Structural and physicochemical properties of lotus seed starch nanoparticles prepared using ultrasonic-assisted enzymatic hydrolysis

Lotus seed starch nanoparticles were prepared by ultrasonic (ultrasonic power: 200 W, 600 W, 1000 W; time: 5 min, 15 min, 25 min; liquid ratio (starch: buffer solution): 1%, 3%, 5%) assisted enzymatic hydrolysis (LS-SNPs represent lotus seed starch nanoparticles prepared by enzymatic hydrolysis and U-LS-SNPs represent lotus seed starch nanoparticles prepared by high pressure homogenization-assisted enzymatic hydrolysis). The structure and physicochemical properties of U-LS-SNPs were studied by laser particle size analysis, scanning electron microscope, X-ray diffraction, Raman spectroscopy, nuclear magnetic resonance and gel permeation chromatography system. The results of scanning electron microscopy showed that the surface of U-LS-SNPs was cracked and uneven after ultrasonic-assisted enzymolysis, and there was no significant difference from LS-SNPs. The results of particle size analysis and gel permeation chromatography showed that the particle size of U-LS-SNPs (except 5% treatment group) was smaller than that of LS-SNPs. With the increase of ultrasonic power and time, the weight average molecular gradually decreased. The results of X-ray diffraction and Raman spectroscopy showed that ultrasonic waves first acted on the amorphous region of starch granules. With the increase of ultrasonic power and time, the relative crystallinity of U-LS-SNPs increased first and then decreased. The group (600 W, 15 min, 3%) had the highest relative crystallinity. The results of nuclear magnetic resonance studies showed that the hydrogen bond and double helix structure of starch were destroyed by ultrasound, and the double helix structure strength of U-LS-SNPs was weakened compared with LS-SNPs. In summary, U-LS-SNPs with the small-sized and the highest crystallinity can be prepared under the conditions of ultrasonic power of 600 W, time of 15 min and material-liquid ratio of 3%.     

Impact of ultrasonication on the aggregation structure and physicochemical characteristics of sweet potato starch

In order to understand the relationship between the aggregation structure and physicochemical characteristics of ultrasonicated sweet potato starches, sweet potato starch modified with different sonication time (15, 20, 25 and 30 min) was studied in this work for developing starch-based ingredients with tailored functionality. SEM, XRD, FTIR, Raman and DSC measurements were conducted to investigate the transformations of morphological features, crystalline structure, short-range ordered structure and ordered molecular structure of starch granules. Not only could pores and cracks be observed at the surface of starch, but also the structural disorganizations were more evidently induced with the treatment time increasing, especially for the degrees of crystallinity, short-range molecular orders and ordered molecular structures. And these disordering in the aggregation structure not only increased the swelling power and solubility but also declined the pasting temperature, peak viscosity, final and breakdown viscosity of gelatinized starch. In addition, the strengthened retrogradation and gel structures formed by the rearrangement and entanglement of starch polymer chains also demonstrated the structural disorganizations of starch granules during ultrasonic treatment. Therefore, the results of this study may provide further insight in understanding the structural basis of starch physicochemical properties.     

Modulating the in vitro digestibility of chemically modified starch ingredient by a non-thermal processing technology of ultrasonic treatment

Chemically modified starch (RS4) was commercially available as a food ingredient, however, there was a lack of knowledge on how ultrasonic treatment (non-thermal technology) modulated the enzymatic resistance of RS4. In this study, structural change of RS4 during ultrasonic treatment and its resulting digestibility was investigated. Results from scanning electron microscopy, particle size analysis, chemical composition analysis, X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy showed that ultrasonic treatment remained the granule morphology, increased the apparent amylose content, reduced the particle size, destroyed the crystalline structure, decreased the helical orders, but enhanced the short-range molecular orders of ultrasonic-processed RS4. In vitro digestibility analysis showed that the total content of rapidly digestible starch and slowly digestible starch was increased, whereas the content of resistant starch was decreased. Overall, ultrasonic treatment substantially reduced the enzymatic resistance of RS4, indicating that RS4 was not stability against the non-thermal processing technology of ultrasonic treatment.     

Physicochemical,structural, and digestive properties of pea starch obtained via ultrasonic-assisted alkali extraction

As a new and clean extraction technology, ultrasonic extraction has been demonstrated with great potential in the preparation of modified starch. In order to increase its added value, it is necessary to modify pea starch to enlarge its application. In this study, the efficiency of combining ultrasonic with alkali in the extraction of pea starch was evaluated and compared to conventional alkali extraction. Ultrasonic-assisted alkali extraction conditions were optimized using single-factor experiments and response surface methodology. The results revealed that maximum yield of pea starch (54.43 %) was achieved using ultrasound-assisted alkali extraction under the following conditions: sodium hydroxide solution with a concentration of 0.33 %, solid/alkali solution ratio of 1:6 (w/v), ultrasonic power of 240 W, temperature of 42 °C, and extraction time of 22 min. The ultrasound-assisted alkali extraction yielded 13.72 % greater pea starch than conventional alkali extraction. On the other hand, morphological, structural, and physicochemical properties of the obtained starch isolates were evaluated. The ultrasound-assisted alkali extraction resulted in pea starch with greater amylose content, water-solubility, swelling power, and viscosity compared with conventional alkali extraction. Furthermore, ultrasonication influenced the morphological properties of pea starch granules, while the molecular structure and crystal type were not affected. Moreover, the ultrasonic-assisted extraction produced starch with a slightly greater resistant starch content. Therefore, ultrasonic-assisted extraction can be suggested as a potential method for extracting pea starch with improved functional properties.     

氢键对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响

本文在杂化密度泛函理论水平上研究了溶剂对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响.在溶剂中,构造了包括氢键作用的超分子体系,在优化结构的基础上分别研究了由极化连续模型模拟的溶剂与该分子的长程相互作用、溶剂与该分子的氢键相互作用以及溶剂与包括氢键作用的超分子体系整体的相互作用对分子的几何结构、非线性光学性质、紫外吸收光谱和电荷分布等特性的影响.结果表明,溶剂中分子电偶极矩、线性极化率和第一超极化率都增大,而溶剂与溶质分子通过氢键形成的超分子结构与单体有着明显区别.因此,氢键对分子结构和性质的影响较大,从而将明显的影响该类分子的非线性光学性质.     

Preparation and characterization of highly lipophilic modified potato starch by ultrasound and freeze-thaw treatments

In order to explore the potential application of combined physical treatment in producing highly lipophilic modified starch, the effects of ultrasound combined with freeze-thaw treatment on the microstructure and physicochemical properties of potato starch were investigated. The samples treated by combined treatment had the roughest structure and the oil adsorptive capacity value increased from 59.62% (native starch, NS) to 80.2% (7 cycles of ultrasound-freeze-thaw treatment starch, 7UT-FTS). Compared to NS, the crystalline type and chemical groups of modified starches did not change, but the relative crystallinity, enthalpy change, and paste viscosity decreased to varying degrees, while the gelatinization temperature increased. The digestibility of raw modified starch was higher than that of NS, but this phenomenon disappeared after gelatinization. 7UT-FTS showed better resist-digestibility than NS after encapsulating oil. Hence, this would be an efficient and environmentally friendly way to produce modified starch with safety, highly lipophilic and heat resistance.     

Combined ultrasound and germination treatment on the fine structure of highland barley starch

Highland barley is a grain crop grown in Tibet, China. This study investigated the structure of highland barley starch using ultrasound (40 kHz, 40 min, 165.5 W) and germination treatments (30℃ with 80% relative humidity). The macroscopic morphology and the barley's fine and molecular structure were evaluated. After sequential ultrasound pretreatment and germination, a significant difference in moisture content and surface roughness was noted between highland barley and the other groups. All test groups showed an increased particle size distribution range with increasing germination time. FTIR results also indicated that after sequential ultrasound pretreatment and germination, the absorption intensity of the intramolecular hydroxyl (–OH) group of starch increased, and hydrogen bonding was stronger compared to the untreated germinated sample. In addition, XRD analysis revealed that starch crystallinity increased following sequential ultrasound treatment and germination, but a-type of crystallinity remained after sonication. Further, the Mw of sequential ultrasound pretreatment and germination at any time is higher than that of sequential germination and ultrasound. As a result of sequential ultrasound pretreatment and germination, changes in the content of chain length of barley starch were consistent with germination alone. At the same time, the average degree of polymerisation (DP) fluctuated slightly. Lastly, the starch was modified during the sonication process, either prior to or following sonication. Pretreatment with ultrasound illustrated a more profound effect on barley starch than sequential germination and ultrasound treatment. In conclusion, these results indicate that sequential ultrasound pretreatment and germination improve the fine structure of highland barley starch.     

The ex-situ and in-situ ultrasonic assisted oxidation of corn starch: A comparative study

The objective of this study was to evaluate the differences in ex-situ (starch treated by ultrasonication and oxidation sequentially, U-OS) and in-situ (starch treated by ultrasonication and oxidation simultaneously, UOS) ultrasonic assisted oxidation process of corn starch, which were studied in contrast to the traditional oxidized starches (OS). Fourier-transform infrared spectra confirmed the successful oxidation of all modified starches samples. In comparison to the OS, the carboxyl contents of U-OS and UOS increased by 56% and 112%, respectively. The same increase trend was also found for the carbonyl contents. The significance raise was attributed to the great increase of pores and specific surface areas in the starch granule after ultrasonic irradiation which promoted the penetration of the sodium hypochlorite into the starch granules with higher chances for chemical reactions. SEM and pore size distribution characterizations further verified this result. However, the method of in-situ ultrasonic assisted oxidation can simultaneously accelerate the increase of pores and the penetration process. Consequently, the starches with higher oxidation degree can be more efficiently prepared by the strategy of in-situ ultrasonic assisted oxidation.     

Ultrasound based modification and structural-functional analysis of corn and cassava starch

In this study, the starch molecules were modified with ultrasonication at two different time intervals by using starch molecules from corn and cassava. This research aimed to examine the effect of the high power ultrasound of 40 kHz voltage and frequency with short time duration on structural and physical properties of corn and cassava starch. Morphology of ultrasonically treated starch granules was observed by scanning electron microscopy (SEM), FTIR, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) and compared with untreated samples. After the ultrasound treatment groove and notch appeared on the surface of the starch granules. The results showed that gelatinization temperature did not change with ultrasound treatments, but enthalpy value decreased from 13.15 ± 0.25 J/g to 11.5 ± 0.29 J/g and 12.65 ± 0.32 J/g to 10.32 ± 0.26 J/g for sonicated corn and cassava starches, respectively. The XRD results revealed a slight decreased in the crystallinity degree (CD) of sonicated corn (25.3,25.1) and cassava starch (21.0,21.4) as compared to native corn (25.6%) and cassava starch (22.2%). This study suggests that non-thermal processing techniques have the potential to modify the starch from different sources and their applications due to starch’s versatility, low cost, and comfort of use after processing with altered physicochemical properties.     

光谱法比较木犀草素及槲皮素与牛血清白蛋白相互作用

在模拟生理pH条件下,采用荧光光谱、紫外-可见吸收光谱、同步荧光光谱和圆二色谱法研究木犀草素及槲皮素与牛血清白蛋白（BSA）的相互作用的异同.结果确定木犀草素及槲皮素对BSA的荧光猝灭是以静态猝灭为主,同时伴随非辐射能量转移猝灭.木犀草素结合BSA的位点与荧光发射基团的距离比槲皮素的小.结合常数Ka表明二者与BSA的结合都属于强的非共价键结合,且结合位点数都约为1.二者均主要通过氢键和范德华力与BSA作用.二者都能影响BSA的酪氨酸残基附近环境的极性,且高浓度下能够引起BSA构象轻微地改变.结果表明黄酮C环上3位羟基的引入会降低其对BSA的亲和力.     

Influence of milk fat globule membrane and milk protein concentrate treated by ultrasound on the structural and emulsifying stability of mimicking human fat emulsions

The primary objective of the present study was to investigate the effectiveness of ultrasonic treatment time on the particle size, molecular weight, microstructure and solubility of milk fat globule membrane (rich in phospholipid, MPL) and milk protein concentrate (MPC). The mimicking human fat emulsions were prepared using modified proteins and compound vegetable oil and the structural, emulsifying properties and encapsulation efficiency of emulsions were evaluated. After ultrasonic treatment, the cavitation caused particle size decreased and structure change of both MPL and MPC, resulting in the enhancement of protein solubility. While, there was no significant change in molecular weight. Modified proteins by ultrasonic may cause a reduction in particle size and an improvement in emulsifying stability and encapsulation efficiency of emulsions. The optimal ultrasonic time to improve functional properties of MPL emulsion and MPC emulsion were 3 min and 6 min, respectively. The emulsifying stability of MPL emulsion was superior to MPC emulsion, which indicated that MPL is more suitable as membrane material to simulate human fat. Therefore, the obtained results can provide basis for quality control of infant formula.     

First principle studies on electronic structure and charge density of potato starch

The electronic and chemical bonding properties of biomaterial potato starch within the density functional theory are presented in this paper, with the aim to be used in electrochemical devices and biomedical applications. In the density of states and projected density of states analysis, the energy difference between the highest occupied molecular orbital and lowest unoccupied molecular orbital is reduced by 2.9 eV, which exhibits the semi-conducting behaviour of modified potato starch in the presence of NaI salt. Calculated charge density predicts the bonding properties and crystal orbital overlap population analysis exhibits the increase of amorphous nature and ionic conductivity due to sodium ion concentration. In this theoretical study, different behaviours of modified potato starch are clearly seen in the presence of NaI salt.

     

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.     

Effect of ultrasonic on the structure and quality characteristics of quinoa protein oxidation aggregates

Protein oxidation leads to covalent modification of structure and deterioration of functional properties of quinoa protein. The objective of this study was to investigate the effects of ultrasonic treatment on the functional and physicochemical properties of quinoa protein oxidation aggregates. In this concern, 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) was selected as oxidative modification of quinoa protein. The microstructure of quinoa protein displayed by scanning electron microscope (SEM) indicated that oxidation induced extensive aggregation, leading to carbonylation and degradation of sulfhydryl groups. Aggregation induced by oxidation had a negative effect on the solubility, turbidity, emulsifying stability. However, according to the analysis of physicochemical properties, ultrasonic significantly improved the water solubility of quinoa protein. The quinoa protein treated by ultrasonic for 30 min exhibited the best dispersion stability in water, which corresponded to the highest ζ-potential, smallest particle size and most uniform distribution. Based on the FT-IR, SDS-PAGE and surface hydrophobicity analysis, the increase of α-helix, β-turn and surface hydrophobicity caused by cavitation effect appeared to be the main mechanism of quinoa protein solubilization. In addition, the hydrophobic region of the protein was re-buried by excessive ultrasonic treatment, and the protein molecules were reaggregated by disulfide bonds. Microstructural observations further confirmed that ultrasonic treatment effectively inhibited protein aggregation and improved the functional properties of quinoa protein.     

High intensity ultrasound treatment of protein isolate extracted from dephenolized sunflower meal: Effect on physicochemical and functional properties

The influence of high intensity ultrasound (HIUS) on physicochemical and functional properties of sunflower protein isolates was investigated. Protein solutions (10% w/v) were treated with ultrasound probe (20 kHz) and ultrasound bath (40 kHz) for 5, 10, 20 and 30 min. Thermal stability of protein isolates was reduced as indicated by differential scanning calorimetry. Minimum thermal stability was observed at 20 min of sonication and increased further with increase in treatment time indicating aggregation at prolonged sonication. SDS-PAGE profile of proteins showed a significant reduction in molecular weight. Further, surface hydrophobicity and sulfhydryl content increased after HIUS treatment indicating partial unfolding of proteins and reduction in the intermolecular interactions. The particle size analysis showed that HIUS treatment reduced the particle size. Less turbid solution were observed largely due to reduction in particle size. HIUS decreased the available lysine content in protein isolates. Solubility, emulsifying capacity, emulsion stability, foaming capacity, foam stability and oil binding capacity were improved significantly, while as, water binding capacity was decreased. The effect of HIUS on physicochemical and functional properties of sunflower protein isolates was more pronounced in probe sonication rather than bath sonication. Protein isolates with improved functional properties can be obtained using high intensity ultrasound technology.     

The non-ideal solvation of NaCl in solvent: a simulation study

The non-ideality of the solvation of NaCl in a family of modified hybrid water solvent environments with varying local structural order is investigated using intensive molecular dynamics simulations. The results show that there are ion clusters of different size in all environments studied. The size distribution of the ion clusters is sensitive to the local structure of the solvent, which is determined by the hydrogen bonding strength. The ions are inclined to be in contact in solvents with high translational order, for competition between structure breaking among solvent molecules and structure formation around hydrated ions.     

Dependence of thermodynamic properties of model systems on some dissipative particle dynamics parameters

The influence of systematic perturbation of input interaction parameters on thermodynamic equilibrium properties is studied employing dissipative particle dynamics (DPD) simulations. The values of both the excess pressure and the surface tension are found to be very sensitive to the values of the soft repulsion parameter between unlike DPD particles for high values of the coarse-graining level (number of water molecules per DPD particle). For the case in which a molecular surfactant is present at the interface we have determined the dependence of these properties on the values of the parameters that characterize the bonding force between polymer beads. No significant differences were found between linear and branched surfactants.     

Effects of ultrasonic–microwave combination treatment on the physicochemical,structure and gel properties of myofibrillar protein in Penaeus vannamei (Litopenaeus vannamei) surimi

The objective of this study was to evaluate the effects of single ultrasound (360 W, 20 min), single microwave (10 W/g, 120 s) and ultrasonic–microwave combination treatment on shrimp surimi gel properties. The structure and physicochemical properties of myofibrillar protein (MP) were also determined. Low-field nuclear magnetic resonance showed that the fluidity of water molecules and the moisture content decreased, the stability and water holding capacity (WHC) increased after single ultrasound, single microwave and ultrasonic–microwave combination treatment. Compared with the traditional water bath treatment, ultrasound and microwave treatment reduced the total sulfhydryl content and promoted the formation of intermolecular disulfide bonds and hydrophobic interactions, which improved the compactness of the network structure of shrimp surimi gel. Moreover, Fourier transform infrared spectroscopy and sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis revealed that these treatments not only inhibited the degradation of MP, but also decreased the α-helix content and increased the β-sheet content. The three treatments also significantly reduced the particle size and decreased the solubility of MP. Overall, the effect of ultrasonic–microwave combination treatment was superior to that of either single treatment.     

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.     

三种蛋白和黄酮结合物中氢键与黄酮稳定性相关性分析研究

运用三维荧光光谱、紫外可见分光光谱以及傅里叶红外光谱等手段研究了蛋白与黄酮分子的相互作用,并结合相关性分析的统计学手段分析了蛋白与黄酮分子相互作用方式对黄酮稳定性的影响。实验结果表明,疏水相互作用是三种蛋白与黄酮分子之间主要的作用力,在牛血清白蛋白与黄酮的结合中有氢键的参与,同时发现在牛血清白蛋白体系中黄酮的稳定性明显增强。通过相关性分析证明蛋白对黄酮稳定性的提高与两者之间的分子间氢键有关,氢键结合作用越强蛋白对黄酮保护越明显。