Kinetic characterisation and thermal inactivation study of polyphenol oxidase and peroxidase from table grape (Crimson Seedless)

Polyphenol oxidase (PPO) and peroxidase (POD) were extracted from a table grape (Crimson Seedless) using Triton X-114 and characterized using spectrophotometric methods. Both PPO and POD were activated by acid shock. However, in the presence of the anionic detergent sodium dodecil sulphate (SDS), PPO was activated whereas POD was inactivated. The enzymes were kinetically characterized and both followed Michaelis–Menten kinetics, although with different values of their kinetic parameters. The Vm/Km ratio showed that Crimson Seedless grape PPO presents a similar affinity for 4-tert-butyl-catechol (TBC) whether activated by acid shock (0.018 min1 ) or SDS (0.023 min1 ). With regards to POD, the Km and Vm values for 2,20 -azinobis(3-ethylbenzothiazolinesulphonic acid) (ABTS) were 0.79 mM and 1.20 lM/min, respectively. In the case of H2O2, the Km and Vm value were 0.4 mM and 0.93 lM/min, respectively. PPO and POD showed similar thermostability, losing >90% of relative activity after only 5 min of incubation at 78 C and 75 C, respectively. In addition, PPO´ s activation energy was similar to that obtained for POD (295.5 kJ/mol and 271.9 kJ/mol, respectively).Ciencias de la Alimentació

Effect of ripening on protein content and enzymatic activity of Crimson Seedless table grape

The evolution of Brix, protein content, polyphenoloxidase activity and peroxidase activity during the ripening of Crimson Seedless table grape was studied in three consecutive years (2006, 2007 and 2008). The total protein content was determined according to Bradford’s dye binding method, and polyphenoloxidase (PPO) and peroxidase (POD) were extracted using Triton X-114 and characterised using spectrophotometric methods. The year had a statistically significant effect on all the studied parameters and there was an interannual correlation in the evolution of protein, PPO, POD and Brix. All the studied parameters were statistically correlated, except POD activity with protein content. Weather conditions during the ripening period had a greater effect on protein content than PPO and POD activity.Ciencias de la Alimentació

Kinetic characterisation and thermal inactivation study of red alga (Mastocarpus stellatus) peroxidase

Peroxidase (POD) was extracted from red alga (Mastocarpus stellatus) using Triton X-114 and characterised by UV-spectrophotometry. Optimum activity using 2,2´ -azinobis(3-ethylbenzothiazolinesulphonic acid) (ABTS) as the H-donor was obtained at pH 5.0. In the presence of the anionic detergent, sodium dodecyl sulphate (SDS), however, POD was inactivated at all the pH values studied and totally inactivated at 1 mM SDS. When the enzyme was kinetically characterised, the KM and Vm values for ABTS were found to be 13 mM and 40 lM/min, respectively. In addition, when the H2O2 concentration was increased, at a fixed concentration of ABTS, the activity was inhibited at the highest H2O2 concentrations. In a study of the effect of several reducing agents, L-cysteine was found to be the most active. A thermal inactivation study showed a first-order inactivation kinetic, and the Arrhenius plot yielded a straight line with a slope equivalent to an activation energy of 121.6 kJ/mol. Significant inactivation occurred at temperatures of >35 C, with >90% of the relative activity being lost after only 5 min of incubation at 48.4 C.Ciencias de la Alimentació

Protective effect of cyclodextrins on the quality parameters of roast preserved pepper

Total phenolics (TP), vitamin C, antioxidant activity and colour of preserved peppers were evaluated at 4, 25 and 50 C storage during 30-day intervals. Except for 4 C, TP decreased during storage at 25 C and 50 C, being softer for fortified samples with b-CDs. The protective effect was evident, since 50 C samples containing b-CDs exhibited lower TP loss (19%) than control samples (38%) for 5 months storage. A decrease in the vitamin C content was observed for both samples as time and temperature progressed. In samples stored at 50 C the protective effect of b-CD only was evident at the first month, since fortified samples showed lower vitamin C loss (10%) than control samples. The fortified samples with b-CDs exhibited lowest antioxidant activity loss (40%) during 90-day storage at 50 C, than control samples (64%). The colour changes were in line with those observed for total phenolics and at the end of study, the presence of 1% b-CDs delayed the darkening of samples at both (25 and 50 C) storage conditions.Ciencias de la Alimentació

Use of cyclodextrins to recover catechin and epicatechin from red grape pomace

The capacity of cyclodextrins (CDs) to extract phenolic compounds from grape pomace was evaluated and compared with that of ethanol/water or aqueous extraction. The extraction method (stirring and ultrasound), temperature and time were also studied. Total phenolic compounds (TPC) and antioxidant activity were measured, and HPLC analysis was used to identify the phenolic compounds. The extracts obtained using the ethanol/water mixture presented the highest TPC content and antioxidant activity, followed by those obtained using CD solutions. The addition of CDs to the extractant agent had a selective effect on the extraction of catechin and epicatechin. The yield of catechin and epicatechin by using aqueous solutions of CDs was similar to that obtained using organic solvents as ethanol.Ciencias de la Alimentació

Efecto de Diferentes Factores: Fertilización, Salinidad y Procesado, sobre Parámetros Objetivos de Calidad en Pimiento

El pimiento es una verdura muy consumida entre la población por la combinación tan atractiva que presenta de color, sabor y valor nutricional que posee. En este trabajo se ha estudiado el efecto de la maduración, tipo de cultivo, uso de biofertilizantes, diferentes concentraciones de estrés salino y el efecto de las ß-CDs en pimiento de V gama, sobre diferentes factores de calidad del pimiento cultivado en invernadero. El tipo de cultivo, ecológico o tradicional, afecto a diferentes parámetros de calidad del fruto de pimiento como son: contenido en proteínas, compuestos fenólicos, vitamina C, actividad peroxidasa, carotenos y color. El pimiento cultivado bajo sistema de producción ecológica presenta un mayor contenido en todos los parámetros anteriormente mencionados, así como un color más intenso. El estadío de maduración afecta a diferentes parámetros de calidad del fruto de pimiento como son: contenido en proteínas, compuestos fenólicos, vitamina C, actividad peroxidasa, carotenos y color. Todos estos parámetros, excepto peroxidasa, aumentan con la maduración, independientemente del sistema de producción utilizado para su cultivo (ecológico o tradicional). La inoculación de plantas de pimiento con rizobacterias suple un aporte deficiente de N a las mismas, consiguiendo unas características físicas en el fruto similares a los frutos procedentes de plantas cultivadas sin deficiencia en N. Respecto a los niveles de peroxidasa, estos son mucho más bajos en frutos de plantas inoculadas con rizobacterias, debido a una menor infección de los tejidos de la planta. La concentración salina del agua de riego afecta a diferentes parámetros de calidad del fruto de pimiento como son: compuestos fenólicos, vitamina C, actividad antioxidante y peroxidasa. Un aumento en la concentración salina del agua de riego provoca una drástica caída en los niveles de vitamina C de los frutos de pimiento maduros. También provoca un descenso, aunque menos acusado, del contenido en compuestos fenólicos, y por lo tanto un descenso en la capacidad antioxidante de dichos frutos. En el caso de peroxidasa, se produce un aumento de dicha actividad enzimática con la salinidad del agua de riego. La presencia del 1% de -CD en el líquido de gobierno reduce la pérdida de capacidad antioxidante de pimiento asado de V gama, ya que protege de su degradación durante el almacenamiento a los compuestos fenólicos, vitamina C, y compuestos responsables del color de dicho fruto. Esto ralentiza la modificación de las características organolépticas del producto, así como la pérdida de sus propiedades nutricionales durante el periodo de vida útil del producto. El uso de detergente Triton X-114 permite extraer la peroxidasa de pimiento libre de fenoles y compuestos coloreados. La isoenzima así extraída presentó un pH óptimo de 4,5 y es poco estable a la temperatura.Ciencias de la Alimentació

Fluorimetric determination of sulphathiazole in honey by means theformation of CDs inclusion complexes

tThe inclusion complex of sulphathiazole in -cyclodextrin has been investigated. A 1:2 stoichiometryof the complex was established and formation constants K2(42.83 ± 3.27 M−1) and K1(4.98 ± 0.36 M−1)were calculated by using the changes produced on the native fluorescence of the drug, when includedon the hydrophobic cyclodextrin cavity. An enhancement in the fluorescence emission of sulphathiazoleand protection of the drug against photochemical reactions has been attained upon inclusion. In solu-tions of -CD dual emission (458 nm) was noticed in STZ. Formation of the inclusion complex of STZshould result in dual emission, which is due to a twisted intramolecular charge transfer band (TICT).A fluorimetric method for the determination of sulphathiazole has been proposed and applied in honeywithout sample treatment. The optimized fluorimetric method showed detection and quantitation limitsof 9.74 ng/g and 32.48 ng/g, respectively. Selectivity is high, showing no cross-reactivity to other chemi-cally related antibiotics. The results obtained for blind honey samples (mean recovery 97%), were in goodagreement with those obtained by liquid chromatography separation and mass spectrometry detection(LC–MS) (mean recovery 102%), showing that the proposed method might be used for the determinationof sulphathiazole residues without expensive equipment.Ciencias de la Alimentació

Protective effect of cyclodextrins on the quality parameters of roast preserved pepper

Total phenolics (TP), vitamin C, antioxidant activity and colour of preserved peppers were evaluated at 4, 25 and 50 C storage during 30-day intervals. Except for 4 C, TP decreased during storage at 25 C and 50 C, being softer for fortified samples with b-CDs. The protective effect was evident, since 50 C samples containing b-CDs exhibited lower TP loss (19%) than control samples (38%) for 5 months storage. A decrease in the vitamin C content was observed for both samples as time and temperature progressed. In samples stored at 50 C the protective effect of b-CD only was evident at the first month, since fortified samples showed lower vitamin C loss (10%) than control samples. The fortified samples with b-CDs exhibited lowest antioxidant activity loss (40%) during 90-day storage at 50 C, than control samples (64%). The colour changes were in line with those observed for total phenolics and at the end of study, the presence of 1% b-CDs delayed the darkening of samples at both (25 and 50 C) storage conditions.Ciencias de la Alimentació

Use of cyclodextrins to recover catechin and epicatechin from red grape pomace

The capacity of cyclodextrins (CDs) to extract phenolic compounds from grape pomace was evaluated and compared with that of ethanol/water or aqueous extraction. The extraction method (stirring and ultrasound), temperature and time were also studied. Total phenolic compounds (TPC) and antioxidant activity were measured, and HPLC analysis was used to identify the phenolic compounds. The extracts obtained using the ethanol/water mixture presented the highest TPC content and antioxidant activity, followed by those obtained using CD solutions. The addition of CDs to the extractant agent had a selective effect on the extraction of catechin and epicatechin. The yield of catechin and epicatechin by using aqueous solutions of CDs was similar to that obtained using organic solvents as ethanol.Ciencias de la Alimentació

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care