Optimal Microwave-assisted Extraction Conditions Research Articles

Enhancement of antioxidant properties of Eisenia bicyclis extracts through combination of green extractions: parameter optimization and comparison

We compared and optimized combined green extraction (CGE) technologies to maximize the antioxidant activity of Eisenia bicyclis through response surface methodology (RSM). Firstly, conventional extraction (CE), microwave assisted extraction (MAE), and supercritical fluid extraction by carbon dioxide (SFE-CO2) were applied to extract and compare antioxidant activities of E. bicyclis. The antioxidant activity results indicated that MAE and SFE-CO2 were superior to CE alone. Based on the optimum conditions for MAE and SFE-CO2, ultrasound-assisted extraction (UAE) and high-pressure processing (HPP) were combining to increase antioxidant activity. SFE-CO2+UAE was selected as the optimum CGE technology. The DPPH-radical scavenging activity and the total phenolic content of E. bicyclis extracts using SFE-CO2+UAE were approximately 2 and 5-fold higher than those of extracts using CE with almost 9-fold higher dieckol content. We demonstrated that E. bicyclis has substantial potential as a natural antioxidant and that CGE is more effective than CE and GE in enhancing antioxidant yields.

Optimization of Microwave-Assisted Polyphenol Extraction and Antioxidant Activity from Papaya Peel Using Response Surface Methodology and Artificial Neural Network

The objective of the present study is to determine the optimal conditions of microwave-assisted extraction (MAE) such as microwave power (MWP), irradiation time (I-time), ethanol concentration (EtOH%), and solvent-to-solid ratio (S/S) for maximizing total polyphenol content (TPC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity from papaya peel. Box-Behnken design (BBD) was used considering MWP 300–600 W, I-time 60-120 s, EtOH% 30-70%, and S/S 30-70 mL/g. Additionally, response surface methodology (RSM) and artificial neural networks (ANN) were employed for modelling, with cross-validation to enhance reliability. These models were combined with the desirability function (DF) and/or genetic algorithm (GA) optimization approaches. Maximizing TPC and DPPH activity while maintaining MWP, I-time, EtOH%, and S/S within their respective ranges using hybrid optimization approaches (RSM-DF: TPC = 1058 mgGAE/100g, and DPPH = 83%, RSM-GA: TPC = 1064 mgGAE/100g and DPPH = 79%, and ANN-GA: TPC = 1086 mgGAE/100g, and DPPH = 83%,) yielded consistent optimal results. An additional optimization approach (RSM-DF: TPC = 955 mgGAE/100g, and DPPH = 90%), aimed at minimizing MWP, I-time, EtOH%, and S/S while maximizing TPC and DPPH activity, showed a significant reduction of approximately 3 L in ethanol consumption for each 100 g of dry samples. The maximized TPC and DPPH activity in all four approaches showed a significant (p < 0.05) alignment with their corresponding validation tests, demonstrating the better performance of these modelling and optimization processes. In terms of assessing the effectiveness of microwave assistance, conventional solvent extraction was also performed, maintaining a 70 mL/g S/S ratio of 55% ethanol at 60°C for 2 h. This method resulted in lower values of TPC (857 ± 23 g GAE/100g) yield and DPPH activity (72 ± 5%) compared to the optimized condition of MAE.

Unlocking the nutraceutical potential of Corylus avellana L. shells: microwave-assisted extraction of phytochemicals with antiradical and anti-diabetic properties.

In recent years, the demand for high-quality natural extracts to be included in nutraceutical formulations has increased sharply. Hazelnut (Corylus avellana L.) shells (HZS) are underrated agricultural by-products that could be exploited as a source of active ingredients with pro-healthy properties. In the present study, a fully green microwave-assisted extraction (MAE) method was established for the first time aiming to recover bioactive constituents from HZS with significant nutraceutical value. Key MAE parameters, including ethanol in water concentration, microwave power, irradiation time and solvent-to-powder ratio, were optimized through response surface methodology utilizing a Box-Behnken design to achieve the highest total phenolic content and antioxidant/antiradical activities in the final extract. The optimal MAE conditions (28% v/v ethanol/water, 270 s, 670 W, and 37 mL g-1) yielded an extract with significant scavenging capacity against reactive oxygen species and remarkable inhibitory activity towards both α-amylase (IC50 = 7.73 μg mL-1) and α-glucosidase (IC50 = 49.44 μg mL-1), demonstrating stronger hypoglycaemic properties than the anti-diabetic drug acarbose. Additionally, fluorescence spectroscopy results highlighted the ability of the optimized extract from HZS (OHS-E) to counteract advanced glycation end-product formation throughout the glycation cascade in a dose-dependent manner. Liquid chromatography/electrospray ionization-tandem mass spectrometry profiling unveiled the presence of fatty acids and phenolic compounds, including lignans, flavonoids, gallic acid derivatives and diarylheptanoids. Lastly, the biocompatibility of OHS-E was attested on HT29-MTX and Caco-2 intestinal cells. Altogether, these findings encourage the potential application of OHS-E as an effective nutraceutical component against type 2 diabetes mellitus and oxidative stress. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Valorization of avocado (Persea americana) residual paste: Microwave-assisted extraction, optimization and addition to an artisanal pork ham

ABSTRACT Recovering biocompounds from industrial by-products is crucial to avoid food waste. Microwave-assisted extraction (MAE) has been employed to recover some biocompounds from vegetal matrices using ethanol and his solutions as solvent. Optimization of MAE conditions over total soluble polyphenols (TSP) and antioxidant capacity (DPPH and FRAP) from avocado residual paste (ARP) from oil industry was carried out. Optimal extract was used to elaborate an artisanal ham. Using response surface methodology (RSM), optimal conditions for MAE were 480 W of power, absolute ethanol as solvent, and extraction time of 180 s. The extract contained TSP of 31.24 mg GAE/g DW, DPPH inhibition of 24.51 mg TE/g DW and FRAP inhibition of 21.58 mg TE/g DW. The extract was added in the ham formulation at 0, 0.5, 1, and 1.5% w/w. Ham with 1% extract had the highest scores for acceptance. Extracts from ARP may be used in ham with adequate sensory attributes.

Optimized microwave-assisted extraction of total phenolic and flavonoid contents from defatted seeds and press residue of Opuntia ficus-indica (l.) mill

Phenolic content of Opuntia ficus indica (OFI) was estimated in samples of seeds and press residue (cake) generated through mechanical oil extraction process. A microwave-assisted extraction (MAE) method was investigated for the optimization of the extracted total phenolic (TPC) and total flavonoid contents (TFC). The influence of extraction parameters on the yields of TPC, TFC were modelled using a second-order regression equation. The optimal MAE conditions were: 61.65 % ethanol concentration, 633.42 W microwave power, 3.59 min irradiation time and 46.28 mL/g solid-to-liquid ratio (SLR) for phenolics extraction, and 54.97 %, 580.04 W, 3.20 min and 47.40 mL/g for flavonoids extraction from defatted seeds powder. The extracts obtained under these conditions showed a TPC and TFC of 416.311±1.154 mg gallic acid equivalent (GAE) per100 g dry weight (DW) and 52.67±0.72 mg quercetin equivalent (QE)/100 g DW, respectively. Regarding press residue, the optimal conditions were 60.26%, 643.89 W, 3.85 min and 47.28 mL/g for phenolics extraction, and 67.96 %, 464.41 W, 2.46 min and 41.04 mL/g for flavonoids extraction; with a TPC and TFC of 400.11±3.14 mg GAE/100 g DW and 38.75±0.16 mg QE/100g DW, respectively. The results of the present study confirmed that OFI seeds and press residues could be considered as a non-negligible source of phenolics with a good antioxidant activity and revealed that MAE is a reliable method for optimizing yields of recovered phytochemicals from such agricultural products derivatives and by-products, with an intent to be scaled-up for industrial, nutraceutical or pharmaceutical applications.

Evaluation of Polyphenolic Profile and Antioxidant Activity of Sea Buckthorn (Elaeagnus rhamnoides (L.) A. Nelson) Leaf and Berry Extracts Obtained via Optimized Microwave-Assisted and Accelerated Solvent Extraction

The aim of this study was to optimize parameters of microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) in terms of extraction temperature and time, microwave power and cycle numbers on the phenolic content of sea buckthorn leaves and berries, using 70% ethanol (v/v) as an extraction solvent. The characterization of phenolic composition in leaf and berry extracts obtained at optimal MAE and ASE conditions was performed with UPLC/ESI-MS2, while antioxidant activity was determined using the ORAC method. The optimal extraction conditions for MAE were 60 °C, 500 W and 15 min for leaves and 60 °C, 300 W, and 10 min for berries. The optimal extraction conditions for ASE from both leaves and berries were 120 °C, 15 min, and 3 cycles. Total phenolic content (TPC) in MAE and ASE extracts from leaves was similar to the TPC determined in extracts obtained by conventional extraction (60 °C/30 min); however, ASE contributed to the higher TPC of the berry extracts. The flavonols kaempferol-3-rutinoside in the leaves and kaempferol in the berries were the most abundant phenols of sea buckthorn. A higher antioxidant activity was found in the leaf extracts obtained by ASE and it correlated with the phenolic content. In general, ASE favored the extraction of all polyphenols from leaves, while MAE was more suitable for the extraction of flavonols from berries, suggesting that the choice of the optimal extraction method is crucial with regard to the target molecules and future applications.

Phytochemical compounds with promising biological activities from Ascophyllum nodosum extracts using microwave-assisted extraction

Phytochemical-rich antioxidant extracts were obtained from Ascophyllum nodosum (AN) using microwave-assisted extraction (MAE). Critical extraction factors such as time, pressure, and ethanol concentration were optimized by response surface methodology with a circumscribed central composite design. Under the optimal MAE conditions (3 min, 10.4 bar, 46.8 % ethanol), the maximum recovery of phytochemical compounds (polyphenols and fucoxanthin) with improved antioxidant activity from AN was obtained. In addition, the optimized AN extract showed significant biological activities as it was able to scavenge reactive oxygen and nitrogen species, inhibit central nervous system-related enzymes, and exhibit cytotoxic activity against different cancer cell lines. In addition, the optimized AN extract showed antimicrobial, and anti-quorum sensing activities, indicating that this extract could offer direct and indirect protection against infection by pathogenic microorganisms. This work demonstrated that the sustainably obtained AN extract could be an emerging, non-toxic, and natural ingredient with potential to be included in different applications.

Efficient extraction of quassinoids and alkaloids from Eurycoma longifolia Jack roots using natural deep eutectic solvents and microwave-assisted extraction

Eurycoma longifolia Jack (EL) extracts have immunomodulatory and anti-inflammatory effects and are utilized in the treatment of male sexual dysfunctions. Water-based extraction methods for hydrophobic and bioactive components of EL are often inefficient and energy-intensive. Therefore, this study aimed to develop an efficient and environmentally friendly method for extracting EL quassinoids and alkaloids using natural deep eutectic solvents (NADESs) and microwave-assisted extraction (MAE). The NADES-based MAE method employed an optimized NADES comprising choline chloride, citric acid, glucose, and water (CCGW). CCGW provided higher extraction yields of eurycomanone (EU, 1.608 ± 0.004 mg/g) and 9-methoxy-canthin-6-one (9MCO, 0.3022 ± 0.0007 mg/g) than water-based extraction under optimal MAE conditions, as determined using Box–Behnken Design of Response Surface Methodology. CCGW effectively extracted both polar quassinoids and less-polar alkaloids from EL roots. While concentrated NADES had an impact on RAW264.7 cell viability, the use of diluted CCGW did not enhance the cytotoxicity of both EU and 9MCO compared to their preparation in water. The anti-inflammatory activity of 9MCO, prepared in diluted CCGW, was equivalent to that of the compound prepared in water. The cytotoxicity of both compounds in Vero cells was higher when coupled with CCGW than their preparation in water. The NADES-based MAE method is an efficient approach for extracting bioactive components from EL.

Microwave-assisted extraction optimization of sesquiterpene lactones from Inula helenium roots: A sustainable approach to reduce energy consumption and carbon footprint.

Inula helenium roots are consumed as natural flavor components and raw or cooked as food, and their extracts are rich in sesquiterpene lactones such as alantolactone (AL) and isoalantolactone (IAL), which have recently attracted great attention due to their pharmacological properties. The industrial utilization of these compounds requires the development of green, efficient, cost-effective, and sustainable extraction protocols. Therefore, this study focused on the optimization of microwave-assisted extraction (MAE) process variables using Face-Centered Central Composite Design (FC-CCD). Then, maceration was applied as a conventional technique, and these techniques were compared in terms of extraction efficiency, morphological changes, antimicrobial activities, carbon emissions, and energy consumption. As a result, optimal MAE conditions, i.e., EtOH: water ratio (X 1) = 100:0, liquid/sample ratio (X 2) = 30:1 mL/g, microwave power (X 3) = 300 W, and irradiation time (X 4) = 5 min, were obtained with AL and IAL yields of 54.99 ± 0.11 (mg/g) and 48.40 ± 0.19 (mg/g), respectively. The extract obtained by MAE had similar or better activity than positive controls in most cases and formed the largest inhibition zones against E. coli (29.5 ± 0.71 mm) and A. niger (34.75 ± 1.06 mm). Morphological changes of I. helenium roots after extraction were observed by scanning electron microscopy. Additionally, MAE was 43.4 times faster than maceration, resulting in 228.6 times less energy consumption and carbon emissions. Based on these findings, it is recommended to use MAE as an industrial green technique for the extraction of sesquiterpene lactones with potential applications in nutraceuticals and food products in terms of sustainable economy and environmental protection.

Microwave-assisted Extraction of Vanillin from Madagascar &lt;i&gt;Vanilla planifolia&lt;/i&gt; beans: Optimization and Modeling

Green MAE (microwave extraction) process was used to extract natural flavors (vanillin) from Madagascar &lt;i&gt;Vanilla planifolia&lt;/i&gt; beans. Experimentally, we used a factor to study the influence of parameters on extraction efficiency, and response surface methodology (RSM) was used to obtain interactions between the key influencing parameters. The present study used response surface methodology (RSM) to optimize extraction parameters for vanillin compounds from &lt;i&gt;Vanilla planifolia&lt;/i&gt; beans from Madagascar. Three independent variables were evaluated that had a major impact on vanillin content: alcohol concentration, microwave power, and solvent/material (S/M) ratio. A central composite rotation design (CCRD) was used to develop the experimental design. The optimal conditions for microwave-assisted extraction to obtain higher vanillin yield in pods are 480 W for microwave power, 72% for alcohol concentration, and 30 ml/g for Solvent/Material ratio, with an irradiation time of 60 min. The conventional Soxhlet method is less efficient than microwave extraction to extract vanillin from pods. In the traditional extraction, the optimal conditions were an extraction time of 16 hours for 90% ethanol as the solvent. The experimental values are close to those predicted by the obtained mathematical model. Vanilla extracts are analyzed by UV Visible spectrophotometry and HPLC.

Comparison of ohmic heating- and microwave-assisted extraction techniques for avocado leaves valorization: Optimization and impact on the phenolic compounds and bioactivities.

Avocado tree pruning activities generate a substantial amount of residual biomass, which includes different parts of the plant, such as leaves, twigs, branches, and small fruits. This study aimed to investigate the impact of different green extraction methods of microwave-assisted extraction (MAE) and ohmic heating-assisted extraction (OHAE) for the phenolic extraction of avocado leaves based on a statistical approach, central composite design (CCD), and response surface methodology (RSM). Water was preferred using as an environmentally and health-friendly solvent for both methods. The phenolic composition, antioxidant activity, and antidiabetic potential of the extracts were identified and comparatively assessed. The developed models exhibited a high degree of reliability with optimal conditions for OHAE and MAE, which were determined as 9.38 V/cm voltage gradient, 6 min extraction time, at 60°C, 5 min, and 1 g dried leaf/100 mL water. Epicatechin was identified as the primary phenolic compound in OHAE extracts, while chlorogenic acid was the dominant compound in MAE extracts. The extracts obtained from OHAE and MAE were tested for their ability to inhibit α-glucosidase activity, with IC50 (mg/mL) values of 0.85 and 1.14, respectively. The DPPH radicals scavenging activity (IC50 mg/L) of OHAE and MAE were detected as 2.96 and 3.41, respectively. In conclusion, both methods yielded extracts rich in polyphenols that displayed high antioxidant activity, but OHAE was found to be superior to MAE in terms of TPC, DPPH, and antidiabetic activities. The results of this study have the potential to make significant contributions toward promoting the principles of a circular economy by facilitating the valorization of the avocado pruning waste.

Microwave-Assisted Extraction Optimization and Effect of Drying Temperature on Catechins, Procyanidins and Theobromine in Cocoa Beans.

Cocoa beans (Theobroma cacao L.) are an important source of polyphenols. Nevertheless, the content of these compounds is influenced by post-harvest processes. In this sense, the concentration of polyphenols can decrease by more than 50% during drying. In this study, the process of procyanidins extraction was optimized and the stability of catechins, procyanidins, and theobromine to different drying temperatures was evaluated. First, the effectiveness of methanol, ethanol, acetone, and water as extract solvents was determined. A Box-Behnken design and response surface methodology were used to optimize the Microwave-Assisted Extraction (MAE) process. The ratios of methanol-water, time, and temperature of extraction were selected as independent variables, whereas the concentration of procyanidins was used as a response variable. Concerning the drying, the samples were dried using five temperatures, and a sample freeze-dried was used as a control. The quantitative analyses were carried out by HPLC-DAD-ESI-IT-MS. The optimal MAE conditions were 67 °C, 56 min, and 73% methanol. Regarding the drying, the maximum contents of procyanidins were obtained at 40 °C. To our knowledge, this is the first time that the stability of dimers, trimers, and tetramers of procyanidins on drying temperature was evaluated. In conclusion, drying at 40 °C presented better results than the freeze-drying method.

Upcycling Fish By-Products into Bioactive Fish Oil: The Suitability of Microwave-Assisted Extraction

The seafood industry is often left out of the food waste discussion, but this sector is no exception, as it generates large amounts of various by-products. This study aimed to explore the potential of the microwave-assisted extraction (MAE) technique to obtain high-quality oil from fish by-products. The independent variables, which were time (1-30 min), microwave power (50-1000 W), and solid/liquid ratio (70-120 g/L) were combined in a 20-run experimental design coupled with the response surface methodology (RSM) for process optimization. The obtained oil yield values were fitted to a quadratic equation to build the theoretical models, which were statistically validated based on statistical criteria and used to predict the optimal MAE condition. The oil yields were significantly affected by the three independent variables through linear, quadratic, and/or interactive effects. Compared to a conventional Soxhlet extraction (SE), the optimal MAE conditions allowed between 60 and 100% of oil to be recovered in less than 19 min and with less solvent consumption. The fatty acid profiles of the oils obtained through SE and optimized MAE were characterized by gas chromatography with flame ionizing detection (GC-FID) after a derivatization process. These oils were constituted mainly of health, beneficial unsaturated fatty acids, such as oleic, docosahexaenoic (DHA), linoleic, and eicosapentaenoic (EPA) acids, which were not affected (p > 0.05) by the extraction methods. Interestingly, the oils obtained through MAE showed the best microbial growth inhibition results may have been due to thermolabile compounds, preserved via this unconventional non-thermal method. The oils also exhibited anti-inflammatory effects via nitric oxide production inhibition and cytotoxic potential especially, against breast and gastric adenocarcinoma cells. However, the threshold of toxicity should be further investigated. Overall, this work emerges as a future-oriented approach to upcycling fish by-products into high-quality oils that can be used in the formulation of pet food and other products.

Optimization of vitamin c extraction of roselle petals (Hibiscus sabdariffa) assisted with microwaves using response surface methodology

Vitamin C contained in roselle petals acts as an antioxidant that provides health benefits. In order to make it easier to use, vitamin C needs to be extracted out of the roselle petal cells in the form of extracted raw roselle juice. The commonly used conventional method has disadvantages that can damage heat-sensitive compounds such as vitamin C. An alternative extraction method used was microwave-assisted extraction. The success of this method in extracting vitamin C was influenced by a few factors, such as the ratio of the roselle petals-water, microwave power, and extraction time. The purpose of this study was to determine the optimum conditions for microwave-assisted extraction of vitamin C in roselle extract and to determine the physical and chemical characteristics of roselle extract produced in the optimum conditions. This study utilized response surface methodology (RSM) in a central composite design (CCD). The optimized factors included the roselle petals-water ratio (5 - 10%), microwave power (150 - 350 W), and extraction time (3 - 7 mins). The parameter response tested in this study was vitamin C. While the extract produced under optimum conditions was also characterized by the total anthocyanin content, total phenols, antioxidant activity, pH value and colour (L, a* and b*). The results showed that the recommended optimum conditions were a 5% roselle petals-water ratio, 250 W of microwave power, and 6.09 mins of extraction time. The verification results show that this optimum condition produced vitamin C higher than the conventional method. The characteristics of roselle extract produced by microwave-assisted extraction at optimum conditions were vitamin C at 9.973±0.508 mg/g, total anthocyanins at 1.771±0.124 mg/100 g, phenol at 30.848±1;899 m/g, IC50 at 6.699±0.627 ppm, pH at 2.133±0.057, colour with an L value of 31.033±0.404, a* value of 1.066±0.155, and b* value of 18.100±0.458.

Recovery of Antioxidants from Tomato Seed Industrial Wastes by Microwave-Assisted and Ultrasound-Assisted Extraction.

Tomato seed (TS) wastes are obtained in large amounts from the tomato processing industry. In this work, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) of antioxidant compounds from TS were optimized by using response surface methodology. The effect of MAE and UAE main extraction parameters was studied on total phenolic content (TPC) and antioxidant activity (DPPH) responses. Antioxidant, structural, morphological, and thermal properties of MAE and UAE extracts were evaluated. A great influence of ethanol concentration was observed in both extraction methods. Optimal MAE conditions were determined as 15 min, 80 °C, 63% ethanol and 80 mL, with a desirability value of 0.914, whereas 15 min, 61% ethanol and 85% amplitude (desirability = 0.952) were found as optimal conditions for UAE. MAE extracts exhibited higher TPC and antioxidant activity values compared to UAE (1.72 ± 0.04 and 1.61 ± 0.03 mg GAE g TS−1 for MAE and UAE, respectively). Thermogravimetric analysis (TGA) results suggested the presence of some high molecular weight compounds in UAE extracts. Chlorogenic acid, rutin and naringenin were identified and quantified by HPLC-DAD-MS as the main polyphenols found by MAE and UAE, showing MAE extracts higher individual phenolics content (1.11–2.99 mg 100 g TS−1). MAE and UAE have shown as effective green techniques for extracting bioactive molecules with high antioxidant activity from TS with high potential to be scaled-up for valorizing of TS industrial wastes.

Modeling the Influence of Extraction Parameters on the Recovery of Antioxidant Compounds of Microwave Extracted Citrus (Citrus reticulata) Peel by Response Surface Methodology

Background: Microwave-assisted extraction (MAE) is a green extraction technology that saves both in energy and time and that bioactive compounds can be extracted without loss as much as in traditional extraction methods. Objectives: This study aims to optimize the MAE process for maximizing the recovery of antioxidant compounds of flavonoids and the activity of radical scavenging of DPPH (2,2-diphenyl-1-picrylhydrazyl) from citrus peels (CP). Methods: The modeling used Box-Behnken Design (BBD) experimental design for optimizing three extraction parameters of time (5, 15, and 25 min), ethanol concentration (50%, 70%, and 90%), and extraction temperature (55, 65, and 75 °C). UHPLC-MS analysis was performed to identify the qualitative flavonoid content in the extract. Results: Our results showed that the optimum MAE conditions that maximize the total flavonoid content and antioxidant activity of the CP extract were extraction time of 16.87 min, 50% ethanol, and temperature at 75°C. The obtained CP extract had a TFC of 14.10 mg QE/g and antioxidant activity of 51.52%, which was in line with the predicted values. Flavonoids of neohesperidin, naringin, hesperidin, narirutin, and nobiletin were identified in the extract of CP. Conclusion: The ethanolic extract of CP was confirmed to have high flavonoids content with potent antioxidant activity.

Optimization of Microwave-assisted Extraction of Carotenoids from Citrus clementina Peels

Background:Citrus fruits, especially clementines, are among the most consumed fruits in the world. Clementine consists of pulp (endocarp) and peel (epicarp) which are rich in carotenoids. After using fruit pulp, peels are usually discarded as waste; the valorization of the latter in the recovery of its beneficial components, mainly carotenoids, may seem to be important.Objective:The main objective of this study is to determine the optimal conditions allowing the extraction of a high carotenoids yield from clementine peels.Methods:The microwave-assisted extraction method (MAE) was applied for extraction of total carotenoids from Citrus clementina peels, and the response surface methodology (RSM) was used to investigate the influence of extraction parameters, including hexane concentration, microwave power, irradiation time, and solvent to solid ratio, on the extraction yield, then the results were modeled using a second order regression. Total carotenoids yield of clementine peel extract obtained under optimal microwave-assisted extraction conditions was compared to extracts performed using two conventional extraction methods (maceration and Soxhlet).Results:The optimal conditions for microwave-assisted extraction were 68 % of hexane concentration using 561 W of microwave power during 7.64 min of irradiation time, 43 ml/g of solvent-tosolid ratio using two successive extractions. Under optimized conditions of microwave-assisted extraction, the recovery of carotenoid content was 186.55 μg/g dry matter (DM), which was higher than that obtained by the two conventional methods, maceration extraction (ME; 160.53 μg/g DM) and Soxhlet extraction (SE; 162.68 μg/g DM).Conclusion:From this study, it can be concluded that microwave-assisted extraction is an efficient method for carotenoid recovery and considering its high yield in reduced time, it could be recommended for extraction of these bioactive compounds from clementine peels.

Recovery of Phenolic Compounds and Antioxidants from Coffee Pulp (Coffea canephora) Waste Using Ultrasound and Microwave-Assisted Extraction

Coffee pulp is a by-product generated from coffee bean production. This waste is a potential source of bioactive compounds, which can be recovered for use as an ingredient for many products. However, this by-product is typically dumped in landfills or made into compost. Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were employed to recover bioactive compounds from coffee pulp waste. Results showed that time and instrument power significantly affected the recovery yield in both UAE and MAE. The temperature was also a significant factor in UAE. The optimal MAE conditions were a radiation time of 70 min, a power of 700 W, and a 50% (v/v) ethanol solvent to sample ratio of 100:5 (mL/g), approximately 47 mg of phenolic compounds, 36 mg of flavonoid, 8 mg of chlorogenic acid, and 6 mg of caffeine could be recovered from 1 g of the material. The optimal UAE condition were an ultrasonic time of 35 min, a temperature of 60 °C, and a power of 250 W; however, bioactive compounds and antioxidant capacity constituted around one half of MAE. Therefore, MAE is recommended as the extraction technique for the bioactive compound and antioxidant recovery from the coffee pulp.

Nutritional and bioactive oils from salmon (Salmo salar) side streams obtained by Soxhlet and optimized microwave-assisted extraction

The efficiency of the microwave-assisted extraction (MAE) technique on recovering nutritional and bioactive oils from salmon (Salmo salar) side streams was evaluated and compared to Soxhlet extraction. The response surface methodology (RSM) coupled with a central composite rotatable design was used to optimize time, microwave power, and solid/liquid ratio of the MAE process in terms of oil yield. The optimal MAE conditions were 14.6 min, 291.9 W, 80.1 g/L for backbones, 10.8 min, 50.0 W, 80.0 g/L for heads, and 14.3 min, 960.6 W, 99.5 g/L for viscera, which resulted in a recovery of 69% of the total lipid content for backbones and heads and 92% for viscera. The oils obtained under optimal MAE conditions showed a healthy lipid profile as well as cytotoxic, antioxidant, anti-inflammatory, or antimicrobial properties. These results highlight that oils from underutilized salmon by-products could be exploited by different industrial sectors under the circular economy approach.

Phenolic Characterization and Bioactivity of Fennel Seed (Foeniculum vulgare Mill.) Extracts Isolated by Microwave-Assisted and Conventional Extraction

The aim of this study was to evaluate the effectiveness of microwave-assisted extraction (MAE) as an environmentally friendly approach compared to conventional heat-reflux extraction (CE) for the isolation of fennel (Foeniculum vulgare Mill.) seed polyphenols and to assess the bioactivity of the obtained extracts. Water, ethanol (30%, v/v) and acetone (30%, v/v) were used as extraction solvents, and the extraction was carried out varying the temperature (40, 60 and 80 °C), irradiation time (5 and 10 min) and microwave power (300 and 600 W). According to the total phenolic content (TPC), 30% acetone at 80 °C after 5 min of irradiation at 300 W proved to be the optimal MAE conditions for obtaining the highest yield of polyphenols. The phenolic profile of both extracts comprised 21 compounds, with cinnamic acids and flavonols being the most abundant. When compared to CE, the MAE extract showed a lower amount of TPC as well as the sum of all identified individual phenols, although both extracts showed similar antioxidant capacity. The antimicrobial activity of the extract with the highest phenolic content was weak, showing inhibitory activity only against Pseudomonas fragi, Shewanella putrefaciens and Campylobacter jejuni strains, while Gram-positive bacteria and yeasts were not sensitive to the extract.