The diversity of cultivars and variation in phytochemical components pose a great threat to the security of foods that contain walnut. The nutrient values of walnut are stipulated according to phytochemical components, which are driven by internal and external factors associated with fruit growth. The objective of this work was to investigate the effects of cultivar and climate zone on the phytochemical components of walnuts. First, differences and relationships of phytochemical components in eleven walnut cultivars harvested from northeastern China were analyzed. Almost all individual phytochemical components among cultivars showed significant differences (p < .05). The results were submitted to correspondence analysis followed by matrix transformation and factor analysis. Fatty acids, amino acids, and minerals (Ca, Na, Fe, Cu, P, and Zn) for the identification and discrimination of eleven walnut cultivars were authenticated. Furthermore, based on essential microelements, essential amino acids, unsaturated fatty acids, and antioxidants, the walnut cultivars realized the precision position in food application. Finally, we confirmed the effects of climate zones on the phytochemical components of walnuts, with variations up to 142%. The climatic factors precipitation and temperature influenced the formation and accumulation of monounsaturated fatty acids, tocopherols, and most minerals. The findings will open promising perspectives for oriented cultivation of walnuts and future application in the food industry.

Bamboo shoot is an indispensable vegetable in Southeastern China, so a survey of heavy metals in bamboo shoots is a relevant topic of interest. The present study sought to analyse the content of seven heavy metals (As, Cd, Cr, Cu, Mn, Pb and Zn) in six bamboo shoot species from Southeastern China. Percentages of 3.8% (Cd) and 8.9% (Pb) of the samples exceeded the maximum limits as established by the Chinese legislation. Further health risk assessment exhibited that the Cd intake contribution of these samples could not be negligible. The hazard index (HI) at average exposure was less than one. The average HI values in moso bamboo shoot were significantly higher than those of other bamboo shoot species. Overall, the results indicated that the intake of bamboo shoots is safe for consumers in Southeastern China.

An inductively coupled plasma mass spectrometer method for estimating trace elements in tree nut oils has been developed which employs microwave digestion equipped with high pressure subassembly. Residual carbon content and residual acidity were determined to evaluate the efficiency of digestion. The best digestion efficiency was obtained using Easyprep™ system with 0.5 g of oil, 4 mL concentrated nitric acid, and 2 mL hydrogen peroxide, and a final temperature of 235 °C. Residual carbon content and residual acidity were estimated as 1.7% (corresponding to 852 mg L⁻¹ of carbon in sample solution) and 7.5%, respectively, and recovery values ranged from 90.7% to 107.7%. Whereas, only 0.2 g of oil could be digested through conventional microwave system with 5 mL concentrated nitric acid and 2 mL hydrogen peroxide at 205 °C (residual carbon content = 3.2%). The developed method has been applied to determine nine trace elements (Cr, Mn, Fe, Ni, Cu, As, Zn, Cd, and Pb) in different categories of tree nut oils, and high content of Fe, Mn, and Zn were found in some of those oils. To the best of our knowledge, the present investigation is the first attempt to analyze trace elements in different categories of tree nut oils consumed in China.

China is the world’s largest walnut producer. There is still a scarcity of comprehensive information on the nutritional quality of Chinese walnuts and the influence of soil on walnut quality. In this study, 273 samples and the corresponding soils from the main English walnut (Juglans regia L.)-producing areas in China were collected. The results revealed that walnut oil contained a high percentage of linoleic acid and γ-tocopherol, with an average content of 62.36% and 77.70%, respectively. Walnut flour is rich in nutritional elements, with the highest content of macro-element K at 3961.29 mg kg⁻¹. In addition, 12 micro-elements with concentrations ranging from 0.01 to 42.34 mg/kg were discovered in walnut flour. The total amino acid profile of walnut flour contains 27.23% of the seven essential amino acids, with the highest amount allocated to leucine at 2.07 g 100 g⁻¹. The Pearson correlation analysis revealed that almost all amino acids showed a significant positive correlation (p < 0.01, r > 0.70). The soil’s content in terms of three trace elements (Fe, Cu, and Zn) has the greatest influence on the nutritional qualities of walnuts. Furthermore, the pH of the soil played a role in determining the qualities of the walnut. These findings provide fundamental information for the consumer selection and trade of walnuts, as well as guidance for the development of high-quality walnuts in China.