This study investigated the distribution, enrichment, and transfer patterns of mineral elements in the soil-plant system of dried tangerine peel (Citrus reticulata ‘Chachi’, or Chenpi) from four production regions: Xinhui, Enping and Boluo in Guangdong Province, and Pubei in Guangxi Province, aiming to identify key element indicators with causal basis for geographical origin discrimination. Citrus reticulata ‘Chachi’ root, surrounding soil, leaf, and peel samples at different maturity stages (green, semi-ripe, and fully ripe) were collected simultaneously from these regions. The contents of 36 mineral elements were determined and systematically analyzed using enrichment factors and principal component analysis (PCA). The results showed that the contents of elements such as B, La, Ce, Pr, Nd, and Sm were significantly higher in the soil sample from Xinhui than in those from the other regions (P < 0.05). Among the four production regions, the leaf and peel samples from Xinhui exhibited the strongest enrichment capacity for Cu, Co, and V. The PCA results revealed the continuous enrichment of rare earth elements (Y, Er, Ho, Dy, etc.) in the soil-plant system of the Boluo region, constituting a key basis for the geographical origin discrimination of Chenpi. This study also found that green peels had the strongest correlation with soil elements, establishing them as sensitive materials for the geographical origin tracing of Chenpi. As fruit maturity increased, the elemental distribution stabilized, and the distribution patterns of macro elements such as K, P, and Ca could effectively discriminate among Xinhui, Enping, and Pubei Chenpi. This study has not only verified the feasibility of using mineral element fingerprinting for the geographical origin discrimination of dried tangerine peel, but has also elucidated the formation mechanism of discriminant indicators from the perspective of elemental migration and accumulation pathways, providing a theoretical basis and scientific evidence for constructing a robust geographical origin traceability system for dried tangerine peel.

This study employed non-targeted metabolomics combined with chemometrics to investigate the effects of different manufacturing processes, harvest times and cultivation methods on the key characteristic components of Liudong tea, a specialty tea cultivar from Guangxi. A total of 23 key components were identified, including (+)-gallocatechin and theaflavinmonogallates. Among them, catechins and their derivatives, as well as flavonoids, predominated, accounting for 82.6% of the total. The key characteristic components with the highest variable importance in the projection (VIP) values for distinguishing Liudong tea from different processing methods and harvest times were terpenes and their derivatives, namely acuminoside@RT 9.77 and (+/-)-sabinene@RT 10.11, while that for distinguishing Liudong tea from different cultivation methods was (+)-catechin. The results indicated that different processing methods, harvest times and cultivation patterns significantly influenced the key characteristic components and their content distribution in Liudong tea. The black tea processing method promoted the formation of theaflavinmonogallates and the hydrolysis of terpenoid glycosides. The later the harvest date, the higher the relative abundance of five key flavonoid components, including kaempferol-3-O-(6’’’-trans-p-coumaroyl-2’’-glucosyl) rhamnoside. Artificial cultivation reduced the relative abundance of some key characteristic components including catechins such as (+)-catechin and their derivatives. This study contributes to understanding the mechanisms underlying the formation of the characteristic quality of different Liudong tea, thereby providing a scientific basis for improving the cultivation techniques and processing methods for the quality control of Liudong tea.

Citri Reticulatae Pericarpium (CRP) has both culinary and medicinal uses, with high medicinal and economic value. However, CRP fraud such as mislabeling of the geographical origin, passing off, and aging time cheating has occurred frequently, which damages consumer interests. In order to ensure the safety and quality of CRP, it is urgent to establish effective techniques for its geographical origin traceability and authentication. In this article, we review recent progress on the application of metabolomics, spectroscopy, DNA analysis, elemental analysis and intelligent sensory analysis in identifying the geographical origin, variety, harvest period and aging time of CRP. Meanwhile, we compare and analyze the advantages and disadvantages of each technique, and propose the existing problems and future research priorities in the field of geographical origin traceability and authentication of CRP.