Sulfite Residues in Restaurant Salads.

Sulfiting agents, which have been used as salad fresheners to prevent the enzymatic browning of restaurant salads, may pose a hazard to sulfite-sensitive asthmatics. Chopped lettuce treated with a commercial salad freshener at the recommended level of 1 tablespoon per gallon (ca. 5.3 g/L) of dip solution can contain as much as 963 mg/kg (ppm) total SO equivalents. Most of the sulfite in chopped lettuce is free SO. If commercial salad fresheners are abused by using levels in excess of 1 tablespoon per gallon, progressively higher levels of residual sulfite are retained on the lettuce. Cole slaw prepared according to a typical commercial formulation contained 350 mg/kg total SO. A survey of lettuce salads, cole slaw and potato salads from 25 local and national chain restaurants and delicatessens in Madison, Wisconsin, showed sulfite residue levels to be well below those of a treated salad, indicating a lack of sulfite use.