Formulations of selected Energy beverages promote pro-oxidant effects of ascorbic acid and long-term stability of hydrogen peroxide

Eco-friendly spark-generated CoxOy nanoparticle-modified graphite screen-printed sensing surfaces for the determination of H2O2 in energy drinks

The modification of graphite screen-printed electrodes (SPEs) is reported using an eco-friendly and extremely fast method based on the direct cobalt pin electrode-to-SPE spark discharge at ambient conditions. This approach does not utilize any liquids or chemical templates, does not produce any waste, and allows the in-situ generation of CoxOy nanoparticles onto the electrode surface and the development of efficient electrocatalytic sensing surfaces for the determination of H2O2. Co-spark SPEs were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy (XPS), revealing the formation of surface confined CoxOy nanoparticles and the diverse oxidation states of cobalt species. Co-spark SPEs were also characterized with cyclic voltammetry and electrochemical impedance spectroscopy. Redox transitions of the surface confined electrocatalysts are demonstrated by electrochemical polarization studies, showing the formation of different oxides (CoxOy), varying the XPS results. Amperometric measurements at 0.3 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of H2O2 over the range 1 - 102 μM, achieving a limit of detection (3σ/m) of 0.6 μM. The interference effect of various electroactive species was effectively addressed by employing dual measurements in the absence and presence of the enzyme catalase. The analytical utility of the method was evaluated in antioxidant rich real-world samples, such as energy drinks, demonstrating sufficient recovery.

Thermal degradation and oxidation of glucosinolates in model systems and Brassica vegetable broth is mediated by redox-active compounds

Glucosinolates (GLSs) are secondary plant metabolites with health-promoting effects found in Brassica vegetables. Recently, next to non-enzymatic degradation yielding nitriles, 4-(methylthio)butyl GLS (4MTB-GLS) was shown to undergo side chain oxidation during thermal treatment, forming 4-(methylsulfinyl)butyl GLS (4MSOB-GLS). Here, we investigated natural plant components and artificial analogs on their capability of altering the thermal reactivity of 4MTB-GLS in vegetable broths and model systems using buffers. Addition of ascorbic acid and dehydroascorbic acid caused varying effects: in broth samples, it increased nitrile formation, while in buffer, 4MSOB-GLS was formed. In further experiments, the antioxidant compounds quercetin and Trolox triggered the side chain oxidation of 4MTB-GLS, while H2S terminated its degradation. A synergistic effect of ascorbic acid and Fe2+ was observed, degrading 98% of 4MTB-GLS to the nitrile after 60 min of boiling. Deepening the understanding of factors that influence the non-enzymatic degradation of GLSs will help to preserve their health-promoting effects.

Demonstration of anti-oxidant properties of mustard seed (Brassica juncea) protein isolate in orange juice

Previous research has shown that formulated and natural beverages containing mixtures of anti-oxidants can produce stable levels of hydrogen peroxide (H₂O₂). The aim of this study was to demonstrate the ultimate anti-oxidant effects of proteins for suppressing H₂O₂, using a protein extract from mustard seed (Brassica juncea). The mustard seed protein isolate (MPI) contained ∼51% protein, and 6.4 mg GAe/g TS of total reducible substances, presumably representing secondary metabolites, including polyphenolics. Dose-dependent suppression of H₂O₂ (present at 110 µM and 550 µM), in fresh and thermally-processed orange juice was complete in the presence of 0.1 mg/mL MPI after 24 hr, with slightly higher anti-oxidant efficacy than the fruit juice-derived reference protein, thaumatin. The combination of thiol-rich amino acid (methionine and cysteine)-containing proteins and other anti-oxidant species in the MPI were highly effective for inhibiting autoxidation-mediated production of H₂O₂ in orange juice, and may be useful for other manufactured beverages.