Microwave-assisted Extraction Of Phenolics Research Articles

Green extraction of phenolics and terpenoids from passion fruit peels using natural deep eutectic solvents

AbstractThis work aimed to optimize the ultrasonic‐assisted extraction (UAE) and microwave‐assisted extraction (MAE) of phenolics and terpenoids from passion fruit peels using natural deep eutectic solvents (NADES). NADES formulated with choline chloride and polyols with organic acids were used to investigate the solubility of phenolics and flavonoids in the solvent. Among these formulations, those derived from lactic acid‐glycerine (LGLY) and citric acid‐glucose (CGLU) exhibited the highest efficiency in extracting phenolics and terpenoids, respectively, when combined with UAE. Then one‐factor experiments were conducted to examine the influence of the UAE conditions (liquid‐to‐solid ratios [LSR], water content in NADES, ultrasonic power, time, and temperature) and MAE conditions (LSR, water content in NADES, ultrasonic power, and time) on the extraction yield of phenolics and terpenoids. The Box‐Behnken design (BBD) model was employed to optimize the extraction conditions with conditional ranges determined based on the results of the one‐factor experiments. The optimal conditions for the CGLU‐based MAE of terpenoids were 387 W of microwave power, 30% water content, 2.4 min, and 20 mL/g of LSR. The optimized conditions for LGLY‐based MAE of phenolics were 299 W, 18.7%, 1.3 min, and 10 mL/g. Total terpenoid content acquired from NADES‐based UAE was higher than NADES‐based MAE, while total phenolic content obtained at the optimal conditions of NADES‐based UAE and MAE was statistically insignificant. The efficiency of the two extraction ways was compared to selecting the favorable extraction method for acquiring phenolics and flavonoids from passion fruit peels. The research proposed that NADES‐based UAE was a green and effective method for attaining phenolics and terpenoids from passion fruit peel.Practical applicationPassion fruit peels are a by‐product of beverage production, which causes environmental pollution and increases treatment costs in the factory. These peels contain various bioactive compounds which benefit human health. The traditional extraction method shows low efficiency and high energy consumption. Thus, the appropriate extraction method and green solvents are needed to improve the extraction efficiency of bioactive compounds and can be directly applied to food products. Ultrasonic‐assisted extraction (UAE) and microwave‐assisted extraction (MAE) combined with natural deep eutectic solvents can enhance the extraction efficiency of bioactive compounds. However, the detailed conditions of UAE and MAE are necessary to compare the performance of the two methods. In addition to showing the significant superiority of UAE with MAE, the research showed the optimized conditions of the UAE process, which can be applied on the industrial scale to extract bioactive compounds and directly add them to food products.

Microwave-assisted extraction of phenolics from Hibiscus sabdariffa calyces: Kinetic modelling and process intensification

Hibiscus sabdariffa is a multi-cropping system endowed with wide ranges of benefits to humans. Being a plant rich in phenolic compounds, the process intensification of extraction method used for recovering the phenolic compounds from this essential plant is inevitable to easily proffer keen information on the extraction behaviours. Thus, the process intensification and kinetic behaviour of microwave-assisted extraction (MAE) for recuperating total phenolics (TP) content from H. sabdariffa calyces were investigated. The impacts of MAE factors such as solid/sample ratio, microwave power and temperature at varied irradiation time were studied. The effective diffusivity was also estimated. In addition, the extract was characterized to tentatively assign the phenolics using Liquid chromatography tandem mass spectrometry of quadrupole time-of-flight (LC-ESI-MS-MS). The achieved results clearly indicated that the MAE process intensification was acheived with TP content of 70.53 mg GAE/g extract in 3 min at solvent/sample ratio of 14:1 mL/g, microwave power of 500 W and 60 °C of temperature where the highest effective diffusivity coefficient was obtained. Out of the two considered kinetic models (second-order rate and power law), the second-order rate model best describes the MAE process intensification with higher coefficients of determination (R2 > 0.99). Moreover, an aggregate of 77 phenolic compounds was assigned in the extract of H. sabdariffa calyx; signifying the wider potentials of the extract industrially. Thus, this study clearly outlined that H. sabdariffa calyx is an embodiment of diverse phenolic compounds; indicating its potential in pharmaceutical and food industries.

Microwave-assisted extraction of phenolics from pomegranate peels: Optimization, kinetics, and comparison with ultrasounds extraction

Recently, there has been much interest in the phenolics of pomegranate peels, because of their health benefits, such as antioxidant activity. Thus, the objective of this work is to optimize an efficient alternative and “green” technique for the extraction of phenolics from pomegranate peels. Microwave-assisted method was found to increase extraction yield, but mainly to shorten the treatment time by over 60 times compared to conventional extraction methods. The effects of solvent type, solvent/solid ratio, and microwave power on the yield of phenolics extraction were studied. The optimum operating conditions were found to be: solvent type, 50% aqueous ethanol; solvent/solid ratio, 60/1 mL/g; power, 600 W. The efficiency of the proposed extraction protocol was compared with that of the ultrasound-assisted extraction, another “green” extraction approach, studied in our previous work. The microwaves method had a yield about 1.7 times higher obtained in a shorter process time (4 min) in comparison to ultrasound-assisted extraction (10 min). These differences were attributed to the intense cell destruction of microwave-treated plant material observed by SEM analysis. The obtained extract presented a high antioxidant activity (radical scavenging activity of 94.91%), due to the high content of punicalagin (143.64 mg/g dry matter) measured by HPLC analysis, that was equivalent to that of the ultrasounds extract (radical scavenging activity, 94.77%; punicalagin content, 138.8 mg/g dry matter).

Microwave-assisted extraction of phenolics with maximal antioxidant activities in tomatoes

Microwave-assisted extraction (MAE) was investigated for extraction of phenolic compounds from tomato with maximised antioxidant activities using response surface methodology (RSM) coupled with a central composite design, and in vitro antioxidant assays (FRAP and ORAC). MAE was more efficient for greater antioxidant activities and higher total phenolic contents than solvent extraction. The optimal MAE processing parameters were 96.5°C, 2.06min, 66.2% ethanol for FRAP, and 96.5°C, 1.66min, 61.1% ethanol for ORAC. The models were successfully applied to 20 tomato cultivars, whose total phenolic contents (TPC) and indexes (TPI) were 489.30–997.45mg gallic acid equivalent/100g dry weight (DW) and 281.34–468.52mg/100gDW, respectively. Eight phenolic compounds were identified. Individual phenolics were 6.10–42.73mg/100gDW. The FRAP, but not the ORAC value showed good correlation with the TPC or TPI. The methodologies developed and the knowledge acquired in this study will provide useful information to tomato breeders and food processors.

Microwave-assisted extraction of phenolics from Canarium album L. and identification of the main phenolic compound

Microwave-assisted extraction (MAE) was applied in the extraction of phenolics from Canarium album L. Effects of various conditions including the solvent, solvent to material ratio, microwave power and irradiation time on extraction yield of phenolics were investigated. In terms of the optimal conditions of MAE, it was concluded that 70% (v/v) of ethanol was the proper extraction solvent, the solvent to material ratio was 10 : 1 (mL : g), and the microwave power and irradiation time were 600 W and 15 s, respectively. Compared with normal stirring extraction and ultrasound-assisted extraction, the MAE of phenolics from C. album L. was more time efficient and gave a high extraction rate. More than 1.2% extraction yield was achieved with MAE, and the purity of the phenolics in the extract product was up to 25%. In addition, by ultraviolet-visible (UV) spectrometry and electrospray ionised mass spectrometry (ESI/MS), the main phenolic compound in the extract product was identified as gallic acid.

Microwave-assisted extraction of phenolics from bean (Phaseolus vulgaris L.)

Abstract Phenolic phytochemicals are associated with many health benefits, and it would be useful to develop improved methods for their extraction from bean. In this work, we showed that microwave-assisted extraction was an effective method. Eight bean types important in the Northarvest region of North America, which includes North Dakota and Minnesota, were chosen for this study. Four temperatures (25, 50, 100 and 150 °C) and three solvents (water, 50% ethanol in water and 100% ethanol) were investigated. As expected, colored beans contained higher concentrations of extractable phenolics, and in most cases the concentration of phenolics was much higher in the hull (testa) than in the cotyledon. Extraction efficiency was superior at higher extraction temperatures. The most effective extraction was achieved at a temperature of 150 °C using 50% ethanol. Total phenolics contents determined by microwave-assisted extraction with water at 100 °C were two to three times those determined by conventional extraction with water at the same temperature.