An extensive analysis of trace element content and antioxidant properties of nuts and dried fruits

This study examined the microelement composition and antioxidant activity of nuts and dried fruits that included soya raisin, golden raisin, malayar raisin, dried apricot, dried prune, walnut, peanut, almond, dried mango, dried melon, apricot with stone, cashew, dried kiwi, dried apple, pumpkin seed, pistachio, hazelnut, and rosehip. Ethanol infusions were assessed using the DPPH and ABTS methods to evaluate their ability to eliminate radicals and determine total phenolic content. Among the tested samples, hazelnuts displayed the lowest antioxidant content alongside high toxicity levels, while cashews exhibited the weakest reactivity. To ascertain the trace element content, the samples underwent processing in microwave ovens, and concentrations of various components were measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The method's accuracy was further validated using a certified sample material (NIST SRM 1515, apple leaves). The concentrations observed in the samples varied as follows: Al: 4.7–172.1 mg/kg, B: 3.3–50 mg/kg, Cu: 5.6–52.6 mg/kg, Fe: 14.1–145.4 mg/kg, Mn: 0.3–51.3 mg/kg, Ni: 1.5–8.7 mg/kg, Sr: 1.75–78.5 mg/kg, and Zn: 5.8–63.9 mg/kg, and the findings were compared with existing literature on similar matrices. Overall, the results underscore the nutritional significance of hazelnuts and dried grapes as natural antioxidant sources, raise concerns about potential health risks associated with potentially toxic metal accumulation, and emphasize the necessity for ongoing analyses to ensure consumer safety. The novelty of this study lies in its analysis of both antioxidants and minerals found in nuts and dried fruits from Kazakhstan, which are significant in everyday diets, festive events, and traditional medicine.