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
Geneva
1974
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.
SORBIC ACID AND ITS CALCIUM, POTASSIUM AND SODIUM SALTS
Explanation
These compounds have been evaluated for acceptable daily intake
by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
Refs No. 6 and No. 13) in 1961 and 1965.
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.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
Sorbic acid did not act as an antimetabolite for essential fatty
acids in the rat. The incorporation of sorbic acid into the diet of
rats did not decrease the efficiency of utilization of calories.
Sorbic acid is used by the animal organism as a source of calories
(Deuel et al., 1954a). Sorbic acid is metabolized similarly to caproic
acid (Cohen, 1937; Witter et al., 1950; Deuel et al., 1954b).
In vitro studies using isolated rat liver particle systems show
oxidation via 2-carbon atom fragments, which recondense to
acetoacetate (Witter et al., 1950). Tissue homogenates or isolated
mitochondria oxidize sorbic acid at the same speed as other fatty
acids (Lang, 1960). The oxygen consumption of liver homogenates of
parent rats fed for 120 days on diets containing 0% and 10% sorbic
acid was similar in both groups. The female controls of the F1
generation showed a significantly increased O2 consumption compared
with male or female F1 rate on 10% sorbic acid (Demaree et al.,
1955). Fasting female rats with exogenous ketonuria when fed sodium
sorbate at various levels with or without additional glucose, produced
similar amounts of ketone bodies in the urine or showed similar
suppression of keto body formation as with caproic acid (Deuel et al.,
1954b). Enzyme studies have shown that a concentration of 0.112% of
sorbic acid inhibited catalase activity by 72 to 77% (Lück, 1957).
Sulfhydryl enzymes in ficin and alcohol dehydrogenase were inhibited
at a concentration of 10-4M. Aldolase and urease were not
significantly inhibited by sorbic acid. Irradiated sorbic acid was a
stronger inhibitor of ficin than sorbic acid (Whitaker, 1959). This
inhibition of dehydrogenase is the main basis for the fungistatic
activity of sorbic acid. It appears to be impossible to give
sufficient sorbic acid to inhibit the dehydrogenase enzyme systems in
the animal body (Melnick, et al., 1954a).
When sorbic acid is incorporated into food it may undergo
oxidation, with the formation of peroxides and secondary oxidation
products. In the presence of sufficient metabolizable carbohydrates
the end-products are carbon dioxide and water. If metabolizable
carbohydrates are not present, acetoacetate and acetone are also
produced (Melnick et al., 1954b).
The metabolism of 1-14C-sorbic acid has been studied by
Fingerhut et al. (1962a); 85% of the activity was found in the expired
CO2, 0.4% in the faeces, 2% in the urine as urea and CO2, 3% in
internal organs, 3% in the skeletal muscles and 6.6% in the other
parts of the carcass. No glycogen was formed from sorbic acid. Most of
the activity was found in the subcutaneous fat deposits and in the
lipids of the organs. There was a linear relationship between dose and
oxidation rate; the half-life of the oxidation was 40-110 minutes in
the dose range from 60-1200 mg/kg bw. In a similar experiment on mice,
also using 1-14C-sorbic acid, these results were confirmed; 81 ± 10%
of the sorbic acid was oxidized to CO2, the dose given ranging from
40-3000 mg/kg bw. About 7% of the activity was excreted as sorbic acid
and 0.4% as trans, trans-muconic acid (Westöö, 1964).
The studies on the metabolism of 14C-labelled sorbic acid were
performed by using either sorbic acid neutralized with sodium
hydroxide (Fingerhut et al., 1962) or the potassium salt (Westöö,
1964).
TOXICOLOGICAL STUDIES
Special studies on reproduction
Mouse
Mice fed for eight months 0 or 40 mg + 2 mg Nisin/kg/day sorbic
acid were mated and allowed to produce F1 to F4 generations. Weight
gains were compared at 3.5 months after weaning. Weight gain was
better than controls in the F4 only (Shtenberg and Ignatev, 1970).
Rat
Groups of five male and five female rats were kept for 120 days
on either 0 or 10% sorbic acid. After 60 days they were mated and
produced similar numbers of off-spring. Fourteen rats of the F1
generation were kept on control diet, 19 on 10% sorbic acid for a
further 70 days and mated. The number of off-spring were similar in
both groups. Females on 10% had normal liver weight but males showed
reduced growth (Demarce et al., 1955).
Acute toxicity
LD50 References
Substance Animal Route (mg/kg bw)
Sorbic acid rat oral 10 500 Deuel et al., 1954a
rat oral 7 400 Witter et al., 1950
oral 7 360 Smyth & Carpenter, 1948
Sodium sorbate rat oral 7 160 Smyth & Carpenter, 1948
Sodium sorbate rat oral 4 000 & Deuel et al., 1954a
5 940
Na-sorbate rat oral 7 200 Witter et al., 1950
Potassium sorbate rat oral 4 920 Mellon Institute, 1954
(solid isomer)
Potassium sorbate rat oral 6 170 Mellon Institute, 1954
(mixed isomer)
K-sorbate rat oral 4 200
Sodium sorbate mouse i.p. 2 500 Rhône-Poulenc, 1965
Potassium sorbate mouse i.p. 1 300 Rhône-Poulenc, 1965
Short-term studies
Mouse
Groups of 25 male or 25 female mice received for two months by
oral intubation daily 40 mg/kg/day sorbic acid. Survival, weight gain
and food consumption were no different from controls: at the end of
the study food was restricted by 50% for five days. Mortality and
weight loss was less than in controls. Physical stress had no effect,
mortality after giving 0.1 ml CC14 was less in sorbic acid treated
mice than controls. Groups of 50 males and 50 females received by oral
intubation 80 mg/kg sorbic acid for three months. Growth was somewhat
restricted compared with controls. When stressed by 90% food
restriction for 18 days there was no difference in mortality from
controls. When given 0.1 ml CC14 mortality was nil compared to 30% in
controls (Shtenberg & Ignatev, 1970).
Rat
Feeding sorbic acid at 1% or 2% in the diet for 80 days had no
adverse effect on the growth of rats nor did any histological
abnormalities appear in internal organs. Only the liver was slightly
enlarged compared with controls (Kramer & Tarjan, 1962). Feeding 1%
sorbic acid in the diet for four months had no effect on blood
cholesterol level while 10% raised the level together with fat
deposition in the internal organs. Leucocytes number was depressed
after two months and there was partial impairment of cholinesterase
activity (Slavkov & Petrowa, 1964). When groups of five male and five
female rats were kept on a diet with 0% and 10% sorbic acid for 120
days appearance, behaviour and food consumption were normal but some
animals at the 10% level showed increased liver/bw ratios (Demarce et
al., 1955).
Tests with two different strains of rats in two separate
laboratories showed that ingestion of diets containing 4% and 8% of
sorbic acid for a period of 90 days did not affect the rate of weight
gain. The animals receiving 4% of sorbic acid showed no abnormality of
renal, hepatic or other tissues. Rats on the 8% diet showed a slight
but statistically significant increase in relative liver weight. The
histopathological appearance of the liver was, however, normal (Deuel
et al., 1954a).
Sorbic acid was shown to produce local sarcomas in rats when
given by repeated subcutaneous injection at the same site in either
arachis oil or in aqueous solution. The potassium salt when
administered under similar conditions failed to produce any tumours.
Sorbic acid in the drinking-water (10 mg/100 ml) for 64 weeks and the
potassium salt given either in the drinking-water (0.3%) or in the
diet (0.1%) for 100 weeks failed to produce any tumours (Dickens et
al., 1966, 1968).
Groups of 10 rats (five male and five female) were fed potassium
sorbate (solid or mixed isomers) at levels of 0, 1, 2, 5 and 10% of
the diet for three months. Body weight gain was initially depressed at
10%, and, to a lesser degree, in the 5% female group. There are no
figures given for the food consumption during this time. At the end of
the experiment, the weights of the rats receiving 10% of either isomer
were slightly depressed, but the food consumption of these animals was
smaller. The food efficiency (weight gain/g food) was practically the
same as in the control group. Relative liver weights were the same in
all groups. Kidney weights were increased at the 10% level, probably
due to the high potassium load. This was also noted to a lesser
degree at the 5% level. Gross pathological examination showed no
abnormalities, even in the 10% level groups (Mellon Institute, 1954).
Rabbit
3.3 g sorbic acid daily/kg bw was tolerated by rabbits without
adverse effects (Kuhn et al., 1937).
Dog
Eight dogs received 1% and eight dogs 2% of the solid or mixed
isomers of potassium sorbate in the diet for three months; four dogs
were used as controls. There were no differences in weight gain. Gross
examination on autopsy showed no evidence of a deleterious effect
attributable to the sorbates (Mellon Institute, 1954).
In dogs fed for three months on a diet containing 50% of cheddar
cheese to which 4% of sorbic acid or 4% of caproic acid had been
added, the response was similar to that in dogs on the same cheese
diet without such supplements. No histopathological differences were
observed in tissues obtained from any of the three groups (Deuel et
al., 1954a).
Long-term studies
Mouse
Groups of 33 male and female mice were injected s.c. up to 44
times with sorbic acid in arachis oil to a total of 31 mg sorbic acid.
Controls had arachis oil only and 33 controls were untreated. Animals
survived on average 40 weeks (range 4-80 weeks). No animal developed
malignant tumours at the site of injection. Spontaneous mammary
carcinomas occurred in equal numbers in untreated and treated groups
(Gericke, 1968). Groups of 50 male and 50 female mice were given
40 mg/kg/day sorbic acid in their diet. No tumours were seen in
control or sorbic acid group. General condition, behaviour, weight
gain and survival were similar in control and test groups. The
relative weights of liver, kidney and testes were lower in the test
group than in controls. 100% starvation for 13 days at the end of the
test increased mortality compared with controls (Shtenberg & Ignatev,
1970).
Rat
Groups of 10 male and 10 female rats received 40 mg/kg/day sorbic
acid in their diet for 18 months. After the end of the test, animals
were starved for 13 days completely but the test groups survived
longer than controls. Weight gain was not measured. Blood pH,
C-reactive protein levels and blood morphology were comparable with
controls and no significant changes were seen in serum ceruloplasmin,
serum complement or phagocytic activity of leucocytes. Tumour results
were not reported (Shtenberg & Ignatev, 1970).
Groups of six rats were given 0.1% K-sorbate in food and 0.3%
K-sorbate in drink for 60 weeks. Survival and general conditions were
satisfactory. No special features were seen at 65 weeks in exploratory
laparotomy nor at 100 weeks when all animals had died. No tumours were
detected (Dickens et al., 1968).
Groups of six rats received by s.c. injection (light) sorbic acid
in water or K-sorbate (light) in water and groups of 12 rats received
SG/sorbic acid (Hoechst) in oil, and K-sorbate (Hoechst) in water. A
control group of 12 received oil only. Dosage was 2 mg/0.5 ml twice
weekly for 56-60 weeks. No local or distant tumours were seen in 12
controls, three of which survived 108 weeks. Sorbic acid (light) in
water produced two local fibrosarcomata at the injection site, all six
animals being dead at 76 weeks. Sorbic acid (Hoechst) in oil produced
no local tumours at all with two animals surviving 108 weeks.
K-sorbate (light) in water produced no local tumours in six rats,
three animals surviving 100 weeks and K-sorbate (Hoechst) in oil also
produced no tumours in 12 rats with two surviving 108 weeks (Dickens
et al., 1968).
Feeding 5% of sorbic acid in the diet to groups of 100 rats for
1000 days in two generations had no effect on weight gain or
reproduction. No ill effects were observed, and no sorbic acid could
be found in the urine (Lang et al., 1967).
The feeding experiment on groups of 100 rats (50 males and 50
females) given 0 and 5% sorbic acid was extended to the whole life-
span of the first generation. The average life-span of the group
receiving sorbic acid was 811 days for the males and 789 days for the
females. In the control group the life-span of the males was 709 days
and for the females 804 days, possibly suggesting protection by sorbic
acid against lung infection. Autopsies were performed on all rats of
the first generation that died during the experiment. There were no
differences in the organ weight of the individual groups nor in the
distribution of the causes of death. In each group (5% sorbic acid and
controls) only two tumours were found. The animals of the second
generation were sacrificed after 250 days of feeding sorbic acid.
Examination of liver, kidney, heart and testes showed no abnormalities
(Lang, 1960: Lang et al., 1967).
Comments:
Sorbic acid is readily metabolized. Both man and rat appear to
utilize identical metabolic mechanisms for oxidation of sorbate. The
long-term studies suggest that the same no-effect level applies to the
salts as to the free acid. Sorbic acid and K-sorbate corresponding to
the specifications do not cause tumours when administered orally or
subcutaneously. The earlier results of s.c. injection with an
unidentified sample remain unexplained. Long-term studies on
parasorbic acid which, it has been claimed, may be produced from
sorbic acid, also produce no evidence of carcinogenic potential when
given orally.
EVALUATION
Level causing no toxicological effect
Rat: 50 000 ppm (5%) in the diet, equivalent to 2500 mg/kg bw per
day.
Estimate of acceptable daily intake for man
mg/kg bw
0-25*
REFERENCES
Cohen, P. P. (1937) J. biol. Chem., 119, 333
Demarce, G. E. et al. (1965) J. Amer. Pharm. Ass. Sci., 44, 619
Deuel, H. J. et al. (1954a) Food Res., 19, 1
Deuel, J. J. et al. (1954b) Food Res., 19, 113
Dickens, F., Jones, H. E. H. & Waynforth, H. B. (1966) Brit. J.
Cancer, 20, 134
Dickens, F., Jones, H. E. H. & Waynforth, H. B. (1968) Brit. J.
Cancer, 22, 762
Fingerhut, M., Schmidt, B. & Lang, K. (1962) Biochem. Z., 335, 118
Gericke, D. (1968) Z. Ernahrungswiss., Suppl. 7, 29
Kramer, M. & Tarjan, R. (1962) Int. Z. Vitaminforsch., 32, 149
Kuhn, R., Köhlei, F. & Köhlei, L. (1937) Hoppe Seyler's Z. Physiol.
Chem., 247, 197
Lang, K. (1960) Arzneimittel-Forsch., 10, 997
* As sum of sorbic acid and calcium, potassium and sodium sorbate
(expressed as sorbic acid).
Lang, K. et al. (1967) Unpublished report
Lück, H. (1957) Biochem. Z., 328, 411
Mellon Institute (1954) Unpublished report
Melnick, D., Luckmann, F. H. & Gooding, C. M. (1954a) Food Res., 19,
44
Melnick, D., Luckmann, F. H. & Gooding, C. M. (1954b) Food Res., 19,
33
Rhône-Poulenc (1965) Unpublished report
Shtenberg, A. J. & Ignatev, A. D. (1970) Fd. Cosmet. Toxicol., 8, 369
Slavkov, B. & Petrowa, A. (1964) Higiena (Sofia) 7, 4, 52
Smyth, H. F. jr & Carpenter, C. P. (1948) J. industr. Hyg. Toxicol.,
30, 63
Westöö, E. (1964) Acta chem. scand., 18, 1373
Whitaker, J. R. (1959) Food Res., 24, 37
Witter, R. F., Newcomb, E. H. & Stotz, E. (1950) J. biol. Chem.,
185, 537
See Also:
Toxicological Abbreviations