Sorbitan monostearate is an emulsifier. This material coats yeast cells and protects the cells from damage by oxygen and assists in the rehydration of the yeast.
Sorbitan monostearate is a mixture of partial stearic and palmitic acid esters of sorbitol and its mono- and dianhydrides. Sourced from plants, allergens are typically part of the protein structure; however, the process used to produce sorbitol eliminates the plant protein.
Sorbitan monostearate is not considered an allergen. It is listed in the FDA GRAS (Generally Recognized As Safe) list of ingredients for use in food products. Sorbitan monostearate is Kosher.