Myofibrillar protein (MP) gels are susceptible to oxidation, which can be prevented by complexing with hydrophilic polyphenols, but may cause gel deterioration. Sodium metabisulfite (Na2S2O5) has been used to induce self-assembly of MP and analyze the impact of self-assembly on the quality of composite gels containing high amounts of (-)-epigallocatechin gallate (EGCG). Hydrophobic forces were confirmed as the main driver of self-assembly. Self-assembly reduced the size of the MP-EGCG complex to approximately 670 nm and increased the gel\'s hydrophobic force by approximately 3.6-fold. The maximum hardness of the Na2S2O5-treated MP-EGCG composite gel was 52.43 g/kg, which was approximately 49% greater than pure MP gel. After oxidative treatment, the Na2S2O5-treated MP-EGCG composite gel had considerably lower carbonyl and dityrosine levels (2.47-μmol/g protein and 450 a.u.) than the control (8.37-μmol/g protein and 964 a.u.). Therefore, Na2S2O5 shows potential as a cost-effective additive for alleviating MP limitations in the food industry.

Houttuynia Cordata (HC) is a widely distributed plant in Asia and is used extensively for both food and medicinal purposes. A preliminary investigation found that HC is often bleached with sodium metabisulfite solution during its field processing, leading to health risks. In this study, the effects of sodium metabisulfite on the quality of HC were comprehensively evaluated using volatile and non-volatile targeted metabolomic methods. The results revealed a positive correlation between the extent of chemical composition changes and the bleaching time. These notable changes mainly occurred at the initial stage of bleaching. Subsequently, an untargeted UPLC/Q-TOF MS method was used to explore the potential chemical bleaching markers in bleached HC. The marker 1-hydroxy-3-oxodecane-1-sulfonic acid was subsequently prepared, isolated, and identified. Market sample verification further validated the accuracy and effectiveness of this marker.

In order to prompt the appearance of the shrimp color, sodium metabisulfite is frequently added in shrimp processing, which is, however, prohibited in China and many other countries. This study aimed to establish a surface-enhanced Raman spectroscopy (SERS) method for screening sodium metabisulfite residues on shrimp surfaces, in a non-destructive manner. The analysis was carried out using a portable Raman spectrometer jointly with copy paper loaded with silver nanoparticles as the substrate material. The SERS response of sodium metabisulfite gives two fingerprint peaks at 620 (strong) and 927 (medium) cm-1, respectively. This enabled unambiguous confirmation of the targeted chemical. The sensitivity of the SERS detection method was determined to be 0.1 mg/mL, which was equal to residual sodium metabisulfite on the shrimp surface at 0.31 mg/kg. The quantitative relationship between the 620 cm-1 peak intensities and the concentrations of sodium metabisulfite was established. The linear fitting equation was y = 2375x + 8714 with R2 = 0.985. Reaching an ideal balance in simplicity, sensitivity, and selectivity, this study demonstrates that the proposed method is ideally suitable for in-site and non-destructive screening of sodium metabisulfite residues in seafood.

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In the present study, the color, total sugar, contents of soluble protein, total polyphenols, total flavonoids, and soluble vitamins, and other indicators of black fungus treated with sodium metabisulfite under different conditions were measured to evaluate the sensory and nutritional changes in black fungus after sulfite treatment. The results showed that use of sodium metabisulfite increased the lightness of black fungus, significantly increased the contents of total polyphenols and reducing sugars in the fungus (p < 0.05), increased the content of soluble protein, and decreased the content of total flavonoids. In addition, sodium metabisulfite destroyed vitamin C and B1 in black fungus. When the concentration of sodium metabisulfite was 0.5% and the soaking time 20 or 30 min, the color of black fungus improved markedly, and nutrients were not negatively affected. Therefore, the use of sodium metabisulfite improved the quality of fungus to a certain extent.

Gluten network formed by oxidation of glutenin sulfhydryl groups is the determinant of dough rheological properties, while chemical reagents including oxidants and reductants are both used as dough rheology improvers under different circumstances. This study compares the impact of sodium metabisulfite (SMBS) and azodicarbonamide (ADA), as the representative reductive and oxidative dough improvers, at series of concentrations that offer or remove the same number of electrons form dough, respectively. The alveographic characterization, protein distribution and glutenin composition analysis, and free sulfhydryl measurement were performed on dough containing redox equivalent SMBS or ADA. Finally, at each optimal concentration, the dough protein network was analyzed with confocal microscopy. Results showed that SMBS increased the free sulfhydryl content, loosened the microstructure of gluten network, and thus enhanced dough extensibility. ADA reduced the free sulfhydryl content, compacted the dough microstructure, thus enhanced the tenacity and baking strength of dough. It is therefore proposed that the reductants reduce disulfide bonds in gluten network and renders the formation of one-dimensional gluten network while oxidants promote the disulfide linkage and formation of three-dimensional gluten network. This study offers a theoretic foundation of differentiating dough rheology improvers for their specified application.

Conventionally, sulfones are prepared by oxidation of sulfides with strong oxidants. Now, a multicomponent reductive cross-coupling involving an inorganic salt (sodium metabisulfite) for the straightforward construction of sulfones is disclosed. Both intramolecular and intermolecular reductive cross-couplings were comprehensively explored, and diverse sulfones were accessible from the corresponding alkyl and aryl halides. Intramolecular cyclic sulfones were systematically obtained from five- to twelve-membered rings. Naturally occurring aliphatic systems, such as steroids, saccharides, and amino acids, were highly compatible with the SO2 -insertion reductive cross-coupling. Four clinically applied drug molecules, which include multiple heteroatoms and functional groups with active hydrogens, were successfully prepared via a late-stage SO2 insertion. Mechanistic studies show that alkyl radicals and sulfonyl radicals were both involved as intermediates in this transformation.

A three-component cross-coupling protocol of boronic acid, sodium metabisulfite, and dimethyl carbonate was developed for the construction of significant functional methyl sulfones, in which introduction of sulfur dioxide at the last stage was successfully achieved in one step. Inorganic sodium metabisulfite was used as an eco-friendly sulfur dioxide source. Green dimethyl carbonate was employed as methyl reagent in this transformation. Diverse functional methyl sulfones were obtained from various readily available boronic acids. Notably, the last-stage modification of pharmaceuticals and the synthesis of Firocoxib were efficiently established through this strategy.

Sodium metabisulfite (SMB) is used as an antioxidant and antimicrobial agent in a variety of drugs and foods. However, there are few reported studies about its side effects. This study is to investigate the SMB effects on the expression of ATP-sensitive K(+) (KATP) and L-type calcium (L-Ca(2+)) channels in rat hearts. The results show that the mRNA and protein levels of the KATP channel subunits Kir6.2 and SUR2A were increased by SMB; on the contrary, SMB at 520 mg/kg significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. This suggests that SMB can activate the expression of KATP channel by increasing the mRNA and protein levels of Kir6.2 and SUR2A, while it inhibits the expression of L-Ca(2+) channels by decreasing the mRNA and protein levels of Cav1.2 and Cav1.3 in rat hearts. Therefore, the molecular mechanism of the SMB effect on rat hearts might be related to the increased expression of KATP channels and the decreased expression of L-Ca(2+) channels.

Sodium metabisulfite (SMB) is most commonly used as the preservative in many food preparations and drugs. So far, few studies about its negative effects were reported. The purpose of this study was to investigate the effect of SMB on the expression of big-conductance Ca(2+)-activated K(+) (BKCa), ATP-sensitive K(+) (KATP), and L-type calcium (L-Ca(2+)) channels in rat aorta in vivo and in vitro. The results showed that the mRNA and protein levels of the BKCa channel subunits α and β1 of aorta in rats were increased by SMB in vivo and in vitro. Similarly, the expression of the KATP channel subunits Kir6.1, Kir6.2, and SUR2B were increased by SMB. However, SMB at the highest concentration significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. These results suggest that SMB can activate BKCa and KATP channels by increasing the expression of α, β1, and Kir6.1, Kir6.2, SUR2B respectively, while also inhibit L-Ca(2+) channels by decreasing the expression of Cav1.2 and Cav1.3 of aorta in rats. The molecular mechanism of SMB-induced vasorelaxant effect might be related to the expression changes of BKCa, KATP, and L-Ca(2+) channels subunits. Further work is needed to determine the relative contribution of each channel in SMB-mediated vasorelaxant effect.