•Ultrasonic cavitation field was monitored in real-time during oil extraction.•Resonance frequency was found and explained by numerical calculation.•Relationship between physical field and cavitation ...oxidation was built.
The ultrasonic extraction of oils is a typical physical processing technology. The extraction process was monitored from the standpoint of the oil quality and efficiency of oil extraction. In this study, the ultrasonic cavitation fields were measured by polyvinylidene fluoride (PVDF) sensor. Waveform of ultrasonic cavitation fields was gained and analyzed. The extraction yield and oxidation properties were compared. The relationship between the fields and cavitation oxidation was established. Numerical calculation of oscillation cycle was done for the cavitation bubbles. Results showed that the resonance frequency, fr, of the oil extraction was 40kHz. At fr, the voltage amplitude was the highest; the time was the shortest as reaching the amplitude of the waveform. Accordingly, the cavitation effect worked most rapidly, resulting in the strongest cavitation intensity. The extraction yield and oxidation properties were closely related to the cavitation effect. It controlled the cavitation oxidation effectively from the viewpoint of chemical and physical aspects.
Sequential delignification of watermelon rind using ultrasonication and deep eutectic solvent (DES) pretreatment methods was demonstrated in this study. The effects of pretreatment factors on ...delignification were investigated using parametric screening and subsequent optimization of significant factors. Plackett–Burman Design was used for the screening of pretreatment variables, while optimization was performed adopting Central Composite Rotatable Design. For the range of variables considered in the study, the screening experiments revealed that the effects of ultrasonication power, ultrasonication frequency, ultrasonication time, DES reaction temperature and DES reaction time on delignification were significant, while the effects of ultrasonication solid-liquid ratio, ultrasonication temperature, hydrogen bond acceptor/hydrogen bond donor molar ratio, and DES solid-to-liquid ratio were not significant. The significant factors were further investigated and maximum lignin removal of 43.56 % was achieved at ultrasonication power 180 W, ultrasonication frequency 60 kHz, ultrasonication time 40 min, reaction temperature 120°C and reaction time 180 min. Synergistic effect between the two pretreatment methods was observed and it correlated positively with the severity of the ultrasound pretreatment. The SEM and FTIR analyses further established the effectiveness of the sequential combinative pretreatment methods on watermelon rind delignification.
•Novel two-pot approach ultrasound-assisted DES pretreatment was demonstrated.•Effect of pretreatment factors on watermelon rind delignification was investigated.•Synergistic effect between ultrasonication and DES pretreatments was observed.•Synergistic effect correlated positively with severity of ultrasound pretreatment.•SEM and FTIR established the effectiveness of the combinative pretreatment methods.
•Oil yield was improved by 8.65–10.21% using sweeping frequency ultrasound (SFU).•Oil extraction time was shortened by 83.33% using SFU assisted method.•Acoustic field was monitored online in time ...and frequency domains.
Sweeping frequency ultrasound (SFU) was used to assist extraction of amur grape (Vitis amurensis) seed (AGS) oil. Extraction conditions and physicochemical properties were optimized and analyzed under different extraction methods. Meanwhile, frequency and time domains were online monitored during SFU assisted extraction of AGS oil. PVDF piezoelectric sensor was used in time domain, and the hydrophone in frequency domain, so as to obtain the time–voltage waveform, signal power, spectrum distribution and other visual models. Physical models of the spatial peak acoustic intensity, charge quantity and work done by electric field force under different ultrasonic conditions were derived. The mathematical model between the work done by electric field force and the spatial peak acoustic intensity under the working state of PVDF piezoelectric sensor was constructed. Results show that the content of AGS oil by SFU assisted extraction was higher than that by organic extraction. Furthermore, the optimal single-frequency was 40 kHz and dual-frequency was 28/33 kHz, and SFU extraction time of 30 min was suitable with higher oil yield of 16.70 % and 16.94 %, respectively. In addition, the selection and combination of SFU also affected the oil oxidation degree. The peak voltage, spatial peak acoustic intensity, signal power and work of electric field force at 28/33 kHz were all higher than those at 40 kHz.
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•The pretreatment efficiency of SFUS was higher than FFUS.•Recommended conditions for SFUS + DES were 40 kHz, 60 min, ChCl-LA, 120 °C, 3 h.•The SFUS + DES pretreatment resulted in ...85.62% LRR of SCB.•After SFUS + DES pretreatment, enzymatic hydrolysis of SCB yielded 86.76% glucose.•The hydrogen bonding of DES Cl- and lignin was responsible for lignin removal.
Sugarcane bagasse (SCB) is an abundant agricultural waste in China and the conversion of the waste into plethora of useful resources is very vital. To achieve this, fractionation of the waste is highly important in the biomass biorefinery. The present study aims at investigating the synergistic role of deep eutectic solvents (DES) with sweeping frequency ultrasound (SFUS) and fixed frequency ultrasound (FFUS) in the fractionation of SCB to enhance the enzymatic saccharification process. Therefore, the effects of ultrasound (US) and DES conditions on the pretreatment efficiency were investigated. Under optimum SCB pretreatment conditions, FFUS (40 kHz, 60 min) + DES (choline chloride (ChCl)-lactic acid (LA), 120 °C, 3 h) and SFUS (40 kHz, 60 min) + DES (ChCl-LA, 120 °C, 3 h), the lignin removal rates were 80.13 and 85.62%, respectively. The hemicellulose removal rates were 78.08 and 90.46%, respectively; and the contents of glucose, xylose and arabinose in the liquid fractions after FFUS + DES pretreatment were 7.07, 17.95 and 3.01%, respectively. However, the yield of glucose, xylose, and cellobiose after enzymatic hydrolysis of the SFUS + DES pretreated SCB were 86.76, 38.68, and 20.76%. Analytical studies revealed that the SFUS + DES pretreatment can effectively destroy the ultrastructure of SCB and reduce the crystallinity of cellulose. Furthermore, the mechanism of pretreatment with SFUS + DES was proposed, which confirmed the excellent performance of SFUS + DES. Thus, the application of SFUS + DES pretreatment was able to improve the removal of lignin and hemicellulose from SCBs.
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•d-Galactose was notably oxidized under dual frequency ultrasound dialysis.•Desalination of salt-rich phase polysaccharide solution was remarkably improved.•Ionic liquid purified ...polysaccharide had its original helical structure preserved.•Assisted dialysis speeded hydrolysis, reducing molecular weight of polysaccharide.•The rheology (elasticity) and morphology demonstrated strong correlation.
Supramolecules extraction using single frequency ultrasound technology application has directional effect as a shortcoming. Thus, optimum disruption of materials for better yield is curtailed. One possible solution to this underperformance is the application of dual frequency ultrasound. Dual frequency ultrasound-assisted extraction (DF-UAE) of crude polysaccharide (SL-C80P) and ionic liquid aqueous two phase system (ILATPS) purified polysaccharide (SL-D10P) of sorghum (Sorghum bicolor L.) leaf sheath was achieved using response surface methodology (RSM). Experimental yield for crude and purified polysaccharide (14.10% and 97.17%) respectively was found to be very close to the predicted (14.88% and 97.40%). Higher desalination levels of (SL-D10P) was also observed after DF-UA dialysis. Surface morphology under scanning electron microscopy and molar ratios of monosaccharides composition of the two samples were different, but Fourier transform infrared spectroscopy was similar. Crude and purified polysaccharides were of helical structures as demonstrated by the congo red assay and recorded molecular weights (1,202,000 and 12,950 g/mol) respectively. The sample, (SL-D10P) displayed more elasticity whiles (SL-C80P) showed more viscosity in rheological terms. Finally, (SL-D10P) aggregated in water, detachable by heat and possessed a notable ABTS scavenging ability, thus remarkable potential for biomolecules protection. In conclusion, a better extraction yield of polysaccharides was achieved.
•PPO was significantly inactivated by 22/40 kHz dual-frequency ultrasound treatment.•TP and FSFPU changed the secondary and tertiary structure of PPO.•TP and FSFPU changed the molecular ...microstructure and reduced the surface roughness.•PPO inactivation by FSFPU treatment was mainly due to protein aggregation.
The effects of thermal processing (TP) and flat sweep frequency and pulsed ultrasound (FSFPU) treatment with different frequency modes on the activity, conformation and physicochemical properties of mushroom polyphenol oxidase (PPO) were investigated. The results showed that the relative enzymatic activity of PPO gradually decreased with increasing temperature and duration, and thermosonication decreased the PPO activity to a greater extent compared with thermal processing. FSFPU treatment with dual-frequency of 22/40 kHz mode showed the most significant effect. Circular dichroism (CD) showed that the content of α-helix and β-turn dropped, while that of β-sheet and random coil raised after FSFPU treatment. The intensity of endogenous fluorescence decreased, indicating that PPO protein unfolded and the tertiary structure was destroyed. The amount of free sulfhydryl, protein aggregation index, and turbidity all rose. Moreover, FSFPU treatment led to the aggregation of protein from the analysis of atomic force microscope (AFM). Conclusively, FSFPU can be used as an effective method to inhibit the activity of endogenous enzymes in food.
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•Natural ternary deep eutectic solvents deconstructed corn straw without pollution.•Ultrasound and microwave enhanced the deconstruction by deep eutectic solvent.•Ultrasound/microwave ...sequential pretreatment increased cellulose content by 76.08%.•The removal of lignin was 46.44% under mild pretreatment conditions.•The mechanism of deconstruction of corn straw was proposed.
Mild and effective pretreatments are essential to deconstruct lignocellulosic biomass so as to reuse cellulose content for value-added products. In this study, sequential multimode-ultrasound and microwave with natural ternary deep eutectic solvent (NATDES) pretreatments were used to deconstruct corn straw and optimized factors such as NATDES, ultrasonic, and microwave parameters. Results indicated that the ultrasound-NATDES or microwave-NATDES pretreatment could remove 37.86% and 52.36% lignin, respectively. When using sequential multimode-ultrasound and microwave assisted NATDES pretreatment, the delignification efficiency increased to 61.50%, and the cellulose content increased from 34.70% to 76.08%. In addition, the delignification of sequential multimode-ultrasound and microwave assisted NATDES pretreatment (under the mild conditions of microwave heating at 60 °C and 60 min) increased to 57.39%, and the cellulose content increased to 59.98%, too. This highlighted the effect of the combined ultrasound and microwave technology. Finally, the microstructural changes of mercury intrusion porosimeters, scanning electron microscopy, thermogravimetric, X-ray diffraction and Fourier transform mid-infrared spectroscopy were conducted to confirm the effectiveness of this method to deconstruct corn straw. A mechanism of the deconstruction of corn straw biomass in NATDES with the assistance of the sequential multimode-ultrasound and microwave heating was proposed. This research could open a window for future use of biomass energy by deconstructing lignocellulosic biomasses using environmentally friendly pretreatment methods.
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•Effects of dry powders and ultrasound on okra pectin characteristics were studied.•Ultrasonic field was monitored to analyze its effect on pectin extraction.•Morphologies of okra ...powders and pectin molecular structure were studied.
Diversiform okra dry powders were prepared and controlled-temperature ultrasonic-assisted extraction (CTUAE) was then utilized to obtain okra pectin (OP) from the preparative powders. During processing of hybrid techniques, 6 types of dry powders were prepared through different drying technologies (hot air drying, HD; freeze-drying, FD) and meshes (60, 80, 120 meshes) at first. Next, the extraction yield, physicochemical and function characteristics, and molecular structure of OP were analyzed with or without CTUAE technique. Meanwhile, the time–frequency domains of acoustic fields during extraction process of OP were monitored to analyze the effects of ultrasonic fields. Results showed that OP main chains with less cracking by FD than that by HD; the yield, GalA, esterification degree (DE), Mw and viscosity of OP increased, but its particle size decreased. Water holding capacity (WHC) and oil holding capacity (OHC) of OP by HD were more prominent. Secondly, HD OP had dendritic rigid chains, while FD OP had flexible chains with multiple branches. For HD OP, as meshes of okra dry powders decreased, GalA, viscosity and emulsification ability decreased; while gel strength and thermal stability increased. For FD OP, the reduction of meshes improved thermal stability. Above all, CTUAE technique increased the yield and GalA, and decreased DE, Mw and particle size of OP. In terms of functional characteristics, the technique also improved gel strength, resilience and viscoelasticity, enhanced emulsifying stability, WHC and thermal stability, and reduced viscosity. Finally, the correlation between functional and structural characteristics of OP was quantified, and some suggestions were made for its application in food areas.
•The ACE-inhibitory activity increased by horn and bath sonication.•Combinations of fixed frequency (bath) produced more ACE-inhibitory peptides.•Changes in structural properties of DWGP after ...sonication were found.•Horn sonication was efficient in preparation of ACE-inhibitory peptides.
The ultrasonic horn and bath reactors were compared based on production of angiotensin-converting-enzyme (ACE) inhibitory peptides from defatted wheat germ proteins (DWGP). The DWGP was sonicated before hydrolysis by Alcalase. Degree of hydrolysis, ACE-inhibitory activity, surface hydrophobicity, fluorescence intensity, free sulfhydryl (SH), and disulfide bond (SS) were determined. The highest ACE-inhibitory activity of DWGP hydrolysate was obtained at power intensity of 191.1W/cm2 for 10min in the ultrasonic horn reactor. The fixed frequency of 33kHz and the sweep frequency of 40±2kHz resulted in the maximum ACE-inhibitory activity. The combined irradiation of dual fixed frequency (24/68kHz) produced significant increase in ACE-inhibitory activity compared with single frequency (33kHz). The ultrasonic probe resulted in significant higher ACE-inhibitory activity compared with ultrasonic bath operating at single or dual fixed and sweep frequencies. The changes in conformation of the DWGP due to sonication were confirmed by the changes in fluorescence intensity, surface hydrophobicity, SHf and SS contents and they were found in conformity with the ACE-inhibitory activity in case of the ultrasonic horn reactor but not in bath reactor.
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