Search Results (328)

A series of Cu-MnO_x/GF catalytic electrodes, with graphite felt (GF) pretreated via microwave modification as the catalyst carrier, were prepared under various hydrothermal conditions and characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, and Raman spectroscopy. The catalytic oxidation activity of catalytic Cu-MnO_x/GF electrodes toward toluene was evaluated in an all-solid-state electrocatalytic device under mild operating conditions. The evaluation results demonstrated that the microwave-modified catalytic electrode exhibited high electrocatalytic activity toward toluene oxidation, with Cu-MnO_x/700W-GF exhibiting significantly higher catalytic activity, indicating that an increase in catalyst loading capacity can promote the removal of toluene. Only CO₂ and CO were detected, with no other intermediates observed in the reaction process. Moreover, the catalytic effect was significantly affected by the relative humidity. The catalytic oxidation of toluene can be fully realized under a certain humidity, indicating that the conversion of H₂O to strongly oxidizing ·OH on the catalytic electrode is a key step in this reaction. Full article

The use of microwaves (MWs) has been proposed as an energy-efficient method for reducing checking. Along with understanding moisture distribution, it is essential to consider structural characteristics to explain how MWs reduce checking. The influence of MWs on these characteristics depends on the food matrix’s dielectric and viscoelastic properties, which vary significantly between fresh and pre-baked dough. This study investigates the effects of MW treatment applied before (MW-O) or after conventional oven baking (O-MW) on low-fat biscuits that are prone to checking. Color (CIELab), thickness, moisture content and distribution, checking rate, texture, sensory properties, energy consumption and baking time were analyzed. The findings suggest that MWs reduce checking rate by eliminating internal moisture differences, while also changing structural properties, as evidenced by increased thickness and hardness. MW-O eliminated checking (control samples showed 100%) but negatively affected color, texture (increased hardness and breaking work), and sensory quality. The O-MW checking rate (3.41%) was slightly higher than in MW-O, probably due to the resulting different structural properties (less thickness, less hardness and breaking work). O-MW biscuits were the most preferred by consumers (54.76% ranked them first), with color and texture close to the control samples. MW-O reduced total energy consumption by 16.39% and baking time by 25.00%. For producers, these improvements could compensate for the lower biscuit quality. O-MW did not affect energy consumption but reduced baking time by 14.38%. The productivity improvement, along with the reduction in checking and the satisfactory sensory quality, indicates that O-MW could be beneficial for the bakery sector. Full article

The impact of processing time, temperature, and sample on solution ratio parameters, along with pulsing microwave pretreatment, was assessed in the osmotic dehydration of waxy skin highbush blueberries. Fresh blueberries were pre-treated with 20% microwave power for 90 s before being subjected to osmotic dehydration for 8 h in a 60 °Brix sucrose solution, with three different sample to solution ratios (1:4, 1:7, and 1:10). Changes in water loss, solid gain, total anthocyanin content, total phenolic content, and total soluble solid content during osmotic dehydration, as well as color and texture changes, were investigated at four temperature levels (room temperature, 60 °C, 65 °C, and 70 °C). The highest rate of reduction in the total soluble solid content in the osmotic solution was observed during the initial hours (0–4 h) of the process. The most effective combination for reducing the total soluble content of the osmotic agent involved the microwave-pretreatment of the blueberries at 70 °C, using a sample to solution ratio of 1:4, resulting in a decrease of 11.98%, compared to 7.83% for non-pretreated samples. The solid gain was found to be affected by the sample to solution ratio × temperature × pretreatment at a 1% probability level (p ≤ 0.01). The temperature, osmotic solution ratio, and microwave pretreatment interacted together to affect the quality parameters of the osmotically dehydrated blueberries, including total anthocyanin content, total phenolic content, and color. Higher temperatures, along with microwave pretreatment, showed the worst effects on the quality characteristics mentioned. Microwave pretreatment did not change the texture significantly in comparison with non-pretreated blueberry samples. The enhancing effect of microwave pretreatment and higher temperatures on the efficiency of the osmotic dehydration process was obvious. An optimized microwave pretreatment can reduce both the required processing time and temperature for the osmotic dehydration of waxy skinned blueberries, which in turn can lead to the higher quality preservation of processed blueberries and lower energy consumption. This could be especially useful for the large-scale processing of waxy skinned berries. Full article

Methods for the improvement of regional lignocellulosic resources (wood and agriculture waste) were studied and analyzed using blends with optimized compositions and a selective pretreatment of the blends using microwaves to enhance their thermochemical conversion and energy production efficiency. A batch-size pilot device was used to provide the thermochemical conversion of biomass blends of different compositions, analyzing the synergy of the effects of thermal and chemical interaction between the components on the yield and thermochemical conversion of volatiles, responsible for producing heat energy at various stages of flame formation. To control the thermal decomposition of the biomass, improving the flame characteristics and the produced heat, a selective pretreatment of blends using microwaves (2.45 GHz) was achieved by varying the temperature of microwave pretreatment. Assessing correlations between changes in the main characteristics of pretreated blends (elemental composition and heating value) on the produced heat and composition of products suggests that selective MW pretreatment of biomass blends activates synergistic effects of thermal and chemical interaction, enhancing the yield and combustion of volatiles with a correlating increase in produced heat energy, thus promoting the wider use of renewable biomass resources for sustainable energy production by limiting the use of fossil fuels for heat-energy production and the formation of GHG emissions. Full article

Chicken feathers constitute a major by-product from the poultry industry, with a potential environmental impact and significant difficulties in their management. This study aimed to develop a sustainable method to hydrolyse chicken feathers and evaluate the effects of microwave (MW) irradiation pre-treatment in the generation of bioactive hydrolysates by simple or sequential hydrolysis with Alcalase. The hydrolysate with MW irradiation pre-treatment and Alcalase (2%, 2 h) (MWA) showed the highest overall antioxidant activity and neprilysin-inhibitory activity (55%), whereas samples without MW irradiation pre-treatment exerted the highest inhibitory activity of dipeptidyl peptidase IV (DPP IV) and angiotensin-converting enzyme (ACE-I), with values close to 50 and 70%, respectively. Mass spectrometry in tandem of bioactive hydrolysates was performed, and an in silico approach was used to characterise the obtained sequences. These results confirmed that MW irradiation pre-treatment improved Alcalase hydrolysis, leading to the generation of bioactive peptides with potential multifunctional properties, including antioxidant, antidiabetic, and antihypertensive activities. Moreover, this study highlights the potential of combining MW irradiation and enzymatic hydrolysis as a sustainable strategy for the revalorisation of chicken feathers. Full article

There is growing interest in measuring the temperature-dependent dielectric properties of bio-tissues using dual-mode techniques (scattering measurements and thermal treatment). Uncooled coaxial antennas are preferred for their direct contact with the measured medium and reduced complexity; however, they exhibit structural changes during ablation due to the thermal expansion of polytetrafluoroethylene (PTFE). This paper presents an experimental study on PTFE expansion in an uncooled coaxial insulated monopole antenna in response to changes in the tissue’s thermal environment. Furthermore, it presents a methodology to mitigate these effects through coaxial annealing. The investigation consists of two distinct experiments: characterising PTFE expansion and assessing the effects of annealing through microwave ablation. This was achieved by simulating the thermal effects experienced during ablation by immersing the test antenna in heated peanut oil. PTFE expansion was measured through camera monitoring and using a toolmaker’s microscope, revealing two expansion modalities: linear PTFE expansion and non-linear plastic deformation from manufacturing processes. The return loss during ablation and consequential changes in the ablated lesion were also assessed. Antenna pre-annealing increased resilience against structural changes in the antenna, improving lesion ellipticity. Therefore, this study establishes a fabrication method for achieving an uncooled thermally stable antenna, leading to an optimised dual-mode ablation procedure, enabling quasi-real-time permittivity measurement of the surrounding tissue. Full article

Pine nut oil (PNO) is highly valued by consumers for its rich content of unsaturated fatty acids, which confer unique nutritional benefits. However, PNO is highly susceptible to lipid oxidation during storage and extraction. This chemical degradation compromises product quality and poses potential risks to food safety. To address this challenge, the food industry is developing antioxidant strategies, including optimizing pretreatment conditions to improve flavor and storage stability. Green extraction technologies such as microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) have been introduced to enhance extraction efficiency and promote environmental sustainability. Light-proof packaging, reduced oxygen environments, and temperature control have also been employed to significantly extend the shelf life of PNO. Furthermore, to maintain the nutritional integrity and safety of PNO while expanding its functional applications in the food industry, several innovative approaches have been employed. These include the incorporation of natural antioxidants, the development of Pickering emulsions, the use of microencapsulation, and the formulation of oleogels. Full article

The body wall of sea cucumbers is rich in nutrients and small-molecule metabolites; however, traditional hot water pretreatment often leads to nutrient loss. To optimise processing techniques, this study compared the effects of microwave pretreatment and conventional hot water pretreatment on nutrient retention and metabolite profiles. Untreated sea cucumber body wall samples served as controls. The samples were subjected to microwave pretreatment (4 W/g, 12 min) or hot water pretreatment (100 °C, 10 min). Nutrient retention rates and metabolite variations were systematically analysed. Microwave pretreatment demonstrated superior retention of protein (96%), crude fat (92%), total sugar (55%), and saponins (40%). It also promotes the accumulation of small-molecule metabolites, including spermidine, tagatose, and melatonin. Notably, the lysine and methionine retention rates were enhanced by 10-fold and 12-fold, respectively, while the vitamin A, vitamin B3, and melatonin retention increased by 2.4-fold, 2-fold, and 3-fold, significantly outperforming traditional pretreatment. These findings highlight the potential of microwave pretreatment as an efficient alternative to conventional methods for preserving the nutritional and functional components of sea cucumbers. Full article

Asphalt pavements face escalating challenges from traffic loading, climate change, and material degradation, necessitating innovative maintenance solutions. Thermally induced self-healing technologies, leveraging the viscoelastic properties of asphalt binders, can autonomously repair microcracks through targeted thermal activation. This review explored thermally induced self-healing in asphalt mixtures, with a focus on leveraging steel slag as a functional aggregate to enhance sustainability and durability. Two thermal-activation methods, electromagnetic induction and microwave heating, were critically analyzed, highlighting their distinct advantages in heating efficiency, depth, and uniformity. Steel slag offers dual benefits: improving mechanical interlock and skid resistance in mixtures while facilitating efficient heat generation via electromagnetic induction or microwave heating. However, challenges such as hydration-induced expansion, heterogeneous slag composition, and energy-intensive heating processes impede widespread adoption. Pretreatment methods, including natural aging, carbonation, and surface modifications, are essential to mitigate volumetric instability and optimize slag performance. Key factors influencing healing efficacy, including binder properties, operational parameters (e.g., microwave power, frequency), and environmental trade-offs, were systematically evaluated. Future research directions emphasized standardized pretreatment protocols, hybrid heating technologies for uniform temperature distribution, and smart-infrastructure integration for predictive maintenance. Full article

Beta-carboline alkaloids (βC-alkaloids) are natural toxins found in various foods, and can also form during the thermal processing of protein-rich ingredients. This study investigated the formation of six βC-alkaloids in pork belly, beef sirloin, mackerel, and cutlassfish subjected to pan-frying, boiling, steaming, and air-frying at 170–250 °C for 2–24 min. Microwave pretreatment (1–5 min) was applied prior to cooking to assess its mitigation potential. Quantification was performed using liquid chromatography tandem mass spectrometry (LC-MS/MS). Pan-frying significantly promoted βC-alkaloid formation, with harman and norharman levels reaching up to 534.63 µg/kg and 217.06 µg/kg in beef sirloin, and 212.44 µg/kg and 533.01 µg/kg in cutlassfish, respectively. Air-frying generated lower alkaloid levels overall compared to pan-frying. Microwave pretreatment effectively mitigated alkaloid formation. The pretreatment of beef sirloin for 2 min resulted in a reduction in the norharman and harmaline levels by 78.4% and 96.5%, respectively. This study provides a comprehensive comparison of six βC-alkaloids across various food types and cooking methods, demonstrating the influence of cooking parameters on alkaloid formation. This study underscores the importance of understanding the thermal formation of natural toxins in foods and offers insight into practical strategies to minimize their occurrence in daily diets. Full article

This study presents an innovative approach to processing refractory zinc-bearing clinker using microwave thermal treatment followed by acid leaching. Microwave irradiation induces phase transformations, converting sphalerite (ZnS) to zincite (ZnO), and generates microcracks that enhance clinker porosity and reactivity. These changes significantly improve zinc dissolution during sulfuric acid leaching. Key parameters—acid concentration, temperature, solid-to-liquid ratio, and leaching time—were optimized, achieving a zinc extraction of 92.5% under optimal conditions (40 g/L H₂SO₄, solid-to-liquid ratio 1:4, 600 °C, 5–7 min) compared to 39.1% without pre-treatment. Thermodynamic analysis confirms the higher reactivity of ZnO, driven by favorable Gibbs free energy and exothermic reaction characteristics. These findings demonstrate the potential of microwave processing to intensify hydrometallurgical processes, offering energy efficiency and environmental benefits for industrial zinc recovery. Full article

Brewer’s spent grain (BSG), the primary byproduct generated by the brewing industry, holds significant potential as an ingredient in aquafeeds. However, its high content of non-starch polysaccharides (NSP) restricts the amount that can be incorporated into fish diets. To address these limitations, various pretreatment methods (physical, chemical, or enzymatic) can be applied prior to its inclusion in feed formulations. The objectives of the present study were (i) to optimize the conditions for enzymatic or microwave pretreatments to enhance the nutritional and functional profile of BSG, (ii) to determine the bioaccessibility and availability of specific nutrients and antioxidant compounds in diets including a high amount of BSG (pretreated or not) using an in vitro assay simulating the digestion of the gilthead seabream (Sparus aurata), and (iii) to evaluate the effect of such diet pretreatments on growth, metabolism, intestinal microbiota, and oxidative status in live fish. For this study, three experimental diets were formulated: one containing 20% untreated BSG (C) and two containing the same amount of BSG pretreated either enzymatically (H) or with microwave heating (MW). Each diet was administered ad libitum to triplicate groups of 22 juvenile sea bream (mean weight 60 g) over a period of three months. The results indicated that the microwave-treated BSG led to improved growth (0.69 ± 0.02%) and feed efficiency (0.80 ± 0.02 weight gain/total feed intake) and enhanced immune status (alkaline phosphatase activity = 11,811.68 ± 3426.92 U/mg SP), compared to the control diet (SGR = 0.59 ± 0.06%; FE: 0.68 ± 0.03 weight gain/total feed intake; alkaline phosphatase activity = 8590.29 ± 3663.44 U/mg SP). Moreover, fish fed on both pretreated BSG diets exhibited significant differences in metabolic parameters and functional profile of their intestinal microbiota when compared to the control group. Consequently, the findings suggest that the pretreatment of BSG, whether by enzymatic or microwave methods, results in notable differences in its nutritional value and the bioavailability of functional components, which, in turn, have a substantial impact on the growth and metabolism of gilthead seabream. Full article

Food waste is a global challenge, with broccoli stalks (~58% of the head’s mass) often discarded despite being rich in fiber, fatty acids, organic acids, sugars, phenolic compounds, and glucosinolates. Pretreatments like microwaving are gaining interest for enhancing nutrient availability and microbial activity by modifying biomass structure and improving fermentation. This study explores microwave pretreatment (2, 4, 6, 9 W/g for 4–7 min) to enhance 24 h fermentation of pasteurized ground broccoli stalks using Lactiplantibacillus plantarum. Analyses included reducing sugars, total phenolics, microbial growth, Cryo-FESEM, and FTIR. Optimal microbial proliferation and preservation of key compounds were achieved at 4 W/g for 5 min. This condition was then compared to pasteurization, freezing/thawing, and autoclaving over a 96 h fermentation. pH, microbial population, and antioxidant properties were measured at 24 h intervals. Pasteurization, with or without microwaving, resulted in faster acidification and microbial growth. Microwaved samples retained the highest phenolic content, while autoclaved ones exhibited the highest flavonoid levels and antioxidant activity. Fermentation did not enhance antioxidant properties; phenolics and DPPH activity decreased after 24 h, while flavonoids and ABTS remained stable. Overall, pretreatments significantly influenced fermentation outcomes of broccoli stalks; microwaving post-pasteurization favored phenolic preservation and microbial proliferation, whereas autoclaving enhanced flavonoids and antioxidant potential. Full article

Spent hops from the supercritical extraction process represent a valuable source of xanthohumol (XN), a prenylated flavonoid with demonstrated anticancer, antidiabetic, antibacterial, and anti-inflammatory properties. However, XN is thermally sensitive and readily isomerizes into the less bioactive iso-XN at elevated temperatures, necessitating mild extraction conditions. Previous studies have shown that the pretreatment of plant biomass can enhance the extraction efficiency of bioactive compounds. In this study, various pretreatment methods—including physical (freeze–thaw, ultrasound, and microwave), chemical (acid and base hydrolysis), and enzymatic approaches—were applied to spent hops prior to extraction, and XN yields were compared to those obtained from untreated samples. The experiments, performed in triplicate, yielded meaningful results which helped understand the raw material’s behavior in applied conditions. Due to the compound’s high thermal sensitivity, ultrasound and microwave pretreatments require precise control to prevent excessive temperature increases, making low-temperature methods more suitable. Additionally, exposure to elevated pH adversely affected XN extraction efficiency, limiting the applicability of strong alkaline pretreatments. Among the evaluated methods, freeze–thaw pretreatment proved to be a simple and effective strategy, enhancing XN extraction yields by up to 10.7 ± 0.7% through the optimization of soaking time, the solid-to-liquid ratio, and the thawing temperature. Identifying an inexpensive and efficient pretreatment method could reduce extraction time while improving yield, contributing to the sustainable utilization of spent hops as an XN source. Full article

Red beetroot (Beta vulgaris L.) is a nutritionally rich root vegetable. It is a potential alternative raw material for pestil, a traditional fruit-based snack. This study aimed to develop a healthy beetroot-based pestil using traditional boiling (95 °C) and novel pretreatment methods, including thermosonication and microwave processing, with and without additional concentration steps. The effects of these methods on heat treatment period, hydroxymethylfurfural (HMF) formation, and the physicochemical, sensorial, nutritional, and chemometric profiles of pestils were evaluated. The beetroot-based snack formulated in this study was hedonically acceptable (≥5/9) and rich in essential minerals (Ca, K, Na, P, Mg) and trace elements (Zn, Fe, Mn), as determined by inductively coupled plasma–mass spectrometry. Total antioxidant capacity (CUPRAC) ranged from 113.11 to 870.78 mg Trolox^® equivalent/100 g dry matter (DM). Total phenolic, flavonoid, and betalain contents varied between 220.6–313.8 mg gallic acid equivalent/100 g DM, 365.08–517.46 mg rutin equivalent/100 g DM, and 314.40–488.66 mg/kg, respectively. Major flavonoids identified and quantified included epicatechin, rutin, isoquercitrin, taxifolin, and quercetin, while major phenolic acids identified were chlorogenic acid, ferulic acid, caffeic acid, o-salicylic acid, p-coumaric acid, and vanillin, using liquid chromatography–electrospray tandem mass spectrometry. Reducing the soluble solids content of the pestil pulp from 40 to 20 Brix degrees, in combination with thermosonication and microwave treatments, significantly shortened the processing time by 10–67%. This approach also reduced the HMF content to the limit of quantification (LOQ). Pretreatment methods significantly (p < 0.05) affected the levels of minerals and bioactive compounds in the pestils. These findings highlight the importance of process optimization to improve overall safety and the nutritional quality of the pestil. Full article