Effects of microwave radiation on the physicochemical properties, structure, and digestibility of the synthesized different crystal forms of malic acid starch ester.

The effects of microwave combined with L-malic acid treatment on the degree of substitution (DS), structure, physicochemical properties, and digestibility of sweet potato starch (A-type), potato starch (B-type), and pea starch (C-type) were evaluated. The order of DS obtained was: DSM-POS > DSM-SPS > DSM-PES. Fourier transform-infrared spectroscopy (FT-IR) showed that the obtained modified starch produced a new absorption band at 1735 cm-1. Scanning electron microscopy (SEM) and polarized light microscopy indicated that different types of native starches exhibited different granular morphologies and appeared to have different degrees of damage, but still had polarized crosses after modification. Sweet potato starch had the smallest particle size, while potato starch had the largest. X-ray diffractometry (XRD) showed that the modified starches still retained the same crystal structure as the native starches, but the relative crystallinity decreased. The apparent viscosity and swelling power of modified starches dropped, but their water/oil holding capacity, amylose content, and resistant starch content all increased. The results demonstrate that the degree of influence on the structure, physicochemical properties, and digestibility of different starches varies under the same modification conditions.

Insights into the changes of structure and digestibility of microwave and heat moisture treated quinoa starch.

In this study, quinoa starch was subjected to microwave and heat moisture treatment (MHT) with various moisture content (15 %, 25 %, 35 %) and microwave power (4.8, 9.6, 14.4 W/g), and its structure and digestibility were investigated. SEM and particle size analysis indicated that MHT caused the agglomeration of starch granules and increased the particle size. Moreover, MHT increased the short-range order structure and relative crystallinity, except for MHT with moisture content (35 %). DSC results demonstrated that the gelatinization temperature and gelatinization enthalpy had a slight improvement after MHT. Moreover, MHT increased the amylose content to some extent. It was worth noting that the digestibility of quinoa starch significantly decreased. After MHT, a part of rapidly digestible starch (RDS) was converted into slowly digestible starch (SDS) or resistant starch (RS). Particularly, when moisture content was 25 %, the starch had a highest SDS + RS content. Thus, this study provided a potential approach using MHT to modulate the digestibility of starch.

Adaptive synchroextracting transform and its application in bearing fault diagnosis.

Time-frequency analysis methods can be used to characterize the time-varying characteristics of a signal. The postprocessing algorithm further enhances this ability. The synchroextracting transform is a typical postprocessing algorithm that has the advantage of energy aggregation. However, based on a short-time Fourier transform, shortcomings such as a fixed window length and amplitude distortion when processing frequency modulation signals are unavoidable. This paper proposes a time-frequency postprocessing algorithm with high adaptability, which is called the adaptive synchroextracting transform (ASET). The filter window width for the ASET is adaptive and is determined by the instantaneous frequency change rate for the signal. On this basis, the improved extraction operator can be used to achieve a high-resolution time-frequency​ representation. This algorithm can be used to better deal with strong frequency modulation signals and has better noise robustness while allowing for signal reconstruction. The effectiveness and practicability of the proposed algorithm are demonstrated by simulation signals and faulty bearing signals.

Structural and physicochemical properties of resistant starch under combined treatments of ultrasound, microwave, and enzyme.

The structural characteristics and physicochemical properties of native corn starch (NCS) and resistant starch (RS) prepared by enzymatic hydrolysis (RS-E), microwave-enzymatic hydrolysis (RS-ME), ultrasound assisted enzymatic hydrolysis (RS-UE), and microwave-ultrasound assisted enzymatic hydrolysis (RS-MUE) were investigated. The results showed that the combined treatments of ultrasound, microwave, and enzyme resulted in increases in RS content, amylose content, and solubility with a decrease in swelling power. RS-MUE exhibited the lowest digestibility, with a 41.71 % RS content. Particle-size distribution and scanning electron microscopy analyses demonstrated that RS samples exhibited larger granule sizes and rougher surfaces with irregular shapes. The Fourier transform infrared spectroscopy and X-ray diffraction pattern analysis demonstrated that no new groups were created during the modification processes, the crystal structure of all RS samples changed from A to B + V, and the short-range order and relative crystallinity of RS-E, RS-ME, RS-UE, and RS-MUE increased. RS-MUE exhibited the highest molecular order R1047/1022 value (0.8769) and relative crystallinity (45.54 %). These results suggested that the new technology combining microwave, ultrasound, and enzyme for improving RS content is effective and has potential for application in the production of RS and low glycemic index foods.

Effects of microwave and conventional heating on physicochemical, digestive, and structural properties of debranched quinoa starch-oleic acid complexes with different water addition.

BACKGROUND: A starch-lipid complex is a new type of resistant starch, which is of great importance for the prevention of chronic diseases such as diabetes. Most starch-lipid complexes usually need to be treated by heating to make them suitable for a variety of applications, and starch-based foods are generally not edible without a heat-treatment process. However, the digestion and structural properties of the starch-lipid complex will be changed after heating. In this study, microwave and conventional heating were used to treat debranched quinoa starch-oleic acid complexes (DQS-OA) with different water addition conditions, and the effects of the two methods on the physicochemical, digestive, and structural properties of DQS-OA were compared. RESULTS: The results of in vitro digestibility showed that the resistant starch content (235.34-269.55 g kg-1 ) of the conventional heating-treated samples was significantly higher than that the microwave-treated samples (141.51-157.99 g kg-1 ). Moreover, after microwave treatment, the short-range molecular order and crystalline structure of DQS-OA were destroyed and the particle size became smaller. In contrast, the thermal stability, enthalpy, and crystallinity of the complexes after conventional heating were improved. The ratio at 1047/1022 cm-1 of complexes has also been increased. CONCLUSION: This study demonstrated that conventional water-bath heating was better than microwave heating in increasing digestion resistance, improving the short-range and long-range molecular order, and promoting the formation of DQS-OA. With an increase in water addition, the influence of microwave or water-bath treatment on the properties of DQS-OA became greater. © 2022 Society of Chemical Industry.

Effects of NaCl and sucrose on the structural and functional properties of debranched quinoa starch-oleic acid complexes under baking.

The effects of different dosage of NaCl and sucrose on the structural and functional properties of debranched quinoa starch-oleic acid complexes (DQS-OA) under baking were investigated. The results showed that the resistant starch content of the baked DQS-OA increased by 17.15 % than DQS-OA. The addition of NaCl destroyed the thermal stability, short-range molecular order and crystalline structure of the complexes. The results of particle size, SEM and amylose content showed that NaCl accelerated the degradation of starch granules, which reduced the enzyme resistance of starch. In contrast, the enthalpy (7.28 J/g-7.78 J/g) and crystallinity (54.29 %-56.69 %) of the samples with sucrose significantly increased, and the molecular structure of the complexes became more ordered. Furthermore, with the increase of sucrose concentration, the resistant starch content also increased from 28.80 % to 31.41 %.

Application of ultrasound-assisted cryoprotectant impregnation for improving the storage quality of snakehead fish fillets.

In aquatic products companies, saccharides and phosphates are often used to impregnate products to improve their quality. Insignificant impregnation effect is a main problem met in the impregnation process. The effect of ultrasonic-assisted impregnation on the storage quality of snakehead fish fillets at -18 °C was studied. For all samples, such parameters as water holding capacity, pH value, salt-soluble protein content, whiteness and cooking loss rate were examined periodically. Furthermore, the changes of moisture distribution and migration in snakehead fish fillets during storage were investigated using low-field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). The results demonstrated that ultrasonic-assisted impregnation showed better anti-freeze and water holding capacity effects than that of cryoprotectant impregnation alone. Therefore, ultrasonic treatment could be used as an effective way to improve the quality of snakehead fish fillets during the frozen process. This study could provide a broad application prospect in aquatic product processing industry.

Recent Trends in the Preparation of Nano-Starch Particles.

Starch is affected by several limitations, e.g., retro-gradation, high viscosity even at low concentrations, handling issues, poor freeze-thaw stability, low process tolerance, and gel opacity. In this context, physical, chemical, and enzymatic methods have been investigated for addressing such limitations or adding new attributes. Thus, the creation of biomaterial-based nanoparticles has sparked curiosity. Because of that, single nucleotide polymorphisms are gaining a lot of interest in food packaging technology. This is due to their ability to increase the mechanical and water vapor resistance of the matrix, as well as hide its re-crystallization during storage in high-humidity atmospheres and enhance the mechanical properties of films when binding in paper machines and paper coating. In medicine, single nucleotide polymorphisms (SNPs) are suitable as carriers in the field of drug delivery for immobilized bioactive or therapeutic agents, as well as wastewater treatments as an alternative to expensive activated carbons. Starch nanoparticle preparations can be performed by hydrolysis via acid hydrolysis of the amorphous part of a starch molecule, the use of enzymes such as pullulanase or isoamylase, or a combination of two regeneration and mechanical treatments with the employment of extrusion, irradiation, ultrasound, or precipitation. The possibility of obtaining cheap and easy-to-use methods for starch and starch derivative nanoparticles is of fundamental importance. Nano-precipitation and ultra-sonication are rather simple and reliable methods for nanoparticle production. The process involves the addition of a diluted starch solution into a non-solvent, and ultra-sonication aims to reduce the size by breaking the covalent bonds in polymeric material due to intense shear forces or mechanical effects associated with the collapsing of micro-bubbles by sound waves. The current study focuses on starch nanoparticle manufacturing, characterization, and emerging applications.

Effects of dual modification of lysine and microwave on corn starch: In vitro digestibility and physicochemical properties.

The effects of lysine addition and microwave treatment (MC) on the digestibility, physicochemical properties and structure of corn starch were investigated. Among all uncooked samples, unmodified corn starch (CS), microwave modified corn starch (MC-CS) and corn starch mixed with lysine (CS-Lys) contained 15.09 %, 14.82 % and 18.86 % slowly digestible starch (SDS), while up to 30.28 % in microwave-lysine modified corn starch (MC-Lys). In contrast to CS, the peak viscosity, breakdown viscosity, setback viscosity and gel enthalpy of MC-Lys were decreased, while the relative crystallinity was increased. Scanning electron microscopy observation showed that corn starch aggregated with each other and was coated by lysine after MC, the particle size distribution range became wider, and the specific surface area decreased. The results showed that the interaction of starch with lysine in the microwave field increased the ordered and aggregated structure of corn starch, resulting in a significant change in the physicochemical properties and digestibility of corn starch. MC-Lys can be added to foods as a nutritional fortification to meet the needs of specific populations for lysine and low carbohydrate.

Comparison of physicochemical properties and digestibility of sweet potato starch after two modifications of microwave alone and microwave-assisted L-malic acid.

The effects of microwave alone (MA) and microwave-assisted L-malic acid (MLA) on the physicochemical properties, structural and digestibility of sweet potato starch were investigated. The results showed that the swelling power, lightness (L⁎) and whiteness index (WI), gelatinization enthalpy of starch decreased by MA and MLA treatment. The starch treated by MLA showed a new characteristic absorption peak at near 1735 cm-1 in the measurement of FT-IR, while the starch treated with MA showed no new characteristic peak. The relative crystallinity of starch modified by MSE and MA decreased, but it still retained A-type crystal structure. Scanning electron microscopy showed that the surface destruction of MSE-modified starch was greater than that of starch modified by MA. MLA increased the content of resistant starch (RS), while MA reduced the content of resistant starch (RS). The relative crystallinity and gelatinization enthalpy of continuous 60 s treatment were lower than those of discontinuous 60 s treatment. These results indicated that MLA had a greater effect on the physicochemical properties, structural and digestibility of starch than MA. Starch modified by MLA can be added to foods as a low-carbohydrate ingredient, and the starch treated by MA is suitable for foods with low swelling, such as noodles.

Closed-Cell Rigid Polyimide Foams for High-Temperature Applications: The Effect of Structure on Combined Properties.

Closed-cell rigid polyimide foams with excellent thermal stability and combined properties were prepared by thermal foaming of a reactive end-capped polyimide precursor powder in a closed mold. The precursor powder was obtained by thermal treatment of a polyester-amine salt (PEAS) solution derived from the reaction of the diethyl ester of 2,3,3',4'-biphenyl tetracarboxylic dianhydride (α-BPDE) with an aromatic diamine mixture of p-phenylenediamine (PDA) and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) in the presence of an end-capping agent (mono-ethyl ester of nadic acid anhydride, NE) in an aliphatic alcohol. The effect of polymer mainchain structures on the foaming processability and combined properties of the closed-cell rigid polyimide foams were systematically investigated. The polyimide foams (100-300 kg/m3) with closed-cell rates of 91-95% show an outstanding thermal stability with an initial thermal decomposition temperature of ≥490 °C and a glass transition temperature of 395 °C. Polyimide foams with density of 250 kg/m3 exhibited compression creep deformation as low as 1.6% after thermal aging at 320 °C/0.4 MPa for 2 h.

Effects on the structure and properties of native corn starch modified by enzymatic debranching (ED), microwave assisted esterification with citric acid (MCAE) and by the dual ED/MCAE treatment.

Native corn starch was modified by enzymatic debranching (ED), microwave assisted citric acid esterification (MCAE), and by dual ED/MCAE. The structure and properties of native starch (NS), and the resulting debranched starch (DS), microwave assisted citric acid esterified starch (MCS), and microwave assisted citric acid debranched starch (MCDS) were determined and compared. Both the morphology and crystalline regions of the modified starches were changed by ED and MCAE. ED increased significantly the amylose content and transparency, but decreased the in vitro enzymatic digestibility, freeze thaw stability and relative crystallinity of DS compared to those of NS. MCAE produced a decrease in amylose content, transparency, in vitro enzymatic digestibility, and relative crystallinity, but increased the freeze-thaw stability of MCS compared to NS, and of MCDS compared to DS. The A-type crystalline structure of NS and DS was changed to B-type crystalline structure after MCAE treatment, and a new FTIR characteristic band at 1735 cm-1 was observed for MCS and MCDS. This work provides insights for producing esterified corn starches by a combined enzyme, microwave and organic acid novel technology.

Multi-Frequency Ultrasonic Extraction of Anthocyanins from Blueberry Pomace and Evaluation of Its Antioxidant Activity.

BACKGROUND: A large amount of blueberry pomace is discarded and wasted. OBJECTIVE: To make full use of blueberry pomace and extract anthocyanins. METHOD: Multi-frequency ultrasound was used to extract anthocyanins from blueberry pomace. The effects of different extraction conditions on the anthocyanin yields were studied. The antioxidant activity of anthocyanins was evaluated, and the main anthocyanin components were identified by HPLC-electrospray ionization (ESI)-MS/MS. RESULTS: The optimal anthocyanin extraction conditions were as follows: dual-frequency ultrasound of 40 + 80 kHz, ultrasonic power of 350 W, extraction temperature of 50°C, and extraction time of 40 min. Compared with single frequency (25 kHz) and tri-frequency ultrasound (25 + 40 + 80 kHz), the anthocyanin yield with dual-frequency ultrasound increased by 15.26% and 5.45% respectively. Furthermore, the antioxidant activities (DPPH, hydroxyl radical scavenging ability, and reducing power) of anthocyanins extracted with dual-frequency ultrasound were all higher than those without ultrasound. Seven kinds of anthocyanins were identified by HPLC-ESI-MS/MS. CONCLUSIONS: Dual-frequency ultrasound had a higher extraction yield than single frequency ultrasound, tri-frequency ultrasound, and no ultrasound. HIGHLIGHTS: Dual-frequency ultrasonic technology provides an effective approach for improving the extraction yield of anthocyanins from blueberry pomace.

Preparation and characterization of PVDF/CaCO3 composite membranes etched by hydrochloric acid.

This study aimed to improve the pore size, porosity, and hydrophobicity of polyvinylidene fluoride (PVDF) membranes for desalination by vacuum membrane distillation (VMD). New membranes were prepared via etching PVDF/calcium carbonate (CaCO3) composite membranes using hydrochloric acid (HCl), depending on the chemical reaction of CaCO3 and HCl. Etched membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), contact angle (CA), atomic force microscope (AFM), and scanning electron microscopy (SEM). The results showed that CaCO3 of composite membranes was completely reacted by 1.5 mol/L HCl after composite membranes had been etched 90 min. The crystallinity of etched membranes was the same as that of PVDF/CaCO3 composite membranes, and no new functional groups appeared in etched membranes, which indicated that etched membranes had good chemical stability. The surface roughness increased and led to the increase of contact angle, which means the hydrophobicity of etched membranes was enhanced. As a result, the increment of permeation flux had been improved in a VMD process. It was found that the maximum flux of etched membrane was enhanced and up to 1.65 times of composite membrane when the concentration of sodium chloride (NaCl) solution was 5.0 wt%, and the maximum flux reached up to 30.9 kg m-2 h-1.

Comparative studies on structure and physiochemical changes of millet starch under microwave and ultrasound at the same power.

As two novel starch modification technologies, the comparative study between microwave (MC) and ultrasound (UC) is of important significance for their applications. The objective of this work is to compare the changes of millet starch with MC and UC, focusing on the viscosity, swelling power (SP), transparency (TR), short-range molecular order (FT-IR spectrum), thermal properties (DSC), long-range molecular order (X-ray diffraction), in vitro enzymatic digestibility, and morphological properties. MC changed the type of the pasting curves form B-type to C-type, and the maximum decrease of the peak viscosity and relative crystallinity of MC starch was 74.9% and 100%, however, these changes for UC starch were only 14.8% and 23.2%. MC decreased the SP, TR, DSC, and ratio of absorbances at 1047/1022 cm-1, but UC caused opposite trend of these properties. Both MC and UC increased the in vitro enzymatic digestibility by 26.7% and 13.3%, respectively. MC also destroyed the original appearance of the starch granules and formed smaller and lamellar gel blocks. In conclusion, MC had greater influence on starch structure and properties than UC, even in a short period.

Physicochemical and in vitro digestion of millet starch: Effect of moisture content in microwave.

In this study, the physicochemical and in vitro digestion of millet starch with different moisture content after microwave treatment were investigated. The structure and property changes of native (NA) and microwave treated (MT) millet starches were characterized using Brabender viscometer, Fourier transforms infrared spectroscopy (FT-IR), Differential scanning calorimeter (DSC), X-ray diffraction (XRD) and Scanning electron microscopy (SEM). Microwave treatment caused a decrease of the peak viscosity, swelling power, ΔH and relative crystalline, and an increase of the transparency, TO, TC, and ΔT. The extent of these changes depended on the moisture content of starches. The in vitro enzymatic digestibility of samples increased greatly, especially at a moisture content of >40%. It is interesting to note that the peak of the hydroxyl group shifted toward the lower wavenumber direction and the decrease of peak intensities at 1047 cm-1 and 1022 cm-1 in FT-IR spectra indicated that higher moisture content enhanced the inter-molecular hydrogen bonding and caused more serious damage to the crystalline and amorphous regions. Cracks and center cavities were observed on the granules surface and the original appearance of starch disappeared gradually as the moisture content increases. In conclusion, high moisture content can enhance the effect of the microwave to millet starch.

Output-only modal analysis of wind turbine tower based on vibration response under emergency stop.

The identification technique of output-only modal parameters is proposed for the large wind turbine tower under emergency stop. Compared with the response of regular operating conditions, the immediate tower structural response under emergency stop much more resembles a state of free vibration, which is more appropriate for the modal identification of the wind turbine tower. The vibration response is measured in the nacelle, which is easy to perform in the field modal test. The variational mode decomposition (VMD) is applied to decompose the vibration response into several band-limited intrinsic mode functions. The free responses of decomposed functions are extracted by applying the random decrement technique (RDT). Finally, the modal damping ratio and natural frequency are identified from each free modal response by using the Hilbert transform method. Simulations and a 1.5 MW wind turbine field modal test results verify the effectiveness of the proposed identification method. The main modal parameters of wind turbine, including weak modes, are effectively extracted by using output-only vibration responses under emergency stop. The modal parameter identification method is provided for the large wind turbine structure under the engineering condition.

Different-frequency ultrasonic effects on properties and structure of corn starch.

BACKGROUND: Ultrasound is widely used to accelerate many reactions and unit operations, but few studies have reported its effects on starch properties and structure. RESULTS: Corn starch suspended in ethanol solution was treated by dual-frequency ultrasound (DFU) and single-frequency ultrasound (SFU). Results showed that the transparency of the starch treated under 20 + 25 kHz DFU improved by 26.94% and 31.70%, respectively, compared to 20 kHz and 25 kHz SFU. Hardness, brittleness, elasticity, adhesiveness, conglutination degree, chewiness and recoverability of starch was reduced after ultrasonic treatment, and with increasing ultrasonic frequency these properties decreased. Its enthalpy value also decreased with ultrasound. Compared with each SFU treatment, enthalpy value decreased by 1.41% and 0.82%, respectively, by DFU. The freeze-thaw stability of starch was also weakened by ultrasound, which was obviously changed by DFU. Under ultrasound, the crystal structure of starch was not damaged, characteristic diffraction peak intensity was significantly reduced and diffuse diffraction features increased, exhibiting a decline in crystal lattice ordering degree. In comparison to SFU, DFU caused a pronounced reduction in starch crystallinity. CONCLUSION: After ultrasonic treatment, the transparency of corn starch paste improved, but its hardness, brittleness, elasticity, adhesiveness, conglutination degree, chewiness and recoverability decreased, as well as starch crystallinity and enthalpy values. DFU was found to be more effective than SFU.

Evaluation of electronspun silk fibroin-based transplants used for facial nerve repair.

OBJECTIVE: To study whether regenerated electrospun silk fibroin (SF) nanofibers as nerve conduits could improve nerve regeneration microenvironment and induce the facial nerve regeneration of Sprague-Dawley rats. DESIGN: Electrospun SF nanofibers were prepared to bridge a 5-mm facial nerve defect in Sprague-Dawley rats. Three months after implantation, a comprehensive morphologic and functional evaluation was performed by electrophysiology, histology, Fluorogold retrograde tracing, and transmission electron micrograph. RESULTS: The SF nanofiber tube exhibited good biocompatibility in vivo, and no distinct regional inflammation response and scar formation was observed. After 3 months of operation, the morphologic and functional investigation has shown a positive evaluation on the nerve repair outcome elicited by SF nanofiber graft and autograft. CONCLUSION: Electrospun SF grafts could promote nerve regeneration after facial nerve injury and become a potential possibility of newly developed nerve grafts as an alternative of autografts to peripheral nerve regeneration.

Electrospun silk fibroin nanofibers promote Schwann cell adhesion, growth and proliferation.

In this study, Schwann cells, at a density of 1 × 10(5) cells/well, were cultured on regenerated silk fibroin nanofibers (305 ± 84 nm) prepared using the electrospinning method. Schwann cells cultured on the silk fibroin nanofibers appeared more ordered, their processes extended further, and they formed more extensive and complex interconnections. In addition, the silk fibroin nanofibers had no impact on the proliferation of Schwann cells or on the secretion of ciliary neurotrophic factor, brain-derived neurotrophic factor or nerve growth factor. These findings indicate that regenerated electrospun silk fibroin nanofibers can promote Schwann cell adhesion, growth and proliferation, and have excellent biocompatibility.