Home About us Contact
|
Home About us Contact | ||
|
|
||
Heating Time (heating + time)
Selected AbstractsCrystallization and Dielectric Properties of SrO,BaO,Nb2O5,SiO2 Tungsten-Bronze Glass-CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2000Jiin-Jyh Shyu The crystallization and dielectric properties of SrO,BaO,Nb2O5,SiO2 glass-ceramics have been investigated. Glass-ceramics that contain strontium barium niobate (SBN) as a primary crystalline phase, which has a tungsten bronze structure, are produced. The formation of crystalline secondary phases also has been studied. The SBN phase shows evidence of both surface nucleation and bulk nucleation, and the crystals have an average composition of Sr0.47Ba0.53Nb2O6. The dendritic morphology of the SBN crystals has been examined. The SBN content and composite dielectric constant each has been studied as a function of heating temperature/time. The highest SBN content and dielectric constant obtained in the present study are 42 vol% and 180, respectively. The dielectric constant of the glass-ceramics is determined primarily by the SBN content and the residual glass phase. The dielectric constant of the randomly oriented SBN crystal in the glass-ceramics is calculated, using dielectric mixture rules, to be ,400. [source] Growth and characterization of Nd, Yb , yttrium oxide nanopowders obtained by sol-gel methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2007A. Rzepka Abstract Nanopowders of Y2O3 pure, doped and codoped by Nd3+, Yb3+ were obtained by sol-gel method. Solution with ethylene glycol was choosed as the proper solution where crystallites of powder with Nd and Yb dopants had the same size. Finally the one-phased compounds of Y2O3 doped 0.5 at% Nd and 1, 2 or 4 at% Yb were obtained. Grain growth and their morphology were investigated in various temperature and time of heating. The changes of crystallite sizes and lattice constants in relation to the heating time and temperature for the composition Y2O3 doped 0.5 at% Nd and 2 at% Yb are presented. Y2O3 containing 0,5 at% of Nd exhibits intense luminescence bands centered at 920 nm, 1100 nm and 1360 nm whereas a single band at about 1020 nm appears in samples co-doped with neodymium and ytterbium. Luminescence spectra recorded did not depend on the sample preparation procedure and size of grains. OH impurity affects critically the relaxation dynamics of luminescent ion in nanopowders. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impact of dilute acid pretreatment on the structure of bagasse for bioethanol productionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2010Wei-Hsin Chen Abstract Dilute acid pretreatment is a commonly used pretreatment method in the course of producing bioethanol from lignocellulosics and the structure variation of the lignocellulosics is highly related to the pretreatment process. To understand the impact of dilute acid pretreatment on the structure of bagasse, four different pretreatment conditions by varying heating time are considered where the bagasse and the pretreated materials are examined using a variety of analysis methods. The obtained results indicate that the thermogravimetric analysis (TGA) is able to provide a useful insight into the recognition of lignocellulosic structure. Specifically, the peak of the TGA of the pretreated materials moves toward the low temperature region, revealing that the lignocellulosic structure is loosened. However, the characteristic of crystal structure of cellulose remains in the pretreated materials. Increasing heating time enhances the pretreatment procedure; as a result, the average particle size of the investigated materials increases with heating time. This swelling behavior may be attributed to the enlarged holes inside the particles in that the surface area decreases with increasing heating time. In addition, when the heating time is increased to a certain extent (e.g. 15,min), some fragments are found at the surface and they tend to peel off from the surface. It follows that the dilute acid pretreatments have a significant effect on the bagasse structure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Use of sunflower oil mixed with jojoba and paraffin oils in deep-fat frying processINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2008Radwan S. Farag Summary The aim of the present study was to increase the stability of sunflower oil during frying process and to obtain low-calorie fried foods. Therefore, sunflower oil was mixed separately with jojoba oil and paraffin oil at ratios of 9:1 and 8:2 (v/v). The frying process was conducted at 180 ° ± 5 °C for 12 h continuous heating time. Some physico-chemical properties (refractive index, viscosity, colour, acid value, peroxide value, thiobarbituric acid test, iodine value and polymer content) of non-fried and binary fried oil systems were measured at various heating periods. The results demonstrated that mixing sunflower oil with jojoba oil or paraffin oil increased the stability and hence improved the quality of sunflower oil during frying process. [source] OIL POINT PRESSURE OF SOYBEANJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2002O.O. AJIBOLA ABSTRACT The effects of processing conditions such as preheating moisture content (6, 8.3, 10 and 12%-wet basis), heating temperature (70, 85, 100 and 115C) and heating time (15, 20, 25 and 30 min) on the oil point pressure of soybean seed was investigated. It was observed that increase in preheating moisture content from 6.0% to 12.0% (wet basis) increases the oil point pressure. The oil point pressure was found to decrease with increase in temperature and heating time from 70C to 115Cand 15 min to 30 min, respectively. It was also observed that increase in the moisture content during expression (postheating moisture content) from 2.6 to 11.6% increases the oil point pressure and the relationship can adequately be represented by a linear model. The postheating moisture content is affected by the initial moisture content, the heating temperature and heating time; therefore these factors affect the oil point pressure. The oil point pressure values obtained in the study were between 10.4 MPa (for sample at a moisture content of 6.0% heated at 115Cfor 30 min) and 17.2 MPa (for sample at a moisture content of 12.0% heated at 70C for 15 min). [source] FIRMNESS OF THERMAL PROCESSED ONION AS AFFECTED BY BLANCHINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2006JAE C. KIM ABSTRACT The pectin methyl esterase enzyme system was shown to be involved in firmness of thermally treated onion in the temperature range 50,70C. Thermal softening of onion at 90 and 100C showed an initial steep negative slope with a shallow negative slope at longer heating time. Low-temperature blanching at 70C was effective to maintain firm onion tissue exposed to excessive heating. Physical strength of onion was substantially diminished when exposed to a commercial sterilization condition where F0, extent of thermal sterilization, was 3, and/or more. Blanching in water for 120 min at 70C resulted in a maximum value for the firmness of commercially sterilized onion. Firmness of onion, blanched in calcium brine at a concentration range of 0.0,1.0% (wt) prior to heat treatment, decreased with increasing severity of thermal sterilization treatment. At F0 = 6, blanching in 0.5% calcium brine resulted in maximum firmness of thermally sterilized onion, approximately 70% of that of raw onion. [source] Chemical Characterization of Tomato Juice Fermented with BifidobacteriaJOURNAL OF FOOD SCIENCE, Issue 5 2010Jong-Ho Koh Abstract:, The objective of this research was to characterize the chemical properties of tomato juice fermented with bifidobacterial species. Tomato juice was prepared from fresh tomatoes and heated at 100 °C prior to fermentation.,Bifidobacterium breve,,Bifidobacterium longum, and,Bifidobacterium infantis,were inoculated in tomato juice and kept at 35 to 37 °C for up to 6 h. Fructooligosaccharide (FOS) was added to tomato juice prior to fermentation. The analyses for brix, total titratable acidity (TTA), pH, color, and lycopene content were conducted to characterize tomato juices fermented with bifidobacterial species. Heat treatment of tomato juice did not cause any significant changes in brix, pH, and TTA. Only the redness of tomato juice was significantly increased, as the heating time increased to 30 min. The tomato juices fermented with,B. breve,and,B. longum,exhibited significant decreases in pH (3.51 and 3.80, respectively) and significant increases in TTA (13.50 and 12.50, respectively) (P,< 0.05).,B. infantis,did not cause any significant change in the chemical properties of tomato juice. The addition of FOS further improved the fermentation of tomato juice by bifidobacterial species. The lycopene contents of tomato juice were significantly increased from 88 to 113 ,g/g by heat treatment at 100 °C (P,< 0.05), however did not exhibit any significant change after fermentation with bifidobacterial species. [source] Fungistatic Activity of Heat-Treated Flaxseed Determined by Response Surface MethodologyJOURNAL OF FOOD SCIENCE, Issue 6 2008Y. Xu ABSTRACT:, The objective of this study was to evaluate the effect of heat treatment on the fungistatic activity of flaxseed (Linum usitatissimum) in potato dextrose agar (PDA) medium and a fresh noodle system. The radial growth of Penicillium chrysogenum, Aspergillus flavus, and a Penicillium sp. isolated from moldy noodles, as well as the mold count of fresh noodle enriched with heat treated flaxseed, were used to assess antifungal activity. A central composite design in the response surface methodology was used to predict the effect of heating temperature and time on antifungal activity of flaxseed flour (FF). Statistical analysis determined that the linear terms of both variables (that is, heating temperature and time) and the quadratic terms of the heating temperature had significant (P < 0.05) effects on the radial growth of all 3 test fungi and the mold count log-cycle reduction of fresh noodle. The interactions between the temperature and time were significant for all dependent variables (P < 0.05). Significant reductions in antifungal activities were found when FF was subjected to high temperatures, regardless of heating time. In contrast, prolonging the heating time did not substantially affect the antifungal activities of FF at low temperature. However, 60% of the antifungal activity was retained after FF was heated at 100 °C for 15 min, which suggests a potential use of FF as an antifungal additive in food products subjected to low to mild heat treatments. [source] The Dielectric Property of Soybean Oil in Deep-Fat Frying and the Effect of FrequencyJOURNAL OF FOOD SCIENCE, Issue 3 2002C. Inoue ABSTRACT: : Suitability of the dielectric constant for real time and continuous evaluation of frying oil was investigated. Measurements of the dielectric capacitance, in the frequency range 1 kHz to 100 kHz, were made on soybean oil heated at several temperatures (180, 200, 220, and 240 °C) for a few d. Frequency dependence was also measured between 50 Hz and 30 MHz. The dielectric constant of the soybean oil increased with increase in the heating time, and was well correlated with acid value, density, and relative viscosity. Our equipment for measuring capacitance would be available for real time and continuous evaluation of frying oil quality in the food industry. [source] Trypsin Inhibitor Activity In Vitro Digestibility and Sensory Quality of Meat-Like Yuba Products as Affected by ProcessingJOURNAL OF FOOD SCIENCE, Issue 3 2002G. Su ABSTRACT: : Soybeans (Glycine max) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. [source] Temperature Profiles in a Cylindrical Model Food During Pulsed Microwave HeatingJOURNAL OF FOOD SCIENCE, Issue 7 2001H.W. Yang ABSTRACT: Cylindrical 2%-agar gel samples were heated by pulsed and continuous microwave applications. The total microwave application time of 3 min was maintained for all experiments. Sample temperature was measured at various depths along the radial dimension to experimentally determine the internal temperature profile as a function of heating time. A local hot spot was observed at the center portion of the sample during the continuous microwave application. This hot spot was less significant during pulsed microwave applications, especially when longer intermittent power-off times were employed. An implicit finite-difference model was used to estimate temperature profiles within the sample during microwave heating. The estimated temperature profiles matched the experimental values well. [source] Raman and infrared studies of synthetic Maya pigments as a function of heating time and dye concentrationJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2007F. S. Manciu Abstract Maya Blue is a famous indigo-based pigment produced by the ancient Mayas. The organic/inorganic complexes inspired by Maya Blue have led to a new class of surface compounds that have novel applications to pigment industries. Materials analyzed in the present work are made by a synthetic route, and demonstrate chemical stability similar to that of the ancient Maya Blue samples. However, we have learned that stable complexes can be synthesized at much higher dye concentrations than used by the Mayas. Analysis by FT-Raman and FT-IR spectroscopy demonstrates the partial elimination of the selection rules for the centrosymmetric indigo, indicating distortion of the molecule. This distortion accounts for the observed color changes, as the molecular orbital structure is modified, allowing the complex to stabilize. The spectroscopic data also shows the disappearance of the indigo NH bonding, as the organic molecules incorporate into palygorskite material. A structural change of indigo to dehydroindigo during heating is suggested by this result. Infrared data confirm the loss of zeolitic water and a partial removal of structural water after the heating process. Evidence of bonding between cationic aluminum and dehydroindigo through oxygen and nitrogen is revealed by FT-Raman measurements at higher dye concentrations. Copyright © 2007 John Wiley & Sons, Ltd. [source] GELLING BEHAVIOR OF RICE FLOUR DISPERSIONS AT DIFFERENT CONCENTRATIONS OF SOLIDS AND TIME OF HEATINGJOURNAL OF TEXTURE STUDIES, Issue 3 2008ALKA KAPRI ABSTRACT Rice flour dispersions, under suitable conditions of processing, can form a gel. The effect of concentration of solids (10,18%) and time (0,75 min) of processing on textural attributes, and viscoelasticity were investigated along with sensory attributes. The textural attribute determined is gel strength, while viscoelasticity was determined in terms of mechanical spectra like storage modulus (G,), loss modulus (G,), complex viscosity (,*) and loss factor (tan ,) during a frequency sweep varying from 0.01 to 40 Hz at a constant stress of 25 Pa. Microstructural observation indicates the swelling of starch granules in the beginning of heating, while damaged granule and leached-out materials are visible at the end of the gelling process. Desirability function analysis has been applied to obtain a rice gel with acceptable textural attributes; a solid concentration of 15.2% and a heating time of 75 min can lead to the development of a gel with a satisfaction level of 0.6. PRACTICAL APPLICATIONS Rice flour gels in the form of hard-set gels, porridges and spreads are popular in several parts of the world particularly for feeding of infants and children. The application of the present study lies in understanding the role of major processing variables on the quality attributes and viscoelasticity of a product, characterization of cooked gels and for developing rice flour-based food gels. The findings may also be extended for the development of other cereal-based gels. [source] COMPARISON OF MECHANICAL TESTS FOR EVALUATING TEXTURAL CHANGES IN POTATOES DURING THERMAL SOFTENINGJOURNAL OF TEXTURE STUDIES, Issue 6 2002W. K. SOLOMON ABSTRACT The changes in the texture of cylindrical samples of potato tissues immersed in water at 60, 70, 80 and 90C for up to 80 min were monitored at each temperature in terms of tangent modulus of elasticity in axial and radial compression tests, and elasticity and viscosity parameters in creep and stress relaxation tests. The magnitude of all mechanical test parameters decreased with an increase in heating time and temperature. The creep and stress relaxation responses of individual potato samples were adequately represented by respective mechanical models (R2= 0.94 to 0.99). The mechanical test parameters followed apparent first-order degradation kinetics due to the effect of thermal softening, and the rate constant was used as an index of the sensitivity of a mechanical test. The radial compression test was relatively more sensitive than the axial test. Based on an overall comparison, the parameters from creep and stress relaxation tests were found to be the most sensitive in describing the textural changes during thermal softening of potatoes. [source] Photoluminescent Properties of SrTiO3:Pr, Al Nanophosphors Synthesized by Microemulsion,Microwave HeatingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Qi Pang A novel approach for the preparation of SrTiO3:Pr, Al nanophosphors by microemulsion,microwave heating is reported in this paper. In comparison with the conventional solid-state sintering processes, this novel method provides a limited small space in a micelle for the formation of nanosized precursors and requires a very short heating time, thus reducing the energy consumption. As a result, small-sized particles with a narrow size distribution and high purity were produced. Transmission electron microscopy characterizations indicated that the synthesized particles were almost spherical with an averaging diameter of ,24 nm and agglomerates slightly. The X-ray diffraction analysis revealed the perovskite cubic structure of SrTiO3:Pr3+ nanoparticles. The luminescent of SrTiO3:Pr, Al phosphors were investigated by photoluminescence. Under 350 nm excitation, SrTiO3:Pr, Al showed a strong red emission, peaking at around 615 nm. The photoluminescence excitation intensity was enhanced by the addition of Al3+ ions. [source] Nutritional comparison of fresh, frozen and canned fruits and vegetables.JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2007Part 1. Abstract The first of a two-part review of the recent and classical literature reveals that loss of nutrients in fresh products during storage and cooking may be more substantial than commonly perceived. Depending on the commodity, freezing and canning processes may preserve nutrient value. The initial thermal treatment of processed products can cause loss of water-soluble and oxygen-labile nutrients such as vitamin C and the B vitamins. However, these nutrients are relatively stable during subsequent canned storage owing to the lack of oxygen. Frozen products lose fewer nutrients initially because of the short heating time in blanching, but they lose more nutrients during storage owing to oxidation. Phenolic compounds are also water-soluble and oxygen-labile, but changes during processing, storage and cooking appear to be highly variable by commodity. Further studies would facilitate the understanding of the changes in these phytochemicals. Changes in moisture content during storage, cooking and processing can misrepresent changes in nutrient content. These findings indicate that exclusive recommendations of fresh produce ignore the nutrient benefits of canned and frozen products. Nutritional comparison would be facilitated if future research would express nutrient data on a dry weight basis to account for changes in moisture. Copyright © 2007 Society of Chemical Industry [source] Mathematical modelling of the heat inactivation of trypsin inhibitors in soymilk at 121,154,°CJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2002Kin-Chor Kwok Abstract Response surface methodology (RSM) was used to investigate the effects of processing temperature and time on the inactivation of trypsin inhibitors (TI) in soymilk. The factorial experimental design consisted of four levels of temperature and six levels of time in a temperature range of 121,154,°C and a time interval of 10,90,s. A quadratic polynomial equation, relating log(% TI retained) as a function of heating time and temperature, was satisfactorily fitted to the experimental data by least squares regression with r2 (correlationcoefficient),=,0.959. Within the range of heating times investigated, TI in soymilk was satisfactorily destroyed to 10% retained at 143 and 154,°C with 62 and 29,s heating time respectively. © 2002 Society of Chemical Industry [source] Electrospun Hybrid Soy Protein/PVA FibersMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2010Daehwan Cho Abstract Rheological behavior and spinnability of biodegradable materials based on SPI and PVA were studied for the production of electrospun fibers. pH level, processing temperature, and heating time were adjusted to investigate the effects of denaturing of soy protein on the rheology of SPI/PVA solutions. The results show that zero shear viscosity and degree of shear thinning of the SPI solution can be controlled by adjusting pH level and thermal treatment. The continuous production of uniform SPI/PVA fibers was achieved by electrospinning. The presence and amount of soy protein in the electrospun fibers was determined by EMPA and elemental analysis, confirming that the SPI was well incorporated into the PVA and remained in the electrospun fibers. [source] Long-Term Properties of Butt-Welded Poly(propylene)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2003Ernst Schmachtenberg Abstract It is still not clear why the long-term properties of plastic weld seams can only be differentiated by the very expensive medium tensile creep tests. One hypothesis for justifying this is based on the change in the structure of the weld seam surroundings, another cites the consumption of antioxidants and the following ageing in the weld seam area to be responsible for this. Butt-welded weld seams made of poly(propylene) were systematically produced under different process parameters. Corresponding to the particular hypothesis, these weld seams were then analyzed in various ways to find correlations or to prove one of the hypotheses. Regarding their short-term weld seam quality, the analyzed weld seams could not be differentiated through short-term tensile or short-term bend test. However, the medium tensile creep tests showed significant differences in both time until failure and long-term weld seam quality. Under long-term loading, the start of the brittle crack could be detected in most weld seams in the fine spherulite-zone or between this zone and the area of the flow lines. This demonstrated again that only long-term tests are suitable for examining different weld seam qualities. Depending on the welding parameters, times until failure decline with increasing heated-tool temperature and heating time. Though these parameters lead to a higher consumption of antioxidants in the weld seam, a degradation was not detected in the breaking area. In fact, increasing heated-tool temperatures and heating times, as well as higher joining pressures lead to a change in the internal structure of the material. This can be seen in morphological structure analyses in the larger bend of the entire weld seam area. A larger bend, however, correlates with higher residual stresses in the weld seam. In the medium tensile creep tests, these residual stresses as well as the tensile stress in the border region and the compressive stress in the middle are superimposed by the tensile stress resulting from the test stress. Thus a greater bend of the weld seam area and higher residual stresses in the weld seam itself lead to shorter times until failure in medium tensile creep tests. Schematic representation of the formation of residual stresses in a weld seam and residual stresses in the different bended weld seam areas. [source] Thermal kinetics of color degradation of mulberry fruit extractMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 2 2003Hyung Joo Suh Abstract The effects of temperature and pH on color degradation kinetics of the mulberry fruit extract were investigated. The absorbance at 510 nm was decreased with increase of heating time, but that at 420 nm was increased with the increase of heating time at 100°C. The change of the browning index (A510/A420) was increased with increase of pH and was lower at pH 2.0 than that at pH 5.0. The browning index variation was adequately described by both the first-order and the zero-order kinetic. However, the zero-order kinetic model was proposed because of the better fit. According to the Arrhenius model, the activation energies for the browning index in the range of 80,100°C for the four different pH values were 30.68 kJ/mol for pH 2.0, 35.87 kJ/mol for pH 3.0, 42.67 kJ/mol for pH 4.0, and 43.49 kJ/mol for pH 5.0. [source] Zero flash ultrasonic micro embossing on foamed polymer substrates: A proof of conceptPOLYMER ENGINEERING & SCIENCE, Issue 11 2009Srikanth G. Vengasandra This article reviews a novel method to produce microembossed features with an aspect ratio of three and negligible flash on polymer surfaces. An embossing technique that utilizes localized heating (ultrasonic energy) was used with polystyrene and polypropylene substrates. It was demonstrated that when foamed substrates were used, the amount of flash produced was negligible compared to nonfoamed substrates, which has been a significant unresolved problem with embossing using localized heating. The depth of microembossed features as a function of heating times and amplitudes of ultrasonic embossing is detailed in this article, along with a characterization of complex embossed geometries. It was seen that embossing depth was generally proportional to heating time and amplitude until the maximum feature depth was achieved. Although this article deals with embossing of microfeatures for lab-on-a-CD applications, it is envisioned that it is also suitable for lab-on-a-chip applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Polystyrene microcellular plastic generation by quick-heating process at high temperaturePOLYMER ENGINEERING & SCIENCE, Issue 7 2000Sumarno Generation of microcellular plastic in the polystyrene-nitrogen system was studied in a batch process. In this study, a quick-heating method was applied to study the effects of saturation temperature, decompression rate and heating time on the microcellular structure for sheet samples with a thickness of 1.3 mm. The saturation pressure in each process was kept constant at 25 MPa. At saturation temperatures above 393 K, we found that, although the solubility of nitrogen increased with increasing saturation temperature, cell density decreased, and the average cell diameter and volume expansion ratio increased. The samples that were saturated at 433 K shattered after microcellular processing. The change in decompression rate affected the supersaturation degree of the dissolved gas in the polymer, and affected the cell structure. Variation of heating time for difference saturation/heating temperature could be used to obtain the optimum relation between cell density, average cell diameter, and volume expansion ratio. [source] Glass Transition Temperatures and Fermentative Activity of Heat-Treated Commercial Active Dry YeastsBIOTECHNOLOGY PROGRESS, Issue 2 2000Carolina Schebor Differential scanning calorimetry thermograms of various samples of commercial instant active dry yeasts revealed a clear glass transition typical of amorphous carbohydrates and sugars. The resulting glass transition temperatures were found to decrease with increasing moisture content. The observed glass curve was similar to that of pure trehalose, which is known to accumulate in large amounts in baker's yeast. The effect of heat treatment at various temperatures on the fermentative activity (as measured by the metabolic production of CO2) of dry yeast was studied. First-order plots were obtained representing the loss of fermentative activity as a function of heating time at the various temperatures assayed. Significant losses of fermentative activity were observed in vitrified yeast samples. The dependence of rate constants with temperature was found to follow Arrhenius behavior. The relationship between the loss of fermentative activity and glass transition was not verified, and the glass transition was not reflected on the temperature dependence of fermentative activity loss. [source] Infrared Heating in Food Processing: An OverviewCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 1 2008Kathiravan Krishnamurthy ABSTRACT:, Infrared (IR) heating provides significant advantages over conventional heating, including reduced heating time, uniform heating, reduced quality losses, absence of solute migration in food material, versatile, simple, and compact equipment, and significant energy saving. Infrared heating can be applied to various food processing operations, namely, drying, baking, roasting, blanching, pasteurization, and sterilization. Combinations of IR heating with microwave heating and other common conductive and convective modes of heating have been gaining momentum because of increased energy throughput. This article reviews aspects of IR heating and presents a theoretical basis for IR heat processing of food materials and the interaction of IR radiation with food components. The effect of IR on food quality attributes is discussed in the context of samples and process parameters. Applications of IR heating in food processing operations and future research potential are also reviewed. [source] Palladium-Catalysed Amination of Electron-Deficient or Relatively Electron-Rich Benzo[b]thienyl Bromides , Preliminary Studies of Antimicrobial Activity and SARsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2004Maria-João R. P. Queiroz Abstract Several diarylamines in the benzo[b]thiophene series were prepared in good to high yields by palladium-catalysed amination of ethyl 3-bromobenzo[b]thiophene-2-carboxylate with anilines and 5-aminoindole in the presence of Pd(OAc)2, BINAP and Cs2CO3 in toluene. The presence of the ester group at the 2-position of the benzo[b]thiophene moiety increases the yields and lowers the heating times relative to the reactions performed with 3-bromobenzo[b]thiophene. When aminopyridines were used instead of anilines, the ligand and the solvent need to be changed to XANTHPHOS and dioxane in the amination reaction. With 2-aminopyridine a one-pot C,N coupling and intramolecular cyclization involving the nitrogen atom of the pyridine ring occurred, with loss of ethanol, giving an interesting fluorescent tetracyclic heteroaromatic compound. The antimicrobial activity, the minimal inhibitory concentrations (MICs) and the structure-activity relationships (SARs) were evaluated. A selectivity with low MICs was observed against Bacillus Cereus, and good results were also obtained against Candida albicans. The acids obtained by hydrolysis of the ester group, as non-proteinogenic ,,,-unsaturated ,-amino acids, can be incorporated into peptide chains to induce conformational constraints. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] THERMAL DEATH TIMES OF ESCHERICHIA COLI IN YOUNG COCONUT ENDOSPERM BEVERAGEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2009ALONZO A. GABRIEL ABSTRACT The decimal reduction times (D values) of Escherichia coli (American Type Culture Collection 25922) were established in a young coconut endosperm beverage, a famous local drink in the Philippines and in many tropical countries. Artificially inoculated cells were heated to 60, 70 and 80C at various heating times prior to survivor enumeration by surface plating onto pre-solidified Eosine Methylene Blue Agar. Results showed that the surviving populations significantly (P < 0.05) decreased with increasing exposure time and temperature. The calculated D values ranged from 0.26 ± 0.01 to 0.56 ± 0.08 min. Validation of the results by establishing the thermal resistance of other E. coli isolates in the coconut beverage medium was recommended. PRACTICAL APPLICATION The study established the thermal inactivation rates of Escherichia coli (American Type Culture Collection 25922) in a young coconut endosperm beverage medium in various heating temperatures. The results obtained from this study may be used in the calculations of appropriate thermal process schedules for the test beverage against the test organism. [source] EFFECTS of THERMAL TREATMENTS ON TEXTURE of SOY PROTEIN ISOLATE TOFUJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2000LEE KAH HUI Effects of three thermal treatments; boiling at 100C and retorting at 110 and 121C, on texture of soy protein isolate tofu were studied for a range of heating times. Retorted tofu showed a shrinkage of 18,25% of its original size and a loss of 6,12% of its original moisture. Tofu processed at high temperatures and long heating times developed higher values of texture profile parameters than tofu processed at lower temperature and shorter heating times. the thermal treatment of tofu at elevated conditions also caused an increase in sensory hardness and a decrease in moistness and overall acceptability of the tofu. the increase in texture profile values appeared to be mirrored by a decrease in protein solubility in 1% sodium dodecyl sulfate solvent and a reduction in moisture content of the tofu. the formation of disulfides linkages at elevated temperatures and during heating at 100C stabilized protein aggregates that were initially formed by hydrophobic interactions. Formation of the disulfides and shrinkage of tofu as a result of moisture loss were suggested as the major reason for decreased sensory values of thermally processed soy protein isolate tofu. [source] Mathematical modelling of the heat inactivation of trypsin inhibitors in soymilk at 121,154,°CJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2002Kin-Chor Kwok Abstract Response surface methodology (RSM) was used to investigate the effects of processing temperature and time on the inactivation of trypsin inhibitors (TI) in soymilk. The factorial experimental design consisted of four levels of temperature and six levels of time in a temperature range of 121,154,°C and a time interval of 10,90,s. A quadratic polynomial equation, relating log(% TI retained) as a function of heating time and temperature, was satisfactorily fitted to the experimental data by least squares regression with r2 (correlationcoefficient),=,0.959. Within the range of heating times investigated, TI in soymilk was satisfactorily destroyed to 10% retained at 143 and 154,°C with 62 and 29,s heating time respectively. © 2002 Society of Chemical Industry [source] Long-Term Properties of Butt-Welded Poly(propylene)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2003Ernst Schmachtenberg Abstract It is still not clear why the long-term properties of plastic weld seams can only be differentiated by the very expensive medium tensile creep tests. One hypothesis for justifying this is based on the change in the structure of the weld seam surroundings, another cites the consumption of antioxidants and the following ageing in the weld seam area to be responsible for this. Butt-welded weld seams made of poly(propylene) were systematically produced under different process parameters. Corresponding to the particular hypothesis, these weld seams were then analyzed in various ways to find correlations or to prove one of the hypotheses. Regarding their short-term weld seam quality, the analyzed weld seams could not be differentiated through short-term tensile or short-term bend test. However, the medium tensile creep tests showed significant differences in both time until failure and long-term weld seam quality. Under long-term loading, the start of the brittle crack could be detected in most weld seams in the fine spherulite-zone or between this zone and the area of the flow lines. This demonstrated again that only long-term tests are suitable for examining different weld seam qualities. Depending on the welding parameters, times until failure decline with increasing heated-tool temperature and heating time. Though these parameters lead to a higher consumption of antioxidants in the weld seam, a degradation was not detected in the breaking area. In fact, increasing heated-tool temperatures and heating times, as well as higher joining pressures lead to a change in the internal structure of the material. This can be seen in morphological structure analyses in the larger bend of the entire weld seam area. A larger bend, however, correlates with higher residual stresses in the weld seam. In the medium tensile creep tests, these residual stresses as well as the tensile stress in the border region and the compressive stress in the middle are superimposed by the tensile stress resulting from the test stress. Thus a greater bend of the weld seam area and higher residual stresses in the weld seam itself lead to shorter times until failure in medium tensile creep tests. Schematic representation of the formation of residual stresses in a weld seam and residual stresses in the different bended weld seam areas. [source] Zero flash ultrasonic micro embossing on foamed polymer substrates: A proof of conceptPOLYMER ENGINEERING & SCIENCE, Issue 11 2009Srikanth G. Vengasandra This article reviews a novel method to produce microembossed features with an aspect ratio of three and negligible flash on polymer surfaces. An embossing technique that utilizes localized heating (ultrasonic energy) was used with polystyrene and polypropylene substrates. It was demonstrated that when foamed substrates were used, the amount of flash produced was negligible compared to nonfoamed substrates, which has been a significant unresolved problem with embossing using localized heating. The depth of microembossed features as a function of heating times and amplitudes of ultrasonic embossing is detailed in this article, along with a characterization of complex embossed geometries. It was seen that embossing depth was generally proportional to heating time and amplitude until the maximum feature depth was achieved. Although this article deals with embossing of microfeatures for lab-on-a-CD applications, it is envisioned that it is also suitable for lab-on-a-chip applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] | |||||||||||||||||||