Effects of High-Intensity Ultrasound Pretreatment on Structure, Properties, and Enzymolysis of Walnut Protein Isolate.

The purpose of this paper was to investigate the effect of high-intensity ultrasonication (HIU) pretreatment before enzymolysis on structural conformations of walnut protein isolate (WPI) and antioxidant activity of its hydrolysates. Aqueous WPI suspensions were subjected to ultrasonic processing at different power levels (600-2000 W) and times (5-30 min), and then changes in the particle size, zeta (ζ) potential, and structure of WPI were investigated, and antioxidant activity of its hydrolysates was determined. The particle size of the particles of aqueous WPI suspensions was decreased after ultrasound, indicating that sonication destroyed protein aggregates. The ζ-potential values of a protein solution significantly changed after sonication, demonstrating that the original dense structure of the protein was destroyed. Fourier transform infrared spectroscopy indicated a change in the secondary structure of WPI after sonication, with a decrease in ß-turn and an increase in α-helix, ß-sheet, and random coil content. Two absorption peaks of WPI were generated, and the fluorescence emission intensity of the proteins decreased after ultrasonic treatment, indicating that the changes in protein tertiary structure occurred. Moreover, the degree of hydrolysis and the antioxidant activity of the WPI hydrolysates increased after sonication. These results suggest that HIU pretreatment is a potential tool for improving the functional properties of walnut proteins.

Effects of high starch content on the physicochemical properties of starch/PBAT nanocomposite films prepared by extrusion blowing.

Starch/PBAT nanocomposite films with high starch content were prepared using one-step compounding and subsequent extrusion blowing. The effects of the starch/PBAT weight proportions on the physicochemical properties of the films were investigated. The X-ray diffraction results demonstrated that the extent of intercalation of the starch/PBAT nanocomposite films increased with the increasing PBAT content. The dynamic mechanical analysis revealed that the compatibility of starch and PBAT improved with increasing PBAT content from 10 wt% to 50 wt%. The strength and flexibility of the films were greatly improved by blending with PBAT. The maximum tensile strength and elongation at break of the starch/PBAT nanocomposite films were 7.4 MPa and 614 %, respectively. The water-vapor barrier properties and hydrophobicity of the films were significantly improved with the increase in the PBAT content. The blown starch/PBAT nanocomposite films incurred low cost and demonstrated excellent mechanical and hydrophobic properties, which are suitable for the food-packaging field.

Effects of preparation conditions on the properties of agar/maltodextrin-beeswax pseudo-bilayer films.

The present study aims to develop an agar/maltodextrin-beeswax (A/M-BW) pseudo-bilayer film with high surface hydrophobicity by adjusting drying temperatures and homogenization conditions. Attenuated total reflectance-Fourier transform infrared determined the chemical components of the upper and lower surfaces of the films. X-ray diffraction characterized the crystalline behavior of film matrix. Scanning electron microscopy explored the distribution patterns of BW and phase separation phenomenon. Atomic force microscopy revealed the surface roughness of film. The pseudo-bilayer film prepared at 8000 rpm for 1 min (A/M-BW-8000-1) had the highest tensile strength (20.57 MPa), Young's modulus (640.60 MPa), contact angle (92.9°), and the lowest water vapor permeability (2.18 × 10-12 g m-1 s-1 Pa-1). The A/M-BW pseudo-bilayer film with excellent surface hydrophobicity and mechanical properties was obtained at higher drying temperature and lower homogenization intensity. The A/M-BW pseudo-bilayer film has promising potential for application in food packaging which requires higher water vapor resistance.

Ultrasound-assisted preparation of octenyl succinic anhydride modified starch and its influence mechanism on the quality.

The purpose of this study was to reveal the influence mechanism of preparing high quality modified starch by ultrasonic-assisted treatment. In this paper, ultrasonic modified starch and octenyl succinic anhydride (OSA) modified starch were prepared under ultrasonic conditions. The effect of ultrasound on the structure and properties of native starch were studied to see whether ultrasound could produce mechanochemical effect on starch granules. Then the mechanism of ultrasonic effect on the quality of OSA-modified starch was revealed by mechanochemical effect. The results showed that the morphology and crystalline regions of starch granules were destroyed after ultrasonic treatment, and the structure and properties of starch granules changed in different stages. These changes showed that ultrasonic treatment produced significant mechanochemical effect on starch granules. Thus the quality of OSA-modified starch prepared by ultrasonic-assisted treatment was improved significantly, and its influence mechanism was analyzed using the theory of mechanochemistry.

Degradation and ozonolysis pathway elucidation of deoxynivalenol.

To explore the degradation products and ozonolysis pathway of deoxynivalenol (DON), DON (~50 mg/L) in acetonitrile solution was treated by ozone at a concentration of 10.84 g/m3 and a flow rate of 80 mL/min for the times ranging from 0 to 9 min. The results showed that DON concentration rapidly reduced from 51.11 mg/L to 14.97 mg/L within 9 min of ozone exposure with 98.30% of degradation rate, and the ozonolysis of DON followed the first-order kinetic model. Four ozonolysis products of DON were identified based on the analysis of Liquid chromatography-quadrupole time-of-flight mass spectra (LC-QTOF/MS). Their structures were similar to that of DON, while the double bond at C9-C10, 12,13-epoxide ring, and the hydroxyl group at C3 or C7 of DON were all destroyed by ozone. It is deduced that the toxicity of ozonolysis products significantly reduced based on the relationship between structure and toxicity of DON. The ozonolysis pathway of DON followed the Criegee reaction mechanism of ozone according to the chemical structures, accurate mass and molecular formulas of these products.

Mechanochemical effect of ultrasound on sweet potato starch and its influence mechanism on the quality of octenyl succinic anhydride modified starch.

The purpose of this study is to reveal the mechanism of preparing high quality modified starch by ultrasonic technology. In this paper, ultrasonic modified starch and octenyl succinic anhydride modified starch with low degree of substitution were prepared under ultrasonic conditions, using sweet potato starch as raw material. The effects of ultrasound on the structure and properties of native sweet potato starch were studied to see whether ultrasound could produce mechanochemical effect on starch. Then the mechanism of ultrasonic effect on quality of octenyl succinic anhydride modified starch was studied by mechanochemical effect. The results showed that after ultrasonic treatment for 1 min, the crystallinity decreased from 37.6 to 33.8% and reaction efficiency increased from 49.43 to 54.39%, while after ultrasonic treatments for 8 and 32-60 min had different changes. These changes showed that ultrasonic treatment produced significant mechanochemical effect on native sweet potato starch. Ultrasound significantly improved the quality of octenyl succinic anhydride modified starch, and its influence mechanism was revealed using the theory of mechanochemistry. This study provides a feasible method for the research of high quality modified starch and lays a theoretical foundation for expanding the application of ultrasound in various fields.

Effects of Preparation Method on the Physicochemical Properties of Cationic Nanocellulose and Starch Nanocomposites.

Nanocellulose (NC) has attracted attention in recent years for the advantages offered by its unique characteristics. In this study, the effects of the preparation method on the properties of starch films were investigated by preparing NC from cationic-modified microcrystalline cellulose (MD-MCC) using three methods: Acid hydrolysis (AH), high-pressure homogenization (HH), and high-intensity ultrasonication (US). When MD-MCC was used as the starting material, the yield of NC dramatically increased compared to the NC yield obtained from unmodified MCC and the increased zeta potential improved its suspension stability in water. The NC prepared by the different methods had a range of particle sizes and exhibited needle-like structures with high aspect ratios. Fourier transform infrared (FTIR) spectra indicated that trimethyl quaternary ammonium salt groups were introduced to the cellulose backbone during etherification. AH-NC had a much lower maximum decomposition temperature (Tmax) than HH-NC or US-NC. The starch/HH-NC film exhibited the best water vapor barrier properties because the HH-NC particles were well-dispersed in the starch matrix, as demonstrated by the surface morphology of the film. Our results suggest that cationic NC is a promising reinforcing agent for the development of starch-based biodegradable food-packaging materials.

Cytotoxicity of Deoxynivalenol after Being Exposed to Gaseous Ozone.

In this study, deoxynivalenol (DON) in aqueous solution was exposed to gaseous ozone for periods ranging from 0 to 20 min. The degradation efficiency and cytotoxicity of DON were investigated after being treated by ozone. The results showed that DON was rapidly degraded from 10.76 ± 0.09 mg/L to 0.22 ± 0.04 mg/L within 15 min (P < 0.05), representing a reduction of 97.95%, and no DON was detected after being exposed to 14.50 mg/L of ozone at a flow rate of 80 mL/min for 20 min. The degradation of DON depended on the ozone exposure time, and followed the first-order kinetic model (R2 = 0.9972). Human hepatic carcinoma (HepG2) and Henrietta Lacks (Hela) cells were used to evaluate the cytotoxicity of DON treated by ozone using the 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. The half-maximal inhibitory concentrations (IC50) values of DON on HepG2 and Hela cells were 2.10 and 1.33 mg/L after 48 h of exposure, respectively, and showed a dose-dependent manner. The cell vitalities of HepG2 and Hela cells on DON were both evidently improved after being exposed to ozone for 15 min, and there were no significant differences between the negative control and that treated at 20 min of ozone exposure. Gaseous ozone can potentially be used as a new method to detoxify DON in agricultural products.

Effects of High-Intensity Ultrasound Pretreatment on Structure, Properties, and Enzymolysis of Soy Protein Isolate.

The objective of this study was to investigate the effects of different high-intensity ultrasonication (HIU) pretreatment on the structure and properties of soybean protein isolate (SPI) as well as enzymatic hydrolysis of SPI by bromelain and antioxidant activity of hydrolysates. The HIU-treated SPI fractions showed a decrease in the proportion of α-helices and ß-turns and an increase in the content of ß-sheets and random coils based on Fourier-transform infrared spectroscopy. Near-infrared spectra and fluorescence spectra analyses provided support for the changes in secondary and tertiary structures of SPI after ultrasound treatment. The particle size of SPI decreased from 217.20 nm to 141.23 nm and the absolute zeta potential increased. Scanning electron microscopy showed that HIU treatment changed apparent morphology. Dynamic and static light scattering of ultrasonicated samples showed that SPI structure had changed from hard-sphere to hollow-sphere or polydisperse and monodisperse gaussian coils. HIU pretreatment significantly increased the hydroxyl-radical scavenging and the degree of hydrolysis of the SPI hydrolysates.

Effects of Citric Acid on Structures and Properties of Thermoplastic Hydroxypropyl Amylomaize Starch Films.

Hydroxypropyl amylomaize starch (HPAS) films were prepared by hot press. The effects of initial pH of HPAS on the mechanical properties, molecular interaction, structure, and cross-linking degree of the resultant films were investigated. A weak acidic condition was suitable for cross-linking of citric acid and HPAS by reactive extrusion. The film of HPAS with an initial pH of 5.66 had the maximum tensile strength of 7.20 MPa and elongation-at-break of 94.53%, and the weight average molecular weight of HPAS increased to 4.17 × 105 g/mol. An appropriate initial pH facilitated the formation of diester bonds between HPAS and citric acid during extrusion, but too low initial pH levels resulted in hydrolysis of starch molecules and reduced the mechanical properties.

Influences of grinding on structures and properties of mung bean starch and quality of acetylated starch.

The aim of this study was to reveal the mechanism of preparing high quality modified starch by grinding. Modified starch and acetylated starch with low degree of substitution were prepared under grinding. The influences of grinding on structures and properties of mung bean starch and quality of acetylated starch were investigated. The influence mechanisms were analyzed using the theory of mechanochemistry and the models of starch granules and molecules. The results indicated that there were pores and umbilical points with loose structure in mung bean starch granules. During the grinding treatment, starch granules were constantly deformed like elastic balls, and starch molecules could keep moving and rearrange, resulting in changes in structures and properties of starch. It could be seen that grinding had a marked mechanochemical effect on starch granules. As a result, the reaction efficiency of the starch rose to 81.61% at 12 h of grinding, and other qualities (solubility and swelling power) were also improved.

Effect of Alkali Treatment on Structure and Properties of High Amylose Corn Starch Film.

Alkali treatment is used for melt extrusion film formation with corn starch, but optimal conditions for this procedure are still unknown. In this study, the changes in properties and structure of high amylose corn starch (70%) films with different concentrations of sodium hydroxide (NaOH), prepared by melting extrusion, were investigated. With increasing sodium hydroxide concentrations, the tensile strength of the high-amylose starch film decreased gradually, while the elongation at break increased. The tensile strength of the high amylose starch (HAS) film with 2% NaOH-treatment was 10.03 MPa and its elongation at break was 40%. A 2% NaOH-treatment promoted the orderly rearrangement of starch molecules and formed an Eh-type crystal structure, which enlarged the spacing of the single helix structure, increased the molecular mobility of the starch, and slowed down the process of recrystallization; a 10% NaOH-treatment oxidized the hydroxyl groups of the high amylose corn starch during extrusion, formed a poly-carbonyl structure, and initiated the degradation and cross-linking of starch molecule chains.

Preparation of high quality starch acetate under grinding and its influence mechanism.

The goal of this study is to reveal mechanism of preparing high quality modified starch by advanced equipment in well-known modified starch enterprises. Corn starch was used as raw material to prepare starch acetate with low degree of substitution under grinding, and the effect of grinding on the quality of starch acetate was studied. The effects of grinding on structures and properties of native corn starch were investigated. The mechanochemical theory was used to analyze the influence mechanism of grinding on quality of starch acetate. The results showed that the reaction efficiency (RE) of starch acetate increased from 70.98% to 85.80% at 4 h of grinding, and other qualities (solubility and swelling power) also increased. However, RE and other qualities of starch acetate were very different at 12 and 20-60 h of grinding. The changes of structures and properties of native starch after grinding showed that grinding has a significant mechanochemical effect on corn starch granules. The models of starch molecules and granules were made to reveal the "secret" of these advanced equipment in well-known modified starch enterprises.

High-Pressure Homogenization Pretreatment before Enzymolysis of Soy Protein Isolate: the Effect of Pressure Level on Aggregation and Structural Conformations of the Protein.

The high-pressure homogenization (HPH) treatment of soybean protein isolate (SPI) before enzymatic hydrolysis using bromelain was investigated. Homogenization pressure and cycle effects were evaluated on the enzymatic degree of hydrolysis and the antioxidant activity of the hydrolysates generated. The antioxidant activity of SPI hydrolysates was analyzed by 1,1-dipheny-2-picrylhydrazyl (DPPH). The sizes and structures of the SPI-soluble aggregate after HPH treatment were analyzed using dynamic and static laser light scattering. The changes in the secondary structure, as measured by Fourier transform infrared spectroscopy (FTIR) and the macromorphology of SPI, were measured by scanning electron microscope (SEM). These results suggested that the HPH treatment (66.65%) could increase the antioxidant activities of the SPI hydrolysates compared with the control (54.18%). SPI hydrolysates treated at 20 MPa for four cycles obtained higher DPPH radical-scavenging activity than other samples. The control was predicted to be a hard sphere, and SPI treatment at 10 MPa was speculated to be Gaussian coil, polydisperse, and then the high-pressure treated SPI became a hollow sphere. Changes in the secondary structures showed protein aggregate formation and rearrangements. The image of SPI varied from a globular to a clump structure, as observed by the SEM. In conclusion, combining HPH treatment and enzymolysis could be an effective way to improve the antioxidant activity of the SPI.

Effects of Organic Modification of Montmorillonite on the Properties of Hydroxypropyl Di-Starch Phosphate Films Prepared by Extrusion Blowing.

The knowledge gained from starch-nanocomposite-film research has not been fully applied commercially because of the lack of appropriate industrial processing techniques for nanofillers and starch films. Three organically modified montmorillonites (OMMTs) were prepared using a semidry kneading method. The effects of the OMMTs on the structures and properties of starch nanocomposite films, prepared by extrusion blowing, were investigated. The X-ray diffraction (XRD) analysis results revealed that the OMMTs with various quaternary ammonium salts possessed differing layer structures and d-space values. The results of the XRD and Fourier-transform infrared spectroscopy (FT-IR) showed that the starch⁻OMMT interaction resulted in a structural change, namely the starch⁻OMMT films possessed a balanced exfoliated and intercalated nanostructure, while the starch⁻MMT film possessed an exfoliated nanostructure with non-intercalated montmorillonite (MMT). The results of the solid-state nuclear magnetic resonance (NMR) analysis suggested that the starch-OMMT nanocomposite possessed comparatively large quantities of single-helix structures and micro-ordered amorphous regions. The starch⁻OMMT films exhibited good tensile strength (TS) (maximum of 6.09 MPa) and water barrier properties (minimum of 3.48 × 10−10 g·m·m−2·s−1·Pa−1). This study indicates that the addition of OMMTs is a promising strategy to improve the properties of starch films.

Detoxification and safety evaluation of aflatoxin B1 in peanut oil using alkali refining.

BACKGROUND: Aflatoxin B1 (AFB1 ) is often detected in peanut oil, which comes from contaminated peanuts. AFB1 in peanut oil seriously threatens the health of consumers. However, there are few methods to effectively remove AFB1 in peanut oil. This study aimed to use an alkali-refining method to degrade AFB1 in peanut oil efficiently without increasing the equipment of oil and fat refining. RESULTS: The optimum detoxifying conditions of AFB1 in peanut oil with alkali refining were established using response surface methodology (RSM), and the safety of peanut oil after being refined with alkali was evaluated based on the Ames tests and HepG2 cell viability. The results showed that AFB1 in peanut oil was decreased from 34.78 to 0.37 µg kg(-1) (98.94% reduction) under the optimum detoxifying conditions, i.e. when the initial temperature of alkali refining was 43.51 °C, the amount of excess alkali was 0.30%, the content of alkali solution was 23.42% and the end temperature of alkali refining was 77.07 °C. The acid value and color of peanut oil refined by alkali were improved significantly, while the peroxide value was increased within an acceptable level. The safety of peanut oil contaminated by AFB1 was improved significantly after being refined with alkali. CONCLUSION: These results indicate that alkali refining is an effective method for removing AFB1 in peanut oil. The optimum detoxifying conditions of AFB1 in peanut oil with alkali refining could be used to guide the production of oil companies for ensuring food safety. © 2015 Society of Chemical Industry.

Ozonolysis efficiency and safety evaluation of aflatoxin B1 in peanuts.

Ozonolysis efficiency of aflatoxin-contaminated peanuts (ACPs) was investigated, and the safety of ACPs untreated/treated by ozone was evaluated after 28-day intragastrically administration in male and female Wistar rats. 89.40% of aflatoxin B1 (AFB1) in peanuts was decomposed by ozone with a concentration of 50mg/L, flow rate of 5L/min for 60h. After 60h, the ozonolysis efficiency of AFB1 was not further improved. In the subchronic toxicity experiment, all rats did not have unusual changes in behavior, and no signs of intoxication were observed except for several dead rats due to inappropriate gavage or anesthesia. The results of subchronic toxicity indicated that rats fed on ACPs alone had significantly decreased in body weight gain and feed conversion efficiency. Most serum biochemical indexes of rats had apparently changed compared with those in the negative control, and gender difference significantly affected most indexes of subchronic toxicity except for the ratios of organ to body weight and histopathological observation. Rats fed on ACPs treated by ozone showed significant beneficial health effects. All the results suggested that the deleterious effects of AFB1 could be highly reduced by ozone, and ozone itself did not show any toxic effects on animals in this processing.

Structures of the ozonolysis products and ozonolysis pathway of aflatoxin B1 in acetonitrile solution.

The ozonolysis of aflatoxin B(1) (400 µg/mL) in acetonitrile solution was conducted with an ozone concentration of 6.28 mg/L at the flow rate of 60 mL/min for different times. The results showed that ozone was an effective detoxification agent because of its powerful oxidative role. Thin-layer chromatography and liquid chromatography-quadrupole time-of-flight mass spectra were applied to confirm and identify the ozonolysis products of aflatoxin B(1). A total of 13 products were identified, and 6 of them were main products. The structural identification of these products provided effective information for understanding the ozonolysis pathway of aflatoxin B(1). Two ozonolysis pathways were proposed on the basis of the accurate mass and molecular formulas of these product ions. Nine ozonolysis products came from the first oxidative pathway based on the Criegee mechanism, and the other four products were produced from the second pathway based on the oxidative and electrophilic reactions of ozone. According to the toxicity mechanism of aflatoxin B(1) to animals, the toxicity of aflatoxin B(1) was significantly reduced because of the disappearance of the double bond on the terminal furan ring or the lactone moiety on the benzene ring.

Effects of extrusion and glycerol content on properties of oxidized and acetylated corn starch-based films.

Oxidized and acetylated corn starch-based films were prepared by casting with glycerol as a plasticizer. The present study investigated the effects of extrusion prior to film-making and glycerol content on the properties of starch films. The films with extrusion exhibited lower tensile strength, higher elongation at break, higher water vapor permeability and higher oil permeability than those without extrusion. Extrusion reduced heat sealability of the films. With the increase of glycerol content, the films became more flexible with higher elongation at break and lower tensile strength. Water vapor permeability, oil permeability and the range between the onset temperature and the melt peak temperature rose as glycerol content increased. The thermograms indicated that plasticizers and biopolymers were compatible. These results suggested that extrusion did no good to starch films while glycerol content had apparent effect on the mechanical and barrier properties of the films.