小青柑表面白霜成分鉴定及安全性评价

Study on the Component Identification and Safety Evaluation of the White-Frosted Citrus reticulata ‘Chachi’

摘要:

小青柑是广受消费者喜爱的新式茶品，在储藏过程中表面会形成“白霜”，“白霜”的主要成分及安全性未知。因此，对正常、白霜和发霉的小青柑的显微结构、表面成分、真菌毒素含量和微生物多样性进行分析。扫描电子显微镜（SEM）观察小青柑表面白霜为针状和块状结晶。通过UPLC/Q-TOF分析，白霜小青柑表皮洗涤液中主要成分为多甲氧基黄酮。定量分析表明，白霜小青柑表皮洗涤液中川皮素含量是正常和发霉小青柑表皮洗涤液的9.15倍和14.9倍，橘皮素含量是正常和发霉小青柑的26.9倍和78.8倍。小青柑表面的真菌和细菌进行多样性分析，表明发霉小青柑中Ogataea、Penicilliusm和Alternaria真菌属显著增加，而白霜小青柑中以上菌属水平与正常组接近。真毒毒素分析中仅发霉小青柑中检出430 μg/kg玉米赤霉烯酮。由此可见，小青柑表面白霜为多甲氧基黄酮析出，主要成分为川陈皮素和橘皮素，并且白霜小青柑表面微生物与正常小青柑相似，未检测出有害真菌毒素，白霜不影响产品安全性。

Abstract:

Xiaoqinggan (XQG), the green small fruit of Citrus reticulata 'Chachi', is the raw material used for processing Citrus Pu’er tea, but many XQG have "white frost" on their surface during storage. Currently, the composition, safety, and formation mechanism of the "white frost" remain unknown. Therefore, the microscopic morphology, surface composition, mycotoxin content, and microbial diversity of normal, white-frosted, and moldy XQG were analyzed. Using scanning electron microscope, the “white frost” on the surface of XQG was found to consist of blocky and needle-like crystals. Through UPLC/Q-TOF analysis, the main components of the surface wash solution from white-frosted XQG were polymethoxyflavones. Through quantitative analysis, the nobiletin content in the surface wash solution of white-frosted XQG was found to be 9.15 times and 14.9 times higher than that of normal and moldy XQG, respectively, while the tangeretin content was 26.9 times and 78.8 times higher, respectively. The diversity analysis of fungi and bacterial communities on the surface of the XQG showed that Ogataea, Penicilliusm, and Alternaria in the moldy XQG increased significantly, while the microbiota levels on the white-frosted XQG surface were found to be similar to those from the normal group. In the mycotoxin analysis, only moldy XQG was found to contain 430 μg/kg of zearalenone. This indicates that the“white frost” on the surface of XQG is formed by the precipitation of polymethoxyflavones, with nobiletin and tangeretin as the main components. Additionally, the microbial profile on the surface of white-frosted XQG is similar to that of normal XQG, with no fungal contamination or no risk of mycotoxin exposure, suggesting that the white-frosted XQG are harmless to humans.