Using LC-MS to examine the fermented food products vinegar and soy sauce for the presence of gluten

A strict, lifelong gluten-free (GF) diet is currently the only treatment for coeliac disease (CD). Vinegar and soy sauce are fermented condiments that often include wheat and/or barley. During fermentation cereal proteins are partially degraded by enzymes to yield peptide fragments and amino acids. Whether these fermented products contain intact or degraded gluten proteins and if they are safe for people with CD remains in question. LC-MS offers the benefit of being able to detect hydrolysed gluten that might be present in commercial vinegar and soy sauce products. LC-MS revealed the presence of gluten in malt vinegar, wherein the identified peptides derived from B-, D- and γ-hordein from barley, as well as γ-gliadin, and HMW- and LMW-glutenins from wheat that are known to contain immunopathogenic epitopes. No gluten was detected in the soy sauces examined despite wheat being a labelled ingredient indicating extensive hydrolysis of gluten during soy sauce production.