Effects of Altitudinal Gradient on Nutritional Quality and Physicochemical Properties of Wrinkled Skin Citrus

The wrinkled skin citrus in Muli County, Liangshan Yi Autonomous Prefecture, Sichuan Province was taken as the research object. The multiple key indicators were measured, such as soluble solids content, pH value, vitamin C content, total acid content, total flavonoids content and mineral content of the wrinkled skin citrus at altitudes of 1300, 1590 and 1900 m above sea level. Combination correlation analysis and principal component analysis were carried out . The intrinsic connections and dominant factors among various indicators were revealed. The effects of different altitude gradients on the nutritional quality and physicochemical properties of wrinkled skin citrus were explored. The results show that regarding physicochemical properties, the soluble solid content peaks at 9.27% at an altitude of 1590 m. The pH value is the lowest at 1300 m(3.66). The vitamin C content reaches its peak at an altitude of 1900 m(26.44 mg/100g). The total acid content is the highest at the 1300 m (0.61%). The total flavonoid content is the highest at 1300 m (11.12mg/g). Among the four mineral elements (Ca, Fe, Mg, Zn), calcium content is most significantly affected by the altitudinal gradient, reaching 101.43 mg/kg at the 1900 m. Correlation analysis indicates the relationships between mineral elements and basic nutritional content. PCA reveals that total acid, total flavonoids, magnesium (Mg), and iron (Fe) are the key indicators influencing the quality of Muli wrinkled skin citrus. The results provide a scientific basis for the subsequent grading of wrinkled skin citrus raw materials, the target utilization of its functional components, and the optimization of high-altitude storage techniques. This study holds significant implications for promoting the upgrading of characteristic industrie in ethnic regions, contributing to rural revitalization and regional coordinated development.