ABSTRACT
This paper focused on factors which affected on different color of northern and southern region vinegar-processed frankincense.Meanwhile,contents of six main boswellic acids were also determined to elaborate the influence of heat in chemical components.Vinegar-processed frankincense from northern and southern region was collected.And different temperature and time were used in the processing of frankincense to receive the vinegar-processed frankincense samples.The color difference meter was utilized combining with the PCA statistic analysis method.The Zorbax ExtendC18 chromatographic column (4.6 mm × 50 mm,1.8 μm) was used with acetonitrile-0.1％ phosphoric acid as the mobile phase and gradient elution.The velocity of flow was 1 mL· min-1.The detection wavelength was 210 nm and 250 nm.The column temperature was 30℃.The results showed that the color of northern region processed frankincense was yellow or pale brown.And the southern region processed frankincense was pale brown or dark brown.It showed the difference on processed degree.The L* value of the northern processed frankincense was 75.327 to 80.746 and the L* value of southern processed was 44.321 to 49.527.The a* value of the northern processed frankincense was 5.378 to 6.502 and the a* value of southern processed was 9.423 to 9.978.There was no significant difference on b*.There were certain differences on L* and a* among vinegar-processed frankincense with the same surface color.The color parameter results of self-made vinegar-processed frankincense indicated that along with changes of processing temperature and time,the color,L* and a* change.Even frankincense processed for 30 min with mild fire,it will not achieve the color parameter value of the southern region vinegar-processed frankincense.However,after 11 min processing with medium fire,the color can be achieved.The content determination results showed that four contents,including α-boswellic acid,β-boswellic acid,3-acetyl-α-boswellic acid and 3-acetyl-β-boswellic acid were increased.Contents of 11-carbonyl-3-boswellic acid and 3-acetyl-11-carbonyl-β-boswellic were decreased after being processed.The range of increasing or decreasing by medium fire was higher than mild fire.At the same temperature,as the increasing of processing time,the content has an increasing or decreasing tendency.It was concluded that temperature was the main factor influencing the color of vinegar-processed frankincense from northern and southern regions.Different processing degrees also make influence on the contents of chemical compounds.The color parameter value can be used to evaluate the color of processed frankincense.