Qualitative and quantitative detection of Sudan I and II adulterated in chili powders by front-face synchronous fluorescence spectroscopy：Aggregation-induced emission in solid food

Abstract Sudan dyes are commonly found adulterants in chili related products. In this work, the unusual fluorescent behaviors of Sudan I and II in solid state were observed for the first time which are attributed to aggregation-induced emission (AIE). Taking advantage of their solid-state AIE properties, front-face synchronous fluorescence spectroscopy (FFSFS) was applied for the rapid and non-destructive determination of Sudan I or II in chili powders. For each dye, 90 adulterated chili powders containing 1–50 mg/g Sudan I or II were prepared. Qualitative and quantitative analyses were achieved by principal component analysis – linear discriminant analysis (PCA–LDA) and partial least square regression (PLSR), respectively. The built models were validated by full cross-validation, five-fold cross-validation and external validation. The sensitivity and specificity in discrimination were both 100%. For PLSR prediction, the coefficients of determination (R2) were greater than 0.96. The relative errors of prediction (REP) were 15.2% and 11.6% for Sudan I and II, respectively. AIE-based FFSFS offers a new route for the application of fluorescence spectroscopy in food authentication.