Coffee: biochemistry and potential impact on health

Coffee is one of the most popular beverages in the world. Development of coffee beans with specific flavor profiles can enhance the quality and value of the product. In this study, the flavor profiles of Arabica coffee (Coffea arabica L.) beans treated with protease, at different enzyme loading, time, and pH, were investigated using gas chromatography tandem mass spectrometry (GC-MS/MS). The coffee beverages were evaluated for their sensory characteristics by Q-Grader (professional coffee taster). The coffee beans obtained from protease hydrolysis exhibited specific and unique volatile compounds or flavor profiles than the control (coffee beans without enzyme loading). Specific volatile profiles in the enzymetreated coffee beans, such as isopropenyl acetate, 2-acetyl-5-methylfuran, and delta-dodecalactone were identified. Coffee beverages obtained from roasted coffee beans from protease fermentation with 0.84% protease, pH 6.2 at 41 h (R-FP5), and 1.00% protease, pH 5.0 at 30 h (R-FP8) were evaluated as specialty coffees (a score of 79.75 points), showing their specific aroma profiles as fruity, spice, mango, dry fruit, ripe fruit, nutty and tamarind notes. The present work revealed that enzymatic fermentation of the green Arabica coffee beans is a promising method for the modulating and improving of specialty coffee with specific acceptable flavors and aromas.

The increasing market interest in coffee beverage, lead coffee growers around the world to adopt more efficient methods to select the best-quality coffee beans. Currently, coffee beans selection is carried out either manually, which is a costly and unreliable process, or using electronic sorting machines, which are often inefficient because some coffee beans defects, such as sour and immature beans, have similar spectral response patterns. In this sense, the present work aimed to assess coffee beans quality using both computer vision and machine learning techniques, such as Support Vector Machine (SVM), Deep Neural Network (DNN) and Random Forest (RF). For this purpose, an algorithm written in Python language was developed to extract shape and color features from coffee beans images. The obtained dataset was then used as input to the machine learning algorithms. The data reported in this study pointed to the importance of color descriptors for classifying coffee beans defects. Among the variables used, the components from RGB (Red, Green and Blue) and HSV (Hue, Saturation and Value) color spaces presented the most relevant contribution for the classification models. Also, the results reported in this study provides evidence that computer vision along with machine learning algorithms can be used to identify and classify coffee beans with a very high accuracy (> 90%). Key words: Deep neural network; classification; artificial intelligence; image processing; granulometry.

Background: Acrylamide is the most powerful carcinogenic and neurotoxic compound widely distributed in thermally processed foods. This compound is formed during early stages of roasting processes of coffee beans through Millard reaction between reducing sugars and asparagine. Due to the huge consumption of coffee throughout the globe, it has been considered as the major dietary source of this dangerous compound. Thus, this study aims to investigate the effect of roasting conditions on sugars and acrylamide contents in the Arabic coffee beans and beverages. Methods: Arabic coffee beans were roasted at 125°C for 30 to 60 min, ground to powders, brewed in boiling water for 20 min and then analysed for sugars and acrylamide contents. Results: Roasting conditions significantly (P ≤ 0.05) reduced the content of both reducing and nonreducing sugars compared to untreated samples. Increasing roasting duration to 40 min significantly (P ≤ 0.05) increased the acrylamide concentration values to the maximum, whereas extending the duration over 40 min (P ≤ 0.05) reduced the acrylamide concentration of coffee beans and beverages. Conclusion: The present study confirms that the process of roasting coffee beans is a significant factor in the formation of acrylamide in Arabic coffee powders and beverages.

Isolation, selection and evaluation of yeasts for use in fermentation of coffee beans by the wet process

Introduction: Coffee is one of the most widely consumed beverages in the world. The desired aroma and flavour of coffee are developed duringroasting which is the most important step in coffee processing. Instant Controlled Pressure Drop Process (DIC) technology is controlled hightemperature and short time process which been used successfully to improving the kinetics of drying, extraction, and decontamination of fresh and dried natural products. The main advantages of DIC are that it is a master controlled temperature and time process, the dwell times are short, reducing the chemical degradation, so new products with superior quality attributes may be developed. Materials and Methods: Two coffee beans varieties were investigated by Brazilian and Ethiopian sources. The raw beans were pre-treated using the DIC process under adopted conditions prior to roasting. A two-factor central composite design was used to optimize the settings of roasting time and roasting temperature on response variables of bulk, true and normalized density, and roasting degree. Also, microscopic analysis using Scanning Electron Microscopy (SEM) and kinetics of the roasting processes are included. Results and Discussion: The obtained results confirmed that the roasted DIC treated beans for both varieties have lower densities, higher roasting degree and lower activation energy needed for roasting compared to the raw beans. The physical properties’ magnitude is highly relevant to coffee origin. Roasting time and the temperature seemed to be of significant regarding all the physical characteristics of the beans, however, time was of topmost significance. Besides, treating coffee been by DIC prior to roasting leads to texture modification and conservation of time and energy needed for roasting. Conclusions: The physical properties of the roasted coffee beans are highly affected and changed with the coffee origin, roasting conditions and pre-treatment of coffee beans prior to roasting using the DIC process. The incorporation of the DIC process prior to roasting seemed to achieve more conservation of time and energy needed for roasting compared to the raw untreated beans. The higher degree of roasting and the competitive roasting activation energy of Brazilian coffee beans give aconclusion that more economic roasting process could be achieved with the Brazilian coffee. The pre-treatment by DIC enhances the remarkable reduction in coffee beans density and increasing in the roasting degrees that are in line with the industrial needs of coffee beverages. Response Surface Methodology is an efficient tool for optimization and mathematical modeling of the coffee roasting process.

Roasting is an important step of coffee processing which affects its quality characteristics. We investigated the effect of microwave and oven roasting on its physicochemical and antioxidant properties, and the fatty acids content. The oil contents of green and roasted coffee beans were determined as 5.75% (green), 9.65% (oven), and 2.70% (microwave). The total phenol content of green coffee beans was decreased by 13.59% and 16.66% on microwave and oven roasting, respectively. Microwave and oven roasting caused a decrease of 34.76% and 37.63%, respectively, in the antioxidant potential of green coffee beans. With few exceptions, the contents of most of the phenolic compounds were increased during roasting of coffee beans. The palmitic acid content decreased, while the oleic, linoleic, linolenic, and arachidonic acid contents of roasted coffee bean oils were increased during roasting. This information could be helpful for securing the maximal health benefits of coffee. Practical applications Coffea arabica is one of the species of coffee which is highly consumed comparing with other species. The antioxidant compounds such as caffeine and chlorogenic acid in coffee beverage play an important role in reducing the prevalence of chronic diseases. Roasting is a vital step for the processing of coffee beans to be used as a beverage. It affects the main constituents of the coffee beans. This study provides the useful information of roasting process on antioxidant activity, phenolic compounds, and fatty acids of coffee beans which can be helpful for reaping the maximum health benefits of coffee.

We investigated the anti-obesity and anti-hyperlipidemic effects of extracts of two roasted coffee beans (Vietnam robusta and Ethiopia mocha sidamo G2) and fermented coffee beans with Monascus rubber mycelium (MR) by solid-state culture. C57B/L6 mice were divided into seven groups: normal diet (ND) group, high fat diet (HFD) group, and HFD groups with hot water extracts from Vietnam robusta coffee beans (HFD-VR), MR-fermented Vietnam robusta coffee beans (HFD-VR-MR), MR-fermented Vietnam robusta coffee beans with 10% brown rice (HFD-VRMR- BR10), Ethiopia mocha sidamo G2 coffee beans (HFD-ES), and MR-fermented Ethiopia mocha sidamo G2 coffee beans (HFD-ES-MR). After 6 weeks, body weight gain and food efficiency ratio were higher in the HFD group, but significantly reduced in the coffee extracts-fed groups. The HFD-ES-MR group showed greater body weight reduction than the HFD-ES group. The serum triglyceride, total cholesterol, and LDL-cholesterol levels as well as the atherogenic index and cardiac risk factor all tended to decrease in groups fed Vietnam robusta coffee extracts compared to the HFD group. These results suggest that Vietnam robusta and Ethiopia mocha sidamo G2 may be used to make functional coffee beverages with anti-obesity and anti-hyperlipidemic activities.

Optimum flavor and aroma of the coffee are developed during the roasting process. However, certain problems exist in the coffee roasting process such as partial charring, over roasting, and poor temperature distribution across the coffee bean (due to the low thermal conductivity of bean), if conditions are not optimized. Hence, uniform temperature distribution across the coffee bean in the roasting process is highly desirable. To achieve these requirements, the broken coffee beans were positioned in a single layer packed bed arrangement using the closed system by circulating hot air. In this experiment, three factors were arranged in a completely randomized design with three levels and three replications. The first factor considered was roasting temperature (200°C, 230°C, and 260°C), second factor was roasting time (5 min, 10 min, and 15 min), and third was particle size (4–6 mm, 2.36–3.35 mm, and 1.7–2.36 mm). The initial moisture content of raw beans (cv. Limu) was determined. The data were collected on selective physical properties of roasted coffee beans and sensory acceptability of prepared beverage. The results showed that the physical properties and sensory acceptability are significantly high ( P < 0.001 ). It depends on the interaction effect of all the studied factors. Among the studies parameters, roasting temperature of 230°C with a particle size range of 4–6 mm showed the steady transition in dry mass loss and change in bulk density with increase in roasting duration. Coffee roasted at 230°C for 10 min with a particle size of 4–6 mm showed the highest sensory acceptability score (89.21). In conclusion, it can be said that a temperature of 230°C, a time of 10 min, and a particle size between 2.36–3.35 mm and 4–6 mm are recommended conditions for the roasting process of coffee beans.

Coffee (<i>Coffea spp.</i>) is one of the most widely consumed beverages in the world. World coffee consumption is around 70% comes from Arabica, 26% from Robusta , and the rest 4% from other varieties. Coffee beverages characteristics are related to chemical compositions of its roasted beans. Usually testing of coffee quality is subjectively tasted by an experienced coffee tester. An objective quantitative technique to analyze the chemical contents of coffee beans using LIBS will be reported in this paper. Optimum experimental conditions was using of 120 mJ of laser energy and delay time 1 &mu;s. Elements contained in coffee beans are Ca, W, Sr, Mg, Na, H, K, O, Rb, and Be. The Calcium (Ca) is the main element in the coffee beans. Roasting process will cause the emission intensity of Ca decreased by 42.45%. In addition, discriminant analysis was used to distinguish the arabica and robusta variants, either in its green and roasted coffee beans. Observed identifier elements are Ca, W, Sr, and Mg. Overall chemical composition of roasted coffee beans are affected by many factors, such as the composition of the soil, the location, the weather in the neighborhood of its plantation, and the post-harvesting process of the green coffee beans (drying, storage, fermentation, and roasting methods used).

The atmosphere CO2 concentration increased from ca. 280, prior to the Industrial Revolution up to ca. 400 μL CO2 L-1 in our days, rising nearly 2 ppm per year actually. The Intergovernmental Panel on Climate Changes (IPCC) estimates at the end of 21st century the [CO2] could reach values between 445 and 1130 μL CO2 L-1, with a potential impact on global temperature and changes in water availability: These changes will have major agricultural and ecological implications. Here are presented some perspectives concerning the potential impacts of these environmental changes on the physiology and, consequently, on the production of Coffea arabica and C. canephora species, which together account for about 99% of the worldwide yielded coffee bean, considering the coffee plant’s requirements mostly focused in temperature.

The coffee berry borer, Hypothenemus hampei, is the most important pest of coffee throughout the world, causing losses estimated at US $500 million/year. The thrips Karnyothrips flavipes was observed for the first time feeding on immature stages of H. hampei in April 2008 from samples collected in the Kisii area of Western Kenya. Since the trophic interactions between H. hampei and K. flavipes are carried out entirely within the coffee berry, and because thrips feed by liquid ingestion, we used molecular gut-content analysis to confirm the potential role of K. flavipes as a predator of H. hampei in an organic coffee production system. Species-specific COI primers designed for H. hampei were shown to have a high degree of specificity for H. hampei DNA and did not produce any PCR product from DNA templates of the other insects associated with the coffee agroecosystems. In total, 3,327 K. flavipes emerged from 17,792 H. hampei-infested berries collected from the field between April and September 2008. Throughout the season, 8.3% of K. flavipes tested positive for H. hampei DNA, although at times this figure approached 50%. Prey availability was significantly correlated with prey consumption, thus indicating the potential impact on H. hampei populations.

Reprint of “The mycobiota of coffee beans and its influence on the coffee beverage”

A study was undertaken to evaluate aflatoxin B1 contamination in coffee beans. 41 samples of green coffee were collected from large lots of material by representative sampling. The raw samples were analyzed and showed no detectable levels of aflatoxin B1. In order to establish the heat stability of the toxin, 3 artificially contaminated samples (average level 10/μg/kg) were roasted atca 200°C for different operation times periods so as to reproduce light and dark roasting procedures. Each sample was roasted both electrically and by gas.The percentage of toxin destruction was up to 93% for light roasted and 99% for dark roasted coffee with a slightly higher rate up to 100% for the electrically roasted coffee for light and dark roasting. In order to evaluate the potential migration of the aflatoxin B1 into the coffee beverage, 1 sample found contaminated after roasting treatment (0.8/°g/kg) was extracted using each of the 3 most common types of coffee makers. Additional destruction of the toxin was observed (up to 99%) in two cases while only 75% of fate was obtained in the third.The process from raw coffee beans to beverage showed a meaningful destruction of aflatoxin B1, ranging from 97 to 100% depending on the extraction technique adopted in the preparation of the beverages.

반응표면분석법에 의해 생두를 실험 조건인 <TEX>$194.82^{\circ}C{\sim}250.00^{\circ}C$</TEX>의 온도 범위에서 7.93~22.07분의 조건으로 커피원두를 배전하여 이화학적 분석, 물리적 특성, 관능검사 등을 실시하여 최적 조건을 설정하였다. 배전 정도가 커짐에 따라 직경, 길이, 두께 모두가 증가하여 전체적인 팽창률은 증가했지만, 겉보기 밀도의 변화는 그 차이가 적은 것으로 나타났다. pH는 증가하는 반면 총산도와 총페놀함량은 감소하는 경향을 나타내었으며, 고형분함량은 증가하는 유의성을 가지고 있는 것으로 나타났다. 색도는 전체적으로 배전에 의해 갈색에서 검은색으로 변화하며 색도값이 감소하는 형태로 나타났다. 관능검사에 의해서는 전체적인 향과 맛에 따라 큰 차이를 보였으며 향이 배전 조건과 연관성이 높은 것으로 나타났다. 유의성을 나타낸 길이, 폭, 향, 고형분 함량과 총페놀함량으로 배전 조건을 설정한 결과, <TEX>$225^{\circ}C$</TEX>에서 20분간 배전하는 것이 본 연구 조건에서는 최적의 배전 조건으로 결정되었다. The consumer awareness concerning coffee beverages has increased in Korea. The objective of this study was to optimize the roasting conditions of coffee bean for consumer's attribute. The optimal roasting conditions for Colombian coffee beans were analyzed by using a central composite design with a quadratic polynomial model by response surface methodology (RSM). The experimental conditions for coffee bean roasting were <TEX>$194.82^{\circ}C{\sim}250.00^{\circ}C$</TEX> and 7.93~22.07 minutes. The responses of sensory attributes. physicochemical and physical properties were analyzed with RSM. The width. length and height of green beans increased when the beans were roasted. The higher degree of roasting gave the higher pH and solid contents but the lower total acidity and total phenolic compounds. In sensory tests, the roasting temperature and time had a significant effect on the flavor score. The optimum roasting condition of Colombian coffee bean predicted for maximizing the length, width, solid contents, total phenolic compounds and flavor score were 20 minutes at <TEX>$225^{\circ}C$</TEX> by RSM.

The mycobiota of coffee beans and its influence on the coffee beverage