Select Committee on GRAS Substances (SCOGS) Opinion: Hydroxypropyl Distarch Phosphate
Hydroxypropyl Distarch Phosphate
- SCOGS-Report Number: 115*
- Type Of Conclusion: 3
- ID Code: 53124-00-8
- Year: 1979
- 21 CFR Section:
A reduction of 7 percent in caloric value as compared with unmodified starch in a 10-day rat feeding test was demonstrated for hydroxypropyl distarch phosphate prepared by treating a phosphate cross-linked cornstarch with 8 percent propylene oxide. However, no reduction in growth rates or feed efficiences were found in 90-day rat feeding studies with hydroxypropyl distarch phosphate prepared by treatment with 5 or 10 percent propylene oxide. Increased cecal weights were observed in both studies at dietary levels of 20 g per kg but no tissue abnormality was found. The only possible pathologic change noted was calcareous deposits within the renal pelvis and pelvic epithelium in rats fed the starch treated with 10 percent propylene oxide. In a 79 -week feeding test with mice, a slightly increased incidence of intratubular nephrocalcinosis, concrements in the renal pelvic space and urinary bladder stones were observed in males. As discussed in the introduction to the opinion on modified starches, this renal alteration is considered to be of doubtful biological importance, but the Select Committee suggests that experiments should be undertaken in due time to clarify its toxicological significance.
As pointed out in the opinion on hydroxypropyl starch, treatment of starch with propylene oxide to introduce hydroxypropyl groups may also result in the formation of propylene chlorohydrin by reaction with chloride ions that may be present. Propylene chlorohydrin has been shown to be mutagenic to Salmonella typhimurium TA 1530 but not to TA 1538. Short-term (22-week) rat feeding experiments have revealed no pathologic changes at dietary levels up to 75 mg propylene chlorohydrin per kg, nor have long-term feeding experiments with hydroxypropyl distarch glycerol shown an increase in tumor incidence in rats. A long-term mice feeding study with hydroxypropyl distarch phosphate containing 4.3 ppm propylene chlorohydrin revealed no increased incidence of neoplastic lesions. Intake of propylene chlorohydrin was about 350 µg per kg body weight. This would be about four orders of magnitude greater than per capita human exposure assuming that hydroxypropylated starches are the only modified starches used in processed foods. In view of the mutagenicity of propylene chlorohydrin in the Ames test, however, the Select Committee suggests that the limits on this residue be reduced to the lowest level consistent with feasible manufacturing practice and that long-term feeding studies be undertaken with graded levels of propylene chlorohydrin to clarify whether the mutagenic activity observed in a bacterial system is an indication of potential mutagenic activity in animals. This modified starch is not currently used in infant foods.
Based on the foregoing considerations, the Select Committee concludes that:
While no evidence in the available information on hydroxypropyl distarch phosphate demonstrates a hazard to the public when it is used at levels that are now current and in the manner now practiced, uncertainties exist requiring that additional studies should be conducted.