The effects of Zataria multiflora on inhibition of polyphenoloxidase and melanosis formation in shrimp (Litopenaeus vannamei)

Shrimp melanosis (black spot) is an important surface discoloration caused by polyphenol oxidase (tyrosinase) enzyme, which oxidizes phenols and leads to insoluble black pigments, the melanins. Sulphiting agents are widely used as melanosis inhibitors; but, the hazards related to sulphated foods, such as allergic reactions and severe disorders in asthmatic patients have created a necessity to find the effective natural alternatives. The current study was accomplished to assay the in vitro antityrosinase effect of Z. multiflora EO as well as its capability to retard the melanosis formation in shrimp during iced storage. According to GC/MS results, carvacrol, thymol and p-cymene were the major components of Z.multiflora EO, representing 50.8, 14.4 and 10.6, respectively. DPPH radical scavenging activity of EO was 0.8±0.02 mg/ml and 63.2% of tyrosinase activity decreased when EO with a concentration of 0.25% was applied. Furthermore, it has been observed that immersing the shrimps in 1% EO aqueous suspension retarded the melanosis formation in shrimp during 10 days of iced storage. It can be concluded that Z. multiflora EO could be used as an effective natural processing aid to increase the shrimp shelf-life during iced storage

Aceite de Kilka común y su dinámica oxidativa primaria y secundaria estabilizada por diferentes variantes de aceite esencial de clavo

The objective of this study was to investigate the properties of clove essential oil extracted by different microwave-assisted methods and to evaluate its effects on the stability of common Kilka oil. Each of these methods was hypothesized to yield a clove essential oil that would have a distinguishable composition and effect when added to common Kilka oil by maintaining its oxidative stability. The oxidation of common Kilka oil was examined by accelerated oxidation using the active oxygen method and Rancimat test. The clove essential oil extracted by microwave-assisted hydrodistillation showed the highest induction period according to the active oxygen method (16.56 h) and the Rancimat induction period (3.64 h) in common Kilka oil and its antioxidant activity was comparable to that of BHT (16.59 h and 4.34 h, respectively) and tocopheryl acetate (16.30 h and 4.02 h, respectively). Furthermore, the microwaveassisted hydrodistillation method resulted in the amount of eugenol that exhibited the highest antioxidant capacity for preserving PUFA in common Kilka oil. Ultimately, clove essential oil can become an efficient natural antioxidant for the oxidative stability of common Kilka oil.El objetivo de este estudio fue investigar las propiedades de los aceites esenciales de clavo que se extrajeron utilizando diferentes métodos asistidos por microondas y evaluar los efectos de estos aceites esenciales en la estabilidad del aceite de Kilka común. Se hipotetizó que cada uno de los métodos produce un aceite esencial de clavo que tendría una composición y un efecto distintivo cuando se agrega al aceite de Kilka común manteniendo su estabilidad oxidativa. La oxidación del aceite de Kilka común se determinó mediante oxidación acelerada utilizando el método de oxígeno activo y Rancimat. El aceite esencial de clavo extraído por hidrodestilación asistida por microondas logró en el aceite de Kilka común un período de inducción, mediante el método de oxígeno activo, más alto (16,56 h) y un período de inducción mediante Rancimat de 3,64 h y su actividad antioxidante fue comparable a la del BHT (16,59 h y 4,34 h, respectivamente) y a la del acetato de tocoferol (16,30 h y 4,02 h, respectivamente). Además, el método de hidrodestilación asistido por microondas influyó en la cantidad de eugenol que presentó una mayor capacidad antioxidante para preservar los PUFAs del aceite de Kilka común. Por último, el aceite esencial de clavo puede convertirse en un antioxidante natural eficiente para la estabilidad oxidativa del aceite de Kilka común

Mejora del rendimiento del biodiesel a partir de aceite de oliva no comestible pre-esterificado mediante transesterificación asistida por microondas

In the present research, biodiesel production from olive oils with different initial free fatty acid concentrations (2.5, 5.0, and 10.0%) was evaluated. A two-stage acid-catalyzed esterification and alkaline-catalyzed transesterification (ACT) process using the microwave heating method was compared with the traditional heating method. Free fatty acid was reduced to less than 2.0% in the first stage. Although no significant difference was observed between microwave and traditional esterification methods in terms of fatty acid reduction, the microwave treatment significantly decreased reaction time by 92.5%. Comparing microwave ACT results with those of the traditional heating method showed that the microwave can significantly increase methyl ester yield and purity, and simultaneously decrease reaction time. Physical constants of methyl esters were also improved using the microwave heating method. Therefore, the microwave heating method can be regarded as an efficient method instead of the two-stage method for biodiesel production. This method is capable of using inedible olive oil with high concentrations of free fatty acids.En la presente investigación, se evaluó la producción de biodiesel a partir de aceites de oliva con diferentes concentraciones iniciales de ácidos grasos libres (2,5, 5,0 y 10,0%). Se comparó un proceso de esterificación en dos etapas catalizada con ácido y transesterificación catalizada alcalina (ACT) usando microondas con el método de calentamiento tradicional. Los ácidos grasos libres se redujeron a menos del 2,0% en la primera etapa. Aunque no se observaron diferencias significativas entre los métodos de esterificación, por microondas y tradicional, en términos de reducción de ácidos grasos, sin embargo, el microondas disminuyó significativamente el tiempo de reacción en un 92,5%. La comparación de los resultados de ACT de microondas con los del método de calentamiento tradicional mostró que el microondas puede aumentar significativamente el rendimiento y la pureza del éster metílico, y simultáneamente disminuir el tiempo de reacción. Las constantes físicas de los ésteres metílicos también se mejoraron usando el método de calentamiento por microondas. Por lo tanto, el método de calentamiento por microondas puede considerarse como un método eficiente en lugar de la producción de biodiésel en dos etapas. Este método es capaz de usar aceite de oliva no comestible con altas concentraciones de ácidos grasos libres

Producción de biodiésel mejorada por esterificación y transesterificación asistida por ultrasonidos de aceite de oliva no comestible

In the first phase of this study, inedible olive oil with different initial free fatty acid concentrations (2.5, 5.0, and 10.0%) was processed through acid-catalyzed esterification. Various heating methods were used for this purpose. The ultrasound-assisted esterification and traditional magnetic stirrer-assisted esterification methods were similar to each other in terms of their effects on free fatty acid reduction. However, the ultrasound reaction time was significantly shorter than that of the traditional magnetic stirrer. In the second phase of this study, biodiesel production was carried out through the ultrasound-assisted transesterification of inedible olive oil. Independent variables were, namely, ultrasound power level (30, 90, and 150 W), methanol/oil mole ratio (3, 9, and 15), catalyst concentration (0.5, 1.0, and 1.5%), ultrasound time (15, 30, and 45 min), and reaction temperature (45, 55, and 65 °C), which affected the yield indices and physicochemical constants of the produced biodiesel. The purest biodiesel (98.95%) and the highest amount of yield (92.69%) were observed when using an ultrasound power level of 90 W, a methanol/oil mole ratio of 9, a catalyst concentration of 1.0%, an ultrasound time of 30 min, and a reaction temperature of 55 °C. Optimizing the reaction conditions of the ultrasound operation can effectively increase the biodiesel yield (92.69%), while reducing the energy consumption (4.775 kWh/kg) and shortening the reaction time (30 min), compared to the traditional magnetic stirrer (77.28%, 2.17 kWh/kg, and 120 min, respectively). Therefore, ultrasound-assisted transesterification can serve as an effective alternative because of its fast and economic operation for making biodiesel out of inedible olive oil.En la primera fase de este estudio, el aceite de oliva no comestible tenía diferentes concentraciones iniciales de ácidos grasos libres (2,5, 5,0 y 10,0%) y se procesó mediante esterificación catalizada por ácido. Se utilizaron varios métodos de calentamiento para este propósito. La esterificación asistida por ultrasonido y los métodos tradicionales de esterificación asistida por agitador magnético fueron similares entre sí en términos de sus efectos sobre la reducción de ácidos grasos libres. Sin embargo, el tiempo de reacción usando ultrasonidos fue significativamente más corto que el de agitador magnético tradicional. En la segunda fase de este estudio, la producción de biodiesel, a partir de aceite de oliva no comestible, se llevó a cabo mediante transesterificación asistida por ultrasonidos. Las variables independientes fueron, nivel de potencia de ultrasonido (30, 90 y 150 W), relación molar metanol/aceite (3, 9 y 15), concentración de catalizador (0,5, 1,0 y 1,5%), tiempo de ultrasonido (15, 30 y 45 min) y temperatura de reacción (45, 55 y 65 °C) que afectaron al rendimiento y a las constantes fisicoquímicas del biodiesel producido. El biodiésel más puro (98,95%) y el mayor rendimiento (92,69%) se observaron cuando se utilizó un nivel de potencia de ultrasonido de 90 W, una relación molar de metanol / aceite de 9, una concentración de catalizador del 1,0%, un tiempo de ultrasonido de 30 min, y una temperatura de reacción de 55 °C. La optimización de las condiciones de reacción de la operación de ultrasonido puede aumentar efectivamente el rendimiento de biodiésel (92,69%), al tiempo que reduce la cantidad de consumo de energía (4,775 kWh/kg) y acorta el tiempo de reacción (30 min), en comparación con el agitador magnético tradicional (77,28 %, 2,17 kWh/kg y 120 min, respectivamente). Por lo tanto, la transesterificación asistida por ultrasonido puede servir como una alternativa eficaz debido a su operación rápida y económica en la producción de biodiesel a partir de aceite de oliva no comestible

Transesterificación asistida por microondas de aceite de semilla de cereza ácida para la producción de biodiesel: comparación con métodos de transesterificación asistida por baño ultrasónico, sonda ultrasónica y óhmica

In this study, sour cherry kernel oil was converted to biodiesel by microwave-assisted transesterification. Evaluations were made of several variables, namely, reaction time (1, 2, 3, 4, and 5 min), microwave power (100, 200, 300, 400, and 500 W), methanol/oil mole ratio (3, 6, 9, 12, and 15), and catalyst (KOH) concentration (0.3%, 0.6%, 0.9%, 1.2%, and 1.5%). The efficiency of fatty acid methyl esters increased in response to lengthier reaction times, greater microwave power, higher methanol/oil mole ratio, and higher catalyst concentrations up to the optimal level. The optimal reaction conditions for microwave-assisted transesterification were 300 W microwave power, 1.2% catalyst concentration, a methanol/oil mole ratio of 1:2, and a reaction time of 4 min. Microwave-assisted transesterification was more effective than ohmic-, magnetic stirrer-, ultrasonic probe-, and ultrasonic bath-assisted transesterification methods. In conclusion, microwave-assisted transesterification can be suggested as a fast, efficient, and economical method compared to other transesterification methods.En este estudio, el aceite de semilla de cereza ácida se convirtió en biodiesel mediante transesterificación asistida por microondas. Se realizaron evaluaciones de varias variables, como tiempo de reacción (1, 2, 3, 4 y 5 min), potencia de microondas (100, 200, 300, 400 y 500 W), relación molar metanol/aceite (3, 6, 9, 12 y 15) y concentración de catalizador (KOH) (0,3%, 0,6%, 0,9%, 1,2% y 1,5%). La eficiencia de los ésteres metílicos de ácidos grasos aumentó en respuesta a tiempos de reacción más prolongados, mayor potencia de microondas, mayor relación molar metanol/aceite y mayores concentraciones de catalizador hasta el nivel óptimo. La condición de reacción óptima de la transesterificación asistida por microondas fue una potencia de microondas de 300 W, una concentración de catalizador del 1,2%, una relación molar de metanol/aceite de 12 y un tiempo de reacción de 4 min. La transesterificación asistida por microondas fue más efectiva que los métodos de transesterificación asistida por baño ultrasónico, óhmico, con agitador magnético y con sonda ultrasónica. En conclusión, la transesterificación asistida por microondas puede sugerirse como un método rápido, eficiente y económico en comparación con otros métodos de transesterificación

Experimental and numerical investigation of tensile and flexural behavior of nanoclay wood-plastic composite

In this study, the effect of wood powder and nanoclay particle content on composites’ mechanical behavior made with polyethylene matrix has been investigated. The wood flour as a rein-forcer made of wood powder was at levels of 30, 40, and 50 wt.%, and additional reinforcement with nanoclay at 0, 1, 3, and 5 wt.%. Furthermore, to make a composite matrix, high-density polyethylene was used at levels of 70, 60, and 50% by weight. Wood-plastic composite (WPC) specimens were manufactured in injection molding. After preparing the specimens, tensile and bending tests were performed on samples. The mechanical properties such as tensile and flexural strength and flexural modulus were measured. Results showed that nanoclay particle content increases flexural modulus, flexural strength, modulus of elasticity, and tensile strength. The experimental test results show that Young’s moduli increased with the volume of wood flour. The biggest modulus of elasticity was achieved in the samples having 50 wt.% of wood powder. Furthermore, the highest value of tensile strength was achieved at the level of 30 wt.%. The highest flexural strength was for the sample containing 50% wood powder by weight. Additionally, a numerical model was made utilizing the Abaqus software using the finite element method (FEM). Comparing the numerical and experimental results, it was found that they are compatible in the linear-elastic and plastic state of the material. There are no crucial differences between experiment and FEM

Mejora de la estabilidad oxidativa del aceite de oliva: Incorporación de Espirulina y evaluación de su sinergismo con ácido cítrico

The effects of different Spirulina concentrations used alone and in combination with citric acid on the oxidative stability of olive oil were assessed. The amounts of primary and secondary oxidation products produced in Spirulina samples were lower than that of the control. The improved oxidative stability indices of Spirulina samples with and without citric acid were in the range of 85.20–94.47% and 258.10–260.21%, respectively. In comparison with the control, Spirulina samples manifested significantly higher carotenoid and chlorophyll contents at the beginning and end of the storage period. The presence of these bioactive compounds results from the presence of Spirulina in the medium and can thus retard the oxidation of olive oil. A higher oxidative stability was reached using BHT in comparison with Spirulina samples. Furthermore, no synergistic action was observed in possible connections between citric acid and Spirulina. In conclusion, Spirulina can enhance oxidative stability and improve the shelf life of olive oil.Se evaluaron los efectos de diferentes concentraciones de Espirulina usadas solas y en combinación con ácido cítrico sobre la estabilidad oxidativa del aceite de oliva. Las cantidades de productos de oxidación primarios y secundarios producidos en muestras de Espirulina fueron menores que las del control. Además, la estabilidad oxidativa de muestras de Espirulina con y sin ácido cítrico estaban en el intervalo de 85,20–94,47% y 258,10–260,21%, respectivamente. En comparación con el control, las muestras de Espirulina mostraron un contenido significativamente mayor de carotenoides y clorofila al inicio y al final del período de almacenamiento. La presencia de estos compuestos bioactivos y la presencia de Espirulina en el medio pueden retardar la oxidación del aceite de oliva. Se obtuvo una mayor estabilidad oxidativa usando BHT en comparación con muestras de Espirulina. Además, no se observó ninguna acción sinérgica en las posibles combinaciones entre el ácido cítrico y la Espirulina. En conclusión, la Espirulina puede mejorar la estabilidad oxidativa y la vida útil del aceite de oliva

Recent advances in the conjugation approaches for enhancing the bioavailability of polyphenols

In recent years, the consumption of functional foods containing health-beneficial ingredients has become increasingly popular. Polyphenols are among the most important functional and bioactive molecules found in a variety of fresh produce and food products. However, the limited solubility of most polyphenols in water can significantly affect their bioavailability, thereby reducing their potential health benefits. To overcome this limitation, various approaches have been explored, including molecular enhancers, nanoparticles, encapsulation systems, and conjugation methods. In this review, we focus on recent advances in conjugation methods for enhancing the bioavailability of polyphenols. We provide a concise overview of the types of polyphenols and bioavailability determination methods and, subsequently, discuss the concept of conjugation methods, including different synthesizing methods, confirmation procedures, and the effects of conjugation on polysaccharides and polyphenols. Overall, this review provides a comprehensive update on recent advances in conjugation methods that can be used to improve the bioavailability of polyphenols and highlights the potential of these approaches to enhance the health benefits of polyphenol-rich foods.fals

Transient behavior of imperfect bi-directional functionally graded sandwich plates under moving loads

An investigation of dynamic behaviors of a sandwich plate containing an imperfect two dimensional functionally graded (2D-FG) core surrounded by two faces on a two-parameter elastic foundation and subjected to a moving load is carried out in this paper. The present sandwich solid is composed of a porous 2D-FG core covered by two homogenous layers. It is assumed that the middle layer has micro voids dispersed uniformly and unevenly through the layer thickness. The fundamental equations are governed within the framework of first-order-shear deformation theory by utilizing Hamilton’s principle, von-Karman geometrical nonlinearity and the principal of mixtures. Newmark direct integration procedure is implemented to transform the dynamic equations into a static form and then the kinetic dynamic relaxation numerical technique in conjunction with the finite difference discretization method are employed to solve the nonlinear partial differential governing equations. Finally, the effects of porosity fraction and scattering patterns, boundary constrains, the variation of materials’ grading indexes and elastic foundation constants on the transient performances of the plate are studied in detail

Geometrically nonlinear thermo-mechanical analysis of graphene-reinforced moving polymer nanoplates

The main target of this study is to investigate nonlinear transient responses of moving polymer nano-size plates fortified by means of Graphene Platelets (GPLs) and resting on a Winkler-Pasternak foundation under a transverse pressure force and a temperature variation. Two graphene spreading forms dispersed through the plate thickness are studied, and the Halpin-Tsai micro-mechanics model is used to obtain the effective Young's modulus. Furthermore, the rule of mixture is employed to calculate the effective mass density and Poisson's ratio. In accordance with the first order shear deformation and von Kármán theory for nonlinear systems, the kinematic equations are derived, and then nonlocal strain gradient scheme is used to reflect the effects of nonlocal and strain gradient parameters on small-size objects. Afterwards, a combined approach, kinetic dynamic relaxation method accompanied by Newmark technique, is hired for solving the time-varying equation sets, and Fortran program is developed to generate the numerical results. The accuracy of the current model is verified by comparative studies with available results in the literature. Finally, a parametric study is carried out to explore the effects of GPL's weight fractions and dispersion patterns, edge conditions, softening and hardening factors, the temperature change, the velocity of moving nanoplate and elastic foundation stiffness on the dynamic response of the structure. The result illustrates that the effects of nonlocality and strain gradient parameters are more remarkable in the higher magnitudes of the nanoplate speed