A chemometric study on the identification of 5-methylfurfural and 2-acetylfuran as particular volatile compounds of oxidized fish oil based on SHS-GC-IMS.

Fish oil develops particular off-odors, mainly fishy odor, from the oxidation of its characteristic fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA). Anchovy oil (AO) was taken as representative of fish oils. This was compared to three vegetable oils with different fatty acid compositions, i.e. camellia, sunflower and linseed oil, and differential volatile compounds were identified by static-headspace gas-chromatography ion-mobility-spectrometry (SHS-GC-IMS) and orthogonal partial-least-squares discriminant analysis (OPLS-DA) during oxidation at 60 °C. Three groups of differential volatile compounds detected at higher concentrations in the AO were screened out and two compounds, identified as 5-methylfurfural and 2-acetylfuran, were characteristic to the AO and not found in the vegetable oils. They were formed from both EPA and DHA, only present in the AO, and their formation mechanisms were proposed. The contents of 5-methylfurfural and 2-acetylfuran increased linearly with the oxidation time and consequently they could be used as oxidative markers of fish oils.

[Rapid quality evaluation of Glycyrrhizae Radix et Rhizoma and Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle based on color digitization and multi-component determination].

To explore the color value changes after processing and further explore the correlations between color values and internal components, we established a rapid evaluation method for the quality of Glycyrrhizae Radix et Rhizoma and Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle. In this study, the color values of Glycyrrhizae Radix et Rhizoma and Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle were digitized by a spectrophotometer, and the standard ranges of color values of the two herbal medicines were established. Further, a discriminant analysis model was established to quickly and accurately distinguish the two herbal medicines. The content of 9 flavonoids and 1 triterpene in Glycyrrhizae Radix et Rhizoma and Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle were determined by HPLC, and Pearson correlation analysis was adopted to analyze the correlations between the color values and the content of 10 components. The standard ranges of L~*, a~*, and b~* values were 65.539 6-68.305 8, 7.296 3-8.467 3, and 29.998 8-32.212 8 for Glycyrrhizae Radix et Rhizoma, and 43.654 3-47.166 4, 14.050 0-15.133 8, and 16.424 6-20.984 8 for Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle, respectively. Glycyrrhizae Radix et Rhizoma had higher L~* and b~* values and lower a~* value than Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle, which indicated that processing with honey decreased the white and yellow values and increased the red value. The original and cross validation of the established discriminant analysis model met the requirements, and the external validation of the model showed the prediction accuracy of 100%. Pearson correlation analysis showed that the a~* value was positively correlated with the content of liquiritin apioside and isoliquiritin apioside(P<0.05), while the L~* and b~* values were negatively correlated with the content of the above two components(P<0.05). After processing with honey, L~* and b~* decreased while a~* increased, and the content of liquiritin apioside and isoliquiritin apioside increased, which was consistent with the content determination results. This study reveals the regularity of the color values of Glycyrrhizae Radix et Rhizoma after processing with honey roasting, as well as the correlations between color values and component content, which provides a basis for the rapid quality evaluation of Glycyrrhizae Radix et Rhizoma and Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle.