Safety evaluation of thaumatin (Talin protein).

Thaumatin, the sweet proteinaceous extract of the arils of Thaumatococcus daniellii (Benth.) has been studied for its subacute toxicity in rats and dogs and its ability to produce anaphylactic antibodies following oral administration to rats and normal human subjects. Thaumatin was readily digested prior to absorption in rats and no adverse effects resulted from its continuous administration to rats and dogs at dietary concentrations of 0, 0.3, 1.0 and 3.0% for 13 wk. It was not teratogenic when administered orally to rats at 0, 200, 600 and 2000 mg/kg body weight/day from day 6 to 15 of gestation and was without effect on the incidence of dominant lethal mutations when administered on five consecutive days to male mice at 200 and 2000 mg/kg/day. The lack of mutagenic potential was confirmed in bacterial mutagenic assays with Salmonella typhimurium (strains TA1535, TA1537, TA1538, TA98 and TA100) and Escherichia coli WP2, at levels of addition of 0.05-50 mg/plate. In rats, thaumatin was found to be a weak sensitizer, comparable with egg albumen, when administered systemically but to be inactive when administered orally. Prick testing of laboratory personnel who had been intermittently exposed by inhalation to thaumatin for periods up to 7 yr showed that 9.3% (13/140) responded positively to commercial thaumatin, while 30.7% were positive to Dermatophagoides pteronyssinus (house dust mite). None of the subjects who gave a positive skin reaction to commercial thaumatin responded to the plant components remaining after removal of the specific sweet Thaumatin proteins. Challenge tests in man did not demonstrate any oral sensitization. The results indicate that thaumatin when used as a flavour modifier and extender, and partial sweetener, is unlikely to be hazardous at the anticipated level of consumption.