Optimisation of the microwave‐assisted extraction process for six phenolic compounds in Agaricus blazei murrill

An efficient microwave‐assisted extraction (MAE) technique was employed in the extraction of phenolic compounds from Agaricus blazei murrill, and phenolic compounds were quantified by High‐performance liquid chromatography (HPLC). The MAE procedure was optimised, validated and compared with other conventional extraction techniques. MAE gave the best result because of the highest extraction efficiency within the shortest extraction time. The optimal conditions of MAE were 60% ethanol, ratio of solid/liquid 1:30, temperature 110 °C, irradiation power 500 W and three extraction cycles, each 5 min. This is the first report on combining MAE with HPLC for the extraction and quantification of phenolic compounds in A. blazei murrill. The developed MAE method provided a good alternative for the extraction of phenolic compounds in A. blazei murrill as well as other materials.     

Effects of Microwave and Ultrasound Assisted Extraction on the Recovery of Soy Proteins for Soy Allergen Detection

The extraction of soy proteins for soy allergen detections is conventionally achieved with PBS buffer for at least 2 h at room temperature or 4 °C. This method has been reported to be inefficient due to time consumption and inadequate protein extraction resulting in false negative allergen detection and mislabeling of foods containing allergenic proteins. This study investigated the application of microwave (MAE) and ultrasound assisted extraction (UAE) techniques to extract and improve recovery of allergens from various soy matrices. Soy proteins were extracted from raw soy flour, soy protein isolate (SPI) and soy milk using MAE at 60, 70, and 100 °C for 5 and 10 min and UAE at 4 and 23 °C for extraction times of 1, 5, and 10 min with PBS, Laemmli and urea buffers. Extracts were analyzed for total proteins, protein profile, and antibody‐based detection (ELISA) of soy proteins. Conventional extraction with each of the buffers was used as controls. Overall, proteins recovered from MAE and UAE samples were higher than recoveries from the controls in all soy matrices. Under all extraction conditions, Laemmli and urea buffer recovered more proteins than PBS. Electrophoresis analysis of protein showed bands around 75, 50, and 33 kDa indicating the presence of soy allergenic proteins β‐conglycinin and glycinin, in all samples. Using sandwich ELISA, control and UAE extracts resulted in high soy protein detection but this reduced in MAE extracts.     

Microwave‐assisted extraction of secoisolariciresinol diglucoside from flaxseed hull

Microwave‐assisted extraction (MAE) of secoisolariciresinol diglucoside (SDG) from defatted flaxseed hull (DFH) was studied. The effects of pre‐soaking methods and extraction parameters (ethanol concentration (0–100%, v/v), microwave energy input (50–390 W), liquid to solid ratio (5:1 to 40:1, mL g^?1) and irradiation time (10–330 s)) on the SDG yield were investigated. Response surface methodology (RSM) was applied to optimise the MAE conditions as irradiation time 90.5 s, ethanol concentration 40.9% (v/v), liquid to solid ratio 21.9:1 (mL g^?1) and microwave power 130 W. The SDG recovery from DFH with MAE was 11.7 g SECO kg^?1 DFH (on dry‐weight basis), which was significantly higher than that of stirring extraction (10.0 g SECO kg^?1 DFH) and Soxhlet extraction (7.60 g SECO kg^?1 DFH). Compared with stirring extraction and Soxhlet extraction, MAE showed its superiority in improving SDG yield and saving time and energy. Copyright © 2007 Society of Chemical Industry     

Effect of microbial transglutaminase on the functional properties of megrim (Lepidorhombus boscii) skin gelatin

This paper examines the effect of a microbial transglutaminase (TGase) on the gelling and viscoelastic properties of a gelatin from megrim (Lepidorhombus boscii) skins. Although TGase extended the setting time of fish gelatin, it was found that melting temperature, gel strength and viscosity in solution at 60 °C were considerably increased by the covalent cross‐linking action of the enzyme, as observed by SDS‐PAGE and SEM. Increasing concentrations of TGase increased the elasticity and cohesiveness of gelatin gels but reduced gel strength and hardness. Partial inactivation of the enzyme was achieved thermally without negatively affecting the properties of the gelatin; whether or not gelatin is thermoreversible depends essentially on the degree of enzyme inactivation. © 2001 Society of Chemical Industry     

Comparison of gelling properties and flow behaviors of microbial transglutaminase (MTGase) and pectin modified fish gelatin

The gelling and structural properties of microbial transglutaminase (MTGase) and pectin modified fish gelatin were compared to investigate their performances on altering fish gelatin properties. Our results showed that within a certain concentration, both MTGase and pectin had positive effects on the gelation point, melting point, gel strength, textural, and swelling properties of fish gelatin. Particularly, low pectin content (0.5%, w/v) could give fish gelatin gels the highest values of gel strength, melting temperature, and hardness. Meantime, flow behavior results showed that both MTGase and pectin could increase fish gelatin viscosity without changing its fluid characteristic, but the latter gave fish gelatin higher viscosity. Both MTGase and pectin could increase the lightness of fish gelatin gels but decreases its transparency. More importantly, fluorescence and UV absorbance spectra, particle size distribution, and confocal microscopy results indicated that MTGase and pectin could change the structure of fish gelatin with the formation of large aggregates. Compared with MTGae modified fish gelatin, pectin could endow fish gelatin had similar gel strength, thermal and textural properties to pig skin gelatin.     

Effects of Concentration,Bloom Degree,and pH on Gelatin Melting and Gelling Temperatures Using Small Amplitude Oscillatory Rheology

Concentration, gel strength (Bloom), and pH effects on both melting and gelling temperatures of gelatin were studied using small amplitude oscillatory rheology. Temperature sweeps were applied to gelatin gel samples for heating and cooling at fixed frequencies. Results showed that melting temperatures were higher than gelling temperatures, and both increased with increasing concentration at pH from 3 to 6 for all gel strength. For constant gelatin concentration and pH, as gel strength increased, melting temperatures decreased, whereas gelling temperatures increased. A mathematical model was obtained which correlates melting and gelling temperatures, respectively, with pH and concentration at fixed Bloom degrees. All gelatin gels showed storage modulus higher (2 to 10 kPa) than loss modulus (50 to 500 Pa).     

Comparative evaluation of atmospheric and vacuum microwave‐assisted extraction of bioactive compounds from fresh and dried Centella asiatica L. leaves

Microwave‐assisted extraction (MAE) involves extraction under higher‐temperature and oxygen‐rich environment, which may cause degradation of bioactive compounds being extracted. Reducing the extraction temperature by reducing the system pressure is thus of interest. Nevertheless, information is lacking on the kinetics of vacuum microwave‐assisted extraction (VMAE) at various pressures. Detailed temperature evolution of a material–solvent mixture during VMAE is also not available. This study investigated the extraction kinetics of triterpene saponins and phenolics from both fresh and dried Centella leaves during MAE and VMAE at various pressures. In the case of fresh leaves, the maximum contents of triterpene saponins were reached when VMAE was performed at 60 kPa, whereas the maximum total phenolics content (TPC) was achieved when the extraction was performed at atmospheric condition. In the case of dried leaves, the maximum triterpene saponins contents as well as TPC were achieved when extraction was performed at atmospheric condition.     

Hydrodistillation and in situ microwave‐generated hydrodistillation of fresh and dried mint leaves: a comparison study

BACKGROUND: Hydrodistillation (HD) has been used since ancient times for the extraction of essential oils (EO). Despite the intrinsic limitations of this technique, it remains the most common method both in the laboratory and on an industrial scale. The main drawbacks are the long extraction time involved and the risk of thermal degradation. Over the last decade, microwave‐assisted extraction (MAE) and in situ microwave‐generated hydrodistillation (MGH) have been shown to be the most promising techniques in improving plant extraction and hydrodistillation. RESULTS: In this study we compare HD with MGH in the extraction of several mint species cultivated in Piedmont: Mentha spicata L. var. rubra, Mentha spicata L. var. viridis and Mentha piperita L. MGH requires either fresh plant or rehydrated material, it is extremely fast and allows a reduction in energy consumption and overall cost. All the EO have been analyzed by gas chromatography‐mass spectrometry. A mechanism of microwave‐generated essential oil extraction has been proposed to explain the differences in the composition of the oil obtained from this environmentally friendly technique. CONCLUSIONS: The yields and composition percentages of the EO obtained by HD and in situ MGH of fresh and dried mint leaves lie in a relatively narrow range, although MGH is faster. MW polarization effects and the water solubility of the components influence extract composition Copyright © 2012 Society of Chemical Industry     

Ultrasound‐assisted extraction of polyphenols from potato peels: profiling and kinetic modelling

Ultrasound‐assisted extraction (UAE) at 33 and 42 kHz has been investigated in the extraction of polyphenols from peels of two potato varieties, cream‐skinned Lady Claire (LC) and pink‐skinned Lady Rosetta (LR), commonly used in snack food production. Extraction efficacy between the UAE‐untreated (control) and the UAE‐treated extracts was assessed on the total phenolic content and antioxidant capacities (DPPH and FRAP). Application of UAE showed significantly higher recovery of phenolic compounds compared to solid–liquid extraction process alone. Lower ultrasonic frequency (33 kHz) was more effective in recovering polyphenols compared to 42 kHz ultrasonic treatment. The liquid chromatography‐tandem mass spectrometry revealed that chlorogenic acid and caffeic acid were the most prevalent phenolics in LR peels, whereas caffeic acid was dominant in LC peels. Peleg's equation showed a good correlation (R² > 0.92) between the experimental values and the predicted values on the kinetics of UAE of phenolic compounds.     

Microwave‐Assisted Extraction,Chemical Structures,and Chain Conformation of Polysaccharides from a Novel Cordyceps Sinensis Fungus UM01

Cordyceps sinensis is a well‐known tonic food with broad medicinal properties. The aim of the present study was to investigate the optimization of microwave‐assisted extraction (MAE) and characterize chemical structures and chain conformation of polysaccharides from a novel C. sinensis fungus UM01. Ion‐exchange and gel filtration chromatography were used to purify the polysaccharides. The chemical structure of purified polysaccharide was determined through gas chromatography‐mass spectrometry. Moreover, high performance size exclusion chromatography combined with refractive index detector and multiangle laser light scattering were conducted to analyze the molecular weight (M_w) and chain conformation of purified polysaccharide. Based on the orthogonal design L₉, optimal MAE conditions could be obtained through 1300 W of microwave power, with a 5‐min irradiation time at a solid to water ratio of 1:60, generating the highest extraction yield of 6.20%. Subsequently, the polysaccharide UM01‐S1 was purified. The UM01‐S1 is a glucan‐type polysaccharide with a (1→4)‐β‐d ‐glucosyl backbone and branching points located at O‐3 of Glcp with a terminal‐d ‐Glcp. The M_w, radius of gyration (R_g) and hydrodynamic radius (R_h) of UM01‐S1 were determined as 5.442 × 10⁶ Da, 21.8 and 20.2 nm, respectively. Using the polymer solution theory, the exponent (ν) value of the power law function was calculated as 0.38, and the shape factor (ρ = R_g/R_h) was 1.079, indicating that UM01‐S1 has a sphere‐like conformation with a branched structure in an aqueous solution. These results provide fundamental information for the future application of polysaccharides from cultured C. sinensis in health and functional food area.     

鸡骨明胶的胶凝特性

通过测定动态流变性质和凝胶强度研究鸡骨明胶的胶凝特性.研究表明,鸡骨明胶的胶凝分为凝胶网络的快速形成阶段和网络的缓慢成长两个阶段.相对分子质量越大,胶凝温度越低;明胶浓度越高、pH值越接近等电点、胶凝温度和熔化温度越高,胶凝时间越短,同时形成的凝胶网络的弹性和凝胶强度大;随着陈化时间的延长或温度降低,凝胶网络弹性和凝胶强度增大,且逐渐稳定;适当浓度的尿素和SDS可以阻止凝胶网络的形成;明胶胶凝网络结构的形成主要借助分子间氢键相互作用,同时静电斥力和疏水相互作用也影响凝胶网络的形成.     

超声-微波协同提取杜仲树皮及树叶中的黄酮类化合物

为优化杜仲黄酮得率,通过脱胶预处理的杜仲树皮及杜仲树叶为材料,运用超声-微波协同提取方法(UMAE),由单因素实验及响应面法考察UMAE提取工艺条件,并利用HPLC结合标准品比对法比较了树皮与树叶黄酮类成分。结果显示:UMAE的最佳提取条件为乙醇浓度58%,液料比70:1(mL:g),温度75℃,微波功率420 W,时间6 min,此时粗黄酮得率为11.80%±0.09%。将超声-微波协同提取方法与单独微波或单独超声法进行比较,其黄酮得率及抗氧化能力(以清除DPPH自由基能力计)均显著高于单独法(p<0.001)。扫描电镜结果显示,超声波与微波协同作用时,植物细胞壁破碎更为彻底,利于黄酮溶出,因此UMAE提取黄酮的提取效率显著优于单独超声及单独微波的提取方法。通过比较树皮与树叶中黄酮成分的含量,发现杜仲树叶中芦丁、槲皮素、山奈酚含量明显高于树皮,说明杜仲树叶更适用于提取黄酮。     

The optimization of microwave-assisted extraction of decursin from Angelica gigas Nakai root

Response surface methodology was used to display the characteristics of microwave‐assisted extraction (MAE) of soluble solids and decursin from Angelica gigas Nakai root, thereby allowing MAE conditions to be optimized. These included ethanol concentration, microwave power and extraction time. The maximal solid yield was predicted to be 44.2% under conditions of 44.9% ethanol concentration, 115.6 W microwave power and 5.8 min extraction time. Decursin content of the extract was estimated to be maximal at 2.52% using 97.7% ethanol, 90.2 W microwave power, and 6.1 min extraction time. The estimated optimal MAE conditions (67% ethanol, 100 W and 6 min) to maximize both components were verified by comparing estimated values with experimental values (42.2% soluble solids, 2.2% decursin), which were higher than those (35.8% solids, 2.0% decursin) obtained by conventional reflux extraction (60% ethanol, 95 °C and 6 h).     

Optimisation of microwave‐assisted extraction of prune (Prunus domestica) antioxidants by response surface methodology

Optimal conditions for microwave‐assisted extraction (MAE) of total phenols (TP), epicatechin gallate and antioxidant activity from prune (Prunus domestica), rejected in transformation process of plum to prune, were determined by response surface methodology. The central composite design was used to study the effects of three independent variables: microwave power, irradiation time and solvent polarity on the TP, epicatechin gallate and antioxidant activity. Epicatechin gallate was identified as a major phenolic compound in prune extract by RP‐HPLC. Microwave power and irradiation time significantly affected all responses (P < 0.01). The highest TP (598.89 mg GAE/100 g prune) was obtained using water as an extraction solvent at 500 W, during 115 s. However, the optimal conditions for epicatechin gallate extraction were ethanol 80%, 435 W and 120 s. MAE is more efficient than conventional extraction method to obtain TP from prune. The experimental values were reasonably close to the predicted values confirming the validity of the predicted models.     

Optimization of various extraction methods for quercetin from onion skin using response surface methodology

Quercertin and typical flavonoids present in onion skin draw interest due to bioactive properties. For utilizing quercetin from onion skin, conventional solvent extraction (CSE), microwave assisted extraction (MAE), and ultrasound assisted extraction (UAE) were employed. Statistic models of each method were proposed to estimate the best possible yield of quercertin employing response surface methodology (RSM). The effects of several independent variables including concentration of ethanol, provided power or the temperature, and reaction time were investigated. From 1 g sample of dried onion skin, the highest yield of each method could be achieved at 16.5 min of process time under 59.2°C for CSE with 59.3% ethanol, 117 s for MAE with 69.7% ethanol, and 21.7 min for UAE using power of 606.4 W with 43.8% ethanol. The most productive method was MAE, whose maximum yield was 20.3 and 30.8% higher than UAE and CSE, respectively.     

Influence of ethanol/water ratio in ultrasound and high‐pressure/high‐temperature phenolic compound extraction from agri‐food waste

The valorisation and management of agri‐food waste are currently hot investigation topics which probe the recovery of valuable compounds, such as polyphenols. In this study, high‐pressure/high‐temperature extraction (HPTE) and ultrasound‐assisted extraction (UAE) have been used to study the recovery of phenolic compounds from grape marc and olive pomace in hydroalcoholic solutions. The main phenolic compounds in both extracts were identified by HPLC‐DAD. Besides extraction yield (total polyphenol and flavonoid content) and the antiradical power, polyphenol degradation under HPTE and UAE has also been studied. HPTE with ethanol 75% gave higher phenolic extraction yields: 73.8 ± 1.4 mg of gallic acid equivalents per gram of dried matter and 60.0 mg of caffeic acid equivalents per gram of dried matter for grape marc and olive pomace, respectively. In this study, the efficient combination of ethanol/water mixture with HPTE or UAE has been used to enhance the recovery of phenolic compounds from grape marc and olive pomace. HPLC‐DAD showed that UAE prevents phenolic species degradation damage because of its milder operative conditions.     

Visco‐Elastic and Flow Properties of Gelatin from the Bone of Freshwater Fish (Cirrhinus mrigala)

The average yield of gelatin from the bone of freshwater fish (Cirrhinus mrigala) was 6.13%. The fluorescence spectra revealed maximum emission at 303 nm indicating the exposure of chromophores to bulk solvent. The amino acid profile of gelatin revealed a higher proportion of glycine and imino acids. The bloom strength of gelled gelatin was 159.8 g. The average molecular weight of fish bone gelatin was 281 kDa as determined by gel filtration technique. The dynamic oscillatory test of gelatin solution as a function of time and temperature revealed gelling and melting temperatures of 8.0 °C and 17.0 °C, respectively. The flow behavior of gelatin solution as a function of concentrations and temperatures revealed non‐Newtonian behavior with pseudo‐plastic phenomenon. The Herschel–Bulkley and Casson models were found suitable to study the flow behavior. The emulsion capacity (EC) of gelatin was inversely proportional to its concentration.     

Characteristics and chemical composition of skins gelatin from cobia (Rachycentron canadum)

Gelatin was obtained from cobia (Rachycentron canadum) skins, which is an important commercial species for marine fish aquaculture, and it was compared with gelatin from croaker (Micropogonias furnieri) skins, using the same extraction methodology (alkaline/acid pre-treatments). Cobia skins gelatin showed values of protein yield, gelatin yield, gel strength, melting point, gelling point and viscosity higher than the values found from croaker skins gelatin. The values of turbidity and Hue angle for cobia and croaker gelatins were 403 and 74 NTU, and 84.8° and 87.3°, respectively. Spectra in the infrared region had the major absorption band in the amide region for both gelatins, but it showed some differences in the spectra. The proline and hydroxyproline contents from cobia skins gelatin (205 residues/1000 residues) was higher than from croaker skins gelatin (188 residues/1000 residues). SDS-PAGE of both gelatins showed a similar molecular weight distribution to that of standard collagen type I. Therefore, cobia skins could be used as a potential marine source of gelatin obtainment for application in diversified industrial fields.     

Comparison of enzyme‐assisted and ultrasound‐assisted extraction of vitamin C and phenolic compounds from acerola (Malpighia emarginata DC.) fruit

This article describes a comparative study of enzyme and ultrasound techniques for the simultaneous extraction of vitamin C and phenolic compounds from acerola fruit. Ultrasound‐assisted extraction (UAE) took only 6 min to achieve the highest level of vitamin C and phenolic compounds as well as antioxidant activity of acerola juice, while enzyme‐assisted extraction (EAE) took up to 120 min to obtain the maximal values. On the basis of kinetic model of second‐order extraction, the extraction rate constant of vitamin C and phenolics in UAE increased approximately 3.1 and 2.7 times, respectively, in comparison with that in EAE. In addition, the maximal level of vitamin C, phenolics and the antioxidant activity evaluated by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), and 2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) methods in UAE was 4.6%, 3.5%, 4.6% and 3.3%, respectively, higher than those in EAE. Obviously, UAE is a useful method for the extraction of antioxidants from plant materials.     

Two Kaempferol Glycosides Separated from Camellia Oleifera Meal by High‐Speed Countercurrent Chromatography and Their Possible Application for Antioxidation

Recently, kaempferol and its glycosides have attracted considerable attention owing to their potentially health‐benefitting properties including protection against chronic diseases. Here, a microwave‐assisted extraction (MAE) method was developed for the extraction of total flavonoid glycosides (FG) from Camellia oleifera meal, a major agrifood waste largely generated as a byproduct from the Camellia oil processing industry. Compared with traditional extraction methods, MAE enables more efficient extraction of FG. High‐speed countercurrent chromatography was then applied to separate FG from MAE extract, and two major compounds were successfully separated with purities above 90.0% as determined by HPLC. These two compounds were further identified by UV, FT‐IR, ESI‐MS, ¹H‐NMR, and ¹³C‐NMR as kaempferol 3‐O‐[α‐L‐rhamnopyranosyl‐(1→6)‐β‐D‐glucopyranosyl]‐7‐O‐β‐D‐glucopyranoside and kaempferol 3‐O‐[β‐D‐glucopyranosyl‐(1→4)‐α‐L‐rhamnopyranosyl]‐7‐O‐α‐L‐rhamnopyranoside, which were for the first time separated from C. oleifera meal. The results of antioxidant activity assay demonstrated that both compounds had excellent scavenging activity for DPPH radical, and exhibited protective effects against H₂O₂‐induced oxidative damage of vascular endothelial cells. The findings of this work suggest the possibility of employing C. oleifera meal as an attractive source of health‐promoting compounds, and at the same time facilitate its high‐value reuse and reduction of environmental burden.