Amino Acid and Mineral Element Analysis and Quality Evaluation of Different Color Fruits of Nitraria in Qinghai

Only three species of Nitraria fruits are distributed in Qinghai Province, which serve as important berry resources in the desert ecosystem of Qinghai. These fruits are rich in nutrients; however, the differences in nutritional characteristics and quality evaluation among different species and fruit colors have not been systematically clarified. To explore the nutritional quality of Nitraria fruits in Qinghai, this study investigated red and purple fruits of Nitraria roborowskii , N. tangutorum , and N. sibirica . The contents of 17 amino acids and 27 mineral elements were determined, analyzed by multivariate chemometric methods, and compared with existing research results for verification. The results showed that the contents of total amino acids, essential amino acids, nonessential amino acids, and total mineral elements in N. sibirica were significantly higher than those in N. roborowskii and N. tangutorum . Among them, the proportion of essential amino acids in purple fruits of N. sibirica reached 0.22, close to the FAO ideal protein standard, and it was rich in functional mineral elements such as zinc and iron, showing high nutritional value. These results are consistent with the existing research on the nutritional specialization of desert berries. Fruit color exerted differential effects on nutritional components: nonessential amino acids and total amino acids were positively affected in red fruits, while mineral element contents were not significantly influenced by color, which agrees with studies on metabolic competition related to anthocyanin biosynthesis. Synergistic accumulation was observed between amino acids and mineral elements. Species inheritance was the dominant factor determining nutritional quality. Al, Val, Ca, V, and Cr were screened as core signature components, which improved the indicator system for the quality evaluation of Nitraria plants. Comprehensive evaluation demonstrated that N. sibirica possessed the best overall nutritional quality, and red fruits were generally superior to purple fruits, with purple fruits of N. sibirica exhibiting the optimal nutritional quality. The results of this study provide a theoretical basis for the precise development of Nitraria germplasm resources in Qinghai, the breeding of superior genotypes, and the research and development of distinctive functional foods from desert plants.