Coffee Drying Research Articles

Thermo-economic analysis of sun drying patio coffee in the Sierra Mariscal, Chiapas-México

This study shows a thermo-economic analysis of patio coffee drying in the Sierra Mariscal Chiapas-México to optimize bed thickness. The drying time, specific energy, thermal efficiency, water-effective diffusivity, and drying batch costs were correlated with bed thickness and solar irradiation. The initial and final coffee moisture contents were 53 % and 11–12 % (w.b). The bed thickness was in terms of kilograms of coffee uniformly spread on a square meter (2.0, 5.0, 10.0, 15.0, and 20.0 kg/m2). The five experimental campaigns involved five tests over a harvest season. The water-effective diffusion coefficient increases with bed thickness (0.38–91.2 × 10−10 m2/s). The solar irradiation requirement and the efficiency of the patio drying linearly increase with bed thickness while specific energy exponentially decreases. The lower specific energy was (7.1–10.4 MJ/kg) for the higher bed thickness (20.0 kg/m2), with (24.0–38.0 h) of drying time and (0.22–0.32) of efficiency. The optimized coffee bed thickness was 10 kg/m2, with a specific energy of 8.8–9.6 MJ/kg. When bed thickness increases, the thermal efficiency increases almost linearly 5.5 times, exponentially reducing the drying cost per batch five times. However, increasing drying times shall lessen the quality of physical-chemical and sensorial coffee.

Energy Analysis and Economy Performance of a Hybrid Solar Dryer for Drying Coffee

This work studies the effect of the drying temperature on the profile of the water content, drying rate, drying efficiency, economic performance, and the quality of Robusta and Arabica coffee beans using the hybrid solar dryer. The drying instrument with the help of LPG heating is used in this research with a specified temperature of 40 ℃, 50 ℃, and 60 ℃. The research is conducted on a sunny day for 1 day for each temperature and coffee beans. The temperature profile shows that the lowest water content in the study is 60 ℃. The drying rate for both 50 ℃ and 60 ℃ are similar and the highest average efficiency of the instrument is at 50 ℃ for both Robusta and Arabica beans. The dominant peak in GCMS analysis result of coffee samples was caffeine with a total area percentage of 30.89%, the description of the coffee bean structure using SEM test resulted in a hole size of 5-10 µm, the obtained fat content was 1.6%, the obtained protein content 17.3%. A hybrid solar dryer is an environmentally friendly solution that enables faster coffee drying, with a payback period of 1.5 years for both coffee bean types.

Influence of drying condition on the drying constants and activation energy for robusta coffee using heat pump drying

Abstract Heat pump drying (HPD) is a method of drying agricultural products which has great potential due to its high efficiency and energy savings. Coffee is a heat sensitive product, HPD was chosen as an alternative to existing drying methods for coffee processing. Understanding of the HPD process is important to know for optimizing the coffee drying process with HPD especially in drying characteristics. The purpose of this research is to determine the number for the drying rate constant and the energy of activation in coffee drying. The material used in this study was wet parchment Robusta coffee beans (Coffea canephora). The research was carried out experimentally for 5 h at 700 lpm air flow with varying drying air conditions by adjusting the drying temperature and specific humidity. The drying temperatures used were 60, 65, 70, 75, and 80 °C. The drying temperature is limited to 80 °C based on SNI 7467-2008. Variations in specific humidity are determined based on temperature settings in the refrigeration system of 10, 15, 20 °C and without a refrigeration system. The maximum drying rate constant was 10.69×10-3 s-1, achieved at a temperature of drying variation of 80 °C while a specific humidity of 6.16 g H2O/kg dry air, while the minimum activation energy value was 23.43 kJ/mol at the same specific humidity. The lowest drying rate constant value was 5.79×10-3 s-1, achieved at a temperature of drying variation of 60 °C and a specific humidity of 17.24 g H2O/kg dry air, while the greatest activation energy level was 26.18 kJ/mol at the same specific humidity.

An innovative dryer for Arabica coffee (Coffea arabica L.) drying: Investigating heat and mass transfer

In the pursuit of advancing post-processing techniques for Arabica coffee, our research introduces a rotary dryer, known as a roto-aerated dryer, marking its first application in coffee drying and surpassing conventional methods. This study delves into the evaluation of heat and mass transfer dynamics between coffee and drying air within the innovative dryer. Characterization of raw materials precedes a series of drying experiments under varied conditions, forming the basis for a mathematical two-phase model elucidating the underlying dynamics of the drying process. Noteworthy is the significantly reduced material residence time (14.60–27.47 min) compared to conventional dryers. Drying rates (0.09–0.24 g water/100 g solid/min) surpass those achieved by other methods. Simulated results from the numerical solution of the two-phase model closely align with experiments (average error of 2.39% for moisture content and 0.89% for temperature). The effective preservation of material quality, particularly acidity, underscores the valuable insights offered for optimizing drying processes, holding substantial potential for advancing the specialty coffee industry.

Calidad física y sensorial del café secado en tres prototipos de secadores solares tipo invernadero

Reducing the drying time of coffee without causing negative effects on cup quality has been the subject of several investigations. The objective was to determine the effect of three variants of a greenhouse-type solar dryer prototype on the physical, sensory and microbiological quality of coffee. The solar dryer prototype with three variants, prototype 1 (P1) greenhouse solar dryer, prototype 2 (P2) solar dryer with air extractor and prototype 3 (P3) solar dryer with air extractor and solar powered heaters, was compared to traditional drying (T0) (cement floor). Drying time, physical grain defects, yield, sensory and microbiological quality were evaluated. The best results were obtained in P3 with a drying time of 52 h (2 ¼ days), with dry parchment coffee beans without primary defects, higher yield in exportable gold coffee (83.24 %), sensory profile of 84.25 points qualified as specialty coffee (with Q Premium grade) and better safety than coffee obtained by traditional drying; demonstrating that the greenhouse type solar dryer with air extractor and solar energy heaters is a sustainable alternative to improve the efficiency of coffee drying while preserving its sensory quality, an essential value for producers to achieve better prices.

A data-driven approach to improve coffee drying: Combining environmental sensors and chemical analysis.

The study introduces a methodology that utilizes data-driven approaches to optimize coffee drying operations. This is achieved through the integration of ambient sensor data and chemical analysis. This statement underscores the significance of temperature regulation, humidity levels, and light intensity within the context of coffee production. There exists a positive correlation between elevated temperatures and increased rates of drying, but humidity has a role in determining the duration of the drying process and the preservation of aromatic compounds. The significance of light intensity in dry processing is also crucial, since excessive exposure can compromise both the taste and quality of the product. The findings of chemical investigations demonstrate a correlation between environmental factors and the composition of coffee. Specifically, increased temperatures are associated with higher quantities of caffeine, while the concentration of chlorogenic acid is influenced by humidity levels. The research additionally underscores the variations in sensory characteristics among various processing techniques, underscoring the significance of procedure choice in attaining desirable taste profiles. The integration of weather monitoring, chemical analysis, and sensory assessments is a robust approach to augmenting quality control within the coffee sector, thereby facilitating the provision of great coffee products to discerning consumers.

Coffee Beans Drying Using Pilot-Scaled Fluidized Bed Dryer Assisted with Zeolite Adsorbent

Drying is a common method applied to agricultural and plantation products to prevent the growth of bacteria and other microorganisms. This research aims to determine the optimum temperature and humidity of the heating air for coffee beans drying in a fluidized bed dryer (FBD) without the addition of adsorbents, to study the effectiveness of zeolite adsorbent as air dehumidifier in order to improve the drying process, and to determine energy consumption in the coffee drying process in an FBD. This research was conducted using 500 grams of Arabica coffee, air temperature variations of 400C, 500C and 600C with an average air velocity of 4.91 m/s. The addition of 1.08 kg of zeolite as an adsorbent was carried out to improve process performance and to reduce the drying time. Coffee bean quality was determined by moisture test using gravimetric method, protein test using Kjeldahl’s method and carbohydrate test using Luff-Schoorl’s method. The results showed that the optimum conditions for drying coffee beans to reduce the moisture content from 28% to 12.45% using an FBD without adsorbent were obtained at a drying air temperature of 500C with a drying time of 3 hours. Coffee bean drying assisted by Zeolite adsorbent was able to reduce the drying time by 11% with the most efficient energy consumption of 76,200 kJ/kg.

Android Based Coffee Dryer Temperature Control System Design

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ANALISIS PENGARUH KALOR TERHADAP MUTU KOPI PADA PENGGUNAAN ALAT PENGERING HYBRID KOPI

Coffee is one of the plantation products that is highly recommended to be developed because it is able to become a source of state income and improve the economy where almost half a million Indonesians are entrepreneurs and coffee farmers. Heat is the process of transferring energy from a substance to another substance due to temperature differences. During this time, the coffee drying process is done in the traditional way. This drying process is not optimal because the temperature cannot be controlled properly, which affects the quality of the coffee. During rainy conditions, coffee is dried for a long time so that mold can occur. However, temperatures that are too high can also have a negative impact on coffee quality, especially on coffee aroma. The solution that can be done is to use a hybrid coffee drying machine. This study aims to analyze the effect of heat on the quality of coffee which in its production uses a hybrid coffee dryer. This research was conducted using the literature study method or literature study. The results showed that heat plays an important role in the quality of coffee quality in a hybrid coffee dryer. The quality of coffee depends on the temperature of the machine. The hybrid coffee drying machine is automatically designed where the temperature in the drying chamber is constant at the minimum temperature.

Investigation of Thin-Layer Drying of Coffee Beans Using a Double-Condenser Compression Refrigeration System: Effects of Air Mass Flux, Specific Humidity and Drying Temperature

The drying process is the key to the quality of the coffee produced. The allowable moisture content of coffee beans is 12%. The air mass flux, specific humidity, and the drying temperature are varied using a bed dryer drying system combined with a double condenser refrigeration system. Robusta coffee beans are used in this research to obtain the characterization of coffee beans. The highest drying rate constant is obtained by 2.44 × 10-4 s-1 directly proportional to the increased air mass flux and drying air temperature, with a value of 1.701 kg/s m2 and 80 °C, but inversely proportional to the specific humidity, with a value of 7.01 g/kg d.a. The lowest activation energy value was 31.88 kJ/mol when the air mass flux was 1.701 kg/s m2, the drying air temperature was 80 °C, and the average specific humidity was 7.01 g/kg d.a. In this work, the developed correlation is proposed to practically predict the activation energy (EA) and the pre-exponential factor (A) with equation and respectively. Based on Ea and A correlation equation, it can be used for designing a bed dryer type coffee drying system for a larger scale.

Analysis on the Performance of Designed Fluidized Bed Dryer for Drying Coffee Beans

Drying coffee beans is an important role in the process of making coffee. Most coffee producers dry their coffee beans under the natural sun, but it was found to be time-consuming and depended on the weather conditions. Fluidized bed dryer is found to be the most recent method to dry the coffee beans. However, not many reported on the performance of fluidized bed dryer in coffee drying. In the present research, the quality of the drying process using fluidized bed dryer was investigated by varying the streamline pattern and temperature distribution in the drying chamber. The result was compared with a different temperature and velocity applied. The simulation in ANSYS was conducted with three different velocities of 10 m/s, 20 m/s and 30 m/s with air temperature of 60 °C, 90 °C and 120 °C. The temperature supply was from the inside of the pipe to the end of the drying chamber. The streamline and the temperature distribution were absorbed between the difference of temperature and the velocity difference. The computational analysis of the simulation showed that the increase in velocity resulted in a temperature rise from 46.72°C to 49.04°C within the drying chamber for constant inlet temperature of 60 °C, and on the other hand the velocity in the drying chamber remains constant at average of 3.22 m/s for inlet velocity of 10 m/s despite the increase in temperature.

Extended Fuzzy Rule Suram for Coffee Drying System

Extended fuzzy rule Suram is an algorithm developed to control a drying system using diesel as an energy source by modifying the value of the fuzzy membership function {0.5,1]. For a coffee drying room control system with solar energy, the bleak rule is based on fuzzy logic with variables of weather, air condition and wind speed. This algorithm is applied to the coffee drying process. The state variable membership function is represented in error values ​​and changes in error with a typical triangular and trapezoidal map for weather variables, air conditions, while wind speed is expressed in terms of wind speed. The results of the analysis of experiments with 16 fuzzy rules to control system output according to weather conditions obtained optimization of the use of solar energy by minimizing the use of electrical energy by heating. This algorithm also adjusts the coffee drying schedule by controlling the chamber, namely through temperature and humidity control. The results of the application of this algorithm show that the efficiency of electrical energy reaches 40,86%.

Effects of hot-air drying on the bioactive compounds, quality attributes, and drying and color change kinetics of coffee leaves.

Drying is a key step that affects the chemical composition and quality of tea. In the present study, we reported the impacts of drying temperature and time on drying and color change kinetics, phytochemical composition, antioxidant activity, and surface microstructure of coffee leaves during hot-air drying. The results showed that drying temperature was positively (p<0.05) correlated with the drying rate (DR), color index a* and total color change ΔE, and total soluble sugar (TSS), while negatively correlated with color indexes b* and L*, soluble protein content, and the DPPH scavenging capacity. Drying time has similar impacts on the color indexes and soluble protein as drying temperature. The content of total free amino acid and TSS increased by 62.5% and 47.4%, respectively, when coffee leaves were dried at 160°C for 24min, under which the total phenolic content and DPPH and ABTS scavenging capacities reached the maximum of 108.04mg GAE/g, 515.07µmol Trolox/g, and 606.70µmol Trolox/g, respectively. Drying significantly decreased the contents of chlorogenic acids and mangiferin and antioxidant activity, while high-temperature short-time drying helped retain phenolic compounds in coffee leaves. The DR fitted Page kinetic model. The color changes fitted the first-order kinetic models and the activation energies ranged from 16.00 to 31.06kJ·mol-1 . Prolonged drying time caused serious wrinkles on the surface of coffee leaves and the stomata closed. PRACTICAL APPLICATION: Drying decreased soluble protein while increasing free amino acid and soluble sugar. High-temperature short-time drying helps retain phenolics in the coffee leaves. The color change of coffee leaves during drying follows first-order kinetic. Prolonged drying time resulted in loosened texture of coffee leaves. Our study suggested that drying coffee leaves at 160°C for 24min results in the coffee leaf tea being of better quality.

Rice husk energy rotary dryer experiment for improved solar drying thermal performance on cherry coffee

This research focuses on testing rotary dryers for the small-scale drying of cherry coffee, using hot air through the conversion of rice husk into thermal with a heat exchanger. Drying cherry coffee with a moisture content of 62% was dried using a rotary dryer and sun drying. Rotary dryer testing for mass variations of 10 kg, 15 kg, and 20 kg. During the drying process, rice husks are not added to the furnace. The results showed that the rotary drying temperature was higher than the sun drying. The final moisture content of sun drying was 13.14%; the average temperature was 29.44 °C for 16 days. The rotary dryer produces final moisture content of 10.71%, 10.45%, and 11.13%. The time required is 1440 min, 1680 min, and 1920 min, respectively. The fastest drying rate occurs at a mass of 10 kg. The highest drying efficiency occurs for a mass of 20 kg. The greater the mass affects the moisture content evaporation, so the drying efficiency is high. During the drying process, there is a decrease in efficiency because the energy absorbed by cherry coffee decreases as the moisture content decreases.

Drying of arabica coffee and its effect on the gene expression and activity of enzymes linked to seed physiological quality

The reduced longevity of coffee seeds has been attributed to their sensitivity to desiccation. Studies related to gene expression and enzyme activity in coffee seeds under drying are important for understanding the effects of drying on their physiological quality. The aim of this study was to investigate the molecular aspects of seeds under different drying methods and associate them with physiological quality. Coffee seeds with different water contents were dried both slowly and rapidly. Enzymatic activity was analysed, as well as the expression of genes that encode the enzymes superoxide dismutase, catalase, peroxiredoxins, isocitrate lyase, and endo-ß-mannanase. There was a significant effect of drying speed and final water content on enzyme activity and on the expression of the different genes analysed. In seeds under rapid drying, there was greater expression of the genes that encode the enzymes catalase and endo-ß-mannanase. Greater expression of the 1 CYS PRX and SOD genes and greater activity of the ICL isoenzymes were found in seeds with superior physiological quality, but greater activity of the endo-β-mannanase and CAT enzymes occurred in seeds with lower physiological quality.

Analysis of Potential Utilization of Sarulla Geothermal Combined Cycle Residual Fluids for Direct Use in The Coffee Industry

The Geothermal Power Plant is one of the new renewable energy power plants. In Indonesia, the realization has reached 2%. Sarulla Operations Limited is the first geothermal power plant in Indonesia, located in North Tapanuli Regency, that utilizes combined cycle technology. Coffee is the leading commodity in the North Tapanuli district, with a plant area of 17,586 hectares. Coffee is dried in the traditional way (open field drying) so that it is still constrained by rain and cloudiness and can only be done during the day. The reinjection well fluid has a temperature of 103°C with a flow rate of 4978 t/h and a pressure of 6–14 Bar. This study analyses the residual fluid energy for coffee drying purposes. Energy and exergy calculations are done manually and using DWSIM software with a total of 24 data points 24 hours a day to represent the availability of dryers both day and night. The results showed that the most energy needed to raise the drying air temperature at night from 15°C to 60°C was 125.62 kW, while the lowest energy needed to raise the drying air temperature during the day from 30°C to 40°C was 27.92 kW. The results of research calculations show the energy potential for residual fluid from geothermal plants to be used for drying coffee for 24 hours, both day and night.

Activation Energy Analysis of Coffee Beans Drying Using Double Condenser Refrigeration System

The coffee drying system that is less efficient with the use of sunlight makes the productivity of coffee farmers in Indonesia less than optimal when the rainy season arrives. In this study, the coffee bean drying process was carried out to make the drying system more effective and efficient by combining a bed dryer-type drying system with a heat pump. The drying air flow used was 550 lpm. Variations in temperature on the evaporator used 10 until 20 °C and without refrigeration. While the electric heating temperatures used are 60 to 80 °C. In addition, this test is also carried out using only electric heaters. The results obtained from this study are the dehumidification process of drying air in the evaporator can improve the drying process of coffee beans. Higher electric heating temperatures will also speed up the drying process. The highest value of activation energy for drying coffee beans on air humidity was 39.6485 kJ/mol at drying conditions without using a refrigeration system and n The lowest activation energy value was obtained at a specific humidity of 0.0079 kg/kg d.a (evaporator temperature 10°C) with a value of 19.9407 kJ/mol. The lower the specific humidity of the drying air, the lower the energy required to evaporate the water in the coffee beans. This activation energy value can then be used as initial data for the numerical simulation of drying coffee beans.

Performance Analysis and Kinetic Modeling of Coffee Beans in Microwave Convective Dryer Integrated Photovoltaic System

The microwave convective dryer integrated photovoltaic has the potential equipment to be used for coffee drying. Therefore, this study aims to examine the performance of microwave convective dryer integrated photovoltaic for coffee bean drying. The kinetics and effectiveness diffusivity were determined to describe the drying process”. Drying model for the coffee bean drying process using variations in sample mass, coffee bean condition, and drying power. The results showed that reducing the water content of coffee beans from 47% (wb) to 11% (wb) required drying times of 10, 8, and 6 minutes at 600 W (medium), 650 W (medium-high), and 700 W (high), respectively. Drying coffee beans with a microwave convective dryer system shows that the Wang and Singh model is the best model for drying coffee beans; resulting in the highest R2 (0.99) and the lowest MBE and RMSE. Therefore, Wang and Singh model can be used to accurately predict the moisture content of dry coffee beans in a microwave convective dryer system. The effective diffusivity of coffee beans increased from 3.19×10-7 m/s to 1.19×10-6 m2/s when the power drying increased from 600 W to 700 W.

Coffee Drying and Processing Method Influence Quality of Arabica Coffee Varieties (Coffee arabica L.) at Gomma I and Limmu Kossa, Southwest Ethiopia

Solar tunnel drying and semiwash processing methods are popular among coffee growers in southwestern Ethiopia. However, the effect of these processing methods on coffee quality has not been studied in detail. The objective of this study was to evaluate the effect of processing and drying methods on the quality of coffee varieties at Gomma-I and Limmu Kossa areas in the 2016/2017 growing season. Two processing methods (fully washed and semiwashed) and three drying methods (solar tunnel, artificial, and natural sun) were compared using three coffee varieties (741, 7440, and 74110) to test their effect on coffee quality. Coffee beans processed by semiwash method and dried by solar tunnel produced nondefective (primary and secondary) coffee beans compared with others at both locations. Similarly, coffee beans processed by semiwashed method recorded the highest mean value for shape and make and body than wet processing method. Best coffee bean color, greenish color, was produced from coffee beans processed by the fully washed processing method. All coffee varieties processed by semiwashed method produced medium pointed acidity, the second most acceptable grade value for coffee quality for all drying methods. Coffee beans processed by the fully washed method produced more flavor than semiwash processing method. Coffee beans dried by sun and solar tunnel drying methods also produced better flavor than artificial drier. In general, all coffee varieties processed by semiwash method and dried by natural sun and solar tunnel method produced higher preliminary total quality and total specialty coffee value, graded under specialty grade Q1. Hence, coffee growers in the study area can use semiwash processing method and solar tunnel dryer as an alternative/complementary processing method since they produce better or equivalent quality product with full wash and natural sun drying method.

Modeling of Forced and Natural Convection Drying Process of a Coffee Seed

HighlightsThe forced and natural convection drying processes of a single coffee grain can be predicted.The moisture distribution profiles depict the drying phenomena and water concentration zones.With accurate predictive drying curves, coffee growers can ensure high-quality coffee beans.Abstract. Different coffee drying technologies face complex tasks in ensuring an acceptable final seed moisture content. This research performed a Finite Element Analysis (FEA) study, simulating a single coffee bean's drying process as a transient mass diffusion model under mechanical and natural convection conditions, so the drying behavior and data of both case scenarios can be foreseen and controlled by a predictive Finite Element Model (FEM). A wet bean was 3D-scanned and digitized as the FEA simulation geometry; the water diffusion between the grain and the atmosphere was defined by a diffusion coefficient subject to the drying air temperature and the grain's moisture content. Three cases were studied: mechanical grain drying at three different temperatures (50, 45, and 40°C) in a forced convection environment; variable natural convection drying under environmental conditions (wet and dry season); and constant natural convection (wet and dry season), including the variation in day/night temperature and relative humidity. The results agree well with the data found in the literature, obtaining the graphical moisture distribution of the phenomena, predictive drying curves, diffusion coefficients, and isotherms. Both simulated drying scenarios provide essential information for coffee growers to improve and control their drying processes, thus obtaining high-quality grains, reducing contamination by microorganisms, and ensuring the integrity of their products. Keywords: Coffea arabica, Coffee Drying, Coffee Seed, Finite Element Model, Moisture Diffusion.