Xiaojie Yu

Pretreatment of defatted wheat germ proteins (by-products of flour mill industry) using ultrasonic horn and bath reactors: Effect on structure and preparation of ACE-inhibitory peptides

The ultrasonic horn and bath reactors were compared based on production of angiotensin-converting-enzyme (ACE) inhibitory peptides from defatted wheat germ proteins (DWGP). The DWGP was sonicated before hydrolysis by Alcalase. Degree of hydrolysis, ACE-inhibitory activity, surface hydrophobicity, fluorescence intensity, free sulfhydryl (SH), and disulfide bond (SS) were determined. The highest ACE-inhibitory activity of DWGP hydrolysate was obtained at power intensity of 191.1 W/cm(2) for 10 min in the ultrasonic horn reactor. The fixed frequency of 33 kHz and the sweep frequency of 40±2 kHz resulted in the maximum ACE-inhibitory activity. The combined irradiation of dual fixed frequency (24/68 kHz) produced significant increase in ACE-inhibitory activity compared with single frequency (33 kHz). The ultrasonic probe resulted in significant higher ACE-inhibitory activity compared with ultrasonic bath operating at single or dual fixed and sweep frequencies. The changes in conformation of the DWGP due to sonication were confirmed by the changes in fluorescence intensity, surface hydrophobicity, SHf and SS contents and they were found in conformity with the ACE-inhibitory activity in case of the ultrasonic horn reactor but not in bath reactor.

Antioxidant peptides from corn gluten meal: Orthogonal design evaluation

Protamex catalyzed corn gluten meal (CGM) hydrolysis peptides (CHP) were prepared. Orthogonal design L16 (4(5)) was used to optimize processing variables of CGM concentration, CGM heat pretreatment (121 °C) time, and enzymolysis pH, temperature, and time. Degree of hydrolysis (DH), undigested residue ratio, molecular weight (MW) distribution and DPPH radical inhibition were selected as analysis indicators. Optimum variables were CGM concentration of 18%, heat pretreatment time of 40 min, and enzymolysis pH, temperature and time of 7.5, 55 °C and 24h, respectively. Verification test showed that CHP IC50 for scavenging hydroxyl radical was the best and then followed by reducing power. Oligopeptides improved after hydrolysis at the expense of di- and tripeptides, suggesting formation of soluble aggregates from low MW peptides. The increase in the DH, oligopeptides, Alanyl-Tyrosine, and antioxidant free amino acids coincided with the improvement in the antioxidant activity of CHP.

Effect of ultrasonic treatment on the degradation and inhibition cancer cell lines of polysaccharides from Porphyra yezoensis.

The exposure of polysaccharides solutions to high-energy ultrasound produces a permanent reduction in viscosity and change in activity. However, the exact mechanism which occurs in the process is still not clear. In this work, degradation of polysaccharides from Porphyra yezoensis (PP) was indirectly and directly judged by intrinsic viscosity and high performance gel permeation chromatography. The degradation process was established with dynamics and affirmed by theoretical derivation. Inhibition of cancer cell lines (SGC-7901, 95D) was also investigated by assays of tetrazolium colorimetric. The intrinsic viscosity of the degraded PP decreased exponentially with increase in ultrasonic time, and theoretical derivation was established and confirmed well. The distribution and new fraction of degraded polysaccharides was found. Ultrasound degraded preferentially large PP molecules and cleavage took place roughly at the centre of the molecules. During ultrasound degradation the molecular weight distribution was narrowed. The inhibition activities of SGC7901 with ultrasound degraded polysaccharides were increased.

Properties and catalytic activity of magnetic and acidic ionic liquids: experimental and molecular simulation.

The exploitation of dual functional magnetic and acidic ionic liquids (MAILs) for hydrolysis of cellulose to platform chemicals can solve some practical challenges through easy separation of products and efficient catalyst recyclability. In this work, seven Cnmim/FeCl4 MAILs were synthesized and investigated with combined experimental and molecular dynamics. The MAILs contained FeCl4(-) anions and exhibited a typical hard magnetic materials behavior with rather strong magnetic susceptibilities. These MAILs were stable up to 250-310°C, the decomposition was started up at 250/310-480-810°C in two steps with the formation of the undecomposed residue. The Gibbs energy for the reaction of glucose/xylose conversion to 5-hydroxymethylfurfural by metal chlorides in the CnmimCl ionic liquid was studied using the density functional theory calculations and the results that C3mim/WCl3 may be the most hopeful catalyst. The MAILs have the potential to open up promising new catalytic systems because of their easy product separation and efficient catalyst recyclability.

Examining of athermal effects in microwave-induced glucose/glycine reaction and degradation of polysaccharide from Porphyra yezoensis.

Many reports claim the existence of athermal effects in microwave-induced reactions, and this challenge the assumption that the thermal effect (heating) is the sole factor in microwave heating. Therefore, microwave-induced Maillard reaction of d-glucose/glycine and degradation of polysaccharide from Porphyra yezoensis (PSPY) were investigated. Browning reactions were monitored by measuring heating rate, UV-absorbance and brown color, UV-vis and synchronous fluorescence spectra, GC/MS analysis and intrinsic viscosity of degradation. Heating of d-glucose/glycine solution produced brown compounds which were detected at A420, and the intermediate products, 2-acetylfuran and 5-methylfurfural, whose fluorescence intensity evidenced their formation. Maximum emission of synchronous fluorescence spectra of samples were at 430-440 nm and 370-390 nm. Both microwave and water bath heating did not cause any compositional changes in the Maillard reaction products. All data failed to show any significant athermal effects of compositional changes in the Maillard reaction products. It can be inferred that some of the reports suggesting the existence of athermal effects, which could ascribe to the different set-up obtained in not well temperature controlled microwave heating systems.

Ultrasound-ionic liquid enhanced enzymatic and acid hydrolysis of biomass cellulose

The purpose of this paper was to investigate the effect of ultrasound-ionic liquid (IL) pretreatment on the enzymatic and acid hydrolysis of the sugarcane bagasse and wheat straw. The lignocellulosic biomass was dissociated in ILs ([Bmim]Cl and [Bmim]AOC) aided by ultrasound waves. Sonication was performed at different frequencies (20, 28, 35, 40, and 50kHz), a power of 100W, a time of 30min and a temperature of 80°C. The changes in the structure and crystallinity of the cellulose were studied by Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The amounts of the total reducing sugars, glucose, cellobiose, xylose and arabinose in the hydrolysates were determined. The results of FT-IR, XRD and TGA revealed that the structure of cellulose of both biomass samples remained intact after the pretreatment, but the crystallinity decreased. The enzymatic and acid hydrolysis of the biomass samples pretreated with the ultrasound-IL result in higher yields of the reducing sugars compared with the IL-pretreated sample. Enzymatic hydrolysis of bagasse and wheat straw pretreated with [Bmim]Cl-ultrasound resulted in maximal yields of glucose at 20kHz (40.32% and 53.17%) and acid hydrolysis resulted in maximal yields of glucose at 40kHz (33.32% and 48.07%). Enzymatic hydrolysis of bagasse and wheat straw pretreated with [Bmim]OAc-ultrasound show maximal yields of glucose at 28kHz and acid hydrolysis at 50kHz. Combination of ultrasound with [Bmim]OAc is more effective than [Bmim]Cl in terms of the yields of reducing sugar.

Vacuum pretreatment coupled to ultrasound assisted osmotic dehydration as a novel method for garlic slices dehydration

This study investigated the effects of multi-frequency mode ultrasound and vacuum technology on the water loss (WL) of garlic slices during osmotic dehydration (OD), and their effects on the microstructure of garlic. A new method of OD for garlic slices was proposed - Vacuum pretreatment coupled to ultrasound assisted osmotic dehydration (VUOD). The results indicated that the WL of the garlic slices treated with VUOD (21.12%) was significantly (p < 0.05) higher than slices treated with normally OD (NOD) (10.67%), vacuum pretreatment OD (VOD) (14.18%), and multi-frequency mode ultrasound assisted OD (UOD) (11.20-13.56%). A mass transfer mechanism of VUOD was proposed. Low-field nuclear magnetic resonance results quantified the moisture migration in the vacuole, cytoplasm and intercellular space, and the cell wall of garlic cells. The quality properties (allicin content, surface color change and firmness) of VUOD treated garlic slices are predominately better than NOD, VOD and UOD treated samples.

Effect of catalytic infrared dry-blanching on the processing and quality characteristics of garlic slices

This study investigates the effects of catalytic infrared (CIR) dry-blanching (CIRDB) on the processing and quality of garlic slices. CIRDB processing parameters of CIR processing temperature, slice thickness and processing time were studied versus the processing characteristics of internal temperature, peroxidase (POD) activity and moisture reduction. Blanched garlic quality characteristics of surface color change (ΔE), allicin retention rate, vitamin C retention rate and microbial content were determined. Hot water blanching (WB) was used as a comparison. The results indicated that increasing CIR processing temperature and/or reducing the slice thickness accelerated internal temperature rise and POD inactivation and moisture reduction. To achieve 90% inactivation of POD, the CIRDB treatment resulted in moisture reductions of 15.87-40.37%, microbial reductions of 1.76-3.91-log, ΔE between 2.03 and 10.01, retention rate of allicin between 10.63 and 33.31%, and retention rate of vitamin C between 55.00 and 81.13%. CIRDB achieved the high-quality garlic products compared with WB.

Improving the extraction of l-phenylalanine by the use of ionic liquids as adjuvants in aqueous biphasic systems

Polyethylene glycol (PEG) is widely used in the polymer-salt systems. However, the low polarity of the PEG-rich phase limits the application of aqueous biphasic systems (ABS). To overcome this disadvantage, a small quantity of ionic liquid (IL) was used as an adjuvant in ABS to enlarge the polarity range. Therefore, an innovative study involving addition of 4wt% imidazolium-based ILs to the PEG 600/NaH2PO4 ABS, aiming at controlling the phase behavior and extraction ability, was carried out. The phase diagrams, the tie-lines and the partitioning behavior of l-phenylalanine and ILs were studied in these systems. The results reveal that l-phenylalanine preferentially partitions for the PEG-rich phase. The addition of 4wt% IL to ABS controls the partitioning behavior of l-phenylalanine, which depends on the type of IL employed. Moreover, it is verified that increasing temperature lead to a decrease in the partition coefficient of l-phenylalanine.