Dark Roast Research Articles

Prediction of roasted coffee bean level from a coffee house-ware using fuzzy logic

Coffee is presently one of the most popular drinks consumed by people around the world. Different types of coffee typically depend on the types of coffee used, the level of roasting of the beans, the brewing methods used, and the extra ingredients added to the coffee. However, coffee characteristics are mainly influenced by a roasting process which highlight the aroma and flavor of coffee beans. In this study, we design a 2 kW household coffee roaster using heating coils as a heat source and controlled by the fuzzy logic algorithm built into the Arduino nano to predict the quality of roasted coffee. The quality of roasted coffee beans is divided in three categories: light roasting, medium roasting, and dark roasting. The body roasting machine consists of three parts; a roaster barrel, a propeller, and reduction gear, which rotates the roasting hopper and reverses the direction of rotation of the propeller. The roasted coffee beans in the tank are thoroughly heated by the heating coils, and the propeller is designed to provide an oblique to sweep the roasted coffee beans in the tank from the wall. The experiment is discussed in detail.

PENGEMBANGAN DAN EVALUASI KINERJA PENYANGRAI KOPI FLUIDISASI BERTENAGA LIQUEFIED PETROLEUM GAS

In this study, a fluidized coffee roaster has been successfully designed, constructed, and tested. This prototype has a capacity of 500 grammes per batch to aid small-scale coffee shops in roasting coffee beans. This fluidized coffee roaster is easy to use, cheap and has an appropriate capacity for the small business requirements. The coffee roasting components of the machine consisted of a blower (600 watts), a heat exchanger, a jet burner, a cylindrical roasting chamber, a chaff and dust collector, and a frame. At a range of airflow of 4-6 m/sec, the average temperature increase in the furnace and roasting chamber was 26 °C and 7.8 °C per minute, respectively. Performance tests revealed that the developed fluidized coffee roaster had been able to roast Robusta and Arabica coffee to light, medium, and dark roasting levels. For Robusta coffee, the time required to achieve light, medium, and dark levels were 8.18, 9.85, and 12.03 minutes, respectively, with final roasting temperatures for each level of 209 °C, 220 °C, and 248°C. For Arabica coffee, the time required was 5.32, 7.67, and 11.72 minutes, respectively with the final roasting temperatures of 207 °C, 210 °C, and 218 °C.

Analisis Kinerja Alat Raosting Kopi Kapasitas 2kg Tipe Silinder Horizontal

Roasting is a process of frying coffee without oil using high temperatures which aims to speed up the process of frying coffee beans. The coffee roasting process aims to form the taste and aroma of the coffee beans. The coffee roasting equipment used in this study was a horizontal cylinder type coffee roaster with a capacity of 2 kg. This machine rotates with an electric dynamo. It has a cylindrical tube with a length of 27.5 cm and the heat comes from an LPG (Liquefied petroleum gas) stove. The purpose of this research is to test the performance of coffee roasting equipment. The data that needs to be measured from this coffee roasting tool is the need for electrical power used, roasting capacity and the change in color of the coffee when it is roasted. The electric power used is 12 volts 15 amperes. The results of the dark roast test at 200°c at 21 minutes. The maximum capacity of this horizontal cylinder type roasting machine is 2 kilograms

Extraction of Diterpene-Phytochemicals in Raw and Roasted Coffee Beans and Beverage Preparations and Their Relationship.

Cafestol and kahweol are expressive furane-diterpenoids from the lipid fraction of coffee beans with relevant pharmacological properties for human health. Due to their thermolability, they suffer degradation during roasting, whose products are poorly studied regarding their identity and content in the roasted coffee beans and beverages. This article describes the extraction of these diterpenes, from the raw bean to coffee beverages, identifying them and understanding the kinetics of formation and degradation in roasting (light, medium and dark roasts) as the extraction rate for different beverages of coffee (filtered, Moka, French press, Turkish and boiled). Sixteen compounds were identified as degradation products, ten derived from kahweol and six from cafestol, produced by oxidation and inter and intramolecular elimination reactions, with the roasting degree (relationship between time and temperature) being the main factor for thermodegradation and the way of preparing the beverage responsible for the content of these substances in them.

A Hybrid Stainless-Steel SPME Microneedle Electrode Sensor for Dual Electrochemical and GC-MS Analysis.

A mechanically robust in-tube stainless steel microneedle solid phase microextraction (SPME) platform for dual electrochemical and chromatographic detection has been demonstrated. The SPME microneedle was fabricated by layer-by-layer (LbL) in-tube coating, consisting of carbon nanotube (CNT)/cellulose nanocrystal (CNC) film layered with an electrically conductive polyaniline (PANI) hydrogel layer (PANI@CNT/CNC SPME microneedle (MN)). The PANI@CNT/CNC SPME MN showed effective analysis of caffeine by GC-MS with an LOD of 26 mg/L and excellent precision across the dynamic range. Additionally, the PANI@CNT/CNC SPME MN demonstrated a 67% increase in sensitivity compared to a commercial SPME fiber, while being highly robust for repeated use without loss in performance. For electrochemical detection, the PANI@CNT/CNC SPME MN showed excellent performance for the detection of 3-caffeoylquinic acid (3-CQA). The dynamic range and limits of detection (LOD) for 3-CQA analysis were 75-448 mg/L and 11 mg/L, respectively. The PANI@CNT/CNC SPME MN was demonstrated to accurately determine the caffeine content and 3-CQA in tea samples and dark roast coffee, respectively. The PANI@CNT/CNC SPME MN was used for semiquantitative antioxidant determination and composition analysis in kiwi fruit using electrochemistry and SPME-coupled GC-MS, respectively.

Impact of roasting on javamide-I/-II in Arabica and Robusta coffee beans

Javamide-I/-II are anti-inflammatory compounds found in coffee beans. However, potential effects of roasting on javamide-I/-II in coffee beans are currently unknown. Therefore, in this paper, the effects of roasting on javamide-I/-II were investigated in Arabica and Robusta beans. Coffee beans were roasted light, medium and dark, and the amounts of javamide-I/-II in the beans were quantified by a HPLC method. The data showed the different amounts of javamide-I/-II in the beans; not detected and ≤ 3.1 mg in Arabica beans, and 0.5–3.7 mg and 1.0–13.8 mg in Robusta beans, respectively. Furthermore, the data showed that roasting process significantly reduced the amounts of javamide-I/-II in both Arabica and Robusta beans (p < 0.05). These data were also confirmed by multivariate analyses. Additionally, these differences were validated in light, medium and dark roast coffee products in the market. Altogether, roasting can have a significant impact on javamide-I/-II amounts in coffee beans.

Novel method for the detection of adulterants in coffee and the determination of a coffee's geographical origin using near infrared spectroscopy complemented by an autoencoder

SummaryCoffee authenticity is a foundational aspect of quality when considering coffee's market value. This has become important given frequent adulteration and mislabelling for economic gains. Therefore, this research aimed to investigate the ability of a deep autoencoder neural network to detect adulterants in roasted coffee and to determine a coffee's geographical origin (roasted) using near infrared (NIR) spectroscopy. Arabica coffee was adulterated with robusta coffee or chicory at adulteration levels ranging from 2.5% to 30% in increments of 2.5% at light, medium and dark roast levels. First, the autoencoder was trained using pure arabica coffee before being used to detect the presence of adulterants in the samples. Furthermore, it was used to determine the geographical origin of coffee. All samples adulterated with chicory were detectable by the autoencoder at all roast levels. In the case of robusta‐adulterated samples, detection was possible at adulteration levels above 7.5% at medium and dark roasts. Additionally, it was possible to differentiate coffee samples from different geographical origins. PCA analysis of adulterated samples showed grouping based on the type and concentration of the adulterant. In conclusion, using an autoencoder neural network in conjunction with NIR spectroscopy could be a reliable technique to ensure coffee authenticity.

The effect of post-brew holding time and carafe type on the sensory properties of drip brew coffee.

Coffee quality is believed to degrade quickly after brewing, and retail establishments discard unsold brewed coffee after a specified holding time period, sometimes as short as 30 min. We used trained sensory panels to evaluate the flavor profiles of light, medium, and dark roast coffees held in three different carafe types (glass on hot plate, thermal jacket, and vacuum insulated) for times ranging from 15 min to 3h. Furthermore, a panel of 93 coffee-industry professionals performed a blind evaluation of fresh (30 min) versus held (180 min) coffee for overall liking and attribute level adequacy. Sourness increased over time, consistent with acidity increasing over time (i.e., higher titratable acidity, lower pH), but only for the light and medium roasts. Dark roasted coffee became significantly more acidic over 3 h post-brew but was not perceived as more sour over time by the sensory panel. Variations were observed between the thermal jacket and vacuum carafes for the light and dark roast, but few differences were observed with storage type in the medium roast. Surprisingly, the panel of coffee industry professionals showed no preference for fresh over held. More sensory attributes decreased than increased over time, suggesting that the primary concern with loss of quality during coffee holding may be the loss of volatile aroma compounds. Hedonic ratings suggest that even if the changes over time are noticeable, they may not negatively impact overall liking. © 2022 Society of Chemical Industry.

The effect of excessive coffee consumption, in relation to diterpenes levels of medium-roasted coffee, on non-high-density lipoprotein cholesterol level in healthy men

This study was designed to determine the levels of coffee oil and diterpenes and evaluate the correlation between the effect of excessive roasted coffee consumption on non-high-density lipoprotein cholesterol (non-HDL) and the roasting degree effect on the levels of coffee oil and diterpenes extracted from Coffea arabica. The coffee oil and diterpenes were extracted using soxhlet and liquid-liquid extraction. Sixty-six healthy normolipidemic male participants were assigned for this study which consisted of two stages. The first stage is the coffee abstaining stage where subjects were requested to abstain from drinking coffee for 2 weeks. The second stage is the coffee drinking stage which consisted of groups (the control group and coffee-drinking group). The levels of TC, TG, LDL-C, HDL-C, and non-HDL were determined in all participants before and after the experiment. The results indicated that the coffee roasting degree demonstrated a significant increase in the levels of coffee oil and diterpenes ranging from 9.31% (green coffee) to 15.64% (dark roast) and from 0.205% (green coffee) to 0.300% (dark roast) for diterpenes. In conclusion, the current study revealed that excessive consumption of medium roasted coffee was associated with elevated non-HDL levels in normotensive nonsmoker healthy men which might be attributed to the positive association between the degree of roasting and diterpenes levels.

Food borne toxicants in coffee: Acrylamide and furan derivative content in Arabica and Robusta coffees with different roasting profiles and varying degrees of roast

<sec><title/> To evaluate mitigation options for both acrylamide and furan and methylfurans a Vietnam Robusta grade 2 and a Brazil Arabica (unwashed) were roasted by tangential, drum and hot air roasting. Three different roasting profiles were followed and three samples (light, medium and dark roast) were obtained per profile. Decaffeinated and steam treated batches of the two coffees were roasted. Special roasts, such as double roast (on 2 days with cooling down in between) or roasting with a sudden temperature change were studied. The contaminants were analyzed by GC-MS – in case of the furans headspace GC-MS – using deuterated standards. </sec><sec><title/> The acrylamide contents were highest in light roasts, and decreased after that with longer roasting time. This was true for both the Robusta and Arabica samples. The content of furan and 2-, 3- and 2-5-methylfurans were low in light roasts and had a maximum in dark roasts. It is possible to minimize the content of either acrylamide and furans, however, a mitigation of both could not be established by changing the roasting parameters or using pretreatments. Among the furans determined 2-methylfuran was most abundant (average around 70%), followed by furan (average around 20%). The special roasts showed no options to minimize both contaminants as did the pretreatments. In the Vietnam Robusta furan related compounds were measured. 5-hydroxymethylfurfural and 5-hydroxymethylfurfuryl-2-carboxylic acid decreased with the degree of roast and time, while furfuryl alcohol and 2-furoic acid contents increased. </sec>

Characteristics of roasting arabica and robusta coffee beans with rotary cylinder tube roast machine with electric heat source

Arabica and Robusta coffee beans have physical differences in general. In the process of roasting coffee beans with different physical forms, it is possible that there will be differences in the roasting temperature and water content of the beans after the roasting process. Arabica and Robusta coffee beans have physical differences in general. In the process of roasting coffee beans with different physical forms, it is possible that there will be differences in the roasting temperature and water content of the beans after the roasting process. In brewing coffee, it can also be affected by the roasting process. There are several factors that need to be considered in the roasting coffea bean namely early moisture of coffea beans, temperature in the roaster and the time it takes for the coffee beans to ripen as desired. The use of heat energy to get a specific aroma and taste in coffee beans is very necessary. The objective of the research is to determine how the criteria of the roast of Arabica coffea beans and Robusta coffee beans using cylindrical roaster rotates with electrical energy as its heat source. The results obtained at the treatment temperature of 205°C using a rotating cylinder tube coffee roaster using an electric heat source takes 78 minutes to reach coffee maturity with a dark roast level of maturity. Analysis of the color of coffee beans after roasting, it was found that Arabica coffee and Robusta coffee were more dominant, showing on the color track-60 with the Agtron Color Classification System scale, where the initial moisture content of dry robusta beans is 12.50% reduced to 3.66% after roasting, while the initial moisture content of arabica beans is 12.36% reduced to 3.54%.

Optimization of QuEChERS and high performance liquid chromatography-fluorescence detection conditions to assess the impact of preparation procedures on EU priority PAHs in coffee samples and their PAHs consumption risk.

The good performance conditions for determination of EU priority PAHs in coffee samples were established to evaluate the effects of roasting degree on the PAHs in coffee beans and the brewing methods on the PAHs transfer from coffee beans to their brews. The consumption risk of the PAHs in coffee products was also assessed. The PAHs levels of the roasted coffee beans were in the order: 923.65 ng/g (dark roast) > 132.20 ng/g (medium roast) > 69.28 ng/g (light roast). Compared with general brewing with the drip bag (PAHs content, 0.30-0.62 ng/mL in coffee brews), the coffee machine brewing (set at 4 bar) induced higher PAHs release into coffee brews (PAHs content, 0.36-2.14 ng/g). The PAHs amounts of the commercial brewed and canned coffee products were 0.32-1.23 ng/g and 0.16-0.46 ng/g, respectively. The consumption risk of the PAHs in the coffee brews and products is a low level of concern.

Heat and Mass Transfer Kinetics on the Chemical and Sensory Quality of Arabica Coffee Beans

Roasting has been used by the coffee industry to promote changes in the physical and chemical structure of coffee beans that influence the sensory quality of coffee beverages. However, there are no standardization rules for the temperature and roasting time. Thus, this study evaluated the influence of four roasting profiles obtained by two different roasters on the chemical and sensory quality of the coffee bean. Baked, light, medium, and dark roasting were evaluated using medium infrared spectroscopy and cupping test. Individual and joint effects of temperature and time for each roasting profile were observed on the loss of grain mass. There are specific regions in the infrared spectrum that can be used as markers to discriminate the roasting profiles and the type of roaster used. Despite the difference observed in the ranges of the infrared spectra, the roasters did not present significant differences in the average of the final sensory notes. This result shows the need to use analytical chemical techniques together with sensory analysis in order to better determine differences between coffee samples. Therefore, differences observed in the chemical analyzes and in the sensory attributes of roasted coffee are related to the roasting profile and type of roaster.

Phospholipidomics and quantum chemistry calculation unravel the changes in phospholipid molecules of flaxseed oil during roasting

Roasting flaxseed significantly improves the antioxidant activities and flavor of its oil; however, the effect of roasting on phospholipid molecules in flaxseed oil is limited. Herein, on the basis of phospholipidomics and quantum chemistry calculation, phospholipidome in raw, light, and dark roasted flaxseed oils and their changes were systematically explored and compared. Seventy individual phospholipid molecules were detected in raw and roasted flaxseed oils. After light roasting, major classes of phospholipid molecules including phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol increased 11.43-, 36.62-, and 67.88-fold, respectively. PE exhibited 92.06 % reduction after dark roasting. The model reaction showed that the main reaction of PE was the Maillard reaction during roasting. Quantum chemistry calculation demonstrated that the reaction energy barriers of the Maillard reaction (96.81 kJ/mol) was much lower than the hydrolysis (188.84 kJ/mol) for PE. The study is expected to provide new insight into the change mechanism of PE during flaxseed processing.

Monitoring In Vitro and In Vivo Aroma Release of Espresso Coffees with Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry

This work presents in vitro and in vivo aroma release analysis of three espresso coffees carried out by PTR-ToF-MS headspace and nosespace analysis, respectively. The products were C. arabica coffees prepared using an espresso coffee machine: a low-caffeine C. arabica var. laurina light roast, a low-caffeine C. arabica var. laurina dark roast, and a single-origin coffee from Ethiopia which were roasted to a medium roast degree. Headspace analysis allowed for discrimination between coffees with a prediction accuracy of 92% or higher. Relevant discriminating compounds were related to the roasting degree and varietal compounds. Coffee nosespace consisted of 35 mass peaks overall. Despite this relatively low number of detected peaks, coffee discrimination was still possible with ≥93% accuracy. The compounds most relevant to the discrimination were those related to the roasting degree. Major differences—both qualitative and quantitative—were found between headspace and nosespace profiles.

Effect of Coffee on the Bioavailability of Sterols.

Absorption at the intestinal epithelium is a major determinant of cholesterol levels in the organism, influencing the entry of dietary cholesterol and the excretion of endogenous cholesterol. Several strategies are currently being followed to reduce cholesterol absorption, using both pharmacological agents or food ingredients with hypocholesterolemic properties. Coffee has recently been shown to affect cholesterol bioaccessibility, although it has not been shown if this translates into a decrease on cholesterol bioavailability. In this work, coffee obtained with different commercial roasting (light and dark) and grinding (finer and coarser) was evaluated regarding their effect on cholesterol absorption through Caco-2 monolayers, mimicking the intestinal epithelium. The fluorescent dehydroergosterol was used as a sterol model, which was shown to permeate Caco-2 monolayers with a low-to-moderate permeability coefficient depending on its concentration. In the presence of coffee extracts, a 50% decrease of the sterol permeability coefficient was observed, showing their potential to affect sterol bioavailability. This was attributed to an increased sterol precipitation and its deposition on the apical epithelial surface. A higher hypocholesterolemic effect was observed for the dark roasting and finer grinding, showing that the modulation of these technological processing parameters may produce coffees with optimized hypocholesterolemic activity.

Caffeine Content of Bondowoso Arabica Ground Coffee with Variation of Roasting Profile and Type of Packages

Bondowoso Arabica coffee is a type of coffee that grows on the slopes of Mount Ijen-Raung. It has a high commercial value and distinctive taste. Coffee processing applications from roasting, grinding, packaging and brewing to storage will affect the quality of coffee. Caffeine is one of the compounds in coffee that contributes to bitterness and has certain pharmacological effects. This study aimed to determine the caffeine content of Bondowoso Arabica coffee harvested on August 2021 which was obtained from Sukosari Lor village with various roast profiles and types of packaging. In this study, Arabica coffee was roasted with light roast, medium roast and dark roast profiles. Then each treatment was mashed to obtain ground coffee. Ground coffee was put in a standing pouch made of polyethylene terephthalate (PET) with a thickness of 75 microns; polypropylene (PP) with a thickness of 100 microns; and polypropylene (PP) with a thickness of 120 microns and then stored for three months. During the storage of first and third months, caffeine levels were measured. Based on the results of the study, the caffeine content was increase along with higher roasting temperature. During the storage process, the caffeine content in ground coffee packaged using PP decreased the most.

Effect of Moisture Contents and Roasting Degree on Quality of Wine Coffee from Arabica Gayo

Wine coffee is a newly diversified coffee product with specific market segments. The term “wine coffee” indicates that the brewed drink has a wine-like flavor. This coffee is going through coffee cherries fermentation for 10 to 30 days. Wine coffee is also known as fermented coffee because it goes through the fermentation process of the fruit before it becomes the coffee beans. As a brand new product, wine coffee processing techniques such as drying and roasting condition are still varied between the producers. Therefore, wine coffee producers need references to have similar perceptions. Nevertheless, the information related to the suitable roasting degree of moisture contents that could elevate the cupping quality of wine coffee is still lacking or not yet available. This study aims to determine the effect of moisture content in wine coffee green beans and roasting degree (light, medium, and dark) on the quality of the coffee wine. The measured parameters were physicochemical properties and the cupping test based on the SCAA standard. This study indicates that the pH value of brewed wine coffee is between 5.02 - 5.37. As the moisture content of the green bean decreased, the pH of its brewed was also decreased. All produced wine coffee in this research had cupping test’s total score varied from 82.00 - 83.75 and classified as specialty coffee qualifications. The distinctive flavor characteristics of coffee wines are obtained at the medium roast level with a total score of 83, 75, namely fruity, raisin, smoky, citrusy, good body, sweet, wine, banana, tangerine, dark caramel. Meanwhile, roasted coffee wine has a sourer taste; the resulting specific flavor such as burnt, tobacco, and a thick body at the dark roast level.

Quantification of Spent Coffee Ground Extracts by Roast and Brew Method, and Their Utility in a Green Synthesis of Gold and Silver Nanoparticles.

Nanotechnology has become increasingly important in modern society, and nanoparticles are routinely used in many areas of technology, industry, and commercial products. Many species of nanoparticle (NP) are typically synthesized using toxic or hazardous chemicals, making these methods less environmentally friendly. Consequently, there has been growing interest in green synthesis methods, which avoid unnecessary exposure to toxic chemicals and reduce harmful waste. Synthesis methods which utilize food waste products are particularly attractive because they add value and a secondary use for material which would otherwise be disposed of. Here, we show that spent coffee grounds (SCGs) that have already been used once in coffee brewing can be easily used to synthesize gold and silver NPs. SCGs derived from medium and dark roasts of the same bean source were acquired after brewing coffee by hot brew, cold brew, and espresso techniques. The total antioxidant activity (TAC) and total caffeoylquinic acid (CQA) of the aqueous SCG extracts were investigated, showing that hot brew SCGs had the highest CQA and TAC levels, while espresso SCGs had the lowest. SCG extract proved effective as a reducing agent in synthesizing gold and silver NPs regardless of roast or initial brew method.

Analysis of Drying Air Temperature on Moisture Content in Coffee Beans Using a Fluidized Bed Dryer with Perforated Plates

Fluidized Bed Dryer with perforated plate bed is used as drying for coffee processing. This study succeeded in reducing the water content of coffee beans by 0.11% within 30 minutes of drying more evenly with fluidization on coffee beans. The level of maturity of coffee beans can be achieved at a control set temperature of 200°C the coffee beans undergo a light roasting process with the center of the coffee beans receiving 83.8°C, at a temperature of 250°C the coffee beans undergo a medium roasting process with the center of the coffee beans receiving 130°C, and at the control set temperature of 300°C the coffee beans underwent a dark roasting process with the center of the coffee beans receiving a temperature of 107.6°C. The advantage of this Fluidized Bed Dryer with perforated plate bed compared to other mechanical dryers lies in its low energy requirements, which depend on the heater and blower power as its main components.