Roasting Stage Research Articles

Investigating the flavor compounds in the cocoa powder production process.

Flavor is one of the most important quality properties of cacao beans, playing a key role in the admissibility of cocoa products, such as cocoa powder. This study examined the industrial processes influencing the flavor of cacao beans. The Ivory Coast cacao beans were used after their alkaline treatment with potassium carbonate (up to pH 7.5–8) and being roasted at 115–120°C for 60–70 min. The volatile components were extracted using Likens–Nickerson simultaneous distillation–extraction (SDE) apparatus. The volatile compound profiles were identified by means of gas chromatography–mass spectrometry (GC–MS), as a result of which several compounds (alcohols, carboxylic acids, aldehydes, ketones, esters, and pyrazines) were recognized. Alkalization and roasting were shown to be two important steps in the cacao beans processing that can affect the final cocoa powder flavor. In addition, pyrazines and esters were two major groups of flavor compounds formed during the roasting stage by the Maillard reaction. The percentage of 2,3,5,6‐tetramethylpyrazine was detected in the cacao beans equal to 0.5%. After the liquor pressing stage, tetramethylpyrazine increased to its highest amount (3%) in cocoa powder. It was found that the cocoa powder contained 2.69% of tetramethylpyrazine, 3.22% isobutyl benzoate, and 1.38% linalool. The highest percentage of increase in the mean amounts of 2,3,5,6‐tetramethylpyrazine, isobutyl benzoate, and linalool were observed in the roasting stage, after which the percentages diminished.

Selective Leaching of Rare Earth Elements (REEs) from Eudialyte Concentrate after Sulfation and Thermal Decomposition of Non-REE Sulfates

Eudialyte, a sodium rich zirconosilicate, is one of the promising sources for REEs (rare earth elements), particularly for HREEs + Y (heavy rare earth elements and yttrium). The key challenge in hydrometallurgical processing is the prevention of silica gel formation and REE separation from resulting multi-element leach solutions. This study deals with the selective extraction of REE from eudialyte concentrate by selective roasting. In this method, metal ions are converted into sulfates, followed by the decomposition of non-REE sulfates in a roasting step and the water leaching of the calcine. The effect of acid addition, roasting temperature, roasting time, pulp density and leaching time is studied. For sufficient conversion of REEs into sulfates, sulfuric acid is added in excess. At a roasting temperature of ≥750 °C sulfates of zirconium, hafnium, niobium, aluminum and iron decompose into sparingly soluble compounds, while REE and manganese sulfates remain stable up to a roasting time of 120 min. The silica present in the calcine is found to be metastable even after roasting. The amount of leached Si4+ is dependent predominantly on the pH value of the leaching medium. Applying the method, REEs can be efficiently separated from zirconium, hafnium, niobium, aluminum and iron. However, only diluted solutions can be produced. Water leaching of calcine at high solid/liquid ratios causes REE losses resulting from formation of double sulfates and gypsum. The acid excess removed from the reaction mixture in the roasting stage can be simply recovered by treatment of the gas phase.

CONTROL OF THE COFFEE ROASTING STAGE USING ARTIFICIAL VISION TECHNIQUES

<p>Artificial vision techniques were used to evaluate its application in the control of the coffee roasting stage. Coffee samples of Colombia and Castillo varieties were obtained and analyzed by comparing images during the roasting stage. A one-way ANOVA analysis exhibited 94.28% of similarity of the coffee varieties studied; a multivariate analysis showed significant differences (p<0.05) for the time factor and its interaction with the variety factor, no differences were observed (p>0.05) for the coffee varieties. Additionally, a Principal Component, with two components demonstrated 90.77% of the variance by differentiating the samples in the different roasting times. Therefore, the proposed technique could be used in the control of the coffee roasting stage.</p>

Study on the effect of roasting temperature on antioxidant activity of early-roasted Java coffee powder (Arabica and Robusta)

The current consumer trend on seeking more health benefits of coffee consumption, mainly due to polyphenols content has led to the increasing popularity of green coffee beans extract or green coffee products. These products include green (raw-unprocessed) coffee powder, which is directly brewed and/or consumed. There is a safety concern in relation to consumption of raw-unprocessed coffee. Meanwhile, high temperature roasting may have influence on the functional properties of coffee, particularly its polyphenols. The objective of this research is to study the effect of roasting temperature at the early roasting stage (95°C, 125°C, and 165°C) on the antioxidant activity of two coffee species, i.e. Java Arabica and Java Robusta. The non-roasted coffees were evaluated for comparison. The IC50 and total phenol were analysed in triplicates. The results showed that Arabica and Robusta coffee powders were significantly differ on the antioxidant activity, where Robusta showed the highest activity as compared to Arabica. The application of heating on coffee beans during roasting tends to decrease antioxidant activity. However, there was a fluctuation where antioxidant activity of coffee reached a peak at early roasting temperature of 95°C.

Energy-efficient mineral carbonation of CaSO4 derived from wollastonite via a roasting-leaching route

Mineral carbonation is an important technique for the sequestration of carbon dioxide (CO2) on a large scale. In this article, indirect carbonation of abundant wollastonite [CaSiO3] mineral combined with the use of a CO2 mineralization cell (CMC) for the recovery of mineralization energy has been proposed. The results of thermodynamic analysis reveal that the described process consumes 73% less energy than that required for the route, in which serpentine is utilized as the mineralization agent. During this process, calcium sulfate (CaSO4) was first derived with recyclable ammonium sulfate (AS) via a roasting-leaching route. The gaseous ammonia produced during the roasting stage was used to capture CO2 from a mixture of flue gases and simultaneously generate ammonium bicarbonate (NH4HCO3) and electricity by the CMC. The obtained NH4HCO3 solution reacted directly with the leaching slurry to mineralize CO2 and regenerate AS at the same time. In this study, process parameters of this route were investigated in detail, and the related extraction mechanism was discussed. It was found that 94.5% of calcium species in wollastonite was converted into CaSO4, 94.8% of which was subsequently carbonated. The extraction efficiency of the roasting stage did not exceed 39% due to its low mass transfer rate resulting from the high viscosity of liquid ammonium bisulfate and presence of silicon dioxide (SiO2) and CaSO4 species on the surface of unreacted wollastonite. Preliminary energy analysis showed that a net reduction of CO2 emission of about 347 kg could be achieved for the mineralization of 1000 kg of CO2.

Optimising the recovery of high-value-added ammonium alum during mineral carbonation of blast furnace slag

A route for the indirect mineral carbonation of blast furnace slag (BFS) with (NH4)2SO4 as a recyclable reagent has been proposed recently. To improve the economy of the process, an improved recovery route was put forward herein, guided by thermodynamic studies and phase diagrams. A purer, and thus higher-value-added byproduct, ammonium alum, can be obtained during the mineral carbonation of BFS. The effects of parameters such as roasting temperature and time, mass ratio of liquid to solid during leaching, and crystallisation temperature were investigated systematically. The results showed that the extraction reaction of BFS with ammonium sulfate occurred not only in the roasting stage but also in the leaching stage. The purity and recovery of aluminium as NH4Al(SO4)2·12H2O can reach 99.6% and 73%, respectively, at the optimal conditions. A preliminary economic evaluation predicted that this route can achieve 2.5 times the profit of the original process.

Carbon Footprint of the Coffee Roasting Process Based on Two Technologies with Different Sources of Energy in Peru

The objective of this study was to determine and to compare the Carbon Footprint (CF) of the coffee roasting process carried out by using two technologies with different sources of energy. To this aim, two coffee roasting companies were selected in the rainforest of Peru. These companies apply concentrated solar and photovoltaic energy, and electricity from the local grid as source of energy during the coffee roasting process. For this determination, primary data was collected from the two companies located in the province of Satipo, Junin, Peru. The information obtained was analyzed according to the procedures and requirements of ISO 14040 (Life Cycle Analysis) to obtain the carbon footprint, and then processed with the software SimaPro to evaluate the environmental impacts due to the effect of climate change. The results indicated a CF of the solar energy roasting process of 0.318 and a CF of the local electricity grid production of 0.744 kg CO2-eq per kg of roasted coffee. This represents a difference in greenhouse gases (GHG) emissions of 134%. Within the factory activities, the stage with the highest environmental impact or hotspot was the roasting stage, where the most sophisticated machines are used and generated emissions from the combustion of fossil fuels. From this, proposals and recommendations to improve the strategies include an approach to clean technologies for a sustainable development in the sector, among others. Keywords: LCA, Carbon Footprint, Roasted Coffee, Renewable Energy, Photovoltaics, Concentrated Solar Energy

MONITOREO DEL TOSTADO DE CAF´E USANDO LA TRANSFORMADA DE FOURIER 2D

The roasting stage during coffee processing is a critical determinant of coffee sensorial features. However, direct monitoring methods are currently not available, which difficult its standardization. In this work, image analysis of the surface of coffee grains is proposed as an indirect monitoring tool of the coffee roasting. Images of coffee grains were obtained from two types of roasting units and processed using 2D Fourier Transform. The results allowed to the identification of a direct correlation between the degree of roasting coffee with scaling exponents obtained fromthe image analysis.

Efficient Separation and Extraction of Vanadium and Chromium in High Chromium Vanadium Slag by Selective Two-Stage Roasting–Leaching

Vanadium and chromium are important rare metals, leading to a focus on high chromium vanadium slag (HCVS) as a potential raw material to extract vanadium and chromium in China. In this work, a novel method based on selective two-stage roasting–leaching was proposed to separate and extract vanadium and chromium efficiently in HCVS. XRD, FT-IR, and SEM were utilized to analyze the phase evolutions and microstructure during the whole process. Calcification roasting, which can calcify vanadium selectively using thermodynamics, was carried out in the first roasting stage to transfer vanadium into acid-soluble vanadate and leave chromium in the leaching residue as (Fe0.6Cr0.4)2O3 after H2SO4 leaching. When HCVS and CaO were mixed in the molar ratio CaO/V2O3 (n(CaO)/n(V2O3)) of 0.5 to 1.25, around 90 pct vanadium and less than 1 pct chromium were extracted in the first leaching liquid, thus achieving the separation of vanadium and chromium. In the second roasting stage, sodium salt, which combines with chromium easily, was added to the first leaching residue to extract chromium and 95.16 pct chromium was extracted under the optimal conditions. The total vanadium and chromium leaching rates were above 95 pct, achieving the efficient separation and extraction of vanadium and chromium. The established method provides a new technique to separate vanadium and chromium during roasting rather than in the liquid form, which is useful for the comprehensive application of HCVS.

Monitoring single coffee bean roasting by direct volatile compound analysis with proton transfer reaction time-of-flight mass spectrometry.

This study applies proton transfer reaction time-of-flight mass spectrometry for the rapid analysis of volatile compounds released from single coffee beans. The headspace volatile profiles of single coffee beans (Coffeea arabica) from different geographical origins (Brazil, Guatemala and Ethiopia) were analyzed via offline profiling at different stages of roasting. The effect of coffee geographical origin was reflected on volatile compound formation that was supported by one-way ANOVA. Clear origin signatures were observed in the formation of different coffee odorants. Copyright © 2016 John Wiley & Sons, Ltd.

Use of NMR-Based Metabolomics To Chemically Characterize the Roasting Process of Chicory Root.

Roasted chicory root (Cichorium intybus) has been widely accepted as the most important coffee substitute. In this study, a nuclear magnetic resonance (NMR)-based comprehensive analysis was performed to monitor the substantial changes in the composition of chicory root during the roasting process. A detailed signal assignment of dried raw and roasted chicory roots was carried out using 1H, 13C, 1H-1H DQF-COSY, 1H-13C edited-HSQC, 1H-13C CT-HMBC, and 1H-13C HSQC-TOCSY NMR spectra. On the basis of the signal assignments, 36 NMR-visible components were monitored simultaneously during roasting. Inulins, sucrose, and most of the amino acids were largely degraded during the roasting process, whereas monosaccharides decreased at the beginning and then increased until the dark roasting stage. Acetamide, 5-hydroxymethylfurfural, di-d-fructose dianhydride, and norfuraneol were newly formed during roasting. Furthermore, a principal component analysis score plot indicated that similar chemical composition profiles could be achieved by roasting the chicory root either at a higher firepower for a shorter time or at a lower firepower for a longer time.

Phase transformation and structure evolution of chromite in the late stages of soda ash roasting process

Soda ash (Na2CO3) roasting of the chromite is commonly used worldwide for the production of chromium compounds. However, chromium conversion yield of the chromite only reached 70–80% in industry owing to slow chromium conversion rate in the late stages of Na2CO3 roasting process, resulting in serious waste of resources. Through XRD, SEM, EDS, TG-DTA and HRTEM analysis, phase transformation and structure evolution of chromite in the late stages of Na2CO3 roasting of chromite were investigated. The results revealed that the chromite transformed from MgCrFe2O4 phase to the MgCr0.4Fe1.6O4 main phase and Mg1.5Na9Si12Al12O48 and NaSiAlO4 minority phases first. The MgCr0.4Fe1.6O4 phase gradually transformed to MgFe1.8Cr0.2O4, MgFe1.9Cr0.1O4 and MgFe2O4 phase. Microstructure, especially of the vacancies, was proved to play the key role in chromium conversion. Vacancies generated by thermal vibration needed greater activated energy, resulting in the low chromium conversion rate of chromite in the late stages of Na2CO3 roasting process.

Recycling of NdFeB Magnets Using Sulfation, Selective Roasting, and Water Leaching

NdFeB magnets currently dominate the magnet market. Supply risks of certain rare earth metals (REMs), e.g., Nd and Dy, demand efficient recycling options that are applicable to different types and compositions with minimum use of chemicals and waste generation. In this study, a hydrometallurgical method is presented, which is adjustable to all NdFeB magnets, regardless of their composition. After completely transforming powdered samples into a sulfate mixture, a suitable selective roasting and water leaching treatment resulted in 95–100 % extraction efficiencies for Nd, Dy, Pr, Gd, Tb, and Eu, while Fe remained in the resultant residue forming a marketable hematite-dominated by-product. Impurities other than Fe were also greatly separated from the leachate thereby enabling the production of a liquid with at least 98 % REM purity. Such a solution then can be directly treated with subsequent shortened downstream processes without pretreatments for impurity removal. Due to decomposition reactions of impurities, including Fe, during the selective roasting stage, the majority of consumed acid is recyclable resulting in an environment-friendly flow sheet.

Asynchronous extraction of vanadium and chromium from vanadium slag by stepwise sodium roasting–water leaching

A novel environment-friendly method based on stepwise roasting has been proposed to extract vanadium and chromium separately from vanadium slag with high chromium content (V–Cr slag), which consists of two stages of sodium roasting–water leaching. Fractional sodium roasting–water leaching is firstly conducted to extract vanadium from the V–Cr slag and 87.9% of vanadium is extracted in optimal conditions. Leaching residue of the fractional roasting stage is then roasted secondarily to extract chromium and 96.4% of chromium is extracted from the leaching residue in optimal conditions. Overall extractions of vanadium and chromium are 98.9% and 96.6%, respectively. Evolution mechanisms of V-bearing and Cr-bearing phases were elucidated by XRD, TG–DSC and SEM-EDS. It is elucidated that V(III) existing as V-spinels in the V–Cr slag is oxidized to water-soluble NaVO3 while Cr(III) remains in the form of Cr-spinels or R2O3 phase (R: Cr, Fe) during the fractional roasting; in secondary roasting, Cr(III) existing as Cr-spinels and R2O3 phase in the leaching residue of fractional roasting stage is oxidized to water-soluble Na2CrO4. Vanadium and chromium have thus been extracted separately and thoroughly at the extraction procedure by controlling the roasting extent of V–Cr slag via the proposed stepwise roasting method. The established method provides new insights for comprehensive utilization of complex minerals containing multiple valuable elements.

Analysis of volatile compounds from a malting process using headspace solid-phase micro-extraction and GC–MS

The aroma of malt is one of the most crucial factors that influence the flavor of beer. To better understand the behavior of aroma during malting process, we identified the volatile compounds from barley, green malt and malt by using headspace solid phase microextraction (SPME) and gas-chromatography/mass spectrometry. A total of 47 volatiles, comprising aldehydes, ketones, alcohols, acids, and furans, were identified during the complete malting process. In particular, the dynamics of 2-methyl-propanal 3-methylbutanal, 2-methylbutanal, hexanal, 2-hexenal and 2-nonenal, commonly considered as key odorants in barley and malt, was highlighted during the process. Among these compounds, the amounts of 2-methyl-propanal, 3-methylbutanal, 2-methylbutanal, and 2-nonenal increased during the roasting stage, and the ones of hexanal, 2-hexenal conversely decreased in the same stage. As to compounds of ketones, alcohols, organic acids and furans, there is no forming regularity for them, which they formed at different stages of the whole malting process. Meanwhile benzaldehyde, benzeneacetaldehyde, 1-hexanol and ethyl acetate were considered as possible key odorants during the whole malting process. Base on the results above suitable manipulation of the malting conditions could be supplied in an industrial scale.

Recovery of iron from cyanide tailings with reduction roasting–water leaching followed by magnetic separation

Cyanide tailing is a kind of solid waste produced in the process of gold extraction from gold ore. In this paper, recovery of iron from cyanide tailings was studied with reduction roasting–water leaching process followed by magnetic separation. After analysis of chemical composition and crystalline phase, the effects of different parameters on recovery of iron were chiefly introduced. Systematic studies indicate that the high recovery rate and grade of magnetic concentrate of iron can be achieved under the following conditions: weight ratios of cyanide tailings/activated carbon/sodium carbonate/sodium sulfate, 100:10:3:10; temperature, 50°C; time, 60min at the reduction roasting stage; the liquid to solid ratio is 15:1 (ml/g), leaching at 60°C for 5min and stirring speed at 20 r/min at water-leaching; exciting current is 2A at magnetic separation. The iron grade of magnetic concentrate was 59.11% and the recovery ratio was 75.12%. The mineralography of cyanide tailings, roasted product, water-leached sample, magnetic concentrate and magnetic tailings were studied by X-ray powder diffraction (XRD) technique. The microstructures of above products except magnetic tailings were also analyzed by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS) to help understand the mechanism.

Electron Spin Resonance (ESR) Studies on the Formation of Roasting-Induced Antioxidative Structures in Coffee Brews at Different Degrees of Roast

The antioxidative properties of coffee brew fractions were studied using electron spin resonance spectroscopy using 2,2,6,6-tetramethyl-1-piperidin-1-oxyl (TEMPO) and Fremy's salt (nitrosodisulfonate) as stabilized radicals. TEMPO was scavenged by antioxidants formed during roasting and not by chlorogenic acid, whereas Fremy's salt was scavenged by all antioxidants tested including chlorogenic acid. The stabilized radical TEMPO allowed the exclusive measurement of roasting-induced antioxidants. The roasting-induced antioxidant activity of coffee brews increased with increasing degree of roast, and most of these antioxidants were formed during the initial roasting stage. The majority of these roasting-induced antioxidants were present in the high molecular weight fractions, indicating that the formation of these antioxidants preferably occurs at specific high molecular weight structures, likely being arabinogalactan and/or protein moieties which might be part of the melanoidin complex. It was found that chlorogenic acids most probably do not lose their antioxidant activity and phenolic characteristics upon incorporation in coffee melanoidins. The parameter fast reacting antioxidants (FRA) was introduced as an alternative for the antioxidative potential. FRA levels showed that coffee fractions rich in roasting-induced antioxidants exposed their antioxidant activity relatively slowly, which must be a consequence of its complex structure. Finally, the melanoidin content and the roasting-induced antioxidant activity showed a positive and linear correlation for the coffee brew fractions, showing that roasting-induced antioxidants are present within melanoidins. This is the first time that the formation of roasting-induced antioxidants could be directly correlated with the extent of Maillard reaction and melanoidin formation in a complex product such as coffee.

Technology and globalisation: who gains when commodities are de-commodified?

Like many primary products, coffee has long been characterised as a commodity with falling terms of trade and volatile prices. Yet, in recent years, there has been growing product differentiation in final markets, with premium prices being earned and high and sustainable incomes being provided. So far, these product rents have been almost entirely appropriated by residents of high-income economies. However, to the extent that growers can learn to improve their product through the systematic application of knowledge throughout the value chain, and consumers are taught to recognise that product variety and quality are determined in the growing rather than the roasting stage of the chain, an alternative outcome is possible. This paper outlines the necessary knowledge flows and concludes with an assessment of who needs to do what if this more favourable outcome for growers is to be realised.