Liquid metals: fundamentals and applications in chemistry.

Post-transition elements, together with zinc-group metals and their alloys belong to an emerging class of materials with fascinating characteristics originating from their simultaneous metallic and liquid natures. These metals and alloys are characterised by having low melting points (i.e. between room temperature and 300 °C), making their liquid state accessible to practical applications in various fields of physical chemistry and synthesis. These materials can offer extraordinary capabilities in the synthesis of new materials, catalysis and can also enable novel applications including microfluidics, flexible electronics and drug delivery. However, surprisingly liquid metals have been somewhat neglected by the wider research community. In this review, we provide a comprehensive overview of the fundamentals underlying liquid metal research, including liquid metal synthesis, surface functionalisation and liquid metal enabled chemistry. Furthermore, we discuss phenomena that warrant further investigations in relevant fields and outline how liquid metals can contribute to exciting future applications.

Effect of long-term ingestion of weakly oxidised flaxseed oil on biomarkers of oxidative stress in LDL-receptor knockout mice.

The effect of oxidised fatty acids on atherosclerosis progression is controversial. Thus, our objective was to evaluate the effect of long-term consumption of weakly oxidised PUFA from flaxseed oil on oxidative stress biomarkers of LDL-receptor(-/-) mice. To test our hypothesis, mice were separated into three groups. The first group received a high-fat diet containing fresh flaxseed oil (CONT-), the second was fed the same diet prepared using heated flaxseed oil (OXID), and the third group received the same diet containing fresh flaxseed oil and had diabetes induced by streptozotocin (CONT+). Oxidative stress, aortic parameters and non-alcoholic fatty liver disease were assessed. After 3 months, plasma lipid profile, glucose levels, body weight, energy intake and dietary intake did not differ among groups. Likewise, oxidative stress, plasma malondialdehyde (MDA), hepatic MDA expressed as nmol/mg portion (ptn) and antioxidant enzymes did not differ among the groups. Hepatic linoleic acid, α-linolenic acid, arachidonic acid and EPA acid declined in the OXID and CONT+ groups. Aortic wall thickness, lumen and diameter increased only in the OXID group. OXID and CONT+ groups exhibited higher concentrations of MDA, expressed as µmol/mg ptn per %PUFA, when compared with the CONT- group. Our results suggest that ingestion of oxidised flaxseed oil increases hepatic MDA concentration and is potentially pro-atherogenic. In addition, the mean MDA value observed in all groups was similar to those reported in other studies that used xenobiotics as oxidative stress inducers. Thus, the diet applied in this study represents an interesting model for further research involving antioxidants.

Effects of optimized mixtures containing phenolic compounds on the oxidative stability of sausages.

Phenolic compounds were applied in a sausage formulation as a substitute for artificial sodium erythorbate used as antioxidant. Five assays were prepared in which sodium erythorbate control at 0.05 g/100 g was replaced with a hydrosoluble mixture containing caffeic acid + carnosic acid (47% + 53%) and a liposoluble mixture containing quercetin + rutin (67% + 33%) in two final concentrations (0.05 g/100 g and 0.08 g/100 g). Physico-chemical, color, texture, and sensory parameters were measured on the first day and after 45 days of storage at 4 °C. All phenolic compound mixtures were able to maintain oxidative stability in the sausages when measured by the malondialdehyde concentration, which was expressed as TBARS. The mixture containing quercetin + rutin at 0.05 g/100 g showed lower malondialdehyde formation after 45 days of storage, and no sensory differences from the sausage adopted as control.

Effect of natural pigments on the oxidative stability of sausages stored under refrigeration.

The objective was to use natural pigments to replace sodium erythorbate (NaEry), a synthetic compound used as an antioxidant in sausage formulations, and to evaluate the oxidative stability of the samples. Six assays were prepared in which sodium erythorbate (ERY) at 0.05 g/100 g was substituted by norbixin (NOR), lycopene (LYC), zeaxanthin (ZEA), beta-carotene (CAR) or dextrose (used as a control (CON)). Physical, chemical, color, texture and sensory parameters were measured on the first day and after 45 days of storage at 4 degrees C. All pigments used in the sausage formulations were able to maintain the oxidative stability of the sausages (MDA equivalents <0.38 mg/kg). Zeaxanthin and norbixin were the most efficient antioxidants of those tested. This antioxidant effect might be associated with the intermediate polarities of these two compounds, which would allow them to concentrate in the membrane lipids or emulsion interface, where lipid oxidation is most prevalent. Other volatile secondary products of oxidation besides MDA should be evaluated in further studies involving natural pigments and sensory oxidative stability.

Effect of the partial substitution of soy proteins by highly methyl-esterified pectin on chemical and sensory characteristics of sausages.

Pectin can be used as a natural emulsifier in food formulations. In this study, textured soybean protein (TSP), used as an emulsifier in commercial sausages, was partially replaced by a mixture containing pectin and isolated soybean proteins, which were either extruded (EXT) or not extruded (MIX), and the chemical and sensory characteristics of samples were evaluated after 60 days of storage at 4 °C. Responses such as oxidation measured by PV and TBARS, hardness, color, pH and sensory characteristics were compared with those of a commercial sausage (CON). The mixture containing highly methyl-esterified pectin, textured soybean proteins and isolated soybean proteins, as emulsifier agent, reduced the hardness (EXT: 21.69±0.98 and MIX: 20.17 ±2.76 N) and the pH (EXT: 5.46±0.03 and MIX: 5.29±0.01) of the samples and increased the concentration of peroxides (EXT: 0.10±0.01 and MIX: 0.15 ±0.01 meq/kg) when compared with samples formulated only with TSP (28.57 ± 2.54 N, pH of 6.92±0.04 and PV = 0.07 ± 0.01 meq/ kg). These effects were likely caused by the anionic character of the emulsifier. However, no sensory difference was observed between the sausages containing highly methyl-esterified pectin, textured soybean proteins and isolated soybean proteins submitted to the extrusion process (EXT) and the control sausages, suggesting that the formulation proposed in this study can be a potential alternative for the further development of sausages that have functional properties or are free of artificial additives.