Fig. 4

Content changes of the four astilbin isomers in SGR samples prepared by different methods. A Changes in the contents of the four astilbin isomers in SGR by boiling (a) and steaming (b) pretreatments compared with un-pretreated SGR samples. B Scatter plot of the contents (μg/g) of the four astilbin isomers throughout the drying process at different sampling times. C Heatmaps of the contents (μg/g) of the four astilbin isomers throughout drying process at different sampling times