Effects Of Heating Methods Research Articles

Effects of heating method and conditions on the quality attributes of black mulberry (Morus nigra) juice concentrate

SummaryBlack mulberry juice was concentrated by different heating methods including conventional heating and microwave heating at different operational pressures (7.3, 38.5 and 100 kPa). The effects of each method of heating on the quality attributes of the concentrated juice were investigated. The final juice concentration of 42°Brix was achieved in 140, 120 and 95 min at 100, 38.5, and 7.3 kPa, respectively, by using a rotary evaporator. Applying microwave energy decreased the required times to 115, 95, and 60 min. The changes in anthocyanin, antioxidant, phenolic content, turbidity, pH value, and acidity during concentration were investigated. Results showed that the degradation of anthocyanins was more pronounced in rotary evaporation comparing to microwave heating method. The higher phenolic concentrations resulted in a smaller EC50 value, which corresponds to a higher antioxidant activity of the mulberry extract.

Effects of heating method and conditions on the evaporation rate and quality attributes of black mulberry (Morus nigra) juice concentrate

Black mulberry juice was concentrated by different heating methods, including conventional heating and microwave heating, at different operational pressures (7.3, 38.5 and 100kPa). The effects of each method on evaporation rate, quality attributes of concentrated juice were investigated. The final juice concentration of 42° Brix was achieved in 140, 120, and 95min at 100, 38.5, and 7.3kPa respectively by using a rotary evaporator. Applying microwave energy decreased required times to 115, 95, and 60min. The changes in color, anthocyanin content during the concentration processes were investigated. Hunter parameters (L, a, and b) were measured to estimate the intensity of color loss. All Hunter color parameters decreased with time. Results showed that the degradation of color and consequently anthocyanins, was more pronounced in rotary evaporation compared to microwave heating method.

Facile synthesis of cuprous oxide using ultrasound, microwave and electric heating: effect of heating methods on synthesis kinetics, morphology and yield

Ultrasound (US) and microwave (MW) irradiation has been applied for rapid syntheses of cuprous oxides from copper sulfate, sodium citrate, sodium carbonate and polyvinylpyrrolidone in water at a relatively low temperature below 50 °C. Compared with conventional electric (CE) synthesis, US and MW heating lead very rapidly to cuprous oxides having a well-defined small cubic morphology in high yield. The rapid syntheses with US (acceleration degree: 48–81 times of CE synthesis) and MW (acceleration degree: 17–18 times of CE synthesis) are due to decreased activation free energy (ΔG≠, of the Eyring equation) or increased pre-exponential factor (A, of the Arrhenius equation). However, the activation energy (Ea) decreases in the order of US > MW > CE synthesis. The decreased activation free energy is due to a small decrease (or relatively high) in activation entropy (ΔS≠) rather than a decreased activation enthalpy (ΔH≠). The accelerated syntheses do not depend noticeably on reaction stages (nucleation and crystal growth) and synthesis methods (US and MW, excluding the acceleration degrees), suggesting the acceleration is mainly due to physical effects including hot spots or transient temperature rather than chemical ones.

D- and Z-values of microflora in tuna mince during moist- and dry-heating

Fish and seafood are prone to rapid microbial spoilage, thus adequate care must be taken in drying of fish. The microbial load and its changes during drying and storage are important information in establishing a standard that will ensure food safety. In order to develop drying procedures leading to low safety risk, it is relevant to determine the decimal reduction time ( D-value) and the thermal resistance constant ( Z-value) during a heating process to identify the effect of temperature on lethality. In the case of drying, microbial changes occurred due to the effects of heat and concentration process. This study was conducted to investigate the changes of endogenous bacterial counts in minced tuna during dry-heating (convection air-drying) and moist-heating (heating in a closed chamber) as a function of temperature. The D-values for total viable counts decreased from 2.52 to 0.26 h for moist-heating and 2.57 to 0.34 h for dry-heating, respectively, when temperature was maintained constant within 60–140°C. In both cases, increasing temperature caused significant decrease in D-values ( P<0.05), whereas the effect of heating methods was not significant ( P>0.05). Thus the heat resistance characteristics of microorganisms in fresh tuna mince was not depended on the changing medium moisture content.

Liquid Holding Capacity of Farmed Atlantic Salmon Muscle at Low Temperature Heating-Effect of Frozen and Ice Storage

This study evaluates the liquid holding capacity of Atlantic salmon muscle during low temperature heating in relation with freezing and ice storage. A part of each fillet was heated from 5 to 40°C at 5°C intervals using two methods, water bath or heat chamber heating, and different storage conditions. According to the total variation of liquid, water or fat loss, the heating temperature was the major factor affecting the muscle liquid holding capacity, the significant increase beginning at 30°C. No effect of heating method or storage time was observed, whereas a significant increase of water and fat losses were obtained with frozen storage. The liquid loss in the packages, principally water, increased with increasing temperature. No alteration of fatty acid composition was observed during heating.

Experimental studies on municipal solid waste pyrolysis in a laboratory-scale rotary kiln

A laboratory-scale, externally heated, rotary-kiln pyrolyser was designed and built. Pyrolysis tests were performed. Solid wastes (paper, paperboard, waste plastics including PVC and PE, rubber, vegetal materials, wood, and orange husk) were tested. The effects of heating methods, moisture contents and size of waste on pyrolysis gas yields and compositions, as well as heating values, were evaluated.

Preparation of Monodisperse and Spherical Powders by Heating of Alcohol-Aqueous Salt Solutions

A method for the preparation of monodisperse and spherical powders from salt solution with a mixed solvent of alcohol and water is demonstrated. The volume ratio of alcohol to water (R/H ratio) in the alcohol-aqueous salt solutions greatly influenced the behavior of the precipitation and the morphology of the resulting particles. The precipitation, by heating an alcohol-aqueous salt solution, occurs by the decrease of dielectric constant of the solvent and thus a decrease in the salt solubility. The morphology and size variation of the resulting particles was explained by considering the parameters determining the colloidal stability in the DLVO theory; the zeta potential and the dielectric constant. During the preparation of the powders by heating of the alcohol-aqueous salt solution, the effect of heating methods on the characteristics of the resulting particles is also demonstrated. A microwave heating, as a uniform and rapid heating method, induced the uniform and rapid precipitation to produce monodisperse and spherical particles.

Effects of heating method during sintering on structure and properties of iron-base materials : N.A. Nikishov et al, Metalloved Term. Obrab. Met, No 1, 1991, 35–37. In Russian

Calculations of chemical equilibria for the Mo-B-N system using the VCS algorithm were carried out for the 30–1727°C temperature range and the 1·3 × 10−3−1 × 107 Pa pressure range. Two BN: Mo molar ratios were selected: 1 : 1 and 2 : 1. It follows from these studies that Mo can react with BN in a very wide range of temperatures and pressures, giving new phases, namely Mo2B, MoB, MoB2, Mo2B5 and MoB4. The formation of these phases is strongly influenced by pressure-temperature parameters. In order to verify theoretical calculations by experiment equimolar and 2 : 1 BN : Mo batches were prepared and heated at 1427°C in vacuum and in argon atmosphere. Phase identification carried out by X-ray diffraction fully corroborated the computational results.Die chemischen Gleichgewichte des Mo-B-N-Systems wurden mit Hilfe des VCS-Algorithmuses im Temperatur- und Druckbereich von 30–1727°C bzw. 1·3 × 10−3−1 × 107 Pa berechnet. Es wurden zwei BN : Mo-Verhältnisse gewählt: 1 : 1 und 2 : 1. Aus den Berechnungen ergab sich, daß Mo in einem weiten Temperatur- und Druckbereich mit BN reagieren kann, und daß sich folgende neue Phasen bilden können: Mo2B, MoB, MoB2, Mo2B5 und MoB4. Die Bildung dieser Phasen hängt stark von der Temperatur und vom Druck ab. Zur Bestätigung der theoretischen Ergebnisse wurden gleichmolare und 2 : 1 BN : Mo Proben hergestellt und im Vakuum bzw. in einer Argonatmosphäre auf 1427°C erwärmt. Die mittels Röntgenbeugung durchgeführte Phasenanalyse bestätigte die berechneten Ergebnisse.On a calculé les caractéristiques de l'équilibre chimique du système Mo-B-N en utilisant l'algorithme VCS, ceci pour des températures comprises entre 30 et 1727°C, et des pressions de 1·3 × 10−3−1 × 107 Pa. Deux rapports molaires BN : Mo ont été sélectionnés: 1 : 1 et 2 : 1. Il ressort de cette étude que Mo et BN peuvent réagir dans un large domaine de température et de pression, donnant de nouvelles phases: Mo2B, MoB, MoB2, Mo2B5 et MoB4. La formation de ces phases est fortement influencée par les paramètres de température et de pression. Afin de vérifier les prédictions théoriques de manière expérimentale, des lots équimolaires et 2 : 1 de BN et Mo ont été préparés, chauffés à 1427°C sous vide ou sous argon. L'identification des phases faite par diffraction X corrobore les résultats numériques.

The effects of heating methods on pool boiling

Saturation pool boiling is studied analytically and experimentally using a 0.5 mm tungsten wire in methanol under atmospheric pressure. Under constant voltage heating, transition boiling is an ‘unsteady’ two mode boiling which may be followed by a ‘steady’ two mode boiling. The locus of ‘steady’ two mode boiling is the equilibrium line which divides the nucleate and film boiling curves into stable and metastable sections. Along this line, the electric current is constant and the lever arm rule applies. Under constant current heating, transition boiling is ‘unsteady’ two mode boiling which changes faster as the current differs more from the equilibrium line current.

Formation of mutagens by heating foods and model systems.

We have demonstrated that the pyrolysis products of amino acids and proteins in model systems are mutagenic. The mutagenic principles in the pyrolyzates of amino acids have been isolated and identified by Sugimura et al. We have isolated and identified amino-alpha-carbolines from pyrolyzed soybean globulin as mutagens. The yield of mutagens by the heating of food constituents is changed by the heating method. Effects of heating methods on the yield of amino-alpha-carbolines were studied in a series of experiments, and the results are shown in this paper. Additionally, it has been shown that by the heating of creatine-sugar mixtures imidazoquinoline or quinoxaline mutagens are formed.

Effect of heating methods on mutagenic activity and yield of mutagenic compounds in pyrolysis products of protein.

Effects of temperature, atmosphere and time of heat treatment of albumin on mutagenic activity toward Salmonella typhimurium TA 98, as well as the yield of mutagens, 3-amino-1-methyl-5H-pyrido[4, 3-b]indole and 2-amino-9H-pyrido[2, 3-b]indole were determined in pyrolysis products. Mutagenic activity and mutagen content in the pyrolyzate increased progressively with heating temperature from 200 to 700°C. The effect of heating temperature differed depending on the heating atmosphere, i.e., N2 or air. At 200°C, pyrolyzate mutagenic activity increased with heating time up to 7h, but the mutagenic principles indicated above were not detected.

Studies on a dynamic adiabatic calorimeter. I. Heat leakage at high temperatures

In dynamic adiabatic calorimetry, the heat exchange between the calorimeter and its surroundings has been measured from room temperature to 800 degrees C, and the effects of heating method, atmosphere, heating rate and heat content of the sample upon the heat leakage are discussed. From these measurements, it is concluded that the necessary conditions for absolute measurement are that the heat leakage be minimal and constant. This may be achieved by using external heating of the sample and controlling the heating rate.