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. HYDROXYPROPYL STARCH Explanation 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. BIOLOGICAL DATA BIOCHEMICAL ASPECTS 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). TOXICOLOGICAL STUDIES 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) LD50 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) Rat 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 Rat 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. Comments: 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. EVALUATION Estimate of acceptable daily intake for man Not limited.* * See relevant paragraph in the seventeenth report, pages 10-11. REFERENCES 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, 963 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) HYDROXYPROPYL STARCH (JECFA Evaluation)