Systematic study of hydroxyl radical production in white wines as a function of chemical composition

Impact of phenolic composition and antioxidant parameters on the ageing potential of Syrah red wines measured by accelerated ageing tests

Fourteen Syrah red wines with different initial composition and antioxidant properties (polyphenols, antioxidant capacity, voltammetric behaviour, colour parameters and SO₂) were selected. Three different accelerated ageing tests (AATs) were then performed on these wines: thermal test at 60 °C (60 °C-ATT), enzymatic test with laccase (Laccase-ATT) and chemical test with H₂O₂ (H₂O₂-ATT). The results showed high correlations between the initial phenolic composition and antioxidant properties of the samples. Partial least squares (PLS) regressions were used in order to establish some models that can predict the AATs test results based on their different initial composition and antioxidant properties. The PLS regression models had overall very good accuracy and involved different explaining variables for each test. The models taking into account all the measured parameters and the phenolic composition alone showed good predictive capacities with correlation coefficients (r²) > 0.89.

Evaluation of the generation of reactive oxygen species and antibacterial activity of honey as a function of its phenolic and mineral composition

The antibacterial activity (ABA) of honey is associated with the generation of reactive oxygen species (ROS), where polyphenols (PFs) play a key role due to their pro-oxidant action modulated by metallic cations. In this work, the contents of PFs, H₂O₂, OH radicals, Cu, Fe, Mn, Zn, and ABA against Staphylococcus epidermidis and Pseudomonas aeruginosa were determined in honeys from central Chile. Then, their relationships were evaluated through partial least squares regression. The average contents of phenolic acids, flavonoids and metals in honey ranged from 0.4 to 4 μg/g, 0.3-1.5 μg/g and 3-6 μg/g, respectively. All honeys showed accumulation of H₂O₂ (1-35 μg/g) and OH radicals. The PLS showed that gallic acid, p-coumaric acid, chrysin, kaempferol, Fe, and Mn stimulate the generation of ROS. Quercetin, Cu, and Zn showed marginal antioxidant effects. PFs favor the ABA of honey against both bacteria and H₂O₂ against S. epidermidis.

Influence of Ultra-High-Pressure Pretreatment Method on Chemical Constituents, Antioxidant and Cytoprotective Activities of Free, Esterified, and Bound Phenolics from Anneslea Fragrans Wall. Leaves

Anneslea fragrans Wall., an edible and medicinal plant, is traditionally used to treat liver and gastrointestinal diseases. This paper aimed to investigate the influence of ultra-high pressure (UHP) pretreatment on the phenolics profiling, antioxidant, and cytoprotective activities of free (FP), esterified (EP), and bound (BP) phenolics from A. fragrans leaves. A total of 32 compounds were characterized and quantified. The davidigenin (44.46 and 113.37 mg/g extract) was the highest in A. fragrans leaves. The vitexin (9), afzelin (10), coreopsin (15), and davidigenin (28) were analyzed with MS² fragment pathways. Results showed that UHP treated A. fragrans leaves had higher total phenolic (TPC) and total flavonoid (TFC) contents of FP, EP, and BP fractions than those in the raw leaves. Moreover, UHP pretreated A. fragrans leaves had higher scavenging activities on DPPH⁺• and ABTS⁺•, and inhibitory effects on the intracellular ROS generation in H₂O₂-induced HepG2 cells. UFP showed the highest inhibition of ROS production among the samples. Therefore, UHP pretreatment method might be used as an effective strategy for elevating the availabilities of A. fragrans leaves to develop functional foods.

Use of vinasse and coffee waste as chelating agent of photo-Fenton landfill leachate treatment

This research studies the use of vinasse (VS) coming from Pisco and caffeic acid (Caa) from solid coffee waste as chelating agents of this process, to carry out a photo-Fenton process using UVc lamps of 254-nm wavelength for 60 min, at the natural pH of the landfill leachate (8.9). Without the chelating agent, there was a removal of UV 254 and COD of 54.2% and 54.7%, respectively, when the photo-Fenton reaction was carried out at pH 3; at pH 6, the removal of UV 254 and COD was 13.1% and 39.2%, respectively, and at pH 8.9, the elimination of UV 254 and COD was 10.8% and 16.1%, respectively. When Caa was used in the landfill leachate (LL) for the photo-catalytic processes carried out at pH 8.9, a removal of 24.1%, 43.0%, and 47.4% of UV 254 was obtained using 5 mg/L, 50 mg/L, and 100 mg/L of Caa. The removal of UV 254 was 27.3%, 30.7%, and 36.3% using 5 mg/L, 50 mg/L, and 100 mg/L of VS, respectively, and the removal of COD was 32.2%, 35.4%, and 39.2% using 5 mg/L, 50 mg/L, and 100 mg/L of VS, respectively. When Caa was used in the LL at pH 8.9, the concentration of total Fe went from 37.5 to 33.2, from 40.2 to 36.8, and from 45.2 to 42.1, using 5 mg/L, 50 mg/L, and 100 mg/L of caffeic acid, respectively. Using VS in the LL at pH 8.9, the concentration of total Fe along the run went from 35.1 to 32.2, from 39.4 to 34.8, and from 42.1 to 40.2, using 5 mg/L, 50 mg/L, and 100 mg/L of VS, respectively. As a result of these processes, it was noted that the use of Caa and VS increases the solubility of Fe at a higher pH.

Selective Oxofunctionalization of Cyclohexane and Benzyl Alcohol over BiOI/TiO2 Heterojunction

Heterogeneous photocatalysis under visible light irradiation allows performing of selective oxofunctionalization of hydrocarbons at ambient temperature and pressure, using molecular oxygen as a sacrificial reagent and potential use of sunlight as a sustainable and low-cost energy source. In the present work, a photocatalytic material based on heterojunction of titanium dioxide and bismuth oxyiodide was used as photocatalyst on selective oxofunctionalization of cyclohexane and benzyl alcohol. The selective oxidation reactions were performed in a homemade photoreactor equipped with a metal halide lamp and injected air as a source of molecular oxygen. The identified oxidized products obtained from oxofunctionalization of cyclohexane were cyclohexanol and cyclohexanone. On the other hand, the product obtained from oxofunctionalization of benzyl alcohol was benzaldehyde. The yield obtained with BiOI/TiO2 photocatalysts was higher than that obtained with pure bismuth oxyiodide. The higher performance of this material with respect to pure BiOI was attributed to its higher specific area.

An assessment of voltammetry on disposable screen printed electrodes to predict wine chemical composition and oxygen consumption rates

The present work aimed at determining the applicability of linear sweep voltammetry coupled to disposable carbon paste electrodes to predict chemical composition and wine oxygen consumption rates (OCR) by PLS-modeling of the voltammetric signal. Voltammetric signals were acquired in a set of 16 red commercial wines. Samples were extensively characterized including SO₂, antioxidant indexes, metals and polyphenols measured by HPLC. Wine OCRs were calculated by measuring oxygen consumption under controlled oxidation conditions. PLS-Regression models were calculated to predict chemical variables and wine OCRs from first order difference voltammogram curves. A significant number of fully validated models predicting chemical variables from voltammetric signals were obtained. Interestingly, monomeric and polymerized anthocyanins can be differently predicted from the first and second wave of the first derivative of voltammograms, respectively. This fast, cheap and easy-to-use approach presents an important potential to be used in wineries for rapid wine chemical characterization.

Impact of oenological antioxidant substances on the formation of 1-hydroxyethyl radical and phenolic composition in SO2 free red wines

BACKGROUND

Different natural substances, chitosan, inactive dry yeasts and freeze-dried aqueous extracts from two wine industry by-products (stems and shoots) were used in red winemaking as possible alternatives to SO₂ . The resistance to oxidation of wines was evaluated by electron paramagnetic resonance. The phenolic composition of wines was analyzed by high-performance liquid chromatography-diode array detection/electrospray ionization mass spectrometry, antioxidant activity was determined by DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and ABTS [2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation] assays and spectrophotometric measurements of color were compared.

RESULTS

The wines elaborated with chitosan and inactive dry yeast presented greater capacity to inhibit the formation of the 1-hydroxyethyl radical compared to the wines elaborated with stem or shoot extracts. The total content of anthocyanins was higher in the wines elaborated with SO₂ ; however, the concentration of flavan-3-ols was higher in the wines with chitosan. In addition, the wines with chitosan and inactive dry yeast presented the highest % polymerization. Wines elaborated with stem extract had a lower concentration of flavonols and stilbenes.

CONCLUSION

Chitosan and inactive dry yeast, which are used as an alternative to SO₂ in winemaking, allow the control of the formation of 1-HER in red wines. Wines with stem and shoot extracts showed a lower resistance to oxidation. © 2020 Society of Chemical Industry.