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.
PROPYLENE GLYCOL 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.
Pancreatic lipase hydrolyzed 70% of propylene glycol monostearate
in vitro at 40° in 15 hours (Balls & Matlack, 1938). Similarly,
steapsin hydrolized 70% of propylene glycol distearate (PGDS)
in vitro at 30° in 18 hours (Long et al., 1958). The absorption,
metabolism and hydrolysis of PGDS was studied in rats using
isotopically labelled compounds, and found to be similar to those of
the glyceryl stearate esters (Long et al., 1958a, 1958b).
Metabolic studies were carried out with 14C-stearyl and
14C-succinate labelled stearyl propylene glycol hydrogen succinate.
The substance was hydrolyzed in vitro by rat pancreatic juice and
bile to yield stearic acid, propylene glycol monostearate, succinic
acid, propylene glycol mono hydrogen succinate, and propylene glycol.
After oral administration to rats, the proportions of radioactivity
appearing in expired CO2 corresponded closely to those obtained when
14C-stearyl soybean oil or 14C-succinic acid were administered.
Likewise, the proportions in urine, faeces and the carcass were
similar. A small part of the radioactivity in urine was as propylene
glycol hydrogen (14C)-succinate. The substance was also found in
the urine of two men (28 and 35 years of age) who took 10 g of
non-radioactive stearyl propylene glycol over a 48 hour period: the
amount of the partially hydrolyzed material recovered corresponded to
about 0.1% of that administered (King et al., 1970).
Oral toxicities studies were performed in the rat for propylene
glycol diacetate. It was shown that propylene glycol diacetate
possesses an LD50 of 13.53 g/kg (Smyth et al., 1941).
Six 21-day-old rats were fed for 40 days a diet containing 60%
propylene glycol ester. The animals showed no adverse effect on body
weight gain. On histological examination of the kidneys no lesions
were observed (Lepkovsky et al., 1935).
Rats in groups of 48 were fed for 13 weeks on diets containing 0,
1.5, 3.36 and 7.52% of propylene glycol monostearate with mono- and
diglycerides added to bring the total fat to 7.52%. There were no
differences between the groups in respect of growth, relative organ
weight (adrenals, gonads, heart, kidneys, liver, spleen, brain),
histology, blood glucose, BUN, plasma cholesterol, plasma glutamate-
pyruvate transaminase, haemoglobin, haematocrit, white cell count,
white cell differential counts, clotting time or urinary analyses
A preparation containing 50% of propylene glycol esterified with
stearic and succinic acids (stearyl propylene glycol hydrogen
succinate), 17% of propylene glycol monostearate and lesser amounts of
other propylene glycol derivatives ("Succistearin") was incorporated
in diets at 2.5, 5 and 10% levels and fed to rats (10 per group) for
six months. It was reported that there was no evidence of gross or
histological pathology attributable to the substance (King et al.,
A preparation named Succistearin was fed at levels of 5 and 10%
in the diet to groups of four dogs for six months. There were no signs
of toxicity (King et al., 1971).
No data are available.
There is evidence that the propylene glycol esters of fatty acids
are hydrolyzed to propylene glycol and fatty acids. Evaluation is
based on the contents of propylene glycol, for which an acceptable
daily intake has been established.
Estimate of acceptable daily intake for man
0-25 mg/kg bw.*
Balls, A. J. & Matlack, M. B. (1938) Biochem. J., 123, 679
Brandner, J. D. (1973) Unpublished report submitted by ICI America
King, W R., Michael, W. R. & Coots, R. H. (1970) Toxicol. appl.
Pharmacol., 17, 519
King, W. R., Michael,.W.R. & Coots, R. H. (1971) Toxicol. appl.
Pharmacol., 18, 26
Lepkovsky, S., Ouer, R. A. & Evans, H. M. (1935) Biochem. J., 108, 431
Long, C. L. et al. (1958a) Arch. Biochem., 77, 428
Long, C. L., Zeitlin, B. R. & Thiesen, R. jr (1958b) Arch. Biochem.,
Smyth, H. F. jr, Seaton, J. & Fisher, L. J. (1941) Ind. Hyg. Tox.,
* Calculated as propylene glycol.