Toxicological evaluation of some food
    additives including anticaking agents,
    antimicrobials, antioxidants, emulsifiers
    and thickening agents


    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.



         Modification is carried out by propylene oxide at levels up to
    25% and the resultant starch is usually lightly oxidized, bleached or
    acid modified after etherification. Substitution may amount to a
    maximum of 40 ether linkages per 100 glucopyranose units if 25%
    propylene oxide is used, and 4-6 ether linkages per 100 glucopyranose
    units if 5% propylene oxide is used.



         In vitro digestibility by pancreatin was estimated by comparing
    the amount of reducing material liberated with that formed from native
    wheat starch. No significant difference could be detected between low
    (1 in 10) and high (4 in 10) substituted starches compared with
    unmodified starch (Kay & Calandra, 1962). In contrast the
    digestibility by pancreatin was found to decrease with increased
    substitution degree. At 0.04 degree the digestibility was 80% of that
    of unmodified starch (Leegwater & Luten, 1971). Corn starch treated
    with propylene oxide -2-C14 to produce hydroxypropyl starch (degree
    of substitution 0.12) was given to a male rat by gavage. 92% of the
    radio-activity was excreted in the faeces and 3.6% in the urine over
    the next 50 hours. The urinary activity was probably derived from
    propyleneglycol in the test material (Leegwater, 1971). Further
    investigation revealed hydroxypropyl maltose to be the major faecal
    metabolite (Leegwater & Speek, 1972; Leegwater et al., 1972).


    Special studies on propylene chlorohydrin

         Propylene chlorohydrin was identified as the residue formed in
    foods fumigated with propylene oxide (Wesley et al., 1965). The
    chlorohydrin is formed by the reaction of the epoxide with the
    chloride of food. Previously, it had been believed that propylene
    glycol, formed by reaction with water in the food, was the residue.
    Propylene chlorohydrin is also formed in starches modified by
    hydroxypropylation. Both propylene chlorohydrin isomers have been
    identified in fumigated foods (Regelis et al., 1966).

         When volatilization was precluded, a combination of high
    temperature and prolonged time in cooking did not appreciably alter
    the propylene chlorohydrin content of food, but when volatilization
    was possible, the chlorohydrin content was reduced 50% by cooking
    (Wesley et al., 1965). When propylene chlorohydrin was added to a
    standard ground laboratory rat diet, 20 minutes of mixing in an open
    mixer at room temperature resulted in a 65% decrease in the propylene
    chlorohydrin content (USFDA, 1969).

    Acute toxicity (propylene chlorohydrin)

    Animal         Route     (mg/kg bw)                    Reference

    Rat            Oral      218                           USFDA, 1969

    Dog            Oral      150 mg/kg - no deaths         USFDA, 1969
                             200 mg/kg - 1/7 deaths
                             250, 300 mg/kg - 6/6 deaths

    Short-term studies  (propylene chlorohydrin)


         Groups of 10 male and 10 female five-week-old rats were fed, for
    25 weeks, diets to which propylene chlorohydrin had been added. The
    planned dietary levels were 0, 1000, 2500, 5000 and 10 000 ppm
    (0%, 0.1%, 0.25%, 0.5% and 1.0%) but analysis of the 10 000 ppm (1%)
    diet after mixing in the test compound (open mixer, 20 minute mixing
    time, room temperature) showed an actual concentration of 3568 ppm or
    35% of the planned level. The 2-chloro isomer constituted 27% of the
    total found. The actual level in this diet, after seven days exposure
    to laboratory conditions, was reduced to 838 ppm (.0838%), with 32% of
    the 2-chloro isomer, or less than 10% of the planned concentration.
    Weight gain in both sexes on the 5000 ppm (0.5%) and 10 000 ppm (1%)
    levels was depressed. The depression was slight in the males on the
    5000 ppm (0.5%) level and both groups of females and moderate in the
    males on the 10 000 ppm (1%) level. Food consumption was slightly
    decreased in these groups but food efficiency was normal. The average
    liver and kidney weights of the males and the liver weight of the
    females on the 10 000 ppm (1%) level were decreased but the organ
    weight/body weight ratios were normal. The decreased spleen weights
    and spleen/body weight ratios in the males and other minor organ
    weight variations appeared to be unrelated to the treatment. No
    effects on haematological values, mortality, or gross or microscopic
    lesions in the tissues were observed (USFDA, 1969).

         Propylene chlorohydrin was administered to groups of 10 male and
    10 female eight-week-old rats by stomach tube in doses of 0, 25, 50,
    75 and 100 mg/kg/day for 22 weeks. The dose for the high level was
    increased from 100 mg/kg to 150 mg/kg in the eleventh week, to
    200 mg/kg in the fourteenth week, and to 250 mg/kg in the sixteenth
    week. Doses of 200 mg/kg and less did not increase mortality. Ail the
    rats on the high level were dead by the nineteenth week with all but
    one of the deaths occurring between the sixteenth and nineteenth weeks
    after the dose had been increased to 250 mg/kg. On the high level,
    weight gain was moderately depressed in the males and slightly
    depressed in the females while the dose was 100 or 150 mg/kg. Both
    sexes lost weight when the dose was increased to 200 mg/kg. Weight
    gain was slightly, but not significantly, decreased in both sexes on
    the 75 mg/kg level. Food consumption was slightly decreased in the
    males of the high level while the dose was 100 mg/kg and decreased to
    a greater extent when the dose was raised. The females on the high
    level also showed a slight decrease in food consumption when the dose
    was increased. With the rats losing weight when the dose was increased
    to 200 mg/kg, the food efficiency values have no meaning. The liver
    weight/body weight ratios of both males and females on the 75 mg/kg
    dose and the liver weight and liver weight/body weight ratio of the
    males on the 25 mg/kg dose were increased, but this increase was not
    accompanied by gross or microscopic alterations in the liver. Other
    organ weight and organ weight/body weight ratio changes did not appear
    to be related to the treatment. No haematological effects or gross or
    microscopic effects on the tissues of the treated rats, at a dose of
    75 mg/kg or less, were seen. The tissues of the high level rats were
    not examined microscopically (USFDA, 1969).

    Acute toxicity

         Application of powder or solutions produced mild irritation in
    rabbits' eyes (Pallotta, 1959). The Schwartz Prophetic Patch Test on
    210 human subjects using powdered high and low modified starch, as
    well as native starch as control, showed no difference after 72 hours
    initial exposure and no evidence of sensitization on 72-hour challenge
    after two weeks (Majors & Ruben König, 1959). The Repeat Insult Patch
    Test in 23 human subjects showed no irritation after nine 24-hour
    exposures and no evidence of sensitization on 24-hour challenge after
    two weeks (Ruben König, 1959).

    Short-term studies


         Groups of 10 male and 10 female rats were fed for 90 days
    diets containing 0, 2, 5, 10 and 25% of highly modified starch
    (25% propylene oxide) and 25% unmodified starch. No systemic toxicity
    was noted. There were no adverse effects regarding mortality,

    urinalysis or haematology at any level. There was slight reduction in
    growth rate at the highest dietary level with lower food utilization
    and without an equivalent increase in food consumption. Mild diarrhoea
    occurred at 25% dietary level. No adverse effects occurred at any
    other level. At autopsy there were no significant differences in the
    organ weights of liver, kidney, spleen, gonad, heart or brain. Gross
    and histological examination of all major tissues revealed no
    abnormalities due to the feeding of highly modified starch (Kay &
    Calandra, 1961). In another experiment groups of 10 male and 10 female
    rats were fed for 90 days on diets containing 0, 5, 15 and 45% of low
    modified starch (5% propylene oxide). Haematological findings at
    12 weeks were comparable for all groups. Body weights did not differ
    significantly from controls but were consistently lower in male rats
    only. Feed efficiency was similar in all groups. Caecal enlargement
    was seen at the 45% and very slightly at the 15% level. No
    histological abnormalities were detected in any major organs, which
    were due to the test substance. The enlarged caeca showed no evidence
    of inflammation or changes in the muscular coat (Feron et al., 1967).

    Long-term studies 

         None available.


         Short-term feeding studies with rats show that many highly
    modified starches are well tolerated.

         The metabolic study in rats using radio-labelled material shows
    that most of the radio-labelled hydroxypropyl-containing moiety is
    excreted in the faeces. No long-term study on this modified starch is
    available but collateral evidence from the long-term study in rats
    with hydroxypropyl distarch glycerol, a more high modified starch,
    indicates that the hydroxypropyl moiety is causing no adverse effects.
    The available evidence for the group of modified starches considered
    indicates that caecal enlargement without associated histopathological
    changes is without toxicological significance.


    Estimate of acceptable daily intake for man

         Not limited.*


    *    See relevant paragraph in the seventeenth report, pages 10-11.


    Feron, V. J., Til, H. P. & de Groot, A. P. (1967) Unpublished report
         No. R 2456 by Centraal Instituut voor Voedingsonderzoek

    Kay, J. H. & Calandra, J. C. (1961) Unpublished report by Industrial
         Bio-Test Laboratories, Inc.

    Kay, J. H. & Calandra, J. C. (1962) Unpublished report by Industrial
         Bio-Test Laboratories, Inc.

    Leegwater, D. C. (1971) Unpublished report No. 3441 by Centraal
         Instituut voor Voedingsonderzoek

    Leegwater, D. C. & Luten, J. B. (1971) Stärke, 23, 430

    Leegwater, D. C. et al. (1972) Carbohydr.Res., 25, 411

    Leegwater, D. C. & Speek, A. J. (1972) Stärke, 24, 373

    Majors, P. A. & Ruben König, H. L. (1959) Unpublished report by Hill
         Top Research Institute, Inc.

    Pallotta, A. J. (1959) Unpublished report by Hazelton Laboratories,
         Inc., 22 May 1959

    Ragelis, E. P., Fisher, B. S. & Klimeck, B. A; (1966) J.O.A.C., 49,

    Ruben König, H. L. (1959) Unpublished report by Hill Top Research
         Institute, Inc., 13 May 1959

    United States Food and Drug Administration (1969) Unpublished report

    Wesley, F., Rourke, B. & Darbishire, O. (1965) J. Fd. Sci., 30, 1037

    See Also:
       Toxicological Abbreviations
       Hydroxypropyl starch  (FAO Nutrition Meetings Report Series 46a)
       Hydroxypropyl starch (WHO Food Additives Series 1)
       Hydroxypropyl starch (WHO Food Additives Series 17)