Analysis of the effects of heat treatment on gliadin immunochemical quantification using a panel of anti-prolamin antibodies.

Antigen-labeled capture enzyme-linked immunosorbent assay with four different anti-gliadin monoclonal antibodies and an anti-gliadin serum and two different sample systems (purified gliadin fractions heat-treated in soluble phase and a model of dough simulating a baking process) were employed to study the effects of heat treatment on gliadin quantification. The analysis of purified gliadins showed that there is no particularly heat stable fraction. Remarkably, omega-gliadin did not present a differential heat stability. Reactivity varied depending on the time-temperature conditions of the treatment, the antibody employed, and the fraction analyzed. Heated dough samples showed an impairment of protein extraction depending on the intensity of the treatment. Capillary electrophoresis analysis of extracts showed that each gliadin group is affected to a different extent; omega-gliadin is less modified. Immunochemical analysis of the heat-treated samples using either of the five antibodies showed a decrease in the quantified gliadin, in concordance to the loss in the extracted proteins. Among the different sources of error in gliadin immunochemical quantification, the impairment in extraction efficiency in heat-treated samples appears as a major drawback to be overcome.