Toxicological evaluation of some food
additives including anticaking agents,
antimicrobials, antioxidants, emulsifiers
and thickening agents
WHO FOOD ADDITIVES SERIES NO. 5
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.
POLYGLYCEROL ESTERS OF FATTY ACIDS
These substances have been evaluated for acceptable daily intake
by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
Ref. No. 13) in 1966.
Since the previous evaluation, additional data have become
available and are summarized and discussed in the following monograph.
The previously published monograph has been expanded and is reproduced
in its entirety below.
The polyglycerol esters of fatty acids include a large group of
closely related compounds of complex composition. However, the
individual components are found as normal constituents of the human
diet, i.e. glycerol, glycerol mono-, di- and tri-fatty acid esters and
individual fatty acids, with the exceptions of the artificially
produced polymers of glycerol, polymers of certain fatty acids and the
actual separate esters between these polymers. These latter compounds
represent the toxicologically important constituents.
In vitro experiments on lipase digestion of polyglycerol esters
showed a slower rate of digestion than that of olive oil and the ester
did not affect the lipase digestion of olive oil (Unilever Research
Digestibility or caloric utilization have been used to
demonstrate metabolic conversion; 16 male and female rats were fed a
diet containing 1% ground-nut oil and 9% polyglycerol ester or 10%
groundnut oil (as control) for six and 12 weeks. Polyglycerol ester
as an energy source was almost equivalent to ground-nut oil, as
measured by growth rate. Digestibility was calculated as 92%. In
another experiment rats were kept on a restricted food intake
(18 calories/day) for 17 days. After realimentation With 9%
polyglycerol ester and 1% ground-nut oil, no adverse effect was noted
on the animals' ability to gain weight. Rats fed polyglycerol ester
for 54 days as 9% of the diet showed no difference in composition of
carcass fat, liver fat, liver free fatty acids and liver phosphorus
when compared with groups fed 1% or 10% ground-nut oil in the diet.
Liver vitamin A levels were unaffected. A polyglycerol ester was shown
to be absorbed by intestinal lymphatics, and chylomicron counts showed
normal lipaemia. Suspensions in water were more slowly absorbed and
reduced the rate of gastric emptying compared with ground-nut oil. The
serum cholesterol level of rats was unaffected by the presence of 10%
polyglycerol ester in a 42% fat diet (Unilever Research Laboratory,
Hydrolysis of the tri- and polyglycerol esters in vitro with
fresh pancreatic juice plus bile showed that 89 to 98% of oleate
esters were hydrolyzed. Eicosanoate compounds were hydrolyzed at a
much slower rate than the oleate esters.
The metabolic fate of polyglycerol esters in rat has been studied
using fatty acid 14C-labelled (oleic acid and eicosanoic acid),
tri- and polyglycerol esters. More than 90% of the 14C label of the
triglycerol and approximately 40% of the polyglycerol was absorbed.
Hydrolysis occurred mainly before absorption. 66 to 70% of the
radioactivity from the oleic acid and 55% from the eicosanoic-labelled
compounds appeared as respiratory CO2 during the test period
(51 hours); most of the remaining activity being incorporated into the
carcass. Rats fed polyglycerol esters labelled with 14C in the tri-
or poly-glycerol moiety excreted the unchanged polymerized glycerol,
primarily in the urine with less than 7% of the 14C label appearing
in respiratory CO2 and the carcass (Michael & Coots, 1971).
Weanling rats were fed each day a restricted 5 g basic diet
supplemented with either 0, 0.5 or 1 g lard or 1 g polyglycerol ester
of various molecular weights prepared from cotton-seed or peanut oil.
After three weeks, the rats were placed on unrestricted diets
containing polyglycerol or lard of 8% for a period of eight weeks.
Weight gain of rats fed the polyglycerol ester was the same as those
fed lard. Autopsy and histopathological examination of liver, kidneys
and ileum showed no compound-related effects. No appreciable residues
of polyglycerol esters were detected in the epididymal fat (Babayan et
Rats given single doses of 7, 14 and 29 g/kg bw of a polyglycerol
ester by intubation showed no signs of any toxic effect. Repeated
dosing with 10 g/kg bw daily over five days caused no deaths. Rats,
injected i.p. with 1, 3 and 7 g/kg bw, showed no adverse effects;
single doses of 10 g/kg bw caused some peritoneal reaction but no
deaths (Unilever Research Laboratory, 1966).
Rabbits dosed orally with 10-29 g/kg bw showed no toxic effects.
Thirteen rats maintained on 9% polyglycerol ester and 1% ground-
nut oil for 17 weeks showed normal kidney function (Unilever Research
Laboratory, 1966). Rats kept 22 weeks on 9% PGE + 1% ground-nut oil
showed no difference in weights of liver, kidney, adrenal, spleen and
testes when compared with controls on 10% ground-nut oil. Gross
autopsy and histological examination of liver revealed no
abnormalities (Unilever Research Laboratory, 1966).
Groups each of 100 rats equally divided by sex were maintained
on diets containing 0, 2.5, 5.0 or 10.0% of polyglycerol ester
(deca-glycerol deca-oleate) for 90 days. There were no adverse effects
on survival, growth, organ weights, body weight ratios and hematologic
parameters. Urinary nitrogen values for female rats in the 10% group
was significantly higher than controls at weeks three and nine of the
study. Autopsy and microscopic examination of tissues did not show any
compound-related effects. The percentage of dietary fatty acids
absorbed, as measured by faecal fatty acids decreased as the level of
polyglycerol ester increased in the diet (King et al., 1971).
Rats were fed polyglycerol ester with a high melting point for
eight months. No residues were detected in depot fat, or in fat of
muscle, liver, kidney or spleen. When the esters were injected
subcutaneously or intravenously, polyglycerol esters were detected in
fatty deposits near the site of injection (Ostertag & Wurziger, 1965).
Eight rats were maintained on a nutritionally adequate biscuit
diet containing 15% of polyglycerol ester of fatty acids (Palsgaard
No. 1016) for five weeks. No abnormalities attributable to the
additive were apparent at autopsy and on histological examinations,
the findings being as in a control group fed 15% of a vegetable oil in
the diet (Briski, 1970).
Groups of 25 male and 25 female mice were fed for 80 weeks on
either polyglycerol ester or ground-nut oil at 5% in their diet. No
adverse effect on body weight, food consumption, peripheral blood
picture and survival rate were noted. Carcass fat of the test group
showed no polyglycerol residues. The levels of free fatty acids,
unsaponifiable material, fatty acid composition of carcass fat and
organ weights were the same in test and control groups, except for the
liver and kidney weights of female mice which were significantly
higher. Microscopic examination of all major organs showed nothing
remarkable (Unilever Research Laboratory, 1966).
A test group of 22 rats, with a control group of 28, were kept
on a diet containing 1.5% of polyglycerol ester for three generations
and maintained for over one year without significant variation in
fertility and reproductive performance. Gross and histological
examination of the third generation revealed no consistent abnormality
related to the test substance (Unilever Research Laboratory, 1966).'
In another experiment 28 male and 28 female rats were fed 5%
polyglycerol ester or ground-nut oil in their diet for two years. No
adverse effects on body weight, food consumption, peripheral blood
picture, and survival rate were noted. Liver function tests and renal
function tests at 59 and 104 weeks were comparable between groups. The
carcass fat contained no polyglycerol and the levels of free fatty
acid, unsaponifiable residue and fatty acid composition of carcass fat
were no different from controls. Organ weights, tumour incidence and
tumour distribution were similar in control and test groups. Complete
histological examination of major organs showed nothing remarkable
(Unilever Research Laboratory, 1966).
Mice were maintained on a diet containing 1% of a polyglycerol
ester emulsifier for a period of 15.5 months. There were no
significant differences between growth rate and longevity of test and
control animals, nor was there any indication of carcinogenic activity
(Bickel et al., 1964).
OBSERVATIONS IN MAN
Thirty-seven volunteers, aged 19 to 24, were fed 2-20 g
polyglycerol ester per day for three weeks in their diet. No
abnormalities were detected in plasma proteins, serum amino-acids,
thymol turbidity, serum bilirubin, total and free serum cholesterol,
serum alkaline phosphatase, SGOT, SGPT, cholinesterase, cholesterol
esterase, 24 hour urine volume, urinary creatinine, urea output, total
and split faecal fat or total faecal nitrogen (Unilever Research
The toxicological assessment of this group of diverse but related
substances is based on an evaluation of satisfactory evidence for one
member and assumes that alterations in the fatty acid distribution or
polyglycerol content of individual members have no toxicological
bearing and only affect the physical and emulsifying properties of
each ester. The metabolic studies point to hydrolysis of these
polyglycerol esters in the gastrointestinal tract and the utilization
and digestibility studies justify the assumption that the fatty acid
moiety is metabolized in the normal manner. Analytical studies have
produced no evidence of cumulation of the polyglycerol moiety in body
tissues. Human studies showed no adverse effects.
It is desirable to have properly conducted biochemical studies on
other members of this group, that do not conform to the specifications
detailed above, particularly those containing short-chain fatty acids.
Level causing no toxicological effect
Rat: 50 000 ppm (5%) in the diet equivalent to 2500 mg/kg bw.
Estimate of acceptable daily intake for man
0.25 mg/kg bw.*
FURTHER WORK OR INFORMATION
Desirable: Properly conducted biochemical studies on other
members of this group that do not conform to the specifications
already established, particularly those containing short-chain fatty
Babayan, V. K., Kaunitz, H. & Slanets, C. A. (1965) J. Amer. Oil Chem.
Soc., 41, 434
Bickel, J., Therkelsen, A. J. & Stenderup, A. (1964) Arzneimittel
Forsch., 14, 238
Briski, B. (1970) Unpublished report, Institute of Public Health of
King, W. R., Michael, W. R. & Coots, R. H. (1971) Tox. Appl. Pharm.,
Michael, W. R. & Coots, R. H. (1971) Tox. Appl. Pharm., 20, 334
Ostertag, H. & Wurziger, J. (1965) Arzneimittel-Forsch., 15, 869
Unilever Research Laboratory (1966) Unpublished report
* As polyglycerol esters of palmitic acid.