Structural and physicochemical characterization of modified starch from arrowhead tuber (Sagittaria sagittifolia L.) using tri-frequency power ultrasound

Sagittaria sagittifolia L. is a well-known plant, belongs to the Alismataceae family. Sonication can improve the functional properties of starch; hence, the aim of this study was to develop ultrasonically modified arrowhead starch (UMAS) using a sophisticated and eco-friendly tri-frequency power ultrasound (20/40/60 kHz) method at 300, 600, and 900 W for 15 and 30 min. Significant (p < 0.05) increases in swelling power, solubility, and water and oil holding capacities were achieved. FTIR spectroscopy corroborated the ordered, amorphous, and hydrated crystals of the sonicated samples. Increases in sonication frequency and power led to significant (p < 0.05) increases in onset gelatinization temperatures. Scanning electron microscopic analysis of sonicated samples showed superficial cracks and roughness on starch granules appeared in a sonication power-dependent manner compared with that of untreated sample. Overall, the ultrasonically-treated samples showed improved physicochemical properties, which could be useful for industrial applications.     

Preparation and characterization of waxy maize starch nanoparticles via hydrochloric acid vapor hydrolysis combined with ultrasonication treatment

The objective of this work was to develop a simple and efficient method to prepare waxy maize starch nanoparticles (SNPs) by hydrochloric acid (HCl) vapor hydrolysis combined with ultrasonication treatment. The size, morphology, thermal property, and crystal structure of the SNPs were systematically studied. HCl treatment introduces a smaller particle diameter of starch particles from 13.73 ± 0.93 μm to 1.52 ± 0.01–8.32 ± 0.63 μm. Further ultrasonication treatment formed SNPs that displayed desirable uniformity and near-perfect spherical and ellipsoidal shapes with a diameter of 150.65 ± 1.91–292.85 ± 0.07 nm. The highest yield of SNPs was 80.5%. Compared with the native starch, the gelatinization enthalpy changes of SNPs significantly decreased from 14.65 ± 1.58 J/g to 7.40 ± 1.27 J/g. Interestingly, the SNPs showed a wider melting temperature range of 22.77 ± 2.35 °C than native starch (10.94 ± 0.87 °C). The relative crystallinity of SNPs decreased to 29.65%, while long-time ultrasonication resulted in amorphization. HCl vapor hydrolysis combined with ultrasonication treatment can be an affordable and accessible method for the efficient large-scale production of SNPs. The SNPs developed by this method will have potential applications in the food, materials, and medicine industries.     

Effects of multi-frequency ultrasound on physicochemical properties,structural characteristics of gluten protein and the quality of noodle

In this study, the influence of multi-frequency ultrasound irradiation on the functional properties and structural characteristics of gluten, as well as the textural and cooking characteristics of the noodles were investigated. Results showed that the textural and cooking characteristics of noodles that contain less gluten pretreated by multi-frequency ultrasonic were ultrasonic frequency dependent. Moreover, the noodles that contain a smaller amount of sonicated gluten could achieve the textural and cooking quality of commercial noodles. There was no significant difference in the cooking and texture characteristics between commercial noodles and noodles with 12%, 11%, and 10% gluten pretreated by single-frequency (40 kHz), dual-frequency (28/40 kHz), and triple-frequency sonication (28/40/80 kHz), respectively. Furthermore, the cavitation efficiency of triple-frequency ultrasound was greater than that of dual-frequency and single-frequency. As the number of ultrasonic frequencies increased, the solubility, water holding capacity and oil holding capacity of gluten increased significantly (p < 0.05), and the particle size was reduced from 197.93 ± 5.28 nm to 110.15 ± 2.61 nm. Furthermore, compared to the control group (untreated), the UV absorption and fluorescence intensity of the gluten treated by multi-frequency ultrasonication increased. The surface hydrophobicity of gluten increased from 8159.1 ± 195.87 (untreated) to 11621.5 ± 379.72 (28/40/80 kHz). Raman spectroscopy showed that the α-helix content of all sonicated gluten protein samples decreased after sonication, while the β-sheet and β-turn content increased, and tryptophan and tyrosine residues were exposed. Through scanning electron microscope (SEM) analysis, the gluten protein network structure after ultrasonic treatment was loose, and the pore size of the gluten protein network increased from about 10 μm (untreated) to about 26 μm (28/40/80 kHz). This work elucidated the effect of ultrasonic frequency on the performance of gluten, indicating that with increasing frequency combination increases, the ultrasound effect became more pronounced and protein unfolding increased, thereby impacting the functional properties and the quality of the final product. This study provided a theoretical basis for the application of multi-frequency ultrasound technology in the modification of gluten protein and noodle processing.     

The pasting properties of sonicated waxy rice starch suspensions

The effect of sonication on the pasting properties of waxy rice starch solutions (5 wt%) was investigated. It has been found that the functionality of starch granules was significantly influenced by the length of sonication and the solution temperature. A comparison of the pasting behaviour showed that the peak and final viscosities of the starch dispersions sonicated at temperatures near the onset temperature of gelatinisation were lower than those of the non-sonicated dispersions. The particle size measurements showed that the size of the heated and sonicated granules were smaller than that of the heated non-sonicated starch granules. Scanning electron microscopy (SEM) observations showed that the starch granule surface was not affected by sonication, and the size exclusion chromatography did not show any reduction in the size of the starch molecules. Based on these observations, the change in the pasting behaviour is explained in terms of the solubilisation of the swollen starch granules and starch aggregates induced by sonication.     

Ultrasound-assisted gelation of β-carotene enriched oleogels based on candelilla wax-nut oils: Physical properties and in-vitro digestion analysis

This study investigated the effects of high-intensity ultrasound (HIU, 95 W, 10 s) on the physical properties, stability and in vitro digestion of β-carotene enriched oleogels. Candelilla wax (3 wt%) and nut oils (peanut, pine nut and walnut oil) with or without β-carotene were used to form oleogels. HIU improved the storage modules (G’) of peanut, pine nut and walnut oleogels without β-carotene from 11048.43 ± 728.85 Pa, 38111.67 ± 11663.98 Pa and 21921.13 ± 1011.55 Pa to 13502.40 ± 646.54 Pa, 75322.47 ± 9715.25 Pa and 48480.97 ± 4109.64 Pa, respectively. Moreover, HIU reduced oil loss of peanut, pine nut and walnut oleogels without β-carotene from 23.98 ± 2.58%, 17.14 ± 0.69% and 24.66 ± 1.57% to 17.60 ± 1.10%, 13.84 ± 0.74% and 18.72 ± 3.47%, respectively. X-ray diffraction patterns showed that HIU did not change the form of the crystal (β-polymorphic and β’-polymorphic) but increased the crystal intensity. Polarized light microscope images indicated that all oleogels showed more visible crystals after HIU. After 120 d of storage, HIU decreased the degradation of β-carotene for peanut oil and walnut oil samples (the contents of β-carotene in peanut and walnut oleogels without HIU after 120 d of storage were 897 ± 2 μg/g and 780 ± 1 μg/g, respectively, and those of sonicated samples were 1070 ± 4 μg/g and 932 ± 1 μg/g, respectively). Furthermore, HIU reduced the release of β-carotene in intestinal digestion. In conclusion, HIU could improve the functional properties of wax-nut oils oleogels and their β-carotene enriched oleogels.     

Depolymerization of microcrystalline cellulose by the combination of ultrasound and Fenton reagent

In this study, the combined use of Fenton reagent and ultrasound to the pretreatment of microcrystalline cellulose (MCC) for subsequent enzyme hydrolysis was investigated. The morphological analysis showed that the aspect ratio of MCC was greatly reduced after pretreatment. The X-ray diffraction (XRD) and degree of polymerization (DP) analyses showed that Fenton reagent was more efficient in decreasing the crystallinity of MCC while ultrasound was more efficient in decreasing the DP of MCC. The combination of Fenton reaction and ultrasound, which produced the lowest crystallinity (84.8 ± 0.2%) and DP (124.7 ± 0.6) of MCC and the highest yield of reducing sugar (22.9 ± 0.3 g/100 g), provides a promising pretreatment process for MCC depolymerization.     

Mechanistic study on ultrasound assisted pretreatment of sugarcane bagasse using metal salt with hydrogen peroxide for bioethanol production

This study presents the ultrasound assisted pretreatment of sugarcane bagasse (SCB) using metal salt with hydrogen peroxide for bioethanol production. Among the different metal salts used, maximum holocellulose recovery and delignification were achieved with ultrasound assisted titanium dioxide (TiO₂) pretreatment (UATP) system. At optimum conditions (1% H₂O₂, 4 g SCB dosage, 60 min sonication time, 2:100 M ratio of metal salt and H₂O₂, 75 °C, 50% ultrasound amplitude and 70% ultrasound duty cycle), 94.98 ± 1.11% holocellulose recovery and 78.72 ± 0.86% delignification were observed. The pretreated SCB was subjected to dilute acid hydrolysis using 0.25% H₂SO₄ and maximum xylose, glucose and arabinose concentration obtained were 10.94 ± 0.35 g/L, 14.86 ± 0.12 g/L and 2.52 ± 0.27 g/L, respectively. The inhibitors production was found to be very less (0.93 ± 0.11 g/L furfural and 0.76 ± 0.62 g/L acetic acid) and the maximum theoretical yield of glucose and hemicellulose conversion attained were 85.8% and 77%, respectively. The fermentation was carried out using Saccharomyces cerevisiae and at the end of 72 h, 0.468 g bioethanol/g holocellulose was achieved. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis of pretreated SCB was made and its morphology was studied using scanning electron microscopy (SEM). The compounds formed during the pretreatment were identified using gas chromatography–mass spectrometry (GC–MS) analysis.     

Effect of ultrasonic pretreatment on the emulsification properties of Clanis Bilineata Tingtauica Mell protein

Clanis Bilineata Tingtauica Mell Protein (CBTMP) is a naturally high-quality insect protein resource, while its poor emulsification has limited its application in food industry. In order to change the present situation, in this research, the ultrasonic pretreatment (0 W, 200 W, 400 W, 600 W, and 800 W) method was used to improve the emulsification properties of CBTMP. Results indicated that ultrasound treatment especially at 400 W could significantly change the particle sizes, further increase the content of sulfhydryl group and surface hydrophobicity. The emulsification properties of emulsions were enhanced (from 4.16 ± 1.07 m²/g to 27.62 ± 2.20 m²/g) by sonicated CBTMP solution. Moreover, the physical stability of the emulsions to salt stress and centrifugation treatment was also promoted. Additionally, rheology revealed that a stronger network was formed at 400 W and all samples exhibited frequency-dependent and amplitude-dependent properties. The experiment demonstrated that ultrasound pretreatment was an effective means to improve the emulsification properties of CBTMP and it could provide a promising perspective for the application of CBTMP in food industry.     

Stimulation of antioxidant activity and γ-aminobutyric acid synthesis in germinated wheat grain Triticum aestivum L. by ultrasound: Increasing the nutritional value of the product

The use of ultrasound to intensify the germination process of Triticum aestivum L. wheat was studied. This method of controlled germination can be used in several sectors of food industry, in particular in bakery. The effect of low-frequency ultrasound (20 kHz) at different intensities and duration on the germination process of Triticum aestivum L. wheat was systematically studied. We have found that 3-minute processing at 227 W/l output reduces the duration of wheat grain germination by 25% (12 ± 2 h) compared to the control samples. The use of ultrasound stimulated γ-aminobutyric acid (GABA) synthesis (18.9 ± 0.5 mg/100 g), increased the antioxidant activity (AOA) (2.86 ± 0.2 mg/g Trolox equivalents) and the amount of flavonoids (0.19 ± 0.03 mg QE/g). The SEM analysis of powder particles of whole-wheat flour made from wheat germinated with ultrasound exposure showed densely packed aggregates of protein matrix. To sum up, controlled ultrasound during wheat grain germination increases the amount of GABA and AOA. The whole-wheat flour is useful for food enrichment.     

Effect of ultrasound on structural and physicochemical properties of sweetpotato and wheat flours

Ultrasound technologies are increasingly used for modification of physicochemical properties of food systems. Effects of ultrasound (20 kHz, 750 W) up to 20 h on physicochemical properties of two varieties of sweetpotato flour were studied and compared with those of commercial wheat flour. Ultrasound induced structural modifications on starch granules mainly in the morphological changes of granules and reduction of the crystallinity. Longer treatment significantly decreased enthalpy change of gelatinization, pasting viscosities, gelling capacity, while increasing in vitro starch digestibility of raw flour. Besides, prolonged treatment reduced total phenolic contents and in vitro antioxidant activities of sweetpotato flours, mainly due to pyrolysis and release of hydroxyl radicals caused by cavitation. The extents of these changes were seen to depend on the treatment time and indicated degradation and modifications of the chemical components (e.g., starch and polyphenol) of flours. This study suggests that ultrasound processing as a non-thermal and energy-saving technique has potential to modify flour functionalities.     

The production of Sr hexaferrite thick films by screen printing

Hydrothermally synthesised Sr hexaferrite (HT-SrM) powder with a distinct plate-like shape and conventional Sr hexaferrite (c-SrM) powder were used to screen print SrM thick films on alumina substrates. In the case of the HT-SrM thick films, a very strong perpendicular magnetic anisotropy has been observed with remanence values of up to 42±2 J/T kg for the perpendicular direction and 15±1 J/T kg for the in-plane direction, and with coercivities of around 159±8 kA/m for both directions when fired at 1300°C. When fired at 1150°C, the remanences were 49±2 and 27±2 J/T kg for the two directions with a higher coercivity of 247±8 kA/m for both directions. The SEM micrographs showed that the platelet grains in the printed films lay with their flat surfaces on the substrate and XRD results revealed that the c-axis of the grains oriented perpendicularly to the film surface. The (0 0 8) plane, which is, for a random oriented sample, a very weak peak, appeared as the strongest in the XRD pattern for the films. EDX and XRD studies indicated significant reaction at the interfaces between the film and the substrate when the sintering temperature was raised to 1350°C.For the SrM thick films obtained from planetary milled ultrafine Sr hexaferrite and conventional Sr hexaferrite powder, a slight in-plane anisotropy could be observed with a coercivity of 318±8 kA/m.     

Effects of ultrasonic treatment on the structural and functional properties of cactus (Opuntia ficus-indica) seed protein

With the steady increase in the consumption of ultra-processed foods, there is growing interest in sustainable diets that include more plant protein. However, little information is available regarding the structural and functional properties of cactus (Opuntia ficus-indica) seed protein (CSP), a by-product of the cactus seed food-processing chain. This study aimed to explore the composition and nutritional value of CSP and reveal the effects of ultrasound treatment on protein quality. Protein chemical structure analysis showed that an appropriate intensity of ultrasound treatment (450 W) could significantly increase protein solubility (96.46 ± 2.07%) and surface hydrophobicity (13.76 ± 0.85 μg), decrease the content of T-SH (50.25 ± 0.79 μmol/g) and free-SH (8.60 ± 0.30 μmol/g), and enhance emulsification characteristics. Circular dichroism analysis further confirmed that the ultrasonic treatment increased the α-helix and random coil content. Amino acid analysis also suggested that ultrasound treatment (450 W) increased the hydrophobic amino acid content. To evaluate the impact of changes in the chemical structure, its digestion behavior was studied. The results showed that ultrasound treatment increased the release rate of free amino acids. Furthermore, nutritional analysis showed that the digestive products of CSP by ultrasound treatment can significantly enhance the intestinal permeability, increase the expression of ZO-1, Occludin and Claudin-1, thus repairing LPS induced intestinal barrier disfunction. Hence, CSP is a functional protein with high value, and ultrasound treatment is recommended. These findings provide new insights into the comprehensive utilization of cactus fruits.     

Temperature effects on the ultrasonic separation of fat from natural whole milk

This study showed that temperature influences the rate of separation of fat from natural whole milk during application of ultrasonic standing waves. In this study, natural whole milk was sonicated at 600 kHz (583 W/L) or 1 MHz (311 W/L) with a starting bulk temperature of 5, 25, or 40 °C. Comparisons on separation efficiency were performed with and without sonication. Sonication using 1 MHz for 5 min at 25 °C was shown to be more effective for fat separation than the other conditions tested with and without ultrasound, resulting in a relative change from 3.5 ± 0.06% (w/v) fat initially, of −52.3 ± 2.3% (reduction to 1.6 ± 0.07% (w/v) fat) in the skimmed milk layer and 184.8 ± 33.2% (increase to 9.9 ± 1.0% (w/v) fat) in the top layer, at an average skimming rate of ∼5 g fat/min. A shift in the volume weighted mean diameter (D[4,3]) of the milk samples obtained from the top and bottom of between 8% and 10% relative to an initial sample D[4,3] value of 4.5 ± 0.06 μm was also achieved under these conditions. In general, faster fat separation was seen in natural milk when natural creaming occurred at room temperature and this separation trend was enhanced after the application of high frequency ultrasound.     

Ultrasound-assisted polysaccharide extraction from Cercis chinensis and properites,antioxidant activity of polysaccharide

The purpose of the study was to improve the extraction of polysaccharide from the leaves of Cercis chinensis Bunge using ultrasound, and compare the difference between boiling and ultrasound extraction in terms of polysaccharide content, monosaccharide compounds, and evaluate how the factors affected the bioactivity. The best conditions, according to the single factor experiments and the Box-Bohnken design (BBD), were an intensity of ultrasound of 180 W, duration of extraction of 40 min, proportion of water to material of 15:1 (g/g), and a higher polysaccharide yield of 20.02 ± 0.55 (mg/g) than in boiling extraction (16.09 ± 0.82 mg/g). The antioxidative experiment suggested the polysaccharide by ultrasound exhibited higher DPPH, hydroxyl radical scavenging capacities, and reducing power at 1.2–1.4 mg/mL, which was superior to the boiling polysaccharide. Further analysis showed that the ultrasonic purified polysaccharides like Gla, N-Glu, and GluA contained more total sugar and uronic acids than the boiling method did. This may indicate that the ultrasonic isolation of the polysaccharides increase the antioxidant activity of the polysaccharides.     

Effects of sonication on the in vitro digestibility and structural properties of buckwheat protein isolates

The present work investigated the effects of sonication at different amplitudes and durations on the in vitro digestibility of buckwheat protein isolates (BPIs). The conformation, particle size and microstructures of the BPIs were also studied to explicate the possible mechanisms of the sonication-induced changes. The results showed that sonication conditions of 20 kHz, pulsed on-time 10 s, off-time 5 s, amplitude of 60% and duration of 10 min (SA6T10) improved the digestibility of BPIs from 41.4% (control) to 58.2%. The tertiary structure analysis showed that sonication exposed the hydrophobic core buried inside the protein molecules and broke the intramolecular crosslinks, based on the increase in the surface hydrophobicity and intrinsic fluorescence and the decrease in the disulphide content. The secondary structure analysis showed that SA6T10 decreased the content of β-turn and β-sheet by 40.9% and 22.4%, respectively, and increased the content of anti-parallel β-sheet, random coil, and α-helix by 40.9%, 30.6%, and 25.5%, respectively. The particle size of the control BPIs (427.7 ± 76.7 nm) increased to 2130.8 ± 356.2 nm in the SA6T10 sonicated sample with a corresponding decrease in the polydispersity index from 0.97 ± 0.04 to 0.51 ± 0.13. Moreover, scanning electron microscopy indicated that sonication broke the macroparticles into smaller fragments and changed the surface state of the proteins. Taken together, sonication has proven to be a promising approach for improving the digestibility of buckwheat proteins, which can be explored as a source of plant-based alternative protein for food applications.     

Effect of melt-processing and ultrasonic treatment on physical properties of high-amylose maize starch

High-amylose maize starch (Hylon VII) was submitted to melt-processing in an internal mixer at 100 °C and 40 rpm for 8 min. Glycerol was used as a plasticiser at different polymer/glycerol ratios. Torque and temperature curves were obtained. After glycerol extraction with ethyl alcohol, the samples were dispersed at 5 g/L, and treated by ultrasound radiation at the same conditions for 30 min. Samples were characterised by ¹H NMR spectrometry, viscosity measurements, and X-ray diffractometry. The results revealed that both glycerol and water had an important role on the crystallinity properties of the resulting products. Melt-processed and sonicated samples showed similar ¹H NMR spectra. Ultrasound treatment caused a significant reduction in intrinsic viscosity for the sample previously processed with the highest glycerol content, probably because of its higher solubility in water.     

Molecular weight distribution,rheological property and structural changes of sodium alginate induced by ultrasound

In this study, the effects of ultrasound with different ultrasonic frequencies on the properties of sodium alginate (ALG) were investigated, which were characterized by the means of the multi-angle laser light scattering photometer analysis (GPC-MALLS), rheological analysis, circular dichroism (CD) spectrometer and scanning electron microscope (SEM). It showed that the molecular weight (M_w) and molecular number (M_n) of the untreated ALG was 1.927 × 10⁵ g/mol and 4.852 × 10⁴ g/mol, respectively. The M_w of the ultrasound treated ALG was gradually increased from 3.50 × 10⁴ g/mol to 7.34 × 10⁴ g/mol while the M_n of ALG was increased and then decreased with the increase of the ultrasonic frequency. The maximum value of M_n was 9.988 × 10⁴ g/mol when the ALG was treated by ultrasound at 40 kHz. It indicated that ultrasound could induce ALG degradation and rearrangement. The number of the large molecules and small molecules of ALG was changed by ultrasound. The value of d_n/d_c suggested that the ultrasound could enhance the stability of ALG. Furthermore, it was found that ALG treated by ultrasound at 50 kHz tended to be closer to a Newtonian behavior, while the untreated and treated ALG solutions exhibited pseudoplastic behaviours. Moreover, CD spectra demonstrated that ultrasound could be used to improve the strength of the gel by changing the ratio of M/G, which showed that the minimum ratio of M/G of ALG treated at 135 kHz was 1.34. The gel-forming capacity of ALG was correlated with the content of G-blocks. It suggested that ALG treated by ultrasound at 135 kHz was stiffer in the process of forming gels. The morphology results indicated that ultrasound treatment of ALG at 135 kHz increased its hydrophobic interaction and interfacial activity. This study is important to explore the effect of ultrasound on ALG in improving the physical properties of ALG as food additives, enzyme and drug carriers.     

Effects of ultrasound treatment on the starch properties and oil absorption of potato chips

As a non-thermal processing method, the ultrasound treatment prior to the frying process has been demonstrated with great potential in reducing the oil absorption of fried food. This research aimed to evaluate the effect of ultrasound pretreatment on starch properties, water status, pore characteristics, and the oil absorption of potato slices. Ultrasound probe set with two power (360 W and 600 W) at the frequency of 20 kHz for 60 min was applied to perform the pretreatments. The results showed that ultrasound pretreatment led to the surface erosion of starch granules and higher power made the structure of starch disorganized. Moreover, the fraction of bound water and immobilized water were changed after ultrasonic pretreatment. Pores with the minor diameters (0.4–3 μm and 7–12 μm) were formed after ultrasound pretreatment. The penetrated surface oil (PSO) content, and structure oil (STO) content were reduced by 27.31% and 22.25% respectively with lower power ultrasound pretreatment. As the ultrasound power increased, the surface oil (SO) content and PSO content increased by 25.34% and 12.89% respectively, while STO content decreased by 38.05%. By using ultrasonic prior to frying, the quality of potato chips has been greatly improved.     

Ultrasonic pretreatment of corn slurry for saccharification: A comparison of batch and continuous systems

The effects of ultrasound on corn slurry saccharification yield and particle size distribution was studied in both batch and continuous-flow ultrasonic systems operating at a frequency of 20 kHz. Ground corn slurry (28% w/v) was prepared and sonicated in batches at various amplitudes (192–320 μm_{peak-to-peak (p–p)}) for 20 or 40 s using a catenoidal horn. Continuous flow experiments were conducted by pumping corn slurry at various flow rates (10–28 l/min) through an ultrasonic reactor at constant amplitude of 12 μm_p–p. The reactor was equipped with a donut shaped horn. After ultrasonic treatment, commercial alpha- and gluco-amylases (STARGEN^TM 001) were added to the samples, and liquefaction and saccharification proceeded for 3 h. The sonicated samples were found to yield 2–3 times more reducing sugars than unsonicated controls. Although the continuous flow treatments released less reducing sugar compared to the batch systems, the continuous flow process was more energy efficient. The reduction of particle size due to sonication was approximately proportional to the dissipated ultrasonic energy regardless of the type of system used. Scanning electron microscopy (SEM) images were also used to observe the disruption of corn particles after sonication. Overall, the study suggests that both batch and continuous ultrasonication enhanced saccharification yields and reduced the particle size of corn slurry. However, due to the large volume involve in full scale processes, an ultrasonic continuous system is recommended.     

Improvement in enzymolysis efficiency and changes in conformational attributes of corn gluten meal by dual-frequency slit ultrasonication action

The influences of dual-frequency slit ultrasound (DFSU) pretreatment with various working parameters on the enzymolysis efficiency and conformational characteristics of corn gluten meal (CGM) were studied. Results indicated that under the conditions of ultrasonic power density of 80 W/L, time of 30 min, ultrasonic intermittent ratio of 5:2 s/s, temperature of 30 °C, and substrate concentration of 50 g/L, the relative enzymolysis efficiency (REE) of CGM reached a maximum of 21.05%, and the protein dissolution rate was 68.50%. In addition, ultrasonication had considerable impact on the conformation of CGM and consequently improved the susceptibility to alcalase proteolysis. Changes in free sulfhydryl (SH_F) and disulfide bonds (SS) groups indicated spatial conformation of CGM was altered following sonication (sonochemical) treatment. Fourier Transform Infrared Spectrum (FITR) analysis showed a reduction in α-helix and β-turn content; and an increase in β-sheet and random coil content of CGM. Alterations in the particle size, particle size distribution, microstructure and surface roughness (R_a, R_q) indicated generation of smaller and more uniform protein fragments of CGM by sonochemical pretreatment. The proposed mechanism of sonicated CGM was elaborated. Our findings suggest that using DFSU in pretreating CGM may be an efficacious approach to enhance proteolysis.