Roasting Method Research Articles

Extraction of vanadium from stone coal by roasting in a fluidized bed reactor

In order to improve leaching efficiency of vanadium pentoxide (V2O5) from stone coal and to reduce its connected environmental pollution, this article investigated the oxidizing roasting of stone coal in a laboratory fluidized bed reactor to optimize the roasting method and conditions. The examined parameters included reaction temperature, reaction time and amount and mixing method of additive. The removal of Cl from the generated effluent gas was implemented using CaO as the adsorbent, and comparison was made between the fluidized bed roasting and static roasting in a muffle oven. The results show that the fluidized roasting is more favorable to leach V2O5 from stone coal, which can shorten roasting time for reaching the maximal leaching rate, while the realized leaching rate is also higher. Comparing the mixing method applied to stone coal and additive, the impregnation method of additive on stone coal not only increased the leaching rate and shortened the roasting time for reaching the maximal leaching rate, but also reduced the amount of additive required. Adding CaO in stone coal roasting sharply decreased the content of Cl-containing gases in flue gas, which can greatly alleviate the possible environmental pollution. The optimal conditions for fluidized bed roasting were found to be impregnating 6wt.% additive on coal, adding 3wt.% CaO and performing roasting at 800°C for 0.75h.

Effects of husk and harvest time on carotenoid content and acceptability of roasted fresh cobs of orange maize hybrids.

Vitamin A deficiency (VAD) is a major public health problem in many developing countries. Orange maize is preferred as green maize and consumed roasted on the cob, especially in Nigeria. This research work was to evaluate the effects of harvest time and husk on the carotenoid contents and sensory properties of roasted orange maize hybrids. The results showed that husk (roasting forms) and harvesting time had significant effects (P ≤ 0.001) on the carotenoids and the sensory properties. There was general increase in β-carotene and provitamin A (PVA) values as the harvesting time increases. The β-carotene and PVA values for roasted orange maize hybrids with husk were higher than those for roasted without husk. Hybrid 5 had the highest β-carotene concentration and PVA value at 27 days after pollination (DAP) and 34DAP when unprocessed and roasted without husk. This information can help researchers in choosing proper roasting methods to increase the retention of high levels of β-carotene and PVA in orange maize that can be delivered to consumers through nutrition education.

Color and volatile analysis of peanuts roasted using oven and microwave technologies.

Roasted peanut color and volatiles were evaluated for different time and temperature combinations of roasting. Raw peanuts were oven roasted at 135 to 204 °C, microwave roasted for 1 to 3 min, or combination roasted by microwave and oven roasting for various times and temperatures. Volatiles were measured using selected ion flow tube mass spectrometry. L* values were used to categorize peanuts as under-roasted, ideally roasted, and over-roasted. The total roasting time in order to achieve ideal color was not shortened by most of the combination treatments compared to their oven roasted equivalents. Oven before microwave roasting compared to the reverse was found to significantly increase the L* value. Peanuts with the same color had different volatile levels. Hexanal concentrations decreased then increased with roasting. Pyrazine levels increased as roasting time increased, although oven at 177 °C treatments had the highest and microwave treatments had the lowest levels. Volatile levels generally increased as roasting time or temperature increased. Oven 177 °C for 15 min generally had the highest level of volatiles among the roasting treatments tested. Soft independent modeling of class analogies based on volatile levels showed that raw peanuts were the most different, commercial samples were the most similar to each other, and oven, microwave, and combination roasting were all similar in volatile profile. Peanuts can be roasted to equivalent colors and have similar volatile levels by different roasting methods. Oven and microwave roasting technologies produced the same roasted peanut color and had similar volatile trends as roasting time increased. Combination roasting also produced ideal color and similar volatile levels indicating that microwave technology could be further explored as a peanut roasting technique.

Industrial Applications of Selected JFS Articles

Industrial Applications of Selected <i>JFS</i> Articles

Processing of a novel powdered herbal coffee (Pistacia Terebinthus L. Fruits Coffee) and its sensorial properties.

In this study, the effects of roasting method, grinding and reduction in oil content on the characteristics of Pistacia terebinthus fruit coffee were investigated. Pistacia terebinthus fruit was roasted by microwave, pan and combined (microwave and convection) methods. The degree of roasting was determined by L*, a*, b* color values. The roasting times were 1,500, 1,900 and 1,620s for microwave, pan and combined roasting methods, respectively. Cold press was used to reduce the oil content both prior to roasting and after the roasting. The oil content was reduced to around 21.5% in all roasting methods to approach to that of coffee beans. Powdered Pistacia terebinthus fruit coffee brews were compared with each other and Turkish coffee in terms of aroma, flavor, acidity aftertaste, and overall acceptability. Sensorial analysis results showed that coffee brews prepared by pressing after the roasting process were better than those pressing prior to roasting.

Removing chlorine of CuCl residue from zinc hydrometallurgy by microwave roasting

Most Zn hydrometallurgy factories adopt Cu2SO4 as a dechlorination reagent from zinc solution nowadays, thus much CuCl residue is produced. The existing process of treating this residue is washing with water or sodium carbonate solution, which would cause a lot of troubles to water treatment and waste discharge. A method of microwave roasting was adopted for dechlorination of CuCl residue. A 1.5 kW microwave roasting equipment with dust collection and tail gas adsorption systems was set up and applied during the experiment. By investigating the effect of temperature, heat preservation time, moisture content of raw material and grain size of samples on the dechlorination, the optimal experimental condition is obtained. When the samples with 2% moisture and <150 μm grain size are microwave roasted at 400 °C for 2 h, the Cl content turns from 14.27% to 1.35% and the dechlorination rate is as high as 90%, while that with conventional heating is only 60%–80%. The phase change of the roasting process investigated with X-ray diffraction verifies that CuCl in CuCl residue is removed by being transformed into CuO.

Antioxidant and Antiradical Activity of Coffee.

This review summarizes published information concerning the determination of antioxidant activity (AA) in coffee samples by various methods (ORAC, FRAP, TRAP, TEAC, etc.) in vitro and limited data of antiradical activity of coffee products in vitro and in vivo. Comparison is carried out of the AA of coffee Arabica and coffee Robusta roasted at different temperatures as well as by different roasting methods (microwave, convection, etc.). Data on the antiradical activity of coffee is provided. The antioxidant activity of coffee, tea, cocoa, and red wine is compared. At the end of this review, the total antioxidant content (TAC) of coffee samples from 21 coffee-producing countries as measured by an amperometric method is provided. The TAC of green and roasted coffee beans is also compared.

Extraction of molybdenum and nickel from Ni–Mo ore by pressure acid leaching

A direct hydrometallurgical route for nickel and molybdenum extraction from a nickel–molybdenum (Ni–Mo) ore using pressure acid leaching was studied. The nickel and molybdenum were extracted by acid leaching under oxygen pressure. Compared with traditional roasting methods, this hydrometallurgical method eliminates SO2 and As2O3 emission (the Ni–Mo ore containing 15%–25% S). Compared with existing alkali leaching recovery of molybdenum process, almost all the nickel and considerable molybdenum were extracted in the acid leaching process. Under oxygen pressure conditions, almost all the nickel and a substantial part of the molybdenum were dissolved into the acid leaching liquor and the other part of the molybdenum was left in the acid leach residue. The acid leach residue was further leached under alkaline (NaOH) conditions. Under optimal experimental conditions, the extraction rates nickel and molybdenum reached 97% and 96%, respectively.

Shelf-life of infrared dry-roasted almonds

Infrared heating was recently used to develop a more efficient roasting technology than traditional hot air roasting. Therefore, in this study, we evaluated the shelf-life of almonds roasted with three different approaches, namely infrared (IR), sequential infrared and hot air (SIRHA) and regular hot air (HA). Nine medium roasted almond samples produced by the aforementioned heating methods were processed at three different temperatures (130, 140 and 150°C), packed in paper bags and then stored at 37°C for three, six or eight months. Shelf-life of the roasted almonds was determined by measuring the changes in colour, peroxide value, moisture content, water activity, volatile components and sensory quality. No significant difference was observed in moisture content and water activity among the almond samples processed with different roasting methods and stored under the same conditions. GC/MS analysis showed that aldehydes, alcohols, and pyrazines were the main volatile components of almonds. Aliphatic aldehydes such as hexanal, (E)-2-octenal, and nonanal were produced as off-odours during storage. Although the overall quality of roasted almonds produced with SIRHA and HA heating was similar during the first three months of storage, their peroxide value and concentration of aliphatic aldehydes differed significantly for different roasting methods and increased significantly in all roasted samples during storage. We postulate that hexanal and nonanal might be better indicators of the shelf life of roasted almonds than the current standard, peroxide value.

Tostación de un concentrado refractario de oro y plata

In processing of precious metal ores with high pyrite content, refractory concentrates are obtained, which are difficult to process. A refractory gold and silver concentrate was leached with sodium cyanide. Results show low extraction percentages, being 34 % of gold and 40 % of silver. A roasting method to oxidize the concentrate was used, making it more susceptible to cyanidation, hence a more efficient way to extract precious metals. The variables include roasting temperature and roasting and cyanidation time. In addition, the hot calcine was added to the leaching solution at room temperature to analyze the effect on particle size and recovery. The best results, although not entirely satisfactory (50 % of gold and 61 % of silver) were obtained by roasting the concentrate for 4 h at 600 °C, followed by cyanidation for 20 h. The lime consumption to raise the pH to about 11.3 was increased markedly to 25 kg/m 3 .

Effect of Roasting Conditions on Color and Volatile Profile Including HMF Level in Sweet Almonds (Prunus dulcis)

Microwave, oven, and oil roasting of almonds were used to promote almond flavor and color formation. Raw pasteurized almonds were roasted in a microwave for 1 to 3 min, in an oven at 177 °C for 5, 10, 15, and 20 min; and at 135 and 163 °C for 20 min, and in oil at 135, 163, and 177 °C for 5 min and 177 °C for 10 min. Volatile compounds were quantified in the headspace of ground almonds, both raw and roasted, by selected ion flow tube mass spectrometry. Strong correlations were found between L value, chroma, and 5-(hydroxy methyl)-2- furfural; and were independent of roasting method. Raw almonds had lower concentrations of most volatiles than roasted almonds. Conditions that produced color equivalent to commercial samples were 2 min in the microwave, 5 min at 177 °C in the oven, and 5 min at 135 °C in oil. Microwave heating produced higher levels of most volatiles than oven and oil roasting at commercial color. Sensory evaluation indicated that microwave-roasted almonds had the strongest aroma and were the most preferred. Oil-roasted almonds showed significantly lower levels of volatiles than other methods, likely due to loss of these volatiles into the oil. Alcohols such as benzyl alcohols and strecker aldehydes including benzaldehyde and methional were at higher concentrations than other volatiles in roasted almonds. The oxidation of lipids to form alkanals such as nonanal and degradation of sugars to form furan type compounds was also observed. The Maillard reaction contributed to the formation of more of the total volatiles in almonds than the lipid oxidation reaction. The level of 5-(hydroxy methyl)-2- furfural (HMF), color, volatile profile, and sensory perception can be used to develop the best roasting method, time, and temperature for almonds. The rate of color development and the production of volatiles differ under different roasting conditions. Based on the color, volatile, and sensory assessments of the 3 almonds, the use of microwave technology as a process for roasting almonds reduces processing time and leads to an almond product with better flavor than oven or oil roasting.

Study on Recovery of Vanadium from Low-Vanadium Slag by Calcified Roasting Methods

Vanadium was recovered by using technology of calcified roasting→alkali leaching→ion exchange→precipitating→deaminizing, the principles of this recovery process were described in detail. Through the experiments, the parameters of roasting, leaching and ion exchange were determined, a new operational, low-polluting method to recovery vanadium was formed. This method not only can overcame the disadvantage of traditional technology, such as long process, serious pollution, but also has advantages such as high recovery and high purity of vanadium. In this study, pure V2O5 products with national standard were obtained. The total recovery was up to 65% or more, which was higher than that of the sodium roasting methods.

Phosphorus Doped Titania Materials: Synthesis, Characterization and Visible-Light Photocatalytic Activity

Hierarchical mesoporous Phosphor-doped titania nanoparticles were synthesized by two different method, that is roasting method and hydrothermal method. The samples prepared by hydrothermal method has much higher photocatalytic activity. In addition, MB degradation performance of the hydrothermal ones is also superior to that of the commercial P25. Therefore, the methylene blue (MB) degradation performance on the phosphorous-doped photocatalyst is much enhanced and superior to that of the commercial P25. The hydrothermal method proves to be very suitable for the synthesis of P-doped titania photocatalyst. The resulting materials were characterized by X-ray diffraction (XRD), nitrogen physical adsorption at 77 K, X-ray photoelectron spectroscopy (XPS), and solar light spectroscopy.

Infrared heating for dry-roasting and pasteurization of almonds

The use of infrared (IR) heating for improving the microbial safety and processing efficiency of dry-roasted almonds was investigated. Almonds were roasted at 130, 140 and 150 °C with three different methods: IR roasting, sequential infrared and hot air (SIRHA) roasting, and traditional hot air (HA) roasting. The heating rate and pasteurization efficacy of almonds under different roasting methods and temperatures were evaluated. Pediococcus sp. NRRL B-2354 was used as a surrogate for Salmonella enterica Enteriditis PT 30 for evaluating the pasteurization efficacy of different processing methods and conditions. When SIRHA roasting at 130, 140 and 150 °C roasting temperatures was used to produce medium roasted almonds, 4.10-, 5.82- and 6.96-log, bacterial reductions were achieved with 38%, 39% and 62% time saving compared to HA roasting at each temperatures, respectively. The decimal reduction time of the bacteria at all roasting temperatures were calculated for SIRHA roasting as 8.68, 3.72 and 1.42 min, respectively, with a correlation coefficient greater than 0.92 and the thermal resistance constant was found as 25.4 °C. The total color change followed zero-order reaction kinetics and the activation energies were 73.58, 52.15 and 67.60 kJ/mol for HA, IR and SIRHA roasting, respectively. No significant difference ( p > 0.05) was observed in sensory quality of medium roasted almonds processed with different roasting methods. We conclude that the SIRHA roasting is a promising new method for the production of dry-roasted pasteurized almonds.

Kinetics of recovering germanium from lignite ash with chlorinating roasting methods

A process of recovering Ge by chlorinating roasting was put forward. GeCl 4 was separated and recovered from lignite ash because of its low boiling point. Kinetic analysis indicates that the chlorinating roasting process fits with the unreacted-core shrinking model and the reaction rate equation corresponds to 1 − 2 a/3 − (1 − a) 2/3 = kt. The apparent activation energy E a is calculated to be 22.36 kJ·mol −1. The diffusion of product layer serves as the rate-controlling step in this process. When the roasting temperature is 250°C, the roasting time is 60 min, the concentration of hydrochloric acid is 10 mol/L, and the ratio of liquid to solid is 10 ( m HCl/ash = 10), and 90% Ge in lignite ash can be recovered.

Effects of coffees before and after special treatment procedure on cell membrane potentials in stomach cells

Coffee, one of the most excessively used beverages worldwide, commences the risk of gastroesophageal reflux (GER), which may lead to gastric ulcers and increase the risk of gastric cancer. Many attempts have been made by the coffee industry to diminish the irritating effect on mucosa by means of altering the extraction methods concerning gerbic acids and the roasting processes. This paper describes the effect of differently produced coffees involving two brands of Darboven and two brands of other coffee roasters. The aim of this study was to prove the results of gastric potential measurements we found in literature by using human AGS gastric epithelial cells (human adenocarcinoma). All four coffee extracts tested differentially affected the membrane resting potential of AGS cells. Coffees no. 1 and no. 2 depolarized the cells, presumably by increasing the cation entry into the cytosol. In marked contrast, coffee no. 4 hyperpolarizes the cells, possibly by H(+) extrusion and/or Cl(-) influx, suggesting that this coffee might increase acidity in the stomach, which might negatively affect the stomach, especially in people with gastroesophageal reflux symptoms. Overall, our data suggest that different roasting methods of coffees affect the membrane potentials of AGS stomach cells, resulting in increased influx of H+ possibly resulting in decreased stomach acidity and thus reducing GER. These results are in good accordance with clinical pharmacological results from potential difference measurements in healthy volunteers we found in the literature.

Preparation of High Purity Amorphous Boron Powder

Amorphous boron powder of high purity (92-94 %) with a particle size of l-2 mm is preferred as a fuel for fuel-rich propellants for integrated rocket ramjets and for igniter formulations. This paper describes the studies on process optimisation of two processes, ie, oxidative roasting of boron (roasting boron in air) and roasting boron with zinc in an inert medium for preparing high purity boron. Experimental studies reveal that roasting boron with zinc at optimised process conditions yields boron of purity more than 93 per cent, whereas oxidative roasting method yields boron of purity - 92 per cent. Oxidative roasting has comparative edge over the other processes owing to its ease of scale-up and simplicity

Antioxidative activity of green and roasted coffee beans as influenced by convection and microwave roasting methods and content of certain compounds

Antioxidative activity of green and roasted coffee beans and its correlation with the concentrations of certain substances (polyphenols, caffeine, 5-hydroxymethylfurfural) and the roasting method (convection and microwave) was determined. Antioxidative capacity was estimated based on the capability of synthetic free radical (1,1-diphenyl-2-picryl hydrazyl, DPPH˙) scavenging and counteracting an oxidation of the model system composed of β-carotene and linoleic acid. Green coffee appeared to display the highest effectiveness. In the case of roasted coffee samples, the results of neither test showed distinct correlation; however they indicated that an application of microwave heating for coffee roasting better protected its antioxidative properties. This relationship corresponded to the polyphenol content in roasted beans.

Effect of the roasting method on the content of 5-hydroxytryptamides of carboxylic acids in roasted coffee beans.

Coffee beans of Coffea liberica (robusta) variety were roasted using convection and microwave heating. For roasting we used green coffee beans of 7.5% moisture content, and beans wetted to 10% moisture content and dried to 5% moisture content. The content of 5-hydroxytryptamides of carboxylic acids C-5-HT (determined by TLC) as the index of substances irritating alimentary canal was investigated in the roasted beans, depending on the bean treatment before roasting and applied roasting method. Analytical results show that predrying of the coffee beans caused 15-30% loss of C-5-HT, depending on the applied drying conditions. The content of C-5-HT in the roasted beans depended on the roasting method and preliminary treatment of the beans prior to roasting. A higher C-5-HT loss occurred in the case of beans subjected to two-stage processing, predrying and roasting. Convection roasting caused higher degradation of C-5-HT than microwave roasting.

99/01627 Life cycle assessment of the selective catalytic reduction : Barzaga-Castellanos, L. et al. Gefahrstoffe Reinhalt. Luft., 1998, 58, (7/8), 313–319. (In German)

The separation of gold and vanadium in the refractory carbonaceous gold ore had been performed by one-step roasting method. The thermodynamic viability of the possible reactions in the process was analyzed based on thermodynamic data. And the effects of experimental parameters such as roasting temperature, roasting time and NaCl dosage on the recovery ratios of gold and vanadium were investigated. Under the optimal conditions of NaCl 10%, roasting temperature 800 °C, roasting time 4 h and air gas flow rate 1 L/min, the recovery ratios of gold and vanadium were 92% and 85.34%, respectively, realizing the effective separation of gold and vanadium. In addition, the reaction mechanism and phase transformation during the roasting process were revealed using SEM, EDS and XRD. Results demonstrated that it was beneficial to the chlorination reaction of gold in the presence of pyrite. In the low-temperature roasting, the chlorination reaction of gold was dominant in the roasting process. And in the high-temperature roasting, the chlorination reaction of gold and the sodium reaction of vanadium were dominant in the roasting process.