The purpose of this study was to identify whether liquid fruit waxes could be added with bleached shellac. The compounds of bleached shellac from different sources were analyzed by targeted metabolomics based on liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) combined with liquid chromatography with evaporative light scattering detection. Twelve target compounds were selected by multivariate statistical analysis including unsupervised principal component analysis (PCA) and supervised partial least squares discriminant analysis (PLS-DA). According to variable importance in the projection (VIP) value, five differential compounds and seven shared compounds were identified. Finally, the viability of this method in the detection of commercial liquid fruit wax products was verified using the shared compounds as biomarkers. These results showed that chromatography combined with mass spectrometry can identify whether bleached shellac could be added in liquid fruit wax.

This study was carried out in order to develop a composite film that serves the dual function of acting as an intelligent indicator for meat freshness and preserving meat using chitosan (CS) as the film-forming substrate, glycerin as the plasticizer, polymethoxy flavones (PMFs) as the bacteriostatic agent and anthocyanin (AC) as the color developing agent. The effects of AC and PMFs on the mechanical, barrier, permeability, indicator and preservative properties of the composite film were investigated. The results showed that the composite film extended the shelf life of pork to 7 d at 4 ℃, this effect being more pronounced than that of blank group without film coating, control groups coated with polyethylene film and CS film. The composite film exhibited blue gray, light brown red and dark brown red colors for fresh, second fresh and spoiled meat respectively, and can enable real-time and non-destructive indication of pork freshness.