Diacetyl is added to some foods for flavoring purposes. It is metabolized in mammals, is of low acute toxicity, and the no-adverse-effect level, based on a 90-day study in rats, is approximately 90 mg per kg body weight. The per capita daily intake of diacetyl added to food, both as a component of starter distillate and as diacetyl itself , is estimated to be less than 0.3mg.
Available studies of the biological effects of commercial starter distillate consist of two report; the one showed that starter distillate exhibited no mutagenic activity in in vitro test systems; the other showed that it was without teratogenic activity when administered orally in doses as high as 1600mg per kg body weight to pregnant mice, rats, hamsters, and rabbits.
The per capita daily intake of starter distillate is about 5mg or about 0.1mg on an anhydrous basis. Diacetyl and acetic acid are major components of starter distillate; total daily per capita intake of all organic components of starter distillate, other than diacetyl and acetic acid, is estimated to be less than 0.08 mg per body weight. Based on the nature of the starting material and the process used to produce starter distillate, the Select Committee has no grounds to suspect that the small amount of unidentified ingredients poses a hazard. It would appear that the possibility of hazard from the addition of starter distillate is minimal. However, no food grade standars exist for starter distillate. It is a mixture of many substances, not all of which have been identified, whose qualitiative and quantitative composition may vary depending on the combinations of microorganism used in the starter culture, and on the conditions of steam distillation. Hence, there is need for establishing practical food grade standards for starter distillate specifying acceptable limits of variability.
In light of these considerations the Select Committee concludes that: There is no evidence in the available information on diacetyl or starter distillate that demonstrates or suggests reasonable grounds to suspect a hazard to the public when they are used at levels that are now current or that might reasonably be expected in the future.