High Heat Stability Research Articles

Fortification of milk protein content with different dairy protein powders alters its compositional, rennet gelation, heat stability and ethanol stability characteristics

Skim milk (SM) was fortified from 3.3 to 4.1% protein using different milk protein powders: skim milk powder (SMP), native phosphocasein (NPC), calcium-reduced phosphocasein (CaRPC), sodium caseinate (NaCas) or calcium caseinate (CaCas). Compared with SMP or NPC, fortification with NaCas and CaRPC, and to a lesser extent CaCas, resulted in milk samples having higher proportions of non-sedimentable casein and calcium, and lower- and higher-levels of κ- and αS1-casein, respectively, as a proportion of non-sedimentable casein. These changes coincided in milk samples fortified with NaCas, CaRPC or CaCas failing to undergo rennet-induced gelation, and having higher heat stability in the region 6.7–7.2 and ethanol stability at pH 6.4. The study demonstrates that the aggregation behaviour of protein-fortified milk samples is strongly influenced by the degree of mineralisation of the protein powder used in fortification, which affects the partitioning of casein and calcium in the sedimentable and non-sedimentable phases.

“Stereoscopic” 2D super-microporous phosphazene-based covalent organic framework: Design, synthesis and selective sorption towards uranium at high acidic condition

So far, only five primary elements (C, H, O, N and B) and two types of spatial configuration (C2–C4, C6 and Td) are reported to build the monomers for synthesis of covalent organic frameworks (COFs), which have partially limited the route selection for accessing COFs with new topological structure and novel properties. Here, we reported the design and synthesis of a new “stereoscopic” 2D super-microporous phosphazene-based covalent organic framework (MPCOF) by using hexachorocyclotriphosphazene (a P-containing monomer in a C3-like spatial configuration) and p-phenylenediamine (a linker). The as-synthesized MPCOF shows high crystallinity, relatively high heat and acid stability and distinctive super-microporous structure with narrow pore-size distributions ranging from 1.0–2.1nm. The results of batch sorption experiments with a multi-ion solution containing 12 co-existing cations show that in the pH range of 1–2.5, MPCOF exhibits excellent separation efficiency for uranium with adsorption capacity more than 71mg/g and selectivity up to record-breaking 92%, and furthermore, an unreported sorption capacity (>50mg/g) and selectivity (>60%) were obtained under strong acidic condition (1M HNO3). Studies on sorption mechanism indicate that the uranium separation by MPCOF in acidic solution is realized mainly through both intra-particle diffusion and size-sieving effect.

Physicochemical properties of skim milk powders prepared with the addition of mineral chelators

The objective of this study was to determine the effect of mineral chelator addition during skim milk powder (SMP) manufacture on the solubility, turbidity, soluble protein, and heat stability (HS). Three chelators (sodium citrate dihydrate, sodium polyphosphate, and disodium EDTA) at 3 different concentrations (5, 15, and 25mM) were added to skim milk concentrate (30% total solids), and the pH was adjusted to 6.65 before spray drying to produce SMP. Spray-dried SMP samples were tested for solubility index (SI). Additionally, samples were reconstituted to contain 9% total solids, adjusted to pH 7.0, and tested for turbidity, protein content from supernatants of ultracentrifuged samples, and HS. Lower SI values were observed for samples treated with 5mM disodium EDTA and sodium polyphosphate than control samples or samples with 5mM sodium citrate dihydrate. Furthermore, lower SI values were observed with an increased level of chelating agents regardless of chelator type. A decreased turbidity value was found with increasing levels of mineral chelating salt treatment. Low turbidity with increasing levels of added chelators may be associated with the dissociation of caseins from micelles. Furthermore, higher protein content was observed in supernatants of ultracentrifuged samples treated with increased level of chelators as compared with the control sample. Higher HS was observed in samples treated with 5mM compared with samples treated with 25mM mineral chelator. The results suggest improved solubility and HS upon addition of mineral chelators to SMP during its manufacture.

Imide Crosslinked Perfluorinated Proton Exchange Membranes by Gas Treatment

Imide crosslinked perfluorinated proton exchange membranes (PEMs) were prepared by treatment of perfluorinated sulfonyl fluoride membranes with ammonia and trimethylamine gases to improve the mechanical properties at an elevated temperature. Tensile testing and infrared (IR) spectroscopy results indicated that imide crosslinks were successfully introduced into the perfluorinated PEMs. The imide crosslink density could be controlled by the gas treatment conditions. The imide crosslinked PEMs showed high mechanical properties and heat stability, i.e. far less creep elongation at elevated temperature than non-crosslinked PEMs. The imide crosslinked PEMs also exhibited a slight decrease in conductivity and cell performance due to a slightly lower ion exchange capacity than that of non-crosslinked PEMs. The introduction of imide crosslinking in PEMs is therefore a method for achieving improved mechanical properties and thermal stability with a minimum decrease in fuel cell performance.

Assembly of three stable POM-based pillar-layer CuI coordination polymers with visible light driven photocatalytic properties

Three new 3D POM-based CuI coordination polymers have been successfully prepared by a hydrothermal reaction. Compounds 1–3 show remarkably high heat stability, acid and alkali resistance, and effectively degrade methylene blue within visible light range.

Preparation of Yeast Hydrolysate Enriched in Cyclo-His-Pro (CHP) by Enzymatic Hydrolysis and Evaluation of Its Functionality.

In this study, we attempted to enrich cyclo-His-Pro (CHP) using enzymatic hydrolysis of yeast and to evaluate the functionality of yeast hydrolysate (YH)-enriched CHP. Flavourzyme offered a better performance in enhancing CHP content than other proteases. The CHP enrichment conditions were optimized as follows: addition of 1% Flavourzyme, 48-h incubation at 60°C, and pH 6.0. The CHP content significantly increased by 20-fold after ultra-filtration (UF). Maximal CHP translation was obtained after heating for 8 h at 50°C and pH 7.0. YH showed poor foaming capacity between pH 3.0 to 9.0. The emulsifying activities of YHs were slightly higher at near acidic pH. Increase in heating temperature and time resulted in decreased CHP content. The results indicate that YH is more heat stable after UF. Therefore, the CHP in YH after UF can be used as a food additive with physiological CHP activity and high heat stability.

Ni segregation and thermal stability of reversed austenite in a Fe–Ni alloy processed by QLT heat treatment

High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used to investigate Ni segregation and thermal stability of reversed austenite (RA) in a Fe–Ni alloy processed by quench–lamellarize–temper (QLT) heat treatment. The results show that the 77 K impact energy of the alloy increases with RA content increasing. As an austenite-stabilizing element, Ni is found to segregate in RA, though Ni is not evenly distributed within RA. The amount of segregations increases near the boundary (twice as high as the balanced content) and decreases to some extent in the center of the RA regions. Ni concentration in matrix near the boundary is lower than that in matrix far from the boundary because of Ni atom transportation from α to γ near the boundary. RA in this alloy has high heat and mechanical stability but is likely to lose its stability and transform to martensite when a mechanical load is applied at ultralow temperatures (77 K), which induces plasticity.

Effects of temperature and feed processing on protease activity and dietary protease on growths of white shrimp,Litopenaeus vannamei, and tilapia,Oreochromis niloticus × O. aureus

Effects of temperature and processing on the stability of a commercial protease were assessed in an in vitro trial followed by growth trials with white shrimp and tilapia. Results showed that the protease has a high heat stability against pelleting, and it could hydrolyse dietary proteins during feed processing. In Exp. 2, white shrimp (3.3 g) fed low fish meal (FM) diet (LFD) with protease addition had similar growth to that fed high fish meal diet, and both had higher weight gain (WG) and lower feed conversion ratio (FCR) than that fed LFD without protease addition (P < 0.05). In Exp. 3, compressed (CD) or extruded (ED) diets containing 30 g kg−1 or 90 g kg−1 FM were supplemented with or without protease and then fed to tilapia (1.7 g) for 8 weeks. WG was improved and FCR decreased (P < 0.05) by the supplementation of protease in 30 g kg−1 FMCD, but not in 90 g kg−1 FMCD and ED diets when compared to those diets without protease supplementation. The digestibility trial with CD indicated the improved apparent digestibilities of dry matter and crude protein by dietary protease in 30 g kg−1 FMCD, but not in 90 g kg−1 FMCD. Results above showed that the protease has a high heat stability and the supplementation of protease in CD with low FM level can improve the growth of shrimp and tilapia.

고기능성 침낭형 온수매트 제작

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Proteolysis of Abnormal Prion Protein with a Thermostable Protease from a Hyper-Thermophilic Archaeon Thermococcus Kodakarensis Kod1

The abnormal prion protein (PrPSc: scrapie-associated prion protein) is considered to be included in the group of infectious agents of transmissible spongiform encephalopathies. Since PrPSc is highly resistant to normal sterilization procedures, the decontamination of PrPSc is a significant public health issue. Tk-subtilisin is a subtilisin-like serine protease identified from a hyperthermophilic archaeon Thermococcus kodakarensis KOD1. Among the subtilisin family of proteases, Tk-subtilisin has significant high heat stability with its highest specific activity at 90°C and a half-life of 50 min at 100°C. In the present study, a hyper-thermostable protease, Tk-subtilisin, was used to degrade PrPSc. Although PrPSc is known to be resistant toward proteolytic enzymes, Tk-subtilisin was able to degrade PrPSc under extreme conditions. The level of PrPSc in brain homogenates was found to decrease significantly in vitro following Tk-subtilisin treatment at 100°C, whereas some protease resistant fractions remain after proteinase K treatment. Rather small amounts of Tk-subtilisin were required to degrade PrPSc at 100°C and pH 8.0. In addition, Tk-subtilisin was observed to degrade PrPSc in the presence of sodium dodecyl sulfate or other industrial surfactants. Although several proteases degrading PrPSc have been reported, practical decontamination procedures using enzymes are not available. This report aims to provide basic information for the practical use of a proteolytic enzyme for PrPSc degradation.

Analysis of Crystal Structure, Electronic and Nuclear Densities, and Local Structure for LiNi0.8Co0.2O2 during Charge Process Using Synchrotron X-Ray and Neutron Sources

INTRODUCTION Positive electrode material, Li(Ni,Co)O2 system, of Li-ion battery has been attractive because it has the advantage in low environmental load due to low Co content. There are many previous works about the Li(Ni,Co)O2 and the aluminum-substituted one because of high heat stability. However, detail structural changes during electrochemical processes are still ambiguous for site occupancy, local structures, and electronic structures even though these would play important roles on the battery characteristics. In this research, we used several quantum beam techniques to reveal the crystal structures, electronic and nuclear densities, and local structures of LiNi0.8Co0.2O2 during charge process. EXPERIMENTAL To synthesize the LiNi0.8Co0.2O2, the precursor was prepared by co-precipitation method. The co-precipitated material was annealed at 800 °C in air for 15 h. The product was identified by powder XRD and ICP-OES. To study change of crystal and electronic structure of this cathode material during electrochemical process, cathode materials were prepared by four charge depths, and were investigated using the synchrotron X-ray diffraction (BL02B2, SPring-8) and neutron diffraction (BL20, J-PARC). The data was analyzed with the Rietveld technique using Rietan-FP and Z-Rietveld, and by the MEM using the Dysnomia and Z-MEM programs. To examine the local structures, X-ray absorption spectroscopy (BL14B2, SPring-8) and X-ray total scattering (BL04B2, SPring-8) were measured. RESULTS AND DISCUSSION The neutron diffraction patterns were measured for the cathode after 2nd discharge process as well as the pristine electrode. It was demonstrated that the crystal structure analysis by ex-situ measurement could be successfully performed even for the electrode with an amount of about 10 mg. The values of 3b-6c bond length decreased and λ2, which expresses the distorted degree of the Li-O6 and M-O6 octahedra, were increased with increasing charge depth. Synchrotron-based experiments using high energy X-ray total scattering and pair distribution function (PDF) analysis (Fig. 1) indicated that the oxygens arranged to crystallographic a-b plane were disturbed in the charge state of 4.3 V after 2nd cycle (Fig. 2). ACKNOWLEDGMENTS This research was supported by the RISING-project of the New Energy and Industrial Technology Development Organization (NEDO), Japan.

Thermal Stability of Chicken Keel Bone Collagen

Acid-soluble and pepsin-solubilized collagen were isolated from chicken keel bone and analyzed by electrophoresis and circular dichroism. The denaturation temperature of chicken keel bone was determined by circular dichroism and compared to denaturation temperature of black drum or alligator bone. Our results show that collagen from chicken keel bone is a mixture of type II and type I, has predominantly the amino acids glycine, proline and hydroxyproline, and its secondary structure is predominantly triple-helix. The onset of the denaturation temperature is 37C; at 44C, 50% of the collagen is denatured and the denaturation is complete at 48.8C making it the highest of vertebrate collagen denaturation temperatures reported in the literature. The high heat stability of chicken keel bone collagen may be in part ascribed to its imino acid content. Because of the high heat stability and low methionine content, chicken keel bone collagen is a high value-added product with several biochemical and biomedical applications. Practical Applications The denaturation temperature of chicken keel bone collagen is above body temperature and allows applications in cosmetics where other types of collagen may be denatured because of their low denaturation temperature. Chicken type II collagen is well tolerated by patients with rheumatoid arthritis and is effective in the treatment of rheumatoid arthritis. Methionine-restricted diet inhibits the growth of solid tumor such as gastric cancer, glioblastoma, medulloblastoma and neuroblastoma. Chicken type collagen may be a medical food for patients with solid tumors mentioned above.

Synthesis and evaluation of odour-active methionyl esters of fatty acids via esterification and transesterification of butter oil

Methionol-derived fatty acid esters were synthesised by both chemical and lipase catalysed esterification between fatty acids and methionol. Beneficial effects of both methods were compared qualitatively and quantitatively by GC–MS/GC-FID results. And the high acid and heat stability of our designed methionyl esters meet the requirement of the food industry. Most importantly, the sensory test showed that fatty acid carbon-chain length had an important effect on the flavour attributes of methionyl esters. Moreover, through Lipozyme TL IM-mediated transesterification, valuable methionol-derived esters were synthesised from the readily available natural material butter oil as the fatty acid source. The conversion of methionol and yield of each methionyl ester were also elucidated by GC–MS-FID.

Thermal, morphological, and conductivity profile of pyridine/thiophene-based polyesters and their miscible blends

New Schiff-base polyesters were prepared from a dihydroxy monomer ( E) -1-(5-(4-hydroxy-3-chlorobenzylidene)thiocarbamoylaminonaphthyl)-3-(4-hydroxy-3-chlorobenzylidene)thiourea. The processable pyridine or thiophene-based poly(azomethine–ester)s (PAEs) possess high molar mass of 111 × 103–127 × 103 g mol−1. The 10% weight loss (521–527°C) and glass transition temperature (287–291°C) depicted high thermal stability. Polyaniline (PAN) doped with dodecylbenzenesulfonic acid (PAN/DBSA), prepared by in situ doping polymerization, was blended in solution/melt with PAEs. Field emission scanning electron microscopy of melt blended PAEs/PAN/DBSA showed nanolevel homogeneity of microstructure accountable for superior electrical conductivity (1.9–2.8 S cm−1). The miscible nanoblends also exhibited high heat stability ( T10; 500–507°C) and mechanical strength (45.51–48.17 MPa) relative to reported azomethine/PAN-based structures.

Crosslinked acellular saphenous vein for small-diameter vascular graft

Patients with congenital and acquired heart diseases or arteriopathy require small-diameter vascular grafts for arterial reconstruction. Autologous veins are the most suitable graft, but when absent, an alternative is necessary. This work addresses the issue. Tissue-engineering efforts to create such grafts by modifications of acellular natural scaffolds are considered a promising area. Homologous saphenous veins harvested from cadavers and organ donors were processed by decellularization with detergent and enzymatic digestion, followed by crosslinking by dye-mediated photooxidation. They were validated for acellularity, mechanical strength, and crosslink stability. In-vitro and in-vivo cytotoxicity and hemocompatibility studies were conducted. Collagen conformity was studied by Fourier transform infrared spectroscopy, and heat stability by differential scanning calorimetry. A limited large animal study was performed. The processing method delivered biocompatible, hemocompatible, effectively crosslinked grafts, with high heat stability of 126 , an enthalpy value of 183.5 J·g(-1), and collagen conformity close to that of the native vein. The mechanical strength was 250% better than the native vein. The presence of extracellular matrix proteins allowed the acellular vein to become a triple-layered vascular structure in the sheep venous system. Crosslinking after decellularization by the dye-mediated photooxidation method could be reproduced in any human vein to obtain a small-diameter vascular grafts.

Efficient secretory expression of the sweet-tasting protein brazzein in the yeast Kluyveromyces lactis

Brazzein is an intensely sweet-tasting protein with high water solubility, heat stability, and taste properties resembling those of carbohydrate sweeteners. In the present study, we describe the expression of the synthetic gene encoding brazzein, a sweet protein in the yeast Kluyveromyces lactis. The synthetic brazzein gene was designed based on the biased codons of the yeast, so as to optimize its expression, as well as on the extracellular secretion for expression in an active, soluble form. The synthesized brazzein gene was cloned into the secretion vector pKLAC2, which contains the yeast prepropeptide signal from the Saccharomycescerevisiae α-mating factor. The constructed plasmid pKLAC2-des-pE1M-brazzein was introduced into the yeast K. lactis GG799. The yeast transformants were cultured for high-yield secretion of the recombinant des-pE1M-brazzein in YPGal medium for 96h at 30°C. The expressed recombinant des-pE1M-brazzein was purified by CM-Sepharose column chromatography and approximately 104mg/L was obtained. The purity and conformational state of the recombinant des-pE1M-brazzein were confirmed using SDS–PAGE, HPLC, and circular dichroism. The identity of the recombinant protein was also confirmed by N-terminal amino acid analysis and taste testing. The purified recombinant des-pE1M-brazzein had an intrinsic sweetness in its minor form, approximately 2130 times sweeter than sucrose on a weight basis. These results demonstrate that the K. lactis expression system is useful for producing the recombinant brazzein in active form at a high yield with attributes useful in the food industry.

Facile assembly and properties of polystyrene microsphere/reduced graphene oxide/Ag composite

A ternary assembly consisting of reduced graphene oxide (RGO), Ag nanoparticles, and polystyrene (PS) microsphere was prepared in aqueous solution by an electrostatic assembly combined with one-step reduction process. The composition and structure of the assembly (PS microsphere/RGO/Ag) were characterized by powder X-ray diffraction, transmission electron microscope, scanning electron microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy. The interactions among RGO, Ag nanoparticles, and PS microsphere were investigated by surface enhanced Raman scattering spectroscopy. The results showed that there existed strong interactions among RGO, Ag nanoparticles, and PS microsphere. Importantly, the assembly showed high heat stability and good dispersion in water.

Investigation of ZnS–SiO2/Ag/ZnS–SiO2 as high stable transparent and conductive multilayer films

Novel transparent conductive ZnS–SiO2/Ag/ZnS–SiO2 multilayer films were prepared on K9 glass substrates by magnetron sputtering at room temperature. The structure of ZnS–SiO2/Ag/ZnS–SiO2 multilayer films were theoretically designed and the optimal thickness of each layer was determined (45nm/11nm/45nm). To obtain better optical and electrical properties, the ZnS–SiO2/Ag/ZnS–SiO2 samples were annealed at various temperatures. The optical, electrical, and structural characteristics of the ZnS–SiO2/Ag/ZnS–SiO2 multilayer films were then investigated. The results show that when the annealing temperature was 200°C, the sample exhibited a low sheet resistance of 9.7Ω/sq and a high optical transmittance of 88.4%. For the sample annealed at 200°C, the average transmittance in the visible range (380–780nm) was calculated and determined as 84.1%. The effects of humidity and temperature on the samples were assessed by an accelerated aging test. The results demonstrate the high damp heat stability of ZnS–SiO2/Ag/ZnS–SiO2 multilayer films.

Effects of inlet air temperature and spray rate of coating solution on quality attributes of turmeric extract coated rice using top-spray fluidized bed coating technique

The addition of natural antioxidants onto white rice kernel can improve its functionality. Curcuminoids that present in turmeric rhizomes possess high antioxidant activity and heat stability. The objective of this study was to investigate the effects of inlet air temperatures and spray rates of turmeric extract solution on quality attributes of the turmeric extract coated rice (TCR) using the top-spray fluidized bed coating technique. The experimental results have shown that inlet air temperature and spray rate of coating solution strongly affected the final moisture content and percentage of fissured kernel of TCR. Almost all of TCR kernels in the bed cracked when their final moisture content was lower than 11.8% wet basis. However, the head coated rice yield of fissured TCR slightly decreased from that of white rice. The color of TCR was uniform over the entire surface. Texture of cooked TCR insignificantly changed from that of uncoated sample. Increasing spray rate provided higher both total phenolic content (TPC) and total antioxidant capacity (TAC) whilst increasing inlet temperature yielded lower TPC but it did not affect TAC. Retentions of TPC and TAC of TCR after cooking remained higher than 90%.

Hexagonal NaYF&lt;sub&gt;4&lt;/sub&gt; Nanotube Arrays Obtained via Solvothermal Process

Hexagonal sodium yttrium fluoride has been successfully synthesized via a facile solvothermal route, using yttrium nitrate, sodium fluoride and polyethanediol as raw materials to react in propanetriol solvent. The as-prepared product was characterized by powder X-ray diffraction, scanning electron microscopy, thermogravimetric and differential thermal analysis, Fourier transform infrared spectrum and energy dispersive X-ray spectrum. The characterization results revealed that the products are hexagonal and denoted as NaYF4. The as-synthesized hexagonal sodium yttrium fluoride composed of hollow-structured nanotubes self-assembled and arrayed orientedly to take on bamboo raft morphology. Hexagonal NaYF4 nanotube arrays exhibited high heat stability. This study provides a simple method to prepare bamboo raft-shaped NaYF4 in large scale, which broads their practical applications.