ABSTRACT
ObjectiveTo explore the quality differences between steamed products and raw products of Citri Reticulatae Pericarpium（CRP）. MethodThe color of steamed products and raw products of CRP was determined from the perspective of appearance by electronic eye technique， and the quality differences between them was objectively characterized by the luminous value（L*）， yellow-blue value（b*）， red-green value（a*） and total chromatic value（E*ab）. Based on this， ultra-high performance liquid chromatography（UPLC） was used to establish a fingerprint evaluation method with the mobile phase of acetonitrile（A）-0.1% formic acid aqueous solution（B） for gradient elution（0-5 min， 5%A； 5-30 min， 5%-20%A； 30-60 min， 20%-52%A）， detection wavelength at 270 nm， flow rate of 0.3 mL·min-1 and column temperature of 30 ℃. The quality differences between steamed products and raw products of CRP were compared from the perspective of chemical composition， and correlation analysis was used to reveal the correlation between the difference in appearance color and the difference in internal chemical composition. ResultAfter being steamed， L*， b* and E*ab of CRP showed an overall decreasing trend， indicating that the color of the steamed products darkened and deepened from yellow to blue but still tended to be yellow， while a* showed an overall increasing trend， indicating that the color of the steamed products tended to red. A total of 24 peaks were identified in the fingerprint profiles of raw products and steamed products of CRP， and 13 of the main peaks were identified. The precision， stability and repeatability studies showed that compared with the reference peak （peak 14， hesperidin）， the relative standard deviations（RSDs） of the relative peak area and relative retention time of the remaining peaks were<3.0%.The results of chemometric statistical analysis showed that there were some differences between raw products and steamed products of CRP， and 7 main differential components were identified， among which 5-hydroxymaltol（peak 1） and 5-hydroxymethylfurfural（peak 2） were the characteristic components of steamed products. The correlation analysis results showed that， in addition to the above two characteristic components， four components of peak 4， peak 10 （vicenin-2）， peak 23 （tangeretin） and peak 24 （5-demethylnobiletin） also correlated significantly with the color change （E*ab） of the samples （P<0.05， P<0.01）. ConclusionBefore and after steaming， not only the chemical composition changes， but also the color. Comparing the characteristic peaks of chemical composition difference and color difference before and after steaming of CRP， it is found that 5-hydroxymaltol， 5-hydroxymethylfurfural and peak 4 are common characteristic difference components， which can provide a reference for establishing the characteristic quality control method of steamed products， and quickly evaluating the quality difference between raw products and steamed products of CRP.