Authentication of gluten-free flour by Fourier-transform infrared spectroscopic technique

Celiac disease is a serious gluten-sensitive autoimmune disease of the small intestine affecting genetically susceptible individuals worldwide. A strict, lifelong gluten-free diet is the only treatment. Currently, the most commonly used methods for gluten test are based upon enzyme-linked immunosorbent assay, which is sample-destructive, and requires cumbersome processing procedures, and therefore are not suitable for high-throughput real-time screening detection of gluten in foods. In this study, a Fourier-Transform Infrared (FT-IR) spectroscopy-based approach was proposed for authentication of gluten-free flour. Three chemical standards including gliadin, gluten, and starch from wheat and 62 different types of flour products were scanned by FT-IR spectroscopy over the wavenumber range of 4000 and 400 cm-1. Notable absorbance differences were observed between the chemical standards of gliadin and gluten and starch from wheat over the wavenumber range of 1800-450 cm-1. The mean absorbance profiles of gluten-free and non-gluten free categories of flour demonstrated varying spectral characteristics between 1800 and 1500 cm-1. The Principal Component Analysis (PCA)- Linear Discriminant Analysis (LDA) models built upon the original absorbance of flour between 1800 and 1500 cm-1 achieved overall prediction accuracies of at least 95.7%. The potential of FT-IR technique in identifying and authenticating gluten-free flour was demonstrated.