Coffee Roast Level, Timing, and Carbohydrate Source Affect Peak Blood Glucose and Area Under the Curve Values in a Randomized Pilot Clinical Trial

The hypothesis was tested that coffee types differing in content of major constituents also differ with regard to cardiometabolic effects. Overweight persons (n = 118) were randomized to consume a dark roast [rich in N-methylpyridinium (NMP)] or medium roast (rich in caffeoylquinic acids, trigonelline) coffee blend for 3 months, after a washout period of 4 weeks. Before and after the intervention period, body weight and 15 further general and biochemical parameters were determined. Participants consumed an average of 4-5 cups per day. Mean body weight, body mass index and waist circumference did not change during the coffee consumption phase in either of the study groups. Systolic blood pressure decreased in the dark roast coffee group only (p < 0.05). High-density lipoprotein cholesterol levels increased in the medium roast coffee group only, and triglyceride levels increased in the dark roast coffee group only. Glucoregulation and insulin levels were not affected, although there was a small increase of hemoglobin A1c values in both groups. An increase of adiponectin levels occurred in the medium roast coffee group only and was negatively associated with NMP concentrations. Differences did not remain statistically significant after correction for multiple testing. Medium and dark roast coffee blends exert small but possibly relevant different cardiometabolic effects. Further studies of health outcomes in relation to coffee constituents seem warranted.

ABSTRACTCarbon monoxide (CO) emitted from roasted coffee is a potential occupational respiratory exposure hazard to workers within the coffee industry. The current study objective was to estimate CO emission factors from commercially available roasted whole bean and ground coffee measured in loose form, not packaged, and to assess the utility of CO monitoring in nonventilated storage spaces such as within coffee roasting and packaging facilities, transport vessels, and cafés. Determinants affecting CO emissions from coffee were investigated, including form (whole bean vs. ground), roast level (light, medium, medium-dark, dark), and age (time since the package was opened). CO emission factors were estimated for roasted coffee samples from a variety of manufacturers purchased from local grocery stores and online. Emission tests were performed on 36 brands of coffee, some with more than one sample per brand and with various roast levels. Decaying source equations or smoothing functions were fitted to the CO concentration measurements. Maximum observed emission factors at the peak of the predicted concentration curve were adjusted by the time required to reach the maximum CO concentration and reported as emission factors (EFbuildup). Ground coffee had a significantly increased EFbuildup (P < 0.0001) compared with whole bean. Roast level did not significantly affect emissions for whole bean (P = 0.72) but did for ground (P < 0.001) coffee. For ground coffee, medium-dark and dark roasts had significantly higher emissions than medium and light roasts. Worst-case emission factors from commercially available whole bean and ground coffee measured in loose form, not packaged, showed that roasted coffee can rapidly emit CO. CO concentrations should be monitored in storage spaces in service and manufacturing facilities as well as transport vessels to ensure exposures do not exceed occupational exposure limits. Storage spaces may need to be ventilated to control CO concentrations to safe levels.Implications: Emission rates of carbon monoxide (CO) from roasted coffee showed that unventilated or underventilated storage spaces should be monitored and ventilated, if necessary, to control CO concentrations to safe levels.

We tested the hypothesis that caffeine ingestion results in an exaggerated response in blood glucose and (or) insulin during an oral glucose tolerance test (OGTT). Young, fit adult males (n = 18) underwent 2 OGTT. The subjects ingested caffeine (5 mg/kg) or placebo (double blind) and 1 h later ingested 75 g of dextrose. There were no differences between the fasted levels of serum insulin, C peptide, blood glucose, or lactate and there were no differences within or between trials in these measures prior to the OGTT. Following the OGTT, all of these parameters increased (P < or = 0.05) for the duration of the OGTT. Caffeine ingestion resulted in an increase (P < or = 0.05) in serum fatty acids, glycerol, and plasma epinephrine prior to the OGTT. During the OGTT, these parameters decreased to match those of the placebo trial. In the caffeine trial the serum insulin and C peptide concentrations were significantly greater (P < or = 0.001) than for placebo for the last 90 min of the OGTT and the area under the curve (AUC) for both measures were 60 and 37% greater (P < or = 0.001), respectively. This prolonged, increased elevation in insulin did not result in a lower blood glucose level; in fact, the AUC for blood glucose was 24% greater (P = 0.20) in the caffeine treatment group. The data support our hypothesis that caffeine ingestion results in a greater increase in insulin concentration during an OGTT. This, together with a trend towards a greater rather than a more modest response in blood glucose, suggests that caffeine ingestion may have resulted in insulin resistance.

Coffee is rich in phenolic compounds, which can be evaluated by the total phenolic or specific individual phenolics. The composition and concentration of phenolics in coffee are affected by various factors, including postharvest and roasting. This study aimed to compare the ratio of phenolic acid (measured as chlorogenic acid) to total phenolic in Bogor arabica coffee, considering different postharvest treatments and roasting levels. The coffee samples were treated with different postharvest (dry, wet, and honey) and roasting processes (light and dark). Green coffee bean was used as a control. The roasting process involved heating the coffee at temperatures ranging from 147.9 to 178.8°C for light roasting, and 190.2 to 200°C for dark roasting (10 minutes each). The color of the coffee beans, concentration of phenolic acid in the coffee extract, and total phenolic in the coffee extract were analyzed using a colorimeter, HPLC, and spectro-photometer respectively. The results showed that roasting significantly intensified the dark color of Bogor arabica coffee. Among the phenolic acids, the 5-CQA isomer emerged as the most dominant and was also the most susceptible to degradation during roasting. As the roasting level increased, the concentration of phenolic acid consistently decreased. Interestingly, the total phenolic initially increased in light roasted coffee but decreased in dark roasted coffee. Green coffee beans exhibited the highest proportion of phenolic acid (83%), whereas dark roasted coffee had the lowest proportion (19%). Although light roasted coffee had the highest total phenolic, its phenolic acid concentration decreased significantly compared to green coffee beans.

We tested the hypothesis that caffeine ingestion results in an exaggerated response in blood glucose and (or) insulin during an oral glucose tolerance test (OGTT). Young, fit adult males (n = 18) underwent 2 OGTT. The subjects ingested caffeine (5 mg/kg) or placebo (double blind) and 1 h later ingested 75 g of dextrose. There were no differences between the fasted levels of serum insulin, C peptide, blood glucose, or lactate and there were no differences within or between trials in these measures prior to the OGTT. Following the OGTT, all of these parameters increased (P [Formula: see text] 0.05) for the duration of the OGTT. Caffeine ingestion resulted in an increase (P [Formula: see text] 0.05) in serum fatty acids, glycerol, and plasma epinephrine prior to the OGTT. During the OGTT, these parameters decreased to match those of the placebo trial. In the caffeine trial the serum insulin and C peptide concentrations were significantly greater (P [Formula: see text] 0.001) than for placebo for the last 90 min of the OGTT and the area under the curve (AUC) for both measures were 60 and 37% greater (P [Formula: see text] 0.001), respectively. This prolonged, increased elevation in insulin did not result in a lower blood glucose level; in fact, the AUC for blood glucose was 24% greater (P = 0.20) in the caffeine treatment group. The data support our hypothesis that caffeine ingestion results in a greater increase in insulin concentration during an OGTT. This, together with a trend towards a greater rather than a more modest response in blood glucose, suggests that caffeine ingestion may have resulted in insulin resistance.Key words: adenosine, skeletal muscle, methylxanthines, glucose uptake, diabetes.

Coffee consumption is a well-known contributor to tooth discoloration, and the extent of staining is influenced by the chemical composition of the coffee. This study investigated the associations of coffee roasting level, chlorogenic acid (CGA) content, absorbance level, and their combined effects with tooth discoloration. Bovine tooth enamel specimens were immersed in light, medium, and dark roasts of four coffee types (two Arabica and two Robusta coffees) for 72 h. High-performance liquid chromatography (HPLC) was used to measure CGA content, absorbance levels were estimated by using pigment concentration, and discoloration was assessed by spectrophotometry. The data were analyzed with the Friedman test. Medium roasts induced the greatest discoloration, and tooth specimens immersed in Ethiopia Arabica exhibited the greatest color difference based on CIEDE2000 (ΔE00 at 72 h: 13.51 ± 4.63). Light roasts induced the least staining, despite having the highest CGA content. Dark roasts showed the highest absorbance, indicating a higher pigment concentration. Friedman analysis revealed a significant difference in color change in relation to roasting level for all coffee types. The present findings indicate that tooth discoloration is caused by the complex interaction of CGA, melanoidins, and roasting level. Because of the interplay of these factors, medium roasting had the greatest effect on discoloration.

ABSTRACTThe consumption of specialty coffee has been growing and attracting an increasing number of enthusiasts both in Brazil and worldwide. Annually, new research is conducted to understand consumer perceptions regarding the nuances of this beverage. This study aimed to explore the sensory perceptions of specialty coffees using the Temporal Dominance of Sensations (TDS) methodology across different roast levels, comparing responses from trained panels and regular consumers. Using samples of Coffea arabica from Minas Gerais in Brazil, the study applied the TDS technique to assess the sensory impact of three distinct roast levels (light, medium, and dark) on both primary (category‐level attributes per the SCA Flavor Wheel) and secondary (sub‐category descriptors) attributes. Coffee samples were analyzed by a panel of trained evaluators based on the Q Grader training protocol and a group of regular specialty coffee consumers. The results revealed distinct sensory profiles across roast levels, with notable differences between trained panelists and consumers. Light roasts were associated with sour and fruity notes, especially by trained panelists, while consumers more often perceived bitter and fermented attributes. Medium roasts showed greater sensory balance, and dark roasts were predominantly bitter for both groups, though trained panelists also identified fermented and alcoholic notes more clearly. Trained evaluators demonstrated greater sensitivity and were able to discern a wider range of sensory attributes. In addition, they spent less time selecting the first sensation and showed higher dominance rates for most attributes compared to the panel of regular specialty coffee consumers for both primary and secondary attributes. This divergence not only emphasizes the role of sensory training in enhancing perceptual acuity but also underlines the importance of aligning coffee sensory claims with consumer expectations and perception.

Background: Coffee is a plant that widely consumed by the community. It contains antioxidant-rich compounds such as caffeine, chlorogenic acid, trigonelin, kafestol, and kahweol. Coffee quality related to the roasting process. This study aimed to determine the effect of different roasting level of robusta coffee extract (Coffea canephora) on liver histopathology of male Sprague Dawley strain white rats (Rattus norvegicus) induced by aspirin. Methods: This research is an experimental study with Post-Test Only Control Group design for 15 days. This research used 30 rats in 5 groups, K(-) (aquadest); K(+) (aspirin 90mg/day); P1 (aspirin and robusta coffee extract Light roast 25mg/kgBW/day); P2 (aspirin and robusta coffee extract Medium roast 25mg/kgBW/day); and P3 (aspirin and robusta coffee extract Dark roast 25mg/kgBW/day). Assessment of liver cell damage using modified Suzuki scoring. Results: Mean score of hepatocyte damage on the histopathological findings was K(-)=0,44; K(+)=1,92; P1=1,28; P2=1,20; and P3=1,68. Data analysis performed using One-Way ANOVA test followed by Post-Hoc LSD and obtained significant results between all groups. Conclusion: There is an effect of roasting level of robusta coffee extract (Coffea canephora) with the roasting level is Medium Roast on liver histopathology of male Sprague Dawley strain white rats (Rattus norvegicus) induced by aspirin. Key Words: aspirin, coffee roasting, liver histopathology, robusta coffee extract.

This study aims to determine the caffeine content of Argopuro Jember robusta coffee beans based on differences in post-harvest processing methods. The research was conducted at the Jember State Polytechnic Agricultural Products Processing (PHP) Laboratory and the Jember State University Integrated Testing Unit Laboratory in June-September 2022. The samples were robusta coffee logs originating from the Argopuro area of ​​Jember. The post-harvest coffee processing process is divided into four (4) methods, namely natural processing (dry process), semi-wet processing, wet (full wash process), and honey processing. Green beans from the results of each processing method are roasted at light, medium, and dark levels. The roasted bean caffeine content test from each post-harvest processing method at each roasting level was carried out descriptively (simple, without repetition). Overall, the caffeine content of the roasted beans produced in this study still meets the SNI 01-3542-2004 standard, a maximum of 2%. The caffeine content of Argopuro Jember robusta coffee roast beans at the light roast level ranges from 1.44-1.65%, 1.38-1.92% for medium roast, and 1.61-1.81% for dark roast. The highest caffeine content in roasted beans at each roasting level is 1.65% (dry process), 1.92% (full wash process), and 1.81% (full wash process), respectively. Meanwhile, roasted beans with the lowest caffeine content with a value of 1.38% are produced using the semi-wet process processing method at a medium roast level. The fluctuations in caffeine values ​​produced in this study indicate that post-harvest processing methods do not affect the caffeine content of roasted beans at light, medium, or dark roast levels.

This study evaluated the effects of Guatemalan coffee extract (G) on the physicochemical, antioxidant, and sensory properties of Yanggaeng at different roasting levels (light, medium, and dark) and concentrations (0%, control group [CON]; 2%, 2; 4%, 4; and 6%, 6). Moisture, ash, fat, protein, and carbohydrate contents varied significantly with G concentration and roasting level, with light roasts exhibiting the highest moisture and fat content, but the lowest ash and carbohydrate content. Colorimetric properties showed a dose-dependent decrease in lightness and an increase in redness and yellowness with the addition of G. Additionally, pH levels increased in light and dark roasts, but decreased in medium roasts, whereas Brix values increased with G, peaking in dark roasts. Antioxidant activity, assessed by total phenolic content and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, improved notably in the medium and dark roasts. Textural properties including hardness, resilience, and chewiness also benefited from the addition of G. Sensory evaluations favored Yanggaeng containing 4–6% G, especially in dark roasts, for attributes such as color, scent, and overall taste. Dark roast concentrations of 4% and 6% were identified as optimal for enhancing the properties of Yanggaeng, supporting the potential of G to develop innovative high-quality desserts tailored to modern consumer preferences.

Beverage color significantly affects perceived sensory quality and consumer preference. Although the color of coffee beans is well known to vary strongly with roast level, little work has examined how roast level and brewing conditions affect the color of the final beverage. Here, we report that the color of full immersion brewed coffee is significantly affected by both roast level and brewing temperature. Coffees from three different origins were each roasted to three different levels (light, medium, and dark) and then brewed at three different temperatures (4, 22, and 92°C). Each sample was brewed toward full extraction and then diluted to precisely 2% total dissolved solids so that differences in concentration would not confound color measurements. Absorbance spectra (UV‐vis) and color tristimulus values (L*a*b*) were then collected and analyzed. We find that roast level had the strongest impact on brew color, and that brew temperature had a significant impact on color for light and medium roasts, with less impact on dark roasts. Qualitatively, the cold brewed coffees tended to be redder, while the hot brewed coffees were blacker. The results suggest that there is an opportunity to manipulate and brand brewed coffee color through judicious choices of roast level and brewing temperature.Practical ApplicationColor serves as an indicator of coffee quality and potentially could affect perceived sensory characteristics. Our results suggest that appropriate control of roast level and brew temperature could yield desired colors for novel coffee products.

Blood glucose, plasma insulin and free fatty acids (FFA) responses, during the 2 h oral glucose tolerance test (OGTT) with 75 g of dextrose, were measured in 30 consecutive patients with acute enterically transmitted non-A, non-B hepatitis. All of these parameters during the OGTT were compared with 10 age-, sex- and weight-matched healthy volunteers from the same community. The fasting blood sugar, insulin and FFA were not different from normal controls (P greater than 0.05). According to the WHO criteria, the blood glucose response during OGTT in these patients was normal in 23%, impaired in 33% and diabetic in 43%. There was significant hyperinsulinaemia (P less than 0.001) in patients with impaired and diabetic GGT and it persisted even at the end of 2 h. None of the abnormal liver function tests correlated with blood sugar, insulin and FFA response during the OGTT. All abnormal responses during the OGTT were, however, transient and returned to normal in all the patients after the recovery from acute hepatitis.

Coffee contains a variety of organic acids (OAs) and chlorogenic acids (CGAs) that contribute to overall sensory properties. Large variations in preparation and measurement methodology across the literature complicate interpretation of general trends. Here, we perform a systematic review and meta-analysis of the published literature to elucidate the concentrations of OAs and CGAs in both Coffea arabica (arabica) and Coffea canephora (robusta), for both green coffee and roasted coffee at multiple roast levels. A total of 129 publications were found to report acid concentration measurements, yielding 8,634 distinct data points. Analysis of the full data set reveals several trends. First, roasted robusta has considerably more acidic compounds than arabica with 2 to 5 times as much total OAs, and much larger amounts of formic and acetic acid. As for CGAs, in both arabica and robusta 5-CQA is the major component, and progressive roasting decreases the concentration of all CGAs. The total amount of CGA present was more dependent on roast level than the type of coffee (arabica vs. robusta). Overall, this meta-analysis suggests that the increases in certain OAs with roast level might play more of a role in the sensory profile of dark roast coffees than previously suspected.

About 70% of the harvested coffee is exported to the industrialized nations for value addition due to lack of processing and logistic facilities in developing coffee producer countries, thus leaving behind a marginal economic return for the growers. This research was conducted to investigate the roasting capacity of an innovatively developed batch-type directly solar radiated roasting system for the decentralized processing of coffee using solar energy. Central composite rotatable design (CCRD) was employed to design the experiments to optimize the coffee roasting process. Experimental results revealed that with an average solar direct normal irradiance (DNI) of 800 W/m2, the roaster was capable of roasting a batch of 2 kg coffee beans in 20, 23, and 25 min subjected to light roasts, medium roasts, and dark roasts, respectively at a drum speed of two revolutions per minute (rpm). The batch-type solar roaster has the capacity to roast 28.8–36 kg of coffee beans depending on dark to light roasting conditions on a clear sunny day with DNI ranging from 650 to 850 W/m2. The system thermal efficiency during coffee roasting was determined to be 62.2%, whereas the roasting efficiency at a corresponding light roast, medium roast, and dark roast was found to be 97.5%, 95.2%, and 91.3%, respectively. The payback period of the solar roaster unit was estimated to be 1038 working sunshine hours, making it viable for commercialization.

The total polyphenolic content and the antioxidant activity have been analyzed in ground beans of green, light, medium and dark roasted coffee by UV-VIS spectrometry. Water coffee extracts showed the highest levels of polyphenols in green and light roasted coffees where the total polyphenolic content (TPC) ranged from 49.19 ± 0.70 to 74.05 ± 0.28 and from 59.79 ± 1.45 to 38.34 ± 1.26 g GAE.kg−1, respectively. In medium roast samples it ranged from 43.90 ± 3.07 to 74.05 ± 0.28g GAE.kg−1 and in dark roast from 37.44 ± 0.63 to 47.41 ± 0.69 g GAE.kg−1. The total antioxidant capacity (TAC) reached the highest values (DPPH inhibition ranging from 69.08 ± 1.33% to 78.55 ± 0.89%) in light roasted coffees. Dark roasted coffees showed both the lowest content of polyphenols as well as the total antioxidant capacity. In case of TPC, statistically significant differences (P˂0.001) have been identified between green coffee and other roasted degrees. Also, dark coffee showed statistically noticeable differences (P˂0.001) in TPC in relation to other roasted stages. Statistically important difference (P˂0.001) has been discovered between the total antioxidant capacity of dark roasted coffee and other roasting levels. The results demonstrated that roasting process affects both the oxidative activity as well as polyphenolic content.