Study of metal release from stainless steels in simulated food contact by means of total reflection X-ray fluorescence

Acid-base potentiometric titration using a stainless steel electrode without oxidative treatment

An AISI 304 stainless steel laminar electrode without oxidative treatment was investigated for the potentiometric titration of hydrochloric acid with sodium hydroxide. The proposed electrode was obtained from metalworking cuttings. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy and X-ray diffraction were used to study the surface morphology and chemical composition of the electrode. The electrode showed a sensitivity of 59.18 ± 0.37 mV/pH, which was reproducible under intermediate conditions. Potentiometric titration showed a curve with deviations from pH 9.5 with respect to the glass electrode. However, this did not affect the quantification as the jumps of the curves coincided. The endpoint was 9.25 mL for both electrodes and the hydrochloric acid concentration was 0.0845 mol/L, with a deviation of 0.0004 mol/L from the standard concentration of 0.0841 mol/L. The nonartificially oxidised electrode did not show any crystalline oxide phases, whereas after oxidation it showed semicrystalline phases of iron and chromium oxides and increased the crystallinity of the steel. Despite the low content of surface oxides, stainless steel electrodes can give a Nernstian response to pH, depending on the surface characteristics of the material. This leads to the need to calibrate any electrode prior to oxidative treatment to rule out a Nernstian response without surface modification.

Evaluation of the Effect of Different Cooking Methods on the Heavy Metal Levels in Crayfish Muscle

The current study investigated the effects of various cooking styles (boiling, frying, and steaming) and seasoning methods (home cooking and ready-to-eat commodity) on levels of nine heavy metals in the crayfish (Procambarus clarkii) muscle. The estimated daily intake (EDI), target hazard quotients (THQ), and target cancer risk (TCR) were used to assess the health risk in the crayfish muscle. The results showed that cooking processes significantly increased the concentration of Cu, which raises a potential risk for children (the THQ values > 1). The levels of toxic heavy metals in the ready-to-eat crayfish muscle were significantly higher than those in household cooking. Especially for As, the THQ values rose to 7.1 and 13.2 for adults and children respectively. Therefore, home cooking is safer than ready-to-eat crayfish, and children should consume crayfish within a limited range. The recommended consumption of the cooked abdominal muscle of crayfish should be 257 and 58 g/day, for children (16 kg) and adults (70 kg), respectively.

Metals release from stainless steel knives in simulated food contact

The release of chromium, nickel, and manganese from knives stainless steel produced in Italy and People's Republic of China was investigated with the aim to check their quality and compliance with Italian Ministerial Decree 21.03.73, which is the most detailed text for the hygiene regulation of packaging, containers, and tools intended for food contact. Temperature effect on metal release is investigated in 18 sets of knives. Tests are performed by simulating discontinuous contact using a 3% glacial acetic acid solution in distilled water at 50°C and 100°C. Chromium, nickel, and manganese quantification is performed by total reflection X-Ray fluorescence. Chemical composition highlights low sulphur content, and most of them belong to the American Iron and Steel Institute (AISI) 420 type A stainless steel group. Tests performed at 100°C revealed higher concentration of released metals. Only three knives tested at 100°C exceed the limit of 100 µg L^-1.

Migration analysis of Cr, Ni, Al, Fe, Mn, Cu, Zn, and Mo in internet-bought food serving stainless-steel utensils by ICP-MS and XRF

A total of 120 internet bought stainless-steel utensil samples intended for food serving were analysed for their release of Cr, Ni, Al, Fe, Mn, Cu, Zn, and Mo. Samples were extracted using simulants under continuous and discontinuous test conditions, extracts were analysed by ICP-MS, and metallic compositions of utensils were indicated by XRF analysis. r² values for all analytes were determined between 0.9982 and 0.9997. RSD and WRm values ranged between 4.5-8.5% and 80-107% for all analytes, respectively, and LOD was in the range of 0.11-25.8 µg/l. Migration results show that 35% of total sample types show non-compliance with the SMLs established by the Nordic guidelines. XRF data show good correlation between the metals' migration levels and their respective compositions in the utensil, and toxicological exposure estimates no significant adverse health effects from food served with articles exceeding the SMLs for Fe, Al, and Ni.