A comparison study: The new extended shelf life isopropyl ester PMR technology versus the traditional methyl ester PMR approach

Polymerization of monomeric reactants (PMR) monomer solutions and carbon cloth prepregs of PMR II‐50 and VCAP‐75 were prepared using both the traditional limited shelf life methanol based PMR approach and a novel extended shelf life isopropanol based PMR approach. The methyl ester and isopropyl ester based PMR monomer solutions and PMR prepregs were aged for up to 4 years at freezer and room temperatures. The aging products formed were monitored using high pressure liquid chromatography (HPLC). The composite processing flow characteristics and volatile contents of the aged prepregs were correlated versus room temperature storage time. Composite processing cycles were developed and six‐ply cloth laminates were fabricated with prepregs after various extended room temperature storage times. The composites were then evaluated for glass transition temperature (T_g), thermal decomposition temperature (T_d), initial flexural strength (FS), and modulus (FM), long term (1000 h at 316°C) thermal oxidative stability (TOS), and retention of FS and FM after 1000 h aging at 316°C. The results for each ester system were comparable. Freezer storage was found to prevent the formation of aging products for both ester systems. Room temperature storage of the novel isopropyl ester system increased PMR monomer solution and PMR prepreg shelf life by at least an order of magnitude, while maintaining composite thermal and mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3549–3564, 2006     

The Effect of Dryer Inlet and Outlet Air Temperatures and Protectant Solids on the Survival of Lactococcus lactis during Spray Drying

The influence of spray-drying conditions, inlet air temperature (130°C to 200°C), outlet air temperature (38°C to 65°C), drying medium (air and nitrogen) and milk-derived protectants (10%, 15%, and 25% lactose; 5% and 10% sodium caseinate; 10%, 25%, and 35% lactose:sodium caseinate (Lac:NaCas, 3:1)) on the survival of Lactococcus lactis ssp. cremoris was studied using a laboratory-scale spray dryer. An inlet air temperature of 130°C and 65°C as the outlet air temperature maintained high survival of the bacteria without sacrificing low moisture content. Inlet air temperature, previously considered to have no significant effect, was shown to play an important role in the survival of bacteria during spray drying. A mixture of Lac:NaCas (3:1) showed a better protective effect on the survival of bacteria than lactose and sodium caseinate individually, and this effect increased with increasing amount of protectant. The results were generalized by substituting whey protein isolate for sodium caseinate. Finally, the positive effect of elimination of oxygen was demonstrated both by replacing air with nitrogen and adding ascorbic acid as an oxygen scavenger to improve survival of the bacteria. Adding an oxygen scavenger would be a better candidate for industrial application considering the potential high cost of manufacturing if nitrogen was used as the atomization and/or drying medium.     

Study on effective storage time of raw natural rubber

The effective storage time (i.e., storage life) of raw natural rubber (NR) was investigated with heat‐accelerated storage aging combined with thermogravimetry (TG) and differential thermal analysis (DTA) method, as well as the heat aging life equation. The test results show that the effective storage time of raw NR can be estimated more conveniently in relatively shorter time by this method. It is found that the effective storage time of raw NR is associated with rubber processing technology and with ambient temperature during storage, but it has little relation with P₀ and PRI. At ambient temperature, the effective storage time of the natural‐coagulated and biological‐coagulated NR is obviously higher than the acetic acid‐coagulated NR; the lower the ambient temperature, the longer the effective storage time. The effective storage time of the acetic acid‐coagulated NR is 12.2–13.4 years at ambient temperature of 30°C, 23.8–25 years at 25°C, and 47.4–47.9 years at 20°C. The effective storage time of the natural‐ and biological‐coagulated NR is 13.7–15.2 years at 30°C, 29.6–30.4 years at 25°C, and about 62.5–65.8 years at 20°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4114–4119, 2006     

Kinetic study for the development of an accelerated oxidative stability test to estimate virgin olive oil potential shelf life

This study proposes an accelerated test performed at mild temperature (40–60 °C) to measure oxidative stability and estimate the potential shelf life of extra‐virgin olive oil (EVOO). The kinetic behavior of normalized oxidation indices (PV, K₂₃₂ and K₂₇₀) and the oxidizing substrate [unsaturated fatty acids (UFA)] during storage of different virgin olive oil samples in darkness and at different temperatures (25–60 °C) is reported for the first time. PV and K₂₃₂ followed an apparent pseudo zero‐order kinetics (R² >0.951) at all the experimental temperatures in all samples, whereas the evolution of K₂₇₀ apparently better fitted a pseudo first‐order kinetics (R² >0.926). The temperature‐dependent kinetics of the oxidation indices and the UFA were well described by the linear Arrhenius equation between 25 and 60 °C (0.960< R² <0.999, p <0.05). The best correlation between loss of PUFA and increase of oxidation product indices was K₂₃₂ (0.581< R² <0.924). The time required to reach the upper limits for PV, K₂₃₂ and K₂₇₀ established for the EVOO category in the current EU legislation correlated well with temperature using a potential equation, making it possible to set up an accelerated stability test at temperatures below 60 °C to estimate the potential shelf life under normal storage temperature conditions.     

Microbial transformation of androst‐4‐ene‐3, 17‐dione by Bordetella sp. B4 CGMCC 2229

BACKGROUND: Microbial transformation of steroids has attracted widespread attention, especially the transformation of those steroids synthesized with difficulty by chemical methods. In this study, microbial transformation of androst‐4‐ene‐3, 17‐dione (AD) by Bordetella sp. B4 was investigated, and the effect of temperature on transformation was studied. RESULTS: Three metabolites were purified by preparative TLC and HPLC, and identified as androsta‐1,4‐diene‐3,17‐dione (ADD), 9α‐hydroxyandrost‐4‐ene‐3, 17‐dione (9α‐OH‐AD), and 3‐hydroxy‐9, 10‐secoandrost‐1, 3, 5‐triene‐9, 17‐dione (3‐OH‐SATD) by nuclear magnetic resonance imaging (NMR), Fourier transform infrared spectroscopy (FTIR) and mass spectroscopy (MS). It was first reported that the genus of Bordetella has the capability of AD degradation. Microbial transformation of AD was performed at 30 °C, 37 °C, 40 °C and 45 °C. The 9α‐OH‐AD yield reached a maximum within 16 h when the strain was cultivated in media with AD as sole carbon at 37 °C. Surprisingly, ADD was produced by the strain cultivated at 40 °C but not at 37 °C, which was different from previous reports. It was deduced that the alcohol dehydrogenase that catalyzed the transformation of AD to ADD may be temperature sensitive. CONCLUSION: Androst‐4‐ene‐3,17‐dione was converted into 9α‐hydroxyandrost‐4‐ene‐3, 17‐dione and other metabolites rapidly by Bordetella sp. B4. It is anticipated that the strain Bordetella sp. B4 CGMCC 2229 can be used in the steroids industry. Copyright © 2009 Society of Chemical Industry     

Sealing glass‐ceramics with near‐linear thermal strain,part III: Stress modeling of strain and strain rate matched glass‐ceramic to metal seals

Thermal mechanical stresses of glass‐ceramic to stainless steel (GCtSS) seals are analyzed using finite element modeling over a temperature cycle from a set temperature (T_set) 500°C to ?55°C, and then back to 600°C. Two glass‐ceramics having an identical coefficient of thermal expansion (CTE) at ~16 ppm/°C but very different linearity of thermal strains, designated as near‐linear NL16 and step‐like SL16, were formed from the same parent glass using different crystallization processes. Stress modeling reveals much higher plastic strain in the stainless steel using SL16 glass‐ceramic when the GCtSS seal cools from T_set. Upon heating tensile stresses start to develop at the GC‐SS interface before the temperature reaches T_set. On the other hand, the much lower plastic deformation in stainless steel accumulated during cooling using NL16 glass‐ceramic allows for radially compressive stress at the GC‐SS interface to remain present when the seal is heated back to T_set. The qualitative stress comparison suggests that with a better match of thermal strain rate to that of stainless steel, the NL16 glass‐ceramic not only improves the hermeticity of the GCtSS seals, but would also improve the reliability of the seals exposed to high‐temperature and/or high‐pressure abnormal environments.     

The rheological behavior and dynamic mechanical properties of syndiotactic 1,2‐polybutadiene

The rheological behavior and the dynamic mechanical properties of syndiotactic 1,2‐polybutadiene (sPB) were investigated by a rotational rheometer (MCR‐300) and a dynamic mechanical analyzer (DMA‐242C). Rheological behavior of sPB‐830, a sPB with crystalline degree of 20.1% and syndiotactic content of 65.1%, showed that storage modulus (G′) and loss modulus (G″) decreased, and the zero shear viscosity (η₀) decreased slightly with increasing temperature when measuring temperatures were lower than 160°C. However, G′ and G″ increased at the end region of relaxation curves with increasing temperature and η₀ increased with increasing temperature as the measuring temperatures were higher than 160°C. Furthermore, critical crosslinked reaction temperature was detected at about 160°C for sPB‐830. The crosslinked reaction was not detected when test temperature was lower than 150°C for measuring the dynamic mechanical properties of sample. The relationship between processing temperature and crosslinked reaction was proposed for the sPB‐830 sample. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Nisin expression production from Lactococcus lactis in milk whey medium

BACKGROUND: Nisin is a commercially available bacteriocin produced by Lactococcus lactis ATCC 11454 and used as a natural agent in the biopreservation of food. In the current investigation, milk whey, a byproduct from dairy industries was used as a fermentation substrate for the production of nisin. Lactococcus lactis ATCC 11454 was developed in a rotary shaker (30 °C/36 h/100 rpm) using two different media with milk whey (i) without filtration, pH 6.8, adjusted with NaOH 2 mol L^?1 and without pH adjustment, both autoclaved at 121 °C for 30 min, and (ii) filtrated (1.20 µm and 0.22 µm membrane filter). These cultures were transferred five times using 5 mL aliquots of broth culture for every new volume of the respective media. RESULTS: The results showed that culture media composed of milk whey without filtration supplied L. lactis its adaptation needs better than filtrated milk whey. Nisin titers, in milk whey without filtration (pH adjusted), was 11120.13 mg L^?1 in the second transfer, and up to 1628‐fold higher than the filtrated milk whey, 6.83 mg.L^?1 obtained in the first^t transfer. CONCLUSIONS: Biological processing of milk byproducts (milk whey) can be considered a profitable alternative, generating high‐value bioproducts and contributing to decreasing river disposals by dairy industries. Copyright © 2008 Society of Chemical Industry     

Effect of vacuum‐packaging on the changes of Russian sturgeon muscle lipids during frozen storage

The changes in fatty acid composition, non‐polar (triglycerols) and polar lipids (phospholipids), total free fatty acids and total cholesterol of Russian sturgeon (Acipenser gueldenstaedtii) were studied during 360 days of storage at ?18°C. It was established that total neutral lipids and phospholipids content decreased and total free fatty acids concentration increased significantly during the frozen storage. Lower non‐polar and polar lipids content and higher free fatty acids concentration of vacuum‐packaged samples in comparison with air‐packaged samples were found. The changes in total cholesterol concentration and phospholipid classes of frozen stored sturgeon were not influenced by the frozen storage period and the type of packaging. It was established that the sturgeon polar lipids consisted mainly of phosphatidylcholine – 54.98 ± 0.85%, phosphatidylethanolamine – 28.42 ± 0.61%, and phosphatidylserine – 8.64 ± 0.45%. The increase of the total free fatty acids concentration was associated with the free n ? 3 PUFA accumulation as a result of hydrolysis of non‐polar and polar lipids. During the frozen storage DHA percentage of non‐polar lipids and phospholipids decreased approximately 3 and 1.75%, respectively. After 360 days of storage at ?18°C the n ? 3/n ? 6 PUFA ratio of total lipids decreased 4.9%.     

Effects of rainbow trout freshness on n‐3 polyunsaturated fatty acids in fish offal

The effects of rainbow trout cold storage on the quality of offal left after fish processing to fillets with skin were determined. The intact farmed rainbow trout were kept at 2 °C in ice for 0, 4, 7, and 14 days of storage. The offal was, immediately after processing, frozen at ?20 °C and analysed after a month‐long frozen storage; fillets (non‐frozen) were analysed as well. Non‐protein nitrogen, volatile bases, trimethylamine, lipid oxidation (peroxide value, anisidine value, UV‐VIS spectra, and fluorescence) and fatty acid composition were determined. The offal consists in 15% of protein and in about 20% of chloroform/methanol‐extractable lipids, with n‐3 polyunsaturated fatty acids (n‐3 PUFA) accounting for 20.37 ± 1.25% of the fatty acids. The fish storage duration was found to exert a significant (p = 0.05) effect on the changes in lipids and nitrogen compounds. No losses of long‐chain n‐3 PUFA in the offal were detected during the 2 wk of storage in ice plus 1 month at ?20 °C. The rainbow trout offal is a valuable – rich and stable – source of n‐3 PUFA.     

Partially constrained recovery of (meth)acrylate shape‐memory polymer networks

The purpose of this study was to characterize the partial strain recovery of a thermoset shape‐memory polymer under a constraining stress. Three polymer networks were synthesized from tert‐butyl acrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) solutions. The molecular weight and the weight fraction of the PEGDMA crosslinking monomer was altered systematically to maintain a constant glass transition temperature (T_g = 54°C) but tailorable rubbery moduli, which varied by almost an order of magnitude for the three polymer networks (E = 1.8–11.3°MPa). The shape‐recovery behavior of the polymers under a constraining stress was characterized for programming temperature below (20°C) and above (70°C) the T_g. The experiments revealed a peak in the recovered strain for samples programmed at 20°C. Recovered strain scaled linearly with the constraining stress by the rubbery modulus. The work performed by the shape‐memory polymer networks was observed to be primarily a function of constraining stress and crosslinking density, while programming temperature had a relatively mild influence; however, the efficiency of the shape‐memory effect was shown to be a function of constraining stress and programming temperature, but was independent of crosslinking density. Maximum work efficiencies (up to 45%) were observed for programming temperature of 70°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Microencapsulation of B. lactis (BI 01) and L. acidophilus (LAC 4) by Complex Coacervation Followed by Spouted-Bed Drying

Microcapsules containing B. lactis and L. acidophilus were produced by complex coacervation and spouted bed dehydrated afterwards. The aim of this study was to evaluate the resistance of these microorganisms in face of the dehydration process, shelf life, and in vitro tolerance to acid pH besides microcapsules and particles morphology by optical microscopic and SEM. The processes of complex coacervation, drying, and formation of the casein/pectin complex were adjusted to microencapsulate L. acidophilus and B. lactis, but were not efficient in protecting these organisms at pH values similar to those of the human stomach. The microorganisms maintained greater viability at a storage temperature of 7°C.     

Viscoelastic properties and structure of the zone‐drawn polyaniline films

The zone‐drawing method was applied to chemically synthesized polyaniline cast films of emeraldine base under various applied tensions and drawing temperatures. The changes in the microstructure and viscoelastic properties of the resulting films were investigated. It was found that the microstructure was strongly affected by the drawing temperature (T_d). The crystallinity, crystallite size, and orientation factor of crystallites, respectively, attained 42%, 23 Å, and 0.975 for the film zone‐drawn at T_d = 170°C, whereas a further increase in the T_d brought about a decrease of these values. The viscoelastic measurements indicated that the dynamic storage modulus attained 12 GPa at room temperature and was 5 GPa at 280°C for the film zone‐drawn at T_d = 210°C, which was comparable to that of the typical engineering plastics. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 566–571, 2000     

Evaluation of a Yarrowia lipolytica Strain Collection for Its Lipid and Carotenoid Production Capabilities

The oleaginous yeast Yarrowia lipolytica is capable of accumulating large amounts of fatty acids in the form of lipids which can serve as a platform polymer for a variety of applications. Additionally, through heterologous gene expression, Y. lipolytica is capable of producing carotenoids. Due to the observation that Y. lipolytica exhibits a high phenotypic inter‐strain variability, robotics and microwell scale cultivations are applied to examine 12 wild type strains of a Y. lipolytica collection. The strains are characterized with respect to their metabolic capabilities for fatty acid production as well as genetically manipulated to produce beta‐carotene. Furthermore, growth and production behavior of the strain collection at different temperatures as well as initial pH are assessed. A molecular discrimination between the strains is achieved by internal transcribed spacer (ITS)‐sequencing and polymerase chain reaction (PCR)‐based methods. The best performing strain with respect to lipid production produces ≈2% lipids per dry cell weight (DCW) and 8 mg g^?1 beta‐carotenoids in yeast nitrogen base (YNB) media. All strains show robust growth from 28 to 34 °C. Practical Applications: Unlocking nature's potential by screening natural isolates shows that even on inter‐strain level sufficient phenotypic diversity may arise. Automated growth‐based characterization of beta‐carotene‐producing strains in terms of media composition, effect of initial pH, and temperature tolerance shows that with modern cultivation techniques, rapid characterization of strain collections is feasible. Combining results of beta‐carotene and lipid formation could help to balance both pathways to improve the storage of hydrophobic compounds in the lipid droplets. The generalized findings could be further transferred to improve the production of any valuable compound, derived from the mevalonate pathway.     

Viability of Lactobacillus plantarum TISTR 2075 in Different Protectants during Spray Drying and Storage

Spray drying was applied for the production of Lactobacillus plantarum TISTR 2075 powder using maltodextrin as the carrier. A survival rate of 0.85% was achieved for this probiotic bacteria after spray drying. To improve the survival of this strain during the spray-drying process and storage, various protectants were added before drying. These included protein, trehalose, fibersol, ascorbic acid, isomalt, palatinose, and gum acacia. The results indicated that trehalose and protein (a combination of soy protein isolate and milk protein concentrate) significantly (P < 0.05) enhanced the viability during spray drying, with survival rates of 57.70 and 25.31%, respectively. Survival of the dried strain was also monitored over a period of 12 months’ storage at 4 and 25°C. Higher temperature induced lower viability of the strain in all protectants during this long-term storage. Accelerated storage tests using temperatures of 37, 45, 60, and 80°C were also applied to the spray-dried powders. A temperature-dependent prediction model was developed to determine the viability of the spray-dried L. plantarum TISTR 2075 in different protectants for long-term storage.     

Preparation of goat milk powder with Lactobacillus casei L61 and antioxidant peptides: optimization of the composite thermal protectants and evaluation of storage stability

Abstract

The Lactobacillus casei L61 has great ability for producing antioxidant peptides. For reducing the mortality of L. casei L61 in spray drying process, the Box-Behnken design (BBD) was adopted to optimize the composite thermal protective agent formula. The results exhibited that the composite thermal protective agent formula of L. casei L61 contained glucose at 6.03% (w/v), skim milk at 18.98?g/L, and glycerol at 12.50?mL/L. Under the optimal conditions, the average survival of L. casei L61 in the fermented goat milk reached 14.58?±?0.72% after heat treatment at 75?°C for 10?min, which was higher than the control (13.14%). The average hydroxyl free radical scavenging activity of L. casei L61 reached 85.09?±?0.98%, which was not significantly different from the predicted value (86.83%). Therefore, the BBD is feasible for optimizing the composite thermal protective agent formula of L. casei L61. Under the optimal conditions with the inlet air temperature of 130?°C and feed rate of 4.5?mL/min, the maximum viable counts and survival rate of L. casei L61 were 7.46?×?10⁸ cfu/g and 23.41?±?1.28%, respectively. More importantly, the storage stability of antioxidative probiotic goat milk powder was predicted by temperature acceleration test. The shelf life of antioxidative probiotic goat milk powder was estimated to be 352?days at 4?°C and 117?days at 25?°C, embodying the great long-term stability. This study provides a technical reference for industrialized production of probiotic goat milk powder.     

Temperature‐stable dielectric and energy storage properties of La(Ti0.5Mg0.5)O3‐doped (Bi0.5Na0.5)TiO3‐(Sr0.7Bi0.2)TiO3 lead‐free ceramics

A new type of (0.7?x)Bi_0.5Na_0.5TiO₃‐0.3Sr_0.7Bi_0.2TiO₃‐xLaTi_0.5Mg_0.5O₃ (LTM1000x, x = 0.0, 0.005, 0.01, 0.03, 0.05 wt%) lead‐free energy storage ceramic material was prepared by a combining ternary perovskite compounds, and the phase transition, dielectric, and energy storage characteristics were analyzed. It was found that the ceramic materials can achieve a stable dielectric property with a large dielectric constant in a wide temperature range with proper doping. The dielectric constant was stable at 2170 ± 15% in the temperature range of 35‐363°C at LTM05. In addition, the storage energy density was greatly improved to 1.32 J/cm³ with a high‐energy storage efficiency of 75% at the composition. More importantly, the energy storage density exhibited good temperature stability in the measurement range, which was maintained within 5% in the temperature range of 30‐110°C. Particularly, LTM05 show excellent fatigue resistance within 10⁶ fatigue cycles. The results show that the ceramic material is a promising material for temperature‐stable energy storage.     

Novel latent initiator for cationic polymerization of epoxides

A novel latent initiator for cationic polymerization of epoxides, a composite catalyst containing aluminum complexes and phenol derivatives protected with tert‐butoxycarbonyl groups (tBOC), is reported. At a certain temperature, protected phenols generate the parent phenols which are coinitiators with aluminum complexes. The deprotection temperature of the tBOC group depends on the structure of the phenol moieties. Bis(p‐t‐butoxycarbonyloxyphenyl)sulfone (Ph1) generates (p‐dihydroxyphenyl)sulfone (PhH1) at around 150°C, the temperature at which the curing of epoxides is conventionally carried out. The thermally generated PhH1 and aluminum complexes initiate the curing of epoxides. Epoxy resin compositions containing these composite catalysts have a long shelf life at room temperature and are cured at around 150°C, showing that the composite catalyst has excellent latent properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 181–187, 2001     

Accelerated crystallization of poly(L‐lactide) by physical aging

The low‐temperature physical aging of amorphous poly(L ‐lactide) (PLLA) at 25–50°C below glass transition temperature (T_g) was carried out for 90 days. The physical aging significantly increased the T_g and glass transition enthalpy, but did not cause crystallization, regardless of aging temperature. The nonisothermal crystallization of PLLA during heating was accelerated only by physical aging at 50°C. These results indicate that the structure formed by physical aging only at 50°C induced the accelerated crystallization of PLLA during heating, whereas the structure formed by physical aging at 25 and 37°C had a negligible effect on the crystallization of PLLA during heating, except when the physical aging at 37°C was continued for the period as long as 90 days. The mechanism for the accelerated crystallization of PLLA by physical aging is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fast responsive and strong swelling hydrogels based on N‐isopropylacrylamide with sodium acrylate

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) gels with N,N‐methylene bisacrylamde (BIS) as crosslinker were prepared by free radical polymerization method at the temperature of 35°C, which was just around the lower critical solution temperature (LSCT) of the hydrogels. The gels synthesized at 35°C demonstrated strong swellability and fast responseability when compared with the gels synthesized at the temperature of 0 and 18°C (below the LCST) and 50 and 80°C (above the LSCT). The response rate and swelling behavior of poly(N‐isopropylacrylamide‐co‐sodium acrylate) gels was investigated and characterized by the temperature‐dependent swelling ratio and swelling and deswelling kinetics. The swelling behavior of the gels indicated that the synthesis temperature was the main factor when the swellability concerned and also had effect on the responseability of the resulting hydrogels. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009