 10 rats fed for 7 days on 4g
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 and Belfort,
1961),
The in vitro digestibility of trimetaphosphate modified starch by
pancreatic mylase was somewhat reduced compared with normal unmodified
starch (Kohn and Kay, 1963a). 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 behaviourial reactions were observed
(Kohn and Kay, 1963a).
In vitro digestibility by pancreatin of corn or potato starch
modified with 0.05 or 0.1 per cent. phosphorus oxychloride was found
to be similar to the unmodified starch. When 0.5 or 1.5 per cent. of
phosphorus oxychloride was used, the resulting crosslinkage
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 per cent.
phosphorus oxychloride in groups of 6 male and 6 female rats receiving
52 per cent. 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 per cent.
phosphorus oxychloride varied between 96.4 and 98.3 per cent. (Kruger,
1970).
Short-term studies
Rat
Groups of 10 male and 10 female rats were fed on a diet containing 10
per cent. rising to 35 per cent. 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
4 test and 2 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 per cent. trimetaphosphate modified or unmodified starch
for 90 days. Eleven controls and 3 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 per
cent. of two types of distarch phosphate (0.085 per cent. esterified
and 0.128 per cent. 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).
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
Temporarily not limited.*
Further work required
See phosphated distarch phosphate.
REFERENCES
Graefe, G. (1964) "Die Stärke", 16, 158
Hixson, 0. F. (1960) Unpublished report H-1004 of Rosner-Hixson
Laboratories
Industrial Biotest Lab. Inc. (1964) Unpublished report submitted by
Corn Products Co.
Kohn, F. E. & Kay, J. H. (1963a) Unpublished report submitted by Corn
Products Co.
Kohn, F. E. & Kay, J. H. (1963c) Unpublished report submitted by Corn
Products Co.
Kohn, F. E,, Kay, J. H. & Calandra, J. C. (1964a) Unpublished report C
submitted by Corn Products Co.
* Except for good manufacturing practice.
Kohn, F. E. & Kay, J. H. (1964C) Unpublished report C submitted by
Corn Products Co.
Rosner, L. (1960) Unpublished report H-1004-1 of Rosner-Hixson
Laboratories
Whistler, R. L. & Belfort, A. M. (1961) Science, 133, 1599