Profiling flavor characteristics of cold brew coffee with GC-MS, electronic nose and tongue: effect of roasting degrees and freeze-drying.

BACKGROUND: Roasting is an important process in the formation of coffee flavor characteristics, which determines the quality of coffee and consumer acceptance. However, the influence of roasting degree on the flavor characteristics of cold brew coffee has not been fully described. RESULTS: In the present study, the flavor characteristics of cold brew coffee with different roasting degrees were compared in detail by using chromatographic and electronic sensory approaches, and the flavor changes induced by freeze-drying were investigated. Pyrazine and heterocyclic compounds were the main aroma compounds in coffee, and gradually dominated with the increase of roasting. Pyridine was consistently present in cold brew coffees of different roasting degrees and showed significant gradient of quantity accumulation. Aroma compounds such as pyrazine, linalool and furfuryl acetate were the main contributors to coffee roasting, floral and fruity flavor. Freeze-drying preserved the fruity and floral aromas of medium-roasted cold brew coffee, whereas reducing the bitterness, astringency and acidity properties that are off-putting to consumers. CONCLUSION: The higher consumer acceptance and enjoyment in medium roast cold brew coffee may be related to its stronger floral and fruity aroma. The aroma profile qualities of freeze-drying processed medium roasted cold brewed coffee were more dominant and more suitable for freeze-drying processing than medium dark roasting. Application of freeze-drying for cold brew coffee will promote the convenience of drinking. The present study provides valuable technical guidance in improving the flavor and quality of cold brew coffee, and also promotes its commercialization process. © 2024 Society of Chemical Industry.

Mechanisms of action of coffee bioactive compounds - a key to unveil the coffee paradox.

The knowledge of the relationship between the chemical structure of food components with their mechanisms of action is crucial for the understanding of diet health benefits. This review relates the chemical variability present in coffee beverages with the mechanisms involved in key physiological events, supporting coffee as a polyvalent functional food. Coffee intake has been related with several health-promoting properties such as neuroprotective (caffeine, chlorogenic acids and melanoidins), anti-inflammatory (caffeine, chlorogenic acids, melanoidins, diterpenes), microbiota modulation (polysaccharides, melanoidins, chlorogenic acids), immunostimulatory (polysaccharides), antidiabetic (trigonelline, chlorogenic acids), antihypertensive (chlorogenic acids) and hypocholesterolemic (polysaccharides, chlorogenic acids, lipids). Nevertheless, caffeine and diterpenes are coffee components with ambivalent effects on health. Additionally, a large range of potentially harmful compounds, including acrylamide, hydroxymethylfurfural, furan, and advanced glycation end products, are formed during the roasting of coffee and are present in the beverages. However, coffee beverages are part of the daily human dietary healthy habits, configuring a coffee paradox.

The multi-targeted bioactive features of coffee compounds reinforce coffee as a functional food beverage.Polysaccharides and melanoidins positively modulate gut microbiota.Caffeine and phenolics are neuroprotective, anti-inflammatory, antidiabetic and antihypertensive.The balance between potential health and harmful compounds configures a coffee paradox.Harmful compounds are present in trace levels in coffee, not conferring toxicity.

Optimization of Sensory Properties of Cold Brew Coffee Produced by Reduced Pressure Cycles and Its Physicochemical Characteristics.

The use of vacuum cycles for the cold extraction of coffee is a new process that leads to a significant reduction in process time of Cold Brew compared to conventional methods. This research aimed at specifying the necessary parameters for producing a consumer-accepted cold brew coffee by applying vacuum cycles. This was achieved by investigating the effect of the number of cycles and of the applied pressure (vacuum) on the physicochemical characteristics of the cold brew coffee, i.e., total dissolved solids (TDS%), pH, acidity, phenol and caffeine content and color. Furthermore, sensory evaluation took place by members of the Specialty Coffee Association of America (SCAA) to specify parameters such as coffee blend, coffee/water ratio, total water hardness and grind size and secondly to determine the optimal pressure and number of cycles for a tasty final beverage. The sensory and physiochemical characteristics of cold extraction coffee were investigated by Principal Component Analysis (PCA). It became evident that coffee extraction by applying two vacuum cycles at 205 mbar pressure produced the lowest intensity of physiochemical properties (caffeine, phenols, acidity, TDS% and pH), and the highest score of sensory characteristics (fragrance, body, acidity, flavor, balance, and aftertaste). Caffeine and phenol concentration of the optimal beverage were 26.66 ± 1.56 mg/g coffee and 23.36 ± 0.79 mg gallic acid/g coffee respectively. The physiochemical characteristics were also compared to a beverage of hot extraction of the same blend and ratio of coffee to water.

Review on factors affecting coffee volatiles: from seed to cup.

The objective of this review is to evaluate the influence of six factors on coffee volatiles. At present, the poor aroma from robusta or low-quality arabica coffee can be significantly improved by advanced technology, and this subject will continue to be further studied. On the other hand, inoculating various starter cultures in green coffee beans has become a popular research direction for promoting coffee aroma and flavor. Several surveys have indicated that shade and altitude can affect the content of coffee aroma precursors and volatile organic compounds (VOCs), which remain to be fully elucidated. The emergence of the new roasting process has greatly enriched the aroma composition of coffee. Cold-brew coffee is one of the most popular trends in coffee extraction currently, and its influence on coffee aroma is worthy of in-depth and detailed study. Omics technology will be one of the most important means to analyze coffee aroma components and their quality formation mechanism. A better understanding of the effect of each parameter on VOCs would assist coffee researchers and producers in the optimal selection of post-harvest parameters that favor the continuous production of flavorful and top-class coffee beans and beverages. © 2021 Society of Chemical Industry.

Investigation of the factors affecting foamability and foam stability of cold brew coffee.

BACKGROUND: In this study, the foamability and foam stability of nitrogen-infused cold brew coffee, as affected by coffee variety (Arabica and Robusta), degree of roast (light, medium, dark), brewing temperature (4, 20, 35 °C), brew ratio (1:5-1:15 w/w; coffee/water), ground particle size (712, 647 and 437 µm volume mean diameter) and beverage temperature (4, 20 and 35 °C), were investigated. RESULTS: Dynamic surface tension of cold brew, as determined from bubble tensiometry, decreased from 65-70 mN m-1 to about 60 mN m-1 as the bubble lifetime increased from 0.1 s to 1 s. Infusing the cold brew coffee (70 mL) with nitrogen gas for 30 s at 50 mL min-1 generated 30-40 mL of foam head. At the same degree of roast, brews prepared from Arabica beans had more stable foam than those from Robusta. Foam stability increased with increasing degree of roast, increasing brewing temperature, decreasing particle size, and decreasing the beverage temperature. By contrast, brew ratio had relatively less effect on foaming properties. Nitrogen-containing constituents present in the 80% (v/v) ethanol-soluble fraction (55.9% of total dissolved solids) of the brew samples were important contributors to foaming, while the 80% (v/v) ethanol-insoluble fraction (42.3% of total dissolved solids) that contained polysaccharides was important in stabilizing the foam. CONCLUSION: The foamability and foam stability of cold brew coffee are significantly affected by coffee variety, degree of roast, brewing temperature, ground particle size, and beverage temperatures. The foam properties are dictated by the low-molecular-weight nitrogen-containing compounds and high-molecular-weight polysaccharides present in the cold brew coffee. © 2022 Society of Chemical Industry.

Process characterization and optimization of cold brew coffee: effect of pressure, temperature, time and solvent volume on yield, caffeine and phenol content.

BACKGROUND: Cold brew coffee, based on cold extraction, is rapidly attracting consumers' preference worldwide. Low total solids yield and long extraction times (up to 24 h) are the main drawbacks of this process. Five different treatments were investigated: the traditional cold extraction method, freezing, lyophilization of coffee beans, use of chaotropic salt and reduced pressure extraction. The latter was optimized by applying a Box-Behnken design. Pressure, vacuum cycles, duration of each cycle and mass of ground coffee to water ratio were the optimization parameters. Yield, caffeine and phenol concentration were the response variables. RESULTS: Caffeine concentration and yield were significantly affected by vacuum cycles and by the combination of vacuum cycles and duration of each cycle. Validation of the derived quadratic models for each response variable was performed. Optimum values for highest extraction yield (22%) and phenol concentration as well as mass transfer coefficients of phenol and caffeine were also determined. CONCLUSIONS: Extraction under reduced pressure might be the best treatment for the acceleration of cold brew coffee extraction. © 2021 Society of Chemical Industry.

Residue behavior and safety evaluation of pymetrozine in tea.

BACKGROUND: Pymetrozine is a widely used pesticide. It is challenging to analyze and difficult to manage due to the large gap in its global maximum residue limits (MRLs) in tea. The development of a high-efficiency detection method for the evaluation of the transfer of residual pymetrozine from tea plantations to tea cups is therefore of prime significance. RESULTS: An analytical method for the determination of pymetrozine residues in tea was established based on Cleanert PCX solid-phase extraction. The average recoveries were 72.2-93.7%, with relative standard deviations (RSDs) of less than 12%. The limits of quantification (LOQs) were 0.005 mg·kg-1 in fresh tea leaves and dry tea, and 0.00025 mg·L-1 in tea brew. Pymetrozine degraded rapidly in tea plants with a half-life (t1/2 ) of 1.9 days in open tea plantations, and decreased by 9.4-23.7% in the green tea-processing procedure, which was concentration dependent. The residual pymetrozine levels in green tea collected at 6 and 21 days were below the MRLs in China and EU at a dosage of 30 g a.i. ha-1 , respectively. The leaching rates of pymetrozine from dry tea to tea brew were 58.7-96.3%. Hazard quotient (HQ) values of pymetrozine were significantly <100% when tea shoots were plucked in 6 days, which indicated a negligible risk to humans. CONCLUSION: This work allows the determination of residual pymetrozine in tea and illustrates a low intake risk with the use of pymetrozine in tea plantations. It could serve as reference for further regulation consideration for maximum residue limits (MRLs). © 2020 Society of Chemical Industry.

Investigating the effects of geographical origin, roasting degree, particle size and brewing method on the physicochemical and spectral properties of Arabica coffee by PCA analysis.

Effects of geographical origin of Coffee Arabica beans (Brazil, Colombia and Peru), roasting degree, particle size and different brewing methods (French press, chemex and cold brew) on physicochemical and spectral properties of coffee samples were investigated in this study. Analyses of pH, total phenolic content (TPC) and total antioxidant activity (TA), UV and fluorescence spectroscopy measurements were performed. Principal component analysis (PCA) was used to obtain the most effective parameters on chemical changes. Results indicated that the increase of roasting degree caused decrements in the intensities of UV-spectra because of the degradation of trigonelline and chlorogenic acid molecules while counterpart trend was observed in the fluorescence spectra due to formation of fluorescence Maillard reaction products (MRP) during roasting. French press and cold brew methods caused similar TPC (1873.33-3818.33 and 2648.88-3824.44 µg/mL gallic acid equivalent, respectively) and TA (0.18-0.32 and 0.16-0.27 µmol/mL Trolox equivalent, respectively) values whereas chemex method showed different physicochemical properties (TPC: 1008.88-3543.88 µg/mL gallic acid equivalent and TA: 0.08-0.26 µmol/mL Trolox equivalent). Roasting degree and brewing method-compared to other parameters-were the most discriminating factors on the basis of UV spectra and fluorescence spectra of coffee brew samples, respectively. All roasting degrees could be distinguished with the rate of 71.42% on PC1 and 23.45% on PC2 of total variance according to UV-spectra while chemex and French press-cold brew methods could be differentiated with the rate of 97.24% on PC1 and 1.79% on PC2 of total variance based on fluorescence spectra on PCA score graphs.

The use of home brew in Pacific Islands countries and territories.

This review examines what is known about the production and use of home brew in the Pacific Islands countries and territories. Data collection involved interviews of 78 men and women from the Marshall Islands, Papua New Guinea, Toga, and Tuvalu. The interviews were conducted in 2013 by local interviewers. The questions fell into four key areas: people's history of home-brew consumption, the reasons for home-brew use, the effects of home brew, and people's perceptions about home brew. An open ethnographic approach revealed that males are the main consumers of home brew, that home brew is consumed in private venues by those with low socioeconomic status, and that there are positive and negative outcomes associated with the use of home brew. Finally, policy implications of the findings are included in this article.

Trends in purchasing cross-border, illicit and home-brewed alcohol: A population study in Great Britain, 2020-2023.

INTRODUCTION: The last 3 years have seen substantial changes in Great Britain (GB) including the COVID-19 pandemic, cost-of-living crisis and policy changes such as minimum unit pricing. We examined changes in purchasing cross-border, illicit and home-brewed alcohol among risky drinkers over this period. METHODS: Data were used from 22,086 adult (≥18 years) increasing/higher-risk drinkers (AUDIT-C ≥5) participating in a monthly cross-sectional survey between October 2020 and August 2023. We estimated time trends in the proportion reporting obtaining alcohol from: (i) cross-border (any/within-GB/international); (ii) illicit; and (iii) home-brewed sources in the past 6 months. RESULTS: Between October 2020 and August 2023, the proportion reporting cross-border alcohol purchases increased (from 8.5% to 12.5% overall; prevalence ratio [PR] = 1.47 [95% CI 1.17-1.86]). This was largely driven by an increase in cross-border purchases abroad (PR = 1.52 [1.13-2.05]), with a smaller, uncertain increase in cross-border purchases within GB (PR = 1.37 [0.96-1.95]). The prevalence of cross-border alcohol purchasing was higher in Wales (13.8% [12.3-15.4%]) and Scotland (6.1% [5.4-6.8%]) than England (3.6% [3.3-3.9%]). There was little change in illicit alcohol purchasing in England or Wales (4.1% [3.7-4.4%]; 4.2% [3.2-5.1%]), but in Scotland it fell from 5.7% to 2.4% (PR = 0.42 [0.19-0.81]). Home-brewed alcohol was rare (GB: 3.1% [2.9-3.4]) and stable. DISCUSSION AND CONCLUSIONS: The proportion of increasing/higher-risk drinkers in GB purchasing cross-border alcohol increased between October 2020 and August 2023, due to an increase in people buying alcohol abroad. Cross-border alcohol purchases within GB were more commonly reported in Wales and Scotland. The small proportion purchasing illicit alcohol did not change substantially in England or Wales, but fell by half in Scotland.

An investigation of the shelf life of cold brew coffee and the influence of extraction temperature using chemical, microbial, and sensory analysis.

The shelf-life of cold and hot water extraction coffees based on sensory and chemical profiles and microbial growth was examined, which also allowed the study of the influence of extraction temperature on the chemical and sensorial profiles of coffee. The shelf life of refrigerated cold- and hot-brewed coffee was limited not by microbial stability but rather by deterioration in sensory attributes. Further work is recommended to elucidate the mechanisms of coffee staling in a refrigerated environment, with particular interest in the degradation products of chlorogenic acid, as a significant decline in chlorogenic acid concentration was found over the storage period. Cold-extracted coffees were found to be chemically and sensorially different beverages from coffees extracted at high temperatures. Additionally, the cold-brewed coffees had greater sensory flavor stability over the storage time than the hot-brewed treatment. Practical application: This study advances the industry's understanding of the shelf life of ready-to-drink bottled cold coffees and demonstrates that lower brewing temperatures lead to greater flavor stability over shelf life. The findings also provide brewing parameters that can help guide product developers in modulating the flavor of commercial cold coffees.

Emancipation in the Gold Coast: The Abolitionist Views of James Hutton Brew.

This article deals with the abolitionist views of James Hutton Brew who argued against the British emancipation model in the Gold Coast. Brew was the proprietor and editor of the Gold Coast Times and discussed the British abolition process in its editorial pages. These articles revealed his thinking on abolition. Brew not only opposed the emancipation process set out by the British, which he felt was contradictory and disconnected from the Gold Coast context, but also argued for an alternative model that involved paying compensation to slave owners and creating a program to accommodate freed slaves. The British Governor portrayed some of the arguments of African abolitionists like Brew as those of slave owners trying to retain their positions. In discussing the ideas of James Hutton Brew, this article contributes to the literature on the historiography of slavery and abolition in Africa.

Evaluation of Physicochemical Characteristics and Sensory Properties of Cold Brew Coffees Prepared Using Ultrahigh Pressure under Different Extraction Conditions.

Although cold brew coffee is becoming increasingly popular among consumers, the long coffee extraction time is not conducive to the further development of the market. This study explored the feasibility of ultrahigh pressure (UHP) to shorten the time required for preparing cold brew coffee. The effects of pressure and holding time on the physicochemical characteristics and sensory evaluation of UHP-assisted cold brew coffee were also determined. The extraction yield; total dissolved solid, total phenol, and melanoid content; antioxidant capacity; and trigonelline and chlorogenic acid contents of UHP-assisted cold brew coffee increased as the pressure increased. The extraction yield and the total dissolved solid, total phenol, total sugar, and chlorogenic acid and trigonelline contents were higher when the holding time was longer. The HS-SPME-GC/MS analysis demonstrated that the furan, aldehyde, and pyrazine contents in coffee increased as the pressure and holding time increased. The pressure did not significantly impact the concentrations of volatile components of esters and ketones in coffee samples. However, the increase in holding time significantly increased the ester and ketone contents. The sensory evaluation results revealed that as pressure rose, the intensities of nutty, fruity, floral, caramel, and sourness flavors increased, whereas bitterness and sweetness decreased. Longer holding time increased nutty, caramel, sour, bitter, sweet, and aftertaste flavors. Principal component analysis (PCA) results indicated that holding time is a more crucial factor affecting the physiochemical indices and flavor characteristics of coffee. UHP can shorten the preparation time of cold brew coffee. Pressure and holding time significantly affected the physiochemical indices and volatile components of UHP-assisted cold brew coffee. UHP-assisted cold brew coffee had lower bitterness, higher sweetness, and a softer taste than conventional cold brew coffee.

Pouring hot water through drip bags releases thousands of microplastics into coffee.

Microplastics (MPs) released from food packaging have attracted widespread attention. In this study, drip bags made from polyethylene (PE), polypropylene (PP), polyester (PET), and rayon selected from eight brands were employed to investigate MPs releasing. Fourier-transform infrared microspectroscopy (µ-FTIR), optical microscope and scanning electron microscope (SEM) were used to study the effects of brewing time and temperature on the release of MPs. The results showed that a single plastic coffee bag steeped at 95 ℃ for 5 min could release more than 10,000 MPs particles into a cup of coffee. Irregular blocks, long strips, and size range of 10-500 µm MPs were easier to be released, implying that consuming 3-4 cups of coffee will lead to an intake of 50 thousand MPs particles daily. Rayon was the primary type of released MPs, accounting for over 80% of the total amount of the released MPs. Our results are hoped to provide evaluation standards of material selection for processing coffee bags.

Acids in brewed coffees: Chemical composition and sensory threshold.

Coffee brewed on light, and very light-roast coffee beans have emerged as a recent trend among specialty coffee drinkers. The acidity of such light-roast coffee, and coffee in general, is an important sensory characteristic, as there is demonstrated a clear correlation between the roast level and perceived acidity in brewed coffee. The acidity is believed to be strongly linked to the content and composition of organic acids in coffee. Still, there is limited literature on acid content in brewed coffee and on the relevance of specific acid concentrations to sensory perception. In this study, we determined concentrations of acids and sugars in French-press brewed specialty coffee. We used varying roast degrees in the light to very light range using five coffees from different geographical locations (Brazil, Bolivia, and Kenya) and determined the sensory detection threshold and recognition for selected acids. The concentration of all individual acids except one (formic) either significantly decreased (citric, malic, and chlorogenic acid) or increased (acetic, lactic, phosphoric, quinic, and glycolic acid) systematically with an increasing roast degree, while no systematic trends were found between the different coffee samples. The sugar content decreased with an increasing roast degree. The sensory detection threshold for malic, acetic, and lactic acid was determined to be above the actual concentration of said acids in the coffee and just below for phosphoric acid, indicating that these compounds are unlikely to individually be perceived in coffee. Only citric acid can be clearly detected in the threshold test (not identified by experts in coffee) in concentrations above the measured concentrations, as the detection threshold was below (<0.16 g/L) the concentration found in the investigated coffees (0.23-0.60 g/L). The measured citric acid concentration was found to be much higher for the Brazil coffees (0.49 ± 0.08 g/L) compared to the Bolivia coffee (0.40 ± 0.11 g/L), and the Kenya coffees (0.30 ± 0.07 g/L). Furthermore, none of the acids added to the coffee were correctly recognized by coffee experts when spiked with measured average concentrations. Combined, the results question the direct relation between individual organic acids and acidity in coffee and point towards a more complex understanding of perceived acidity.

Effect of Extraction Methods on Aroma Profile, Antioxidant Activity and Sensory Acceptability of Specialty Coffee Brews.

Specialty coffees from various geographical origins were processed using different extraction methods. Four extraction techniques were employed: cold brew (CB), espresso (ES), French press (FR), and aeropress (AE). The potential health benefits of coffee brews were linked to their antioxidant activity, as determined by the DPPH assay, and total polyphenol content (TPC) measured through the Folin-Ciocalteu reducing-capacity assay. The Columbia (C) espresso coffee type (omni-roasting) exhibited the highest antioxidant activity (86.31 ± 0.70) µmol/100 mL, with a TPC value of (44.41 ± 0.35) mg GAE/g. Quantitative analyses of caffeine and chlorogenic acid were conducted using high-performance liquid chromatography (HPLC). The evaluation of coffee aroma profiles involved the application of headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) and was complemented by sensory analysis following the Specialty Coffee Association (SCA) standard protocol. The predominant volatile compounds found in all samples included furans, phenols, pyrazines, and terpenes. The EY espresso type (medium dark roasting) had the highest levels of most coffee volatiles. The C cold brew type (omni-roasting) was rated as the preferred coffee in terms of its sensory characteristics and flavour. In summary, ES and CB were found to be more effective extraction methods for the parameters assessed.

Bioactive profile and microbiological safety of Coffea arabica and Coffea canephora beverages obtained by innovative cold extraction methods (cold brews).

Coffee cold brews have been gaining prominence and popularity among consumers worldwide. However, only a few studies have systematically analyzed their chemical composition or evaluated microbiological safety aspects. This study aimed to evaluate the survival of Bacillus cereus and Escherichia coli in cold brews prepared from roasted and ground Coffea arabica and C. canephora seeds using the following preparation methods: immersion without filter (INF), immersion in a cotton filter bag (ICF), vacuum (Vac.) and cold dripping (Drip.). Traditional hot dripping methods using filter paper (HDFP) and cotton filter (HDCF) were also tested for comparison. Water at 4 °C or 25 °C was intentionally contaminated (105 CFU/mL) with cells of Escherichia coli ATCC 25922 (EC) and Bacillus cereus F4433 (BC) before coffee extraction and refrigeration at 4 °C. Coffee concentrations of 5, 10, and 15% were tested. Analyses of pH, soluble solids, nine chlorogenic acids and two lactones (CGA), caffeine, trigonelline, and melanoidins were performed. Results were compared by ANOVA, followed by the Fisher's test, Pearson correlation, Variable Importance in Projection (VIP), and Cluster analyses, with a significance level of 5%. EC and BC were not detected (<10 CFU/mL and < 1 CFU/mL, respectively) after preparing C. arabica and C. canephora hot brews. In cold brews, the higher the extraction of soluble solids and bioactive compounds (with the highest occurring at 25 °C), the lower the counts of inoculated microorganisms during 24 h of storage. BC was not detected after 24 h of extraction and/or storage in the drinks obtained by ICF and Drip. at 5%, 10%, and 15% and INF and Vac. at 15%. EC was not detected in ICF and Drip. at 10 and 15%, and in INF at 15%. C. canephora brews exhibited higher levels of soluble solids, CGA, caffeine, and melanoidins than C. arabica brews. Based on these results, it can be concluded that in the absence of thermal processing as in hot brews, more concentrated cold brews, such as 15%, produced at 25 °C by dripping and immersion methods, are preferable for later dilution due to the higher content of soluble solids and bioactive compounds that contribute reducing the number of microorganisms in the beverage.

Influence of Flow Rate, Particle Size, and Temperature on Espresso Extraction Kinetics.

Brewing espresso coffee (EC) is considered a craft and, by some, even an art. Therefore, in this study, we systematically investigated the influence of coffee grinding, water flow rate, and temperature on the extraction kinetics of representative EC components, employing a central composite experimental design. The extraction kinetics of trigonelline, caffeine, 5-caffeoylquinic acid (5-CQA), and Total Dissolved Solids (TDS) were determined by collecting and analyzing ten consecutive fractions during the EC brewing process. From the extraction kinetics, the component masses in the cup were calculated for Ristretto, Espresso, and Espresso Lungo. The analysis of the studied parameters revealed that flow rate had the strongest effect on the component mass in the cup. The intensity of the flow rate influence was more pronounced at finer grindings and higher water temperatures. Overall, the observed influences were minor compared to changes resulting from differences in total extracted EC mass.

Variables Affecting the Extraction of Antioxidants in Cold and Hot Brew Coffee: A Review.

Coffee beans are a readily available, abundant source of antioxidants used worldwide. With the increasing interest in and consumption of coffee beverages globally, research into the production, preparation, and chemical profile of coffee has also increased in recent years. A wide range of variables such as roasting temperature, coffee grind size, brewing temperature, and brewing duration can have a significant impact on the extractable antioxidant content of coffee products. While there is no single standard method for measuring all of the antioxidants found in coffee, multiple methods which introduce the coffee product to a target molecule or reagent can be used to deduce the overall radical scavenging capacity. In this article, we profile the effect that many of these variables have on the quantifiable concentration of antioxidants found in both cold and hot brew coffee samples. Most protocols for cold brew coffee involve an immersion or steeping method where the coffee grounds are in contact with water at or below room temperature for several hours. Generally, a higher brewing temperature or longer brewing time yielded greater antioxidant activity. Most studies also found that a lower degree of coffee bean roast yielded greater antioxidant activity.

Fan Assisted Extraction of Volatile Carbonyl Compounds from Coffee Brews Based on the Full Evaporation Technique.

In this work, the fan assisted extraction approach is originally exploited to determine volatile compounds in liquid samples based on the full evaporation technique. The feasibility of this strategy was firstly evaluated using model solutions containing different volatile carbonyl compounds. Different media, volumes of sample, temperatures of extraction, and times of extraction were tested. Linear regressions presenting r > 0.999, intermediate precision values < 6%, and recoveries within 76-95% were attained using a period of extraction of 10 min, a volume of sample solution of 5 µL, and a temperature of extraction of 50 °C. Analyses of brewed coffees were performed. The slopes of the calibration curves obtained using aqueous model solutions and brewed coffee samples were not significantly different. These results revealed no matrix effect under the selected experimental conditions, enabling the use of the external calibration method for quantification purposes. Twenty-four volatile carbonyl compounds were identified in brewed coffee, which elucidates the sensitivity of this approach.