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Effect of Basket Geometry on the Sensory Quality and Consumer Acceptance of Drip Brewed Coffee
Abstract
In this work, discrimination tests, descriptive analysis, consumer tests, and total dissolved solids (TDS) were used to evaluate the effects of brew basket geometry on the sensory quality and consumer acceptance of drip brewed coffee. Two basic geometries, semi‐conical and flat‐bottom, were evaluated in conjunction with coffee roast and particle size. Initial discrimination tests showed that small differences in median particle size were not discernable, but that coffees brewed using either semi‐conical or flat‐bottom filter baskets were significantly different (P < 0.05, N = 45). Additionally, coffee brewed in the semi‐conical basket had significantly higher %TDS, and we estimated a sensory difference threshold of 0.24 %TDS. A subsequent descriptive analysis (DA) showed significant differences by roast for 11 attributes and by grind for six attributes. Although brewing geometry, as a single factor, was only significantly different for three independent attributes (smoke aroma , sweetness , and tobacco flavor ), roast × geometry interactions were significant for six attributes (berry flavor , bitterness , burnt wood/ash , citrus flavor , earthy flavor , and sourness ) and the grind × geometry interaction was significant for two attributes (bitterness and floral aroma ). Attributes showing significant interactions with brewing geometry were also key drivers of consumer liking/disliking. Overall consumer liking (9‐point hedonic scale) was analyzed by cluster analysis (N = 85), which revealed four distinct preference clusters. For each cluster, a particular basket geometry and/or roast level showed lesser acceptance. Overall, the results strongly corroborate the hypothesis that basket geometry affects the sensory quality of drip brewed coffee.
Practical Application
Most Americans consume drip brewed coffee. Improving our understanding of the effects of basket geometry, roast level, and grind size on the total dissolved solids, sensory properties, and acceptability of drip brewed coffee gives producers and consumers alike an opportunity to optimize the sensory quality of their coffee.
... It is well established that consumption temperature will change flavor perception of coffee [23,24], so an otherwise identical coffee will be perceived differently if served hot versus cold. Likewise, a substantial amount of research shows that brewing the same coffee to different TDS and PE values will vastly change the sensory profile [14,16,18,25]. Less strong, lower TDS coffee has repeatedly been shown to be sweeter than higher TDS coffees [14,16,25], while sourness and bitterness increased with TDS [13,14,16]. ...
... Likewise, a substantial amount of research shows that brewing the same coffee to different TDS and PE values will vastly change the sensory profile [14,16,18,25]. Less strong, lower TDS coffee has repeatedly been shown to be sweeter than higher TDS coffees [14,16,25], while sourness and bitterness increased with TDS [13,14,16]. Titratable acidity was shown to correlate positively with TDS independent of brew temperature in hot brewed coffee, at least over the range 87 to 93 • C [15]. ...
... Rubber flavor: Perception of rubber flavor in coffee has been shown to be the strongest driver of penalties to consumer liking [25]. One possible explanation for rubber flavor might be differences in the concentrations of 2,4-dimethyl-1,3-thiazole, (ethyldisulfanyl)ethane, or styrene, all compounds shown to correlate with rubber flavor [41]. ...
Cold brew coffee is often described as sweeter or less acidic than hot brew coffee. Such comparisons, however, are potentially confounded by two key effects: different brew temperatures necessarily change the extraction dynamics and potentially alter the resulting brew strength, and different consumption temperatures are well known to affect perceived flavor and taste. Here, we performed a systematic study of how extraction temperature affects the sensory qualities of full immersion coffee. The investigation used a 3 × 3 × 3 factorial design, with coffee from three different origins representing different post-harvest methods (washed, honey-processed, and wet-hulled), each roasted to three different levels (light, medium, and dark), and each brewed at three different temperatures (4 °C, 22 °C, and 92 °C). All coffees were brewed to equilibrium, then diluted to precisely 2% total dissolved solids (TDS) and served at the same cold temperature (4 °C). We find that four attributes exhibited statistically significant variations with brew temperature for all origins and roast levels tested, with bitter taste, sour taste, and rubber flavor all higher in hot brewed coffees, and floral flavor higher in cold brewed coffee. However, there were strong interactions with origin and roast, with several additional attributes significantly impacted by temperature for specific origins and roast levels. These results provide insight on how brew temperature can be used to modulate the flavor profile of full immersion coffee.
... Ground coffee beans range in particle size from around 1800 µm down to <300 µm ( Figure 4). Smaller particle size generally increases the intensity of positive and negative sensory attributes due to the greater surface area for extraction [79]. Ideally, the particle size is matched to the brew method to adjust the rate of extraction to enhance the positive and diminish the negative sensory attributes [12]. ...
... Ideally, the particle size is matched to the brew method to adjust the rate of extraction to enhance the positive and diminish the negative sensory attributes [12]. The ground size is poorly described and inconsistent in the literature [23,56,[78][79][80][81], with descriptive definitions used, such as fine, medium, and coarse [79]. Generally, descriptions specify the following: fine ground (300 to 600 µm), medium ground (600 to 800 µm), and coarse ground (800 to >1000 µm) ( Figure 4) [23,56,[78][79][80][81]. Brew methods utilize different particle sizes, ranging from medium-coarse (Plunger/French Press), medium (Immersion Dripper, Cupping), medium-fine (Pour Over/Filter) and fine (Column/Aeropress) [55,[82][83][84][85]. Cupping as an immersive method requires a medium style grind for ideal extraction. ...
... Ideally, the particle size is matched to the brew method to adjust the rate of extraction to enhance the positive and diminish the negative sensory attributes [12]. The ground size is poorly described and inconsistent in the literature [23,56,[78][79][80][81], with descriptive definitions used, such as fine, medium, and coarse [79]. Generally, descriptions specify the following: fine ground (300 to 600 µm), medium ground (600 to 800 µm), and coarse ground (800 to >1000 µm) ( Figure 4) [23,56,[78][79][80][81]. Brew methods utilize different particle sizes, ranging from medium-coarse (Plunger/French Press), medium (Immersion Dripper, Cupping), medium-fine (Pour Over/Filter) and fine (Column/Aeropress) [55,[82][83][84][85]. Cupping as an immersive method requires a medium style grind for ideal extraction. ...
The terroir of coffee is defined as the unique sensory experience derived from a single origin roasted coffee that embodies its source. Environmental conditions such as temperature, altitude, shade cover, rainfall, and agronomy are considered the major parameters that define coffee terroir. However, many other parameters such as post-harvest processing, roasting, grinding, and brewing can combine to influence the perception of terroir. In this review, we discuss the contribution of these parameters and their influence on coffee terroir. Assessment of terroir requires defined sensory descriptors, as provided by the World Coffee Research Lexicon, and standardized roast level, grind size, and brew method. The choice of the post-harvest processing method is often environmentally dependent, suggesting that an inclusion into the coffee terroir definition is warranted. Coffee terroir is often not intentionally created but results from the contributions of the Coffea species and variety planted, environmental and agricultural parameters, and both the harvest and post-harvest method used. The unique combination of these parameters gives the consumer a unique cup of coffee, reminiscent of the place the coffee was produced.
... Furthermore, coffee can be evaluated using a cupping procedure or using trained panellists [6]. Many studies have investigated the consumer acceptability of different coffees [10][11][12][13]. To enhance sweetness, consumers also add milk or cream to their coffee [14]. ...
... All coffee was brewed and served fresh for each session of sensory testing. Coffee was prepared in a brewing machine using 1200 g of water and 66 g of coffee in a brew basket [10]. Then, the coffee was served in a 200 mL ceramic mug (8 cm height, 7.5 cm opening diameter, and 5.5 bottom diameter) and was preheated following the procedure by Frost et al. [10]. ...
... Coffee was prepared in a brewing machine using 1200 g of water and 66 g of coffee in a brew basket [10]. Then, the coffee was served in a 200 mL ceramic mug (8 cm height, 7.5 cm opening diameter, and 5.5 bottom diameter) and was preheated following the procedure by Frost et al. [10]. Approximately 100 g of coffee was poured into the cup, and the milk or PBA (10 g) was added to the coffee. ...
Consumers have begun to use plant-based alternatives (PBAs) in their coffee instead of dairy products. PBAs can include soy milk, rice milk, coconut milk, almond milk, oat milk, and hemp milk. The objective of this study was to investigate consumer acceptability and sensory perception of coffee with added dairy milk and added oat, soy, and almond PBAs. Consumers (n = 116) that frequently add milk to their coffee (n= 58) and consumers that usually use PBAs (n = 58) were recruited to participate in the study. They evaluated four different coffee samples with the addition of dairy milk as well as soy, almond, and oat PBAs. Overall, the consumers liking increased when they perceived sweetness in their coffee. The plant consumers (usually added PBAs to their coffee) liked the milk addition significantly less than the dairy consumers (usually added dairy to their coffee). In addition, the plant consumers were able to differentiate between the almond and soy PBAs, while the dairy consumers grouped them together. More studies need to be completed to investigate a wider range of PBAs, dairy products, and varieties of coffee.
... The drip brew basket geometry plays a role in the sensory properties of the coffee, with a flat-bottomed drip brew basket yielding a lower TDS and many different sensory properties than a semi-conical drip brew basket 13 . Batali et al. examined the role of TDS via temporal fractionation of a drip brew, and found that attributes like bitter, sour, and smoky were positively correlated with TDS, while attributes like sweet, fruity, and floral were negatively correlated with TDS 14 . ...
... We emphasize that our study was purely quantitative (i.e., sensory descriptive analysis rather than hedonic preference), but previous studies have identified attributes that are drivers of liking or disliking for consumers. Research from Frost et al. has indicated that a majority of consumers dislike bitterness and astringency in coffee products, whereas attributes like floral are positive drivers of liking 13 , which might indicate that the bottom third of the coffee brewing control chart ("Weak", cf. Fig. 1) might be more "ideal" for many consumers. ...
... Descriptive analysis procedure. To compare samples, a generic descriptive analysis that combined elements of the Quantitative Descriptive Analysis and Spectrum methods previously demonstrated successful 13,14,54 was utilized using Red Jade sensory science software (RedJade, Redwood City, CA, USA). Three aromas, 22 flavours, two mouthfeels, and four basic tastes were evaluated (Table 1). ...
The brew temperature is widely considered a key parameter affecting the final quality of coffee, with a temperature near 93 °C often described as optimal. In particular, drip brewers that do not achieve a minimum brew temperature of 92 °C within a prescribed time period fail their certification. There is little empirical evidence in terms of rigorous sensory descriptive analysis or consumer preference testing, however, to support any particular range of brew temperatures. In this study, we drip-brewed coffee to specific brew strengths, as measured by total dissolved solids (TDS), and extraction yields, as measured by percent extraction (PE), spanning the range of the classic Coffee Brewing Control Chart. Three separate brew temperatures of 87 °C, 90 °C, or 93 °C were tested, adjusting the grind size and overall brew time as necessary to achieve the target TDS and PE. Although the TDS and PE both significantly affected the sensory profile of the coffee, surprisingly the brew temperature had no appreciable impact. We conclude that brew temperature should be considered as only one of several parameters that affect the extraction dynamics, and that ultimately the sensory profile is governed by differences in TDS and PE rather than the brew temperature, at least over the range of temperatures tested.
... [32][33][34][35][36] The assessors evaluated the intensities of the descriptors though 6 h training sessions conducted over 2 days to provide consistent and reliable sensory panels with the assistance of the Coffee Taster's Flavor Wheel. 37,38 A terminology and reference standard for Turkish coffee was compiled in harmony with previous research studies. 6,18,[31][32][33]36,37,39 The basis for the choice of term list developed from trained assessors during training sessions and the list of flavor and taste attributes for the Turkish coffee were generated at the end of the descriptive panels. ...
... 37,38 A terminology and reference standard for Turkish coffee was compiled in harmony with previous research studies. 6,18,[31][32][33]36,37,39 The basis for the choice of term list developed from trained assessors during training sessions and the list of flavor and taste attributes for the Turkish coffee were generated at the end of the descriptive panels. The 20 descriptors and their definitions as flavor (aromatics) and taste attributes are listed in Table 1. ...
BACKGROUND
This study was carried out in order to investigate the role of post‐harvest methods and roasting degree on the sensory profile of Turkish coffees and to compare the results between two sensory panels: Turkey and Brazil. Bourbon variety of Arabica coffee beans processed by three different post‐harvest methods (natural, pulped natural and fully washed) and roasted at three different roasting degrees (light, medium and dark).
RESULTS
Ground coffee in powder size was heated with cold water and prepared in a Turkish coffee machine. Twenty assessors – ten Turkish and ten Brazilian – were selected and trained to assess 20 flavor attributes of nine Turkish coffee samples. Sensory evaluation results showed that the effects of roasting method on flavor development were perceived more dominantly than effects of post‐harvest methods. For the first time, this study highlighted the sensory analysis of Turkish coffees assessed by Turkish and Brazilian assessors.
CONCLUSION
Turkish coffee flavor profiles were significantly influenced by roasting method and no significant effects of post‐harvest method were observed. Sensorial properties of Turkish coffee were affected by several factors, such as geographical origin and techniques used for preparation of coffee beans, cultural tradition, lifestyle, social behavior and habit. © 2021 Society of Chemical Industry.
... These several factors have been shown to affect consumer acceptability or preference and the descriptive flavor profiles of brewed coffee. Researching the effects of different brewing methods and appliances on the sensory profiles of coffees can help coffee companies have a better understanding of the products they market and what type of consumer group(s) they should be marketing to [43,121,122]. The high temperature usually used in the extraction process increases the volatility of several of the chemical compounds that account for the flavor attributes in coffee [2,[123][124][125]. ...
... The flavor terms that had these two interactions also were the drivers of liking for the consumers, and these included terms such as bitterness, berry flavor, burnt wood/ash, citrus flavor, earthy flavor, sourness, and floral aroma. These findings suggest that to maintain consistency, baristas need to consider the geometry of the brew basket in addition to the roast degree and grind level of roasted beans when preparing drip-brewed coffees [121]. ...
Flavor continues to be a driving force for coffee’s continued growth in the beverage market today. Studies have identified the sensory aspects and volatile and non-volatile compounds that characterize the flavor of different coffees. This review discusses aspects that influence coffee drinking and aspects such as environment, processing, and preparation that influence flavor. This summary of research studies employed sensory analysis (either descriptive and discrimination testing and or consumer testing) and chemical analysis to determine the impact aspects on coffee flavor.
... The triangle test was approved by the UC Davis Institutional Review Board (Protocol: 1797623-1) and was conducted following the methodology in Ref. [30]. According to Ref. [31]; a triangle test is a discrimination analysis used to establish if a perceivable difference between two products exists. ...
Prolonged storage and long-distance transportation of green coffee beans exposes them to undesirable fluctuations in temperature (T) and relative humidity (r.h.), which can change the physical (wet-basis moisture content (MCwb), water activity (Aw), and color) and sensory characteristics of the coffee. High humidity also supports mold growth, decay, and microbial activities. Thus, the objective of this study was to evaluate the efficacy of commercially available desiccants for preserving the moisture content of green coffee between 10-12% MCwb, when stored in either hermetic packages and/or jute sacks, and to assess the corresponding impact on sensory quality. A conventional coffee storage and transportation period from Brazil to Italy with a duration of 42 days was mimicked in environmental chambers. Treatments in a 3 × 3 factorial design consisting of three packaging materials (GrainPro SuperGrain bag, GrainPro TranSafeliner, and/or jute sacks) and desiccants (Drying Beads®, CaCl2, or no desiccants) were evaluated. Additionally, four different mass ratios of green coffee to desiccant ranging from 50 to 300 – g coffee per g desiccant were also evaluated. The MCwb, Aw, and color of all samples were measured approximately weekly over 42 days. In comparison to the control (no desiccant, and only jute sacks), we observed a statistically significant impact for all tested desiccants and hermetic packages for maintaining the proper MCwb, Aw, and color. No significant difference was observed for the different desiccant masses tested when they were placed inside the hermetic packaging, but the desiccants were ineffective without the hermetic packaging. Triangle test and descriptive sensory evaluation yielded no significant differences between the use of hermetic packages with or without desiccants.
... Batali et al. [10] examined the role of TDS using time fractionation of drip infusions and found that attributes such as hot, sour, and smoky flavours were positively correlated with TDS, and attributes such as sweet, fruity, and floral flavours were negatively correlated with TDS. Frost et al. [26] characterised the effect of TDS and EY on the sensory quality of drip coffee, concluding that coffee with a higher TDS was more acidic and that coffee with a lower TDS was sweeter. Brewing temperatures, however, had little effects on the sensory profile of drip coffee when sensory attributes were investigated with brewing and TDS parameters [10]. ...
The aim of this study was to determine the effect of total dissolved solids (TDS), extraction yield (EY), and grinding on total polyphenols (TP), total flavonoids (TF), and total antioxidant capacity (TAC) in a fermented specialty coffee prepared using different methods of filtration (Hario V60, Aeropress, and the French press). The concentrations of antioxidant compounds differed between the TDS treatments and the methods of preparation. The TP and TF with Hario V60 were the highest at a TDS of 1.84%. The TP with Aeropress was at its highest at a TDS of 1.82%. TAC with the French press was at its highest at a TDS of 1.58%. EY was at its highest with fine grinding (Hario V60 > French press > Aeropress at 25.91%, 21.69%, and 20.67%, respectively). French press coffees had the highest TP (p = 0.045). Hario V60 coffee had the highest TF, but the TAC of the coffees remained comparable for all methods. EY and TDS influenced TP, TF, and TAC in the coffee beverages using the finest grinding size for all methods of preparation. The finer the grind, the higher the antioxidant activity of the beverages. Measuring coffee extractions should be one of the most important processes in fermented coffee preparation.
... 7. Trying to experiment. Even basket geometry can change a coffee flavour (Frost et al. 2019). ...
Caffeination can open tired eyes and enhance focus. Over-caffeination, furthermore, can lead to errors but also to unexpected discoveries that might not have happened without 30 hours of sleep deprivation and 500mg of caffeine in our bodies. This paper presents exactly such a discovery. Upon much staring into our coffee cups, empty anew, the thought struck us: coffee in space. Caffeine may not be the only key. HL Tau, Taurus, bull... Taurine! We grinded some red bourbon for a new pour-over, and developed the new, coffee-groundsbreaking Large Astrocomical Taurine Tester Experiment (LATTE) in just 1/4 of a day. We felt bull-ish about our chances of making a great discovery! We installed LATTE, aimed it at the well-known young star HL Tau, and there it was: an abundance of taurine gas beautifully outlining a cup of cosmic flat white, with the ring structure of HL Tau turning out to be latte art performed by a skillful cosmic barista. The first Robusta discovery of coffee in space. Speaking of coffee, we hope you have a nice hot cup with you, and we encourage you to pun-tinue all the way to the end of this bean-grinding paper.
... Brewing is the most common way to prepare roasted coffee beans for consumption. While there are numerous ways to brew coffee, nearly all require slowly infusing ground coffee beans with water [138,139]. Numerous variables must be considered for successful coffee brewing, as the process will affect the taste of the coffee and the active compound in it. The volatile ingredient is dissolved and lost during the brewing process, while the water-soluble component is dissolved in the water. ...
Coffee is consumed not just for its flavor, but also for its health advantages. The quality of coffee beverages is affected by a number of elements and a series of processes, including: the environment, cultivation, post-harvest, fermentation, storage, roasting, and brewing to produce a cup of coffee. The chemical components of coffee beans alter throughout this procedure. The purpose of this article is to present information about changes in chemical components and bioactive compounds in coffee during preharvest and postharvest. The selection of the appropriate cherry maturity level is the first step in the coffee manufacturing process. The coffee cherry has specific flavor-precursor components and other chemical components that become raw materials in the fermentation process. During the fermentation process, there are not many changes in the phenolic or other bioactive components of coffee. Metabolites fermented by microbes diffuse into the seeds, which improves their quality. A germination process occurs during wet processing, which increases the quantity of amino acids, while the dry process induces an increase in non-protein amino acid γ-aminobutyric acid (GABA). In the roasting process, there is a change in the aroma precursors from the phenolic compounds, especially chlorogenic acid, amino acids, and sugars found in coffee beans, to produce a distinctive coffee taste.
... As well as imparting taste and flavor themselves, acids are generally recognized as flavor precursors for quality descriptors of coffee . Perceived acidity is one of the main categories that coffee industry professionals use to score coffee quality, and hedonic testing has shown sourness to be a major driver of consumer liking (Cotter et al. 2021, Frost, Ristenpart, andGuinard 2019). Seemingly small changes to the pH and titratable acidity of the brew affect the flavor profile and influence consumer liking . ...
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.
... The extraction rate for each nonvolatile compound was calculated considering the relation between the extraction efficiency and the extraction time used in each BM. These results were expected because French ress is considered a full immersion technique where the ground coffee and water are well mixed (Frost, Ristenpart, & Guinard, 2019). This fact, together with higher temperatures (90 ± 3 • C) used in HB, help facilitate more soluble and volatile compounds to be present in the drink in less time (5 min), compared to cold methods that require longer times ( -14 h) to compensate for the low temperature (19 ± 2 • C). ...
This study evaluated the effects of different roasting profiles (time/temperature) and brewing methods on the physicochemical and sensory characteristics of coffee brews. Cold brewing (dripping and immersion) and hot brewing (French press) methods were studied to understand the effects of water temperature and technical brewing method conditions on the chemical compound extraction in coffees roasted at high-temperature short time (HTST) and low-temperature long time (LTLT). The results showed that coffee beverages were clearly differentiated concerning the roasting profile when hot water was used (90 ± 3 ◦C) in brewing. Separation of beverages according to the water temperature used in brewing was observed. Notably, hot brewing coffees were distinguished from cold brewing (19 ± 2 ◦C) based on a higher titratable acidity and abundance of some furan compounds. The non-volatile extraction rate increased at higher brewing temperatures. At the same brewing temperature, dripping exhibited a higher extraction rate than immersion brewing, which suggests that the coffee extraction process is affected by the design and operation of the cold brewing system. Coffee beverages brewed with HTST and cold dripping displayed the highest value in total dissolved solids (TDS), extraction yield, as well as the highest caffeine, trigonelline, 4- and 5-caffeoylquinic acids (CQAs) contents. Regardless of the roasting profile, coffees brewed by cold dripping were perceived with more bitter and roasted flavors. In contrast, cold immersion and hot coffee beverages showed remarkable sweetness, nutty, caramel, and malt attributes. In turn, these attributes showed an inverse correlation with caffeine concentration, trigonelline, CQAs, and TDS. The findings of this study demonstrate that volatile and non-volatile compounds present in roasted coffee depend on time-temperature roasting conditions; in turn, their presence in the resulting beverages are related to the extraction of the operational conditions of coffee brewing methods.
... The extraction rate for each nonvolatile compound was calculated considering the relation between the extraction efficiency and the extraction time used in each BM. These results were expected because French ress is considered a full immersion technique where the ground coffee and water are well mixed (Frost, Ristenpart, & Guinard, 2019). This fact, together with higher temperatures (90 ± 3 • C) used in HB, help facilitate more soluble and volatile compounds to be present in the drink in less time (5 min), compared to cold methods that require longer times ( -14 h) to compensate for the low temperature (19 ± 2 • C). ...
This study evaluated the effects of different roasting profiles (time/temperature) and brewing methods on the physicochemical and sensory characteristics of coffee brews. Cold brewing (dripping and immersion) and hot brewing (French press) methods were studied to understand the effects of water temperature and technical brewing method conditions on the chemical compound extraction in coffees roasted at high-temperature short time (HTST) and low-temperature long time (LTLT). The results showed that coffee beverages were clearly differentiated concerning the roasting profile when hot water was used (90 ± 3 °C) in brewing. Separation of beverages according to the water temperature used in brewing was observed. Notably, hot brewing coffees were distinguished from cold brewing (19 ± 2 °C) based on a higher titratable acidity and abundance of some furan compounds. The non-volatile extraction rate increased at higher brewing temperatures. At the same brewing temperature, dripping exhibited a higher extraction rate than immersion brewing, which suggests that the coffee extraction process is affected by the design and operation of the cold brewing system. Coffee beverages brewed with HTST and cold dripping displayed the highest value in total dissolved solids (TDS), extraction yield, as well as the highest caffeine, trigonelline, 4- and 5-caffeoylquinic acids (CQAs) contents. Regardless of the roasting profile, coffees brewed by cold dripping were perceived with more bitter and roasted flavors. In contrast, cold immersion and hot coffee beverages showed remarkable sweetness, nutty, caramel, and malt attributes. In turn, these attributes showed an inverse correlation with caffeine concentration, trigonelline, CQAs, and TDS. The findings of this study demonstrate that volatile and non-volatile compounds present in roasted coffee depend on time-temperature roasting conditions; in turn, their presence in the resulting beverages are related to the extraction of the operational conditions of coffee brewing methods.
... The quality of the dendogram obtained after HCA was evaluated by the cophenetic correlation coefficient, which represent a statistical criterion widely used selecting the hierarchical clustering method when there is no prior knowledge of the pattern of clustering (Matta, Tomé, Salgado, Cruz, & Silva, 2015). Regards TCATA data, consumer citation proportion for each product at 0.1 s increments were smoothed using cubic smoothing spline and plotted (Castura, Antúnez, Giménez, & Ares, 2016) and penalty lift was calculated as the difference between overall hedonic means of "checked" and "not checked" sensory descriptors (Meyners et al., 2013;Frost, Ristenpart, & Guinard, 2019). ...
Ohmic heating (OH, 0, 2, 4, 6, 8, or 10 V cm⁻¹, 72 °C/15 s, 60 Hz) at Dulce de leche processing was investigated. The equipment consisted in an ohmic heating chamber, and rectangular 316 stainless steel electrodes positioned 10 cm apart. OH-treated milk resulted in improvements in the quality parameters of Dulce de leche, with a decrease in energy expenditure (69.85-141.86 vs 1260 kJ) and hydroxymethylfurfural (HMF) levels (7.64-8.54 vs 9.53 μmol L⁻¹), an increase in product homogeneity, and formation of volatile compounds important for the sweetness of Dulce de leche (butanoic acid and 2-furan methanol). In addition, the physicochemical composition, fatty acid profile, and health indices (atherogenic, thrombogenic, desired fatty acids, and hypercholesterolemic saturated fatty acids) of the products remained without changes. In particular, the use of higher electric field (> 6 V cm⁻¹) led to a 14-78% decrease in process time, and improved volatiles profile. OH has proven to be a suitable technology for milk treatment, resulting in improvements in the quality parameters of Dulce de leche with positive impact at the process time and energy expenditure.
Industrial relevance
The Dulce de Leche processing is characterized by long cooking times to acquire its typical characteristic color and flavor. Normally, it is used pasteurized milk as raw material. Ohmic heating decreased the total time of processing in Dulce de leche manufacturing, providing an economy at the in the energy costs without significant change at the quality parameters of the final product.
... The quality of the dendogram obtained after HCA was evaluated by the cophenetic correlation coefficient, which represent a statistical criterion widely used selecting the hierarchical clustering method when there is no prior knowledge of the pattern of clustering (Matta, Tomé, Salgado, Cruz, & Silva, 2015). Regards TCATA data, consumer citation proportion for each product at 0.1 s increments were smoothed using cubic smoothing spline and plotted (Castura, Antúnez, Giménez, & Ares, 2016) and penalty lift was calculated as the difference between overall hedonic means of "checked" and "not checked" sensory descriptors (Meyners et al., 2013;Frost, Ristenpart, & Guinard, 2019). ...
This study aimed to evaluate the effects of the application of ohmic heating (OH) to milk (0, 2, 4, 6, 8, or 10 V cm⁻¹, 72-75 °C/15 s) on the sensory profiling of dulce de leche (DL) evaluated using Preferred attribute elicitation (PAE) and Temporal Check-all-that-apply (TCATA) methodologies. In addition a consumer test was also performed. OH-DL samples presented increased scores for all the sensory attributes evaluated. Low or intermediate strength electric fields contributed to increase bitter taste and decrease DL aroma and sweet taste of the products, without impact on the overall liking. When high strength electric fields were applied, higher brightness, fluidity and DL flavor scores were observed, as well as, lower intensities in consistency and sandiness scores, resulting in increased acceptance by consumers. From TCATA data, it could be observed that the perception of all sensory attributes increased as well as increased the strength of the electric fields. Overall, the adoption of electric fields with higher strength in ohmic heating during DL processing is advised, since they improved the intensity and perception of desirable intrinsic DL sensory attributes as well as improved DL overall liking.
... Thawed coffee beans were ground to setting 5 ('percolator') on a Mahlkönig Guatemala grinder, yielding a particle size of 1200 ± 44 μm. 17 Commercial drip brewers (Wilbur Curtis Co. G4 Gold Cup) were used to brew the samples. Each set of fractions was brewed with 210 g of ground coffee and a 3.8 L dose of water at 91°C dispensed continuously for 3 min 20 s, followed by a 2 min 'drip out' where the brewed coffee continued to drain by gravity. ...
Background:
The composition of drip brew coffee versus brewing time has been chemically characterized in previous studies, and it is known that the total dissolved solids (TDS) systematically decreases with each fraction during the brew. Little information exists regarding the corresponding sensory attributes versus time, however, and it is unclear how TDS correlates with flavor profile.
Results:
Standard drip brews were fractionated into distinct samples by switching in an empty carafe every 30 seconds during the brew. Using a trained sensory descriptive panel, we found that most taste and flavor attributes decreased with brew time, e.g., the earlier fractions were systematically more bitter and more sour than later fractions. Surprisingly, however, several flavor and taste attributes increased in time, e.g., later fractions were systematically sweeter and more floral than earlier fractions. Since later fractions had lower total dissolved solids (TDS), these results indicate that perceived sweetness in drip brew coffee is negatively correlated with TDS. Mass spectrometry measurements of the monosaccharide content in the brews showed that none of the fractions had perceptible concentrations of any monosaccharide.
Conclusion:
The results of the sensory analysis and the monosaccharide analysis suggest that perceptible sweetness in coffee is a consequence of masking effects and/or the presence of sweet-associated aromas and flavors. The results further suggest that unique flavor profiles could be obtained from the same coffee grounds by judicious combinations of specific fractions. This article is protected by copyright. All rights reserved.
The classic Coffee Brewing Control Chart (BCC) was originally developed in the 1950s. It relates coffee quality to brew strength and extraction yield, and it is still widely used today by coffee industry professionals around the world to provide guidance on the brewing of coffee. Despite its popularity, recent experimental studies have revealed that sensory attributes and consumer preferences actually follow much more complicated trends than those indicated by the classic BCC. Here, we present a methodology to synthesize the results of these recent studies on drip-brewed coffee to generate new versions of the BCC: a new Sensory BCC that displays a broad array of statistically significant sensory attributes across typical total dissolved solids and percent extraction ranges, a new Consumer BCC that highlights the existence of two preference clusters with different likes and dislikes across those ranges, a new Sensory and Consumer BCC that combines both sensory descriptive and consumer preferences on the same chart, and a more streamlined BCC that omits consumer preferences and focuses on the overarching sensory descriptive trends. The new BCCs provide more accurate insight on how best to brew coffee to achieve desired sensory profiles. PRACTICAL APPLICATION: Through the manipulation of yield and extraction parameters, the new Sensory and Consumer Coffee Brewing Control Chart presented here can be used by brewers of drip coffee to design coffees with specific sensory profiles and match the preferences of different consumer types.
There are numerous techniques and technologies used in the brewing of coffee today. This study is aimed to design an umbrella experiment to examine the impacting key factors consistent across all methods of extraction. These factors were identified as: grind size, roast type, steep time, grind to water as a mass-to-mass ratio and temperature. Samples were prepared by grinding the beans, weighing the beans and adding the appropriate amount to a rectangular glass vessel. Distilled water was used. French press was selected as the brewing technique. No agitation after the addition of grind was allowed. Water was heated to initial temperature and added to the vessel and a timer was started. Upon time completion aliquots were taken and analysed using a prism-based automatic temperature compensation (ATC) refractometer. Minitab 19.2020.1 (64-bit) was used for analysis of variance and optimisation. In the initial design of experiments, the five factors were considered at different levels. Three factors found significant in impacting %TDS (total dissolved solids) were: total steep time, grind-to-water ratio and roast type. To further refine the experiments, 2 ³ full-factorial design was conducted for these three factors. Finally, optimisation was done to determine the factor levels to produce a cup of coffee for the target %TDS of 1.26. This research found that it is best to use medium roast coffee that is ground fine with a 0.08 grind-to-water ratio, with an initial temperature of 195 Fahrenheit in a French press, and the ideal steep time is 7 min. Previous studies have focused on the extraction methods. In this study, the method of extraction has been removed as a variable. Hence, the findings are very useful for food industry.
Background:
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 minutes. 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 minutes to 3 hours. 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.
Results:
Sourness increased over time, consistent with acidity increases 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 three hours 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.
Conclusions:
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. This article is protected by copyright. All rights reserved.
This study aimed to assess the effect of roasting degree and brewing techniques on the sensory profile of Turkish coffee and espresso. Descriptive analysis of coffee samples was carried out for 20 flavor attributes by ten Turkish and ten Brazilian assessors. Light, medium, and dark roasted coffee beans were brewed with the decoction method and pressure method. Turkish coffee samples were prepared by automatic machine and cezve, which is the traditional method. The roasting degree and brewing method had a significant impact on the sensory profile of coffee samples. Turkish assessors perceived lightly roasted coffee beverages as sour (6.53 and 6.56 for Turkish coffee with machine and espresso) and pungent notes (7.46 for espresso), while Brazilian assessors perceived them as fruity (5.63 for espresso) and sweet attributes (5.76 and 5.90 for Turkish coffee with cezve and espresso). Roasted (7.83), burnt/acrid (7.96), and bitter (8.13) notes became dominant with the degree of roasting in espresso coffees in the Turkish panel. Brazilian assessors perceived Turkish coffee samples made with cezve and dark roasted beans as roasted (6.53), burnt/acrid (6.66), bitter (6.80), and ashy‐sooty (7.26) notes.
Bu araştırmada üçüncü nesil kahve demleme yöntemlerine yönelik tüketicilerin duyusal değerlendirmeleri incelenmektedir. Araştırma bağlamında altı farklı tekniklerle yapılan üçüncü nesil kahve demleme türü üzerinden araştırma gerçekleştirilmiştir. Araştırmada Chemex, Pour over, Syphon, Aeropress, Moka pot ve French press kahve demleme yöntemleri üzerinden değerlendirme gerçekleştirilmiştir. Duyusal değerlendirme sürecinde bağlılık etki puanı altında 0-1 arasında değerlendirme yapılmıştır. Araştırmada veri toplamak için her bir kahve demleme yöntemini daha önceden deneyimlemiş 15 katılımcıya kartopu örneklem yöntemi kullanılarak ulaşılmıştır. Araştırmanın veri analiz sürecinde katılımcıların her bir kahve demleme yöntemine vermiş olduğu puanların ortalamaları alınarak beş duyu organına yönelik değerlendirme gerçekleştirilmiştir. Ortalamalar grafik yardımıyla açıklanmıştır. Araştırma sonuçlarına göre tat alma duyusunda en yüksek puanı Chemex, koku duyusunda en yüksek puanı Pour over, görme ve duyma duyusunda en yüksek puanı Syphon ve dokunma duyusunda ise en yüksek puanı French press almıştır.
Although the roles of coffee origin, roasting degree, and consumption methods on the sensory properties of coffee have been actively discussed, the type of water used in brewing plays as important a role as coffee beans, roasting degree, and brewing skills in deciding coffee quality. As water is an essential ingredient in coffee brewing, we must consider its role in the process. This study analyzed the impact of three types of water (depending on total dissolved solids [TDS]) on consumer liking (appearance, flavor, taste, aftertaste, and overall) and coffee emotion lexicons at three roasting degrees (three water types × three roasting points). A total of 167 consumers evaluated their liking for nine coffee samples and conveyed their emotion lexicons utilizing the check-all-that-apply method. For coffee extraction, purified water, tap water, and bottled water from Australia were used for the evaluation and they had TDS content of approximately 0, 100, and 200 ppm, respectively. An analysis of variance demonstrated that all sensory attributes had significant differences, except for aftertaste. Consumer liking decreased in relation to increasing TDS at the medium and dark roasting points. Coffee brewed using purified water was preferred by coffee consumers at medium and dark roasting points. Additionally, when they had their highly preferred coffee samples, they experienced positive emotions, such as feeling energetic, nostalgic, independent, adventurous, and focused.
Brewing is the final and key step in the production of the coffee beverage. Extraction related metrics such as the total dissolved solids (TDS), percentage extraction yield (PE) of solutes, and brew temperature (BT) are widely believed to govern the flavor and corresponding consumer acceptance of the resulting brew, as summarized in the industry standard “Coffee Brewing Control Chart.” In this study, we investigated how the three factors of TDS, PE, and BT affected consumer acceptance of a medium roast, single‐origin coffee and whether consumer preference segmentation would be observed based on these variables. A cohort of 118 mostly college‐age, self‐reported consumers of black coffee tasted coffees that varied in BT, TDS, and PE. For each coffee, consumers rated overall acceptance on the 9‐point hedonic scale; the adequacy of serving temperature, flavor intensity, acidity, and mouthfeel using 5‐point just‐about‐right (JAR) scales; and described the flavor using a check‐all‐that‐apply list of 17 attributes. Cluster analysis revealed two consumer segments whose preferences varied most strongly with TDS. Response surface methodology relating liking to TDS and PE produced dome‐ and saddle‐shaped surfaces for the two segments, respectively. External preference mapping and penalty analysis indicated that overall flavor intensity as well as acidity heavily influenced the preferences of the two clusters. The Coffee Brewing Control Chart's “ideal” coffee should therefore be reconsidered to reflect consumer preference segmentation.
Practical Application
This research informs the way coffee brewers manipulate brew strength and extraction of drip brew coffee for optimal consumer acceptance; and justifies a reform of the standard “Coffee Brewing Control Chart” in its representation of an “ideal” coffee as we uncovered two consumer preference segments with different positive and negative sensory drivers of liking.
The sensory qualities of brewed coffee are strongly correlated with the total dissolved solids (TDS) and extraction yield ( E ) of the brew. Here, we derive a predictive model for the TDS and E of full immersion brewed coffee using a pseudo-equilibrium desorption approach. Assuming a single, species-averaged equilibrium constant K yields theoretical predictions indicating that the TDS is approximately inversely proportional to the water/coffee mass brew ratio, while E is independent of the brew ratio. Our experimental results strongly accord with both theoretical predictions, and indicate that E is approximately 21% over a wide range of brew ratios. An analysis of the standard oven-drying method for measuring E indicates that it yields significant underestimates of the true value at equilibrium, due to retained brew within the spent moist grounds. We further demonstrate that K is insensitive to grind size, roast level, and brew temperature over the range 80-99°C. Taken together, our results indicate that full immersion brewing offers precise control over the TDS at equilibrium but little control over E , and that practitioners should pay careful attention to their brew ratio as the most important parameter for full-immersion brewing.
Drip brewed coffee is traditionally quantified in terms of its strength, also known as total dissolved solids (TDS), and its brewing yield, also known as percent extraction (PE). Early work in the 1950s yielded classifications of certain regimes of TDS and PE as “underdeveloped,” “bitter,” or “ideal,” with the modifiers “weak” or “strong” simply correlated with TDS. Although this standard is still widely used today, it omits a rich variety of sensory attributes perceptible in coffee. In this work, we used response surface methodology to evaluate the influence of TDS and PE on the sensory profile of drip brewed coffee. A representative wet‐washed Arabica coffee was roasted to three different levels (light, medium, or dark), with each roast then brewed to nine target brews that varied systematically by TDS and PE. Descriptive analysis found that 21 of the 30 evaluated attributes differed significantly across the brews for one or more experimental factors, yielding linear or second‐order response surfaces versus TDS and PE. Seven attributes exhibited a significant response surface for all three roast levels tested: burnt wood/ash flavor , citrus flavor , sourness , bitterness , sweetness , thickness , and flavor persistence . An additional seven attributes also showed a significant response surface fit across some but not all roasts. Importantly, sweetness exhibited an inverse correlation with TDS irrespective of roast, while dark chocolate flavor and blueberry flavor decreased with TDS for medium roast. These results provide new insight on how to optimize brewing conditions to achieve desired sensory profiles in drip brewed coffee.
Practical Application
This research provides guidance on how best to achieve specific flavor profiles in drip brewed coffee.
Sensory analysis is a key method to assess flavor quality and to characterize consumer preference and acceptance, whereas instrumental analysis helps to identify flavor compounds. The combination of sensory analysis and instrumental analysis provides a platform for revealing key flavor compounds associated with consumer liking. This review discusses sensory evaluation, aroma analysis, and separation techniques using coffee as a central theme where possible to explore the aforementioned techniques. Emerging statistical methodologies are discussed along with their role in tying together discrete studies to reveal important flavor compounds that are either positively or negatively associated with consumer liking. Coffee is very widely studied, a fact that may be partially ascribed to its immense popularity in modern society. To this end, more than 100 sensory lexicons have been developed and implemented to describe specific coffee characteristics and around 1,000 volatile compounds have been identified in coffee. As a remarkably complex sample coffee has provided substantial impetus for adoption of new analytical approaches such as multidimensional separation technologies. This review describes common and emerging analytical techniques that have been employed for coffee analysis, with a particular emphasis placed on those associated with determination of volatile compounds. A comprehensive list of volatile compounds reported in coffee from 1959–2014 is included herein.
This study compared projective mapping (PM) with check‐all‐that apply (CATA) with 24 consumers to traditional preference mapping with 257 consumers for evaluation of drivers of liking for brewed black coffees. For the PM exercise, black coffee consumers (n = 24) evaluated 11 coffees and placed them on a two‐dimensional plane based on similarities and then selected attributes from a provided list (PMCATA) to describe each coffee. These consumers also scored liking of each coffee. PMCATA and liking evaluations were completed in duplicate. A trained descriptive analysis (DA) panel (n = 8) documented properties of the coffees in quadruplicate and black coffee consumers (n = 257) were recruited for traditional consumer acceptance testing. Landscape segmentation analysis (LSA) was applied to trained panel data and consumer acceptance scores. Data from the PMCATA exercise was analyzed using multiple factor analysis (MFA). Consumer groups from the PMCATA exercise were differentiated by preferences for light or dark roast attributes. Similarly, determination of ideal points by LSA revealed that consumer groups were defined primarily by differences in preference for different roast types and roast‐related attributes. Based on the similarities in regard to product characterization and consumer segmentation, these results demonstrate that PMCATA can be an effective preliminary alternative to traditional methods for profiling and consumer preferences of complex products like coffee.
Practical application
Descriptive analysis (DA) and consumer acceptance testing for preference mapping can be time and cost intensive. This study demonstrates that projective mapping, combined with check‐all‐that‐apply (PMCATA) profiling by consumers, can be used as a rapid method for understanding a product landscape and acceptability of products with particular attributes. It is unlikely that PMCATA will replace preference mapping practices; however, it might serve as an effective alternative for researchers and developers when time or budget is constrained, or as an initial screening step for understanding a product category.
Although from a food safety point, coffee is considered a shelf-stable product, changes in volatiles over time due to out-gassing and chemical reactions lead to perceivable differences in coffee aroma and “freshness”. Previous studies have looked at the impact of storage conditions on ground or brewed coffee. This study seeks to answer the question of how coffee consumers perceive the smell of coffee grounds of whole beans that have been stored under different conditions: freezer vs. room temperature for 9 weeks compared to a newly roasted control (stored for 1 day). Green beans from the same production lot were roasted to two different levels to also evaluate the impact of roast level on aroma changes. Using projective mapping (PM) followed by ultra-flash profiling (UFP), 48 coffee consumers evaluated, using only smell, 6 different freshly ground coffee samples presented in blind duplicates. In parallel, the profiles of 48 previously reported important coffee volatiles were measured by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) to relate chemical changes to perceivable sensory aroma changes. Overall, consumer product maps mimicked the instrumental measurements in that the lighter roast coffees showed smaller changes due to storage conditions compared to the dark roast samples. Consumers also perceived the frozen dark roast samples to be more similar to the newly roasted control than the samples stored at room temperature.
The extraction kinetics and equilibrium concentrations of caffeine and 3-chlorogenic acid (3-CGA) in cold brew coffee were investigated by brewing four coffee samples (dark roast/medium grind, dark roast/coarse grind, medium roast/medium grind, medium roast/coarse grind) using cold and hot methods. 3-CGA and caffeine were found at higher concentrations in cold brew coffee made with medium roast coffees, rather than dark roast. The grind size did not impact 3-CGA and caffeine concentrations of cold brew samples significantly, indicating that the rate determining step in extraction for these compounds did not depend on surface area. Caffeine concentrations in cold brew coarse grind samples were substantially higher than their hot brew counterparts. 3-CGA concentrations and pH were comparable between cold and hot brews. This work suggests that the difference in acidity of cold brew coffee is likely not due to 3-CGA or caffeine concentrations considering that most acids in coffee are highly soluble and extract quickly. It was determined that caffeine and 3-CGA concentrations reached equilibrium according to first order kinetics between 6 and 7 hours in all cold brew samples instead of 10 to 24 hours outlined in typical cold brew methods.
Coffee is one of the most common beverages in the world. However, a sensory lexicon for determining descriptive differences resulting from breeding, agronomic, processing, storage, and brewing modifications is needed. This study developed a sensory lexicon for brewed coffee. More than 100 different coffee samples from 14 countries around the world were used to create this lexicon in four Phases. A highly trained panel assessed all coffee samples using descriptive analysis. The sensory panel identified 110 attributes (many used both for aroma and flavor) and references. Principal component analysis was used to map the scores obtained during the validation phase. For this phase the coffee lexicon allowed the panelists to describe specific characteristics that were present in the coffee samples such as sweet, nutty and fruity notes, as well as the differentiation of notes such as burnt, smoky, astringent, acrid and bitter. The developed attributes and references were successfully used by the trained panel to describe a wide range of coffee samples. The lexicon is considered “living” because additional terms should be added as needed to expand the lexicon to include attributes that are not included here. The terminology developed during this study is clear, easy to reproduce in future research, and accompanied by reference standards that provide a guide for future studies. This lexicon will provide an important tool for the coffee industry to conduct sensory evaluation to improve the understanding of coffee quality. It is a “living” lexicon that can be added to when samples exhibit notes that were not present in the samples used for this lexicon development.
The original Coffee Taster's Flavor Wheel was developed by the Specialty Coffee Assn. of America over 20 y ago, and needed an innovative revision. This study used a novel application of traditional sensory and statistical methods in order to reorganize the new coffee Sensory Lexicon developed by World Coffee Research and Kansas State Univ. into scientifically valid clusters and levels to prepare a new, updated flavor wheel. Seventy-two experts participated in a modified online rapid free sorting activity (no tasting) to sort flavor attributes of the lexicon. The data from all participants were compiled and agglomeration hierarchical clustering was used to determine the clusters and levels of the flavor attributes, while multidimensional scaling was used to determine the positioning of the clusters around the Coffee Taster's Flavor Wheel. This resulted in a new flavor wheel for the coffee industry. The new SCAA and WCR Coffee Taster's Flavor Wheel can be used as an important tool for communication in the coffee industry, to standardize the description of coffee flavors in a replicable way throughout the coffee value chain, and to educate coffee consumers. It brings industry and science closer together, unifying communication and enabling problem solving of issues critical to the specialty coffee industry. Both the lexicon and flavor wheel are living documents, so there is flexibility and space for additional coffee flavor descriptors as trained panels gain more experience with these tools.
Coffee is prepared by the extraction of a complex array of organic molecules from the roasted bean, which has been ground into fine particulates. The extraction depends on temperature, water chemistry and also the accessible surface area of the coffee. Here we investigate whether variations in the production processes of single origin coffee beans affects the particle size distribution upon grinding. We find that the particle size distribution is independent of the bean origin and processing method. Furthermore, we elucidate the influence of bean temperature on particle size distribution, concluding that grinding cold results in a narrower particle size distribution, and reduced mean particle size. We anticipate these results will influence the production of coffee industrially, as well as contribute to how we store and use coffee daily.
The preparation of a cup of coffee may vary between countries, cultures and individuals. Here, an analysis of nine different extraction methods is presented regarding analytical and sensory aspects for four espressi and five lunghi. This comprised espresso and lungo from a semi-automatic coffee machine, espresso and lungo from a fully automatic coffee machine, espresso from a single-serve capsule system, mocha made with a percolator, lungo prepared with French Press extraction, filter coffee and lungo extracted with a Bayreuth coffee machine. Analytical measurements included headspace analysis with HS SPME GC/MS, acidity (pH), titratable acidity, content of fatty acids, total solids, refractive indices (expressed in °Brix), caffeine and chlorogenic acids content with HPLC. Sensory analysis included visual, aroma, flavor and textural attributes as well as aftersensation. The technical differences in the extraction methods led to a higher concentration of the respective quantities in the espressi than in the lunghi. Regarding the contents per cup of coffee, the lunghi generally had a higher content than the espressi. The extraction efficiency of the respective compounds was mainly driven by their solubility in water. A higher amount of water, as in the extraction of a lungo, generally led to higher extraction efficiency. Comparing analytical data with sensory profiles, the following positive correlations were found total solids - texture/body, headspace intensity - aroma intensity, concentrations of caffeine/chlorogenic acids - bitterness and astringency.
Check-all-that-apply (CATA) questionnaires have seen a widespread use recently. In this paper, we briefly review some of the existing approaches to analyze data obtained from such a study. Proposed extensions to these methods include a generalization of Cochran's Q to test for product differences across all attributes, and a more informative penalty analysis. Multidimensional alignment (MDA) is suggested as a useful tool to investigate the association between products and the attributes. Comparisons of real products with an ideal are useful in identifying specific improvements for individual products. Penalty and penalty-lift analyses are used to identify (positive and negative) drivers of liking. The methods are illustrated by means of CATA study on whole grain breads.
There is growing interest of international markets in differentiated agricultural products from the tropics. Coffee is a tropical crop of relatively high quality, whose value is increasing as consumer demand in developed countries for specialty coffee. Smallholders in emerging markets can benefit by capitalizing on the natural resource variability in their production system and from the knowledge that they have about this variability. The objective of this paper is to illustrate the benefits of systematically targeting management practices by coffee growers to improve attributes of their product. Data from case studies in Colombia and Mexico show statistically significant differences in beverage quality of coffees grown under different production conditions such as slope aspect, varieties, times of harvest, and shade levels. Possible intervention options can be selected by growers in terms of their ease of implementation, the likely improvement of quality that they achieve and the resource intensiveness they require. The conclusion is that optimum management is site specific so that it is not possible to make any blanket recommendations. Using continuous management cycles of implementation, observation, interpretation and evaluation the site specificity provides growers an opportunity to improve management over time to produce a higher quality product.
Roasted coffee samples of the two major trade species (Coffea arabica and C. canephora) were studied to identify sensory descriptors that might be used to determine blends production and evaluation, following the expectations of consumers. Coffee beans were roasted at 220 + 10 °C, for 7, 9, and 11 min, and the sensory profiles of the beverages were assessed. From descriptive analysis the eigenvalues allowed the identification of two principal components (PCs), being the variance between samples 68.9% and 21.1%. In the first PC the characteristic odor, astringency, body, bitter flavor, burned aroma, and residual, typical, and burned tastes prevailed. The correlation coefficient between the second PC and citric acid flavor and aroma reached 0.96 and 0.78, respectively. It was concluded that in beverages of these species, the descriptors of both components can be separated according to bean roasting time. Considering roasting time, the overall quality was also rated.
Coffee quality, in the present context of overproduction worldwide, has to be considered as a main selection criterion for
coffee improvement. After a definition of quality, and an overview of the non genetic factors affecting its variation, this review
focuses on the genetic factors involved in the control of coffee quality variation. Regarding the complexity of this trait, the
different types of quality are first presented. Then, the great variation within and between coffee species is underlined, mainly
for biochemical compounds related to quality (caffeine, sugars, chlorogenic acids, lipids). The ways for breeding quality traits
for cultivated species, Coffea arabica and Coffea canephora are discussed, with specific challenges for each species. For C.
arabica, maintaining a good quality in F1 intraspecific hybrids, introgressed lines from Timor hybrid, and grafted varieties
are the main challenges. For C. canephora, the improvement is mainly based on intraspecific and interspecific hybrids, using
the whole genetic variability available within this species. An improvement is obtained for bean size, with significant genetic
gains in current breeding programmes. The content in biochemical compounds related to cup quality is another way to improve
Robusta quality. Finally, ongoing programmes towards the understanding of the molecular determinism of coffee quality,
particularly using coffee ESTs, are presented.
A robust and reproducible model was developed to predict the sensory profile of espresso coffee from instrumental headspace data. The model is derived from 11 different espresso coffees and validated using 8 additional espressos. The input of the model consists of (i) sensory profiles from a trained panel and (ii) on-line proton-transfer reaction mass spectrometry (PTR-MS) data. The experimental PTR-MS conditions were designed to simulate those for the sensory evaluation. Sixteen characteristic ion traces in the headspace were quantified by PTR-MS, requiring only 2 min of headspace measurement per espresso. The correlation is based on a knowledge-based standardization and normalization of both datasets that selectively extracts differences in the quality of samples, while reducing the impact of variations on the overall intensity of coffees. This work represents a significant progress in terms of correlation of sensory with instrumental results exemplified on coffee.
Sensory analysis is one of the most important techniques to assess coffee quality. This study aimed to evaluate the sensory effect of inoculating two varieties of coffee (Ouro Amarelo and Mundo Novo) processed by a semi-dry method, with three yeast strains (Saccharomyces cerevisiae CCMA 0200 and CCMA 0543 and Torulaspora delbrueckii CCMA 0684, respectively) obtained from the Culture Collection of Agriculture Microbiology (CCMA). Two sensory analysis techniques were used (cup taste and temporal dominance of sensations analysis). Pulped coffee beans were inoculated with the respective yeast strains and compared to a non-inoculated (control) sample. Ouro Amarelo showed the highest scores for the attributes evaluated compared to variety Mundo Novo. The use of strains CCMA 0543 and CCMA 0684 improved the beverage sensations of both coffee varieties. Variety Ouro Amarelo inoculated with CCMA 0543, highlighted acidity and nuts sensations and Mundo Novo inoculated with CCMA 0543 and CCMA 0684 treatments, respectively, reduced the astringency sensation. The addition of CCMA 0543 starter culture highlighted the acidity of the coffee, improving the sensory results among the yeast strains, for both coffee varieties. The use of two sensory analysis techniques provided better descriptive and comparative analysis of the sensory characteristics of the treatments.
To obtain a cup of coffee with a balanced aroma, every step in the coffee production chain is crucial, including the final brew preparation, in order to achieve the optimal result in-cup. In this study, the role of the physico-chemical properties (volatility and polarity) of coffee odorants during extraction was investigated. The extraction kinetics of 20 key coffee odorants from a coffee bed were measured using quantitative in-cup aroma analysis. The kinetics differed depending on the coffee odorants properties. The extraction speed could be correlated with the odorants’ polarity. Higher polar components, such as 2,3-butanedione, were released much faster from the coffee bed as compared to lower polar ones such as β–damascenone. In contrast, the odorants’ volatility did not seem to play a major role. Due to the different kinetics of extraction of the coffee odorants, the in-cup aroma balance changed continuously as more water passed through the coffee bed.
The aim of this work was to study the extraction behavior of the main coffee antioxidants (caffeoylquinic acids, melanoidins and caffeine) and the antioxidant capacity, during brewing time in the most widely consumed coffee brew methods (filter and espresso) in coffee. Antioxidant capacity by colorimetric assays (Folin–Ciocalteau, ABTS and DPPH) and electron spin resonance spectroscopy techniques (Fremy's salt and TEMPO) were analyzed. In espresso coffee, more than 70% of the antioxidants (except dicaffeoylquinic acids, diCQA) of a coffee brew were extracted during the first 8 s. In filter coffee, a U-shape antioxidants extraction profile was observed, starting later (after 75 s) in Vietnam coffee than in Guatemala one, probably due to different wettability. Other technological parameters, such as turbulences and a longer contact time between water and ground coffee in filter coffeemaker, increased extraction efficiency, mainly in less polar antioxidant compounds as diCQA. In conclusion, these technological factors should be considered to optimize coffee antioxidants extraction that can be used as ingredients for functional foods.
Twenty-two microfragrance strips (18 food-related odours, three non-food odours and one blank) were evaluated for degree of liking in quadruplicate by 30 subjects in each of 16 countries. The structures generated by principal component and cluster analyses of the data were similar to the actual geographic distribution of these countries. It is concluded that degree of liking of food-related aromas varies across regions, probably due to differences in traditional food habits and availability of regional flavour sources.
In the hedonic scale method the stimuli (actual samples or food names) are presented singly and are rated on a scale where the 9 categories range from "dislike extremely" to "like extremely." History, methods of use in laboratory and field, analysis of the data, reliability, essential characteristics, applications, special effects requiring control, and interpretation of results are discussed and evidence is cited for the method's validity for predicting food behavior. Major advantages of the method are: Ss can respond meaningfully without prior experience, it is suitable for use with a wide range of populations, the data can be handled by the statistics of variables, and results are meaningful for indicating general levels of preference. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Variations in the composition of brewed coffee as a function of brewing time were monitored using gas chromatography-mass spectrometry. Batches of coffee were produced using flow rates of 50-500 mL/min, which resulted in brewtimes of 4.42-31.07 min. While most components increased in concentration with longer brewing times, several showed significant losses beyond 8 min, indicating an optimum brewtime of 7-9 min.
To investigate the influence of roasting time and temperature on the degradation of the bitter precursors 3-O-caffeoyl quinic acid (1), 5-O-caffeoyl quinic acid (2), and 4-O-caffeoyl quinic acid (3) as well as the formation of bitter tastants during coffee roasting, we prepared coffee brews from beans roasted either at 260 degrees C for 60-600 s or for 240 s at 190-280 degrees C. By means of HPLC-UV/vis and HPLC-MS/MS, bitter-tasting monocaffeoyl quinides (4-8), dicaffeoyl quinides (9-11), and 4-vinylcatechol oligomers (12-20) as well as the parent bitter precursors 1-3 were quantitatively analyzed in these brews. Quinides 4-11, exhibiting a coffee-typical bitter taste profile, were found to be preferentially formed under slight to medium roasting degrees and were observed to be degraded again to generate harsh bitter-tasting 4-vinylcatechol oligomers under more severe roasting conditions, thus matching the change in bitter taste quality observed by means of sensory studies. In addition, quantitative studies of the release profile of bitter compounds from ground coffee upon water percolation revealed that compounds 1-8 were rapidly extracted, dicaffeoyl quinides 9-11 were released rather slowly, and, in particular, compounds 12-17 were found to show strong retention to the ground coffee material. These data imply that the knowledge-based control of the roasting and/or the extraction conditions might be helpful in tailoring the bitter taste signature of coffee beverages.
The formation of several key odorants, such as 2-furfurylthiol (FFT), alkylpyrazines, and diketones, was studied upon coffee roasting. The approach involved the incorporation of potential precursors in green coffee beans by means of biomimetic in-bean and spiking experiments. Both labeled and unlabeled precursor molecules were used, and the target analytes in the roasted coffee samples were characterized in terms of their isotope labeling pattern and abundance. The biomimetic in-bean experiments ruled out the 2-furaldehyde route to FFT as suggested by model studies. Furthermore, no evidence was found for the incorporation of the arabinose C5 skeleton into FFT. Pathways proposed for the formation of alkylpyrazines and diketones were confirmed, and a new mechanism is suggested for the formation of 2-ethenyl-3-ethyl-5-methylpyrazine. The role of amino acids, for example, alanine, and free sugars was substantiated. The results underscore the potential of this methodology to provide better understanding of the formation pathways occurring in complex food systems, which may be different from those obtained in model experiments.
Hot beverages such as tea, hot chocolate, and coffee are frequently served at temperatures between 160 degrees F (71.1 degrees C) and 185 degrees F (85 degrees C). Brief exposures to liquids in this temperature range can cause significant scald burns. However, hot beverages must be served at a temperature that is high enough to provide a satisfactory sensation to the consumer. This paper presents an analysis to quantify hot beverage temperatures that balance limiting the potential scald burn hazard and maintaining an acceptable perception of adequate product warmth. A figure of merit that can be optimized is defined that quantifies and combines both the above effects as a function of the beverage temperature. An established mathematical model for simulating burns as a function of applied surface temperature and time of exposure is used to quantify the extent of thermal injury. Recent data from the literature defines the consumer preferred drinking temperature of coffee. A metric accommodates the thermal effects of both scald hazard and product taste to identify an optimal recommended serving temperature. The burn model shows the standard exponential dependence of injury level on temperature. The preferred drinking temperature of coffee is specified in the literature as 140+/-15 degrees F (60+/-8.3 degrees C) for a population of 300 subjects. A linear (with respect to temperature) figure of merit merged the two effects to identify an optimal drinking temperature of approximately 136 degrees F (57.8 degrees C). The analysis points to a reduction in the presently recommended serving temperature of coffee to achieve the combined result of reducing the scald burn hazard and improving customer satisfaction.
The existing literature on socially responsible purchasing relies heavily on stated preference measures elicited through surveys that utilize hypothetical market choices. This paper explores consumers' revealed purchasing behavior with regard to fair trade coffee and is apparently the first to do so in an actual market setting. In a series of experiments, we investigated differences in consumer responsiveness to relative price changes in fair trade and non-fair trade brewed coffees. In order to minimize the hypothetical bias that may be present in some experimental settings, we conducted our experiments in cooperation with a vendor who allowed us to vary prices in an actual coffee shop. Using a choice model, we found that purchasers of fair trade coffee were much less price responsive than those of other coffee products. The demonstration of low sensitivity to price suggests that the market premiums identified by stated preference studies do indeed exist and are not merely artifacts of hypothetical settings.
US Patent No. 3 693 535. Washington DC: US Patent and Trademark Office
- E Abel
When machine tastes coffee: Instrumental approach to predict the sensory profile of espresso coffee
- C. Lindinger
- D. Labbe
- P. Pollien
- A. Rytz
- M. A. Juilleret
- C. Yeretzian
- I. Blank