Cooking-Induced Corrosion of Metals

Uptake of metal ions into rice occurs while it is being cooked in metal vessels, leading to corrosion of the utensils. This study deals with silver, copper, and aluminum uptake during cooking in respective vessels, with a special emphasis on silver. The metal uptake is routed through solution, enhanced in the presence of specific anions like carbonate, and attenuated when the rice is polished. The concentration of silver in rice increases with the time of cooking with a concomitant decrease in the concentrations of Fe and Zn, suggesting a substitution mechanism for metal ion uptake. The results for some common rice varieties of use across the Indian subcontinent are presented. Similar behavior was observed for cooking in copper and aluminum vessels. Among the three metals studied, aluminum showed reduced uptake. Studies have been done to probe the interaction of metal ions with glucose and sucrose, and efficient complex formation was detected with all these ions, implying that starch can also form complexes with them. The cooking practices used in this study are reminiscent of local customs and practices that were chosen deliberately to relate to the true implications of these results

Subsurface thermal behaviour of tissue mimics embedded with large blood vessels during plasmonic photo-thermal therapy

<p><b>Purpose:</b> The purpose of this study was to understand the subsurface thermal behaviour of a tissue phantom embedded with large blood vessels (LBVs) when exposed to near-infrared (NIR) radiation. The effect of the addition of nanoparticles to irradiated tissue on the thermal sink behaviour of LBVs was also studied.</p> <p><b>Materials and methods:</b> Experiments were performed on a tissue phantom embedded with a simulated blood vessel of 2.2 mm outer diameter (OD)/1.6 mm inner diameter (ID) with a blood flow rate of 10 mL/min. Type I collagen from bovine tendon and agar gel were used as tissue. Two different nanoparticles, gold mesoflowers (AuMS) and graphene nanostructures, were synthesised and characterised. Energy equations incorporating a laser source term based on multiple scattering theories were solved using finite element-based commercial software.</p> <p><b>Results:</b> The rise in temperature upon NIR irradiation was seen to vary according to the position of the blood vessel and presence of nanoparticles. While the maximum rise in temperature was about 10 °C for bare tissue, it was 19 °C for tissue embedded with gold nanostructures and 38 °C for graphene-embedded tissues. The axial temperature distribution predicted by computational simulation matched the experimental observations.</p> <p><b>Conclusions:</b> A different subsurface temperature distribution has been obtained for different tissue vascular network models. The position of LBVs must be known in order to achieve optimal tissue necrosis. The simulation described here helps in predicting subsurface temperature distributions within tissues during plasmonic photo-thermal therapy so that the risks of damage and complications associated with <i>in vivo</i> experiments and therapy may be avoided.</p

Unusual Accumulation of Silver in the Aleurone Layer of an Indian Rice (<i>Oryza sativa</i>) Landrace and Sustainable Extraction of the Metal

Uptake of noble metals by cereal plants is not reported in literature. Our study of 505 native rice landraces showed that nine of them accumulate silver at a high concentration when grown in the same soil. Among these, a medicinal rice landrace from West Bengal, <i>Garib-sal</i> was found to accumulate silver at an especially high concentration in the grains. Cultivation of <i>Garib-sal</i> rice in three successive years in Basudha farm in the rice growing period of June–October confirmed that for the same concentration of silver in the soil (∼0.15 mg/kg), <i>Garib-sal</i> accumulates it in the grains to the extent of ∼15 mg/kg. Laboratory experiments also demonstrated that silver uptake by <i>Garib-sal</i> is significantly greater than for other varieties grown on the same soil, and that the metal accumulates mostly in the grain. To detect the location of deposition of silver in the grains, secondary ion mass spectrometry was performed. The images reveal that the silver is concentrated in the aleuronic layer of the rice bran. Its concentration decreases in the subaleurone and becomes negligible in the endosperm. Accumulation of silver does not alter the grain morphology and chemical characteristics. The metal may be extracted from the bran after milling of the rice, thereby causing no loss of the foodstuff