*3.1. Anthocyanidins Contents in PCC Samples*

Anthocyanidins contents of the PCC samples were analyzed by the HPLC method (the results are shown in Table S1), and the content distribution of the anthocyanidins fractions is shown in Table 1. Four kinds of anthocyanidins were detected, with cyanidin the most abundant one in PCC, which was a coincidence with the previous report [2]. Cyanindin had the largest range of content variation from 93.5 to 12,802.4 mg/kg, and the average content was 5741.2 mg/kg. In most samples, cyanidin accounted for more than 95% of the total anthocyanidins. The content distribution range of cyanidin in the selected samples was wide, which can well represent PCC samples with different contents of anthocyanidins; it meant that it was a suitable sample set for establishing of NIR model.


**Table 1.** Distribution of anthocyanidins contents in purple leaf Chinese cabbage (mg/kg).

nd1: not detected.

Delphinidin was detected in most PCC samples, with a content up to 193.7 mg/kg, and the average content was 159.4 mg/kg. Compared to cyaniding, pelargonidin and peonidin were much lower in PCC, whose average contents were 52.3 mg/kg and 45.5 mg/kg, respectively, accounted for less than 1% content to the total anthocyanidins in PCC.
