Effect of Basket Geometry on the Sensory Quality and Consumer Acceptance of Drip Brewed Coffee

Sensory analysis of the flavor profile of full immersion hot, room temperature, and cold brewed coffee over time

With the growing popularity of cold brewed coffee comes a need for brewing efficiency while preserving the desirable flavor profile. Despite the wide use of full immersion brewing techniques, the effect of brew time on the dynamic sensory profiles of full immersion brewed coffee remains underexplored. Here, we investigated the relationship between coffee sensory quality and extraction dynamics, measured as Total Dissolved Solids (TDS) and Extraction (E) of full immersion brewed coffee at various roast levels, and brewing temperatures (4 °C, 22 °C and 92 °C), over brew time using a generic descriptive analysis method. Specifically, different brew time points were selected for different temperatures based on five targeted coffee extraction stages. Furthermore, the unique experimental design also explored a sensory-driven engineering research process. Roast level had the greatest impact on the sensory profile of the coffees, followed by brewing temperature, but brew time, especially the longer brew times as TDS plateaued, had subtler impacts than expected. Twenty-five of 28 sensory attributes were significantly different among the 30 coffee samples, indicating a single source green coffee blend can produce a wide range of complex sensory profiles using different combinations of roast level, temperature, and brew time. Specifically, the intensity of sweetness was negatively correlated with TDS, and 19 other attribute intensities were positively correlated with TDS. Interestingly, we found that certain long time cold brews had similar sensory profiles to those of some short time hot brews, suggesting the sensory profiles of certain hot brews and cold brews could possibly be matched through controlled preparation. Overall, our study demonstrated an approach of integrating food engineering and sensory analysis for product development, and our findings provide valuable insights into the extraction dynamics and sensory quality of full immersion brewed coffee and opens new brewing avenues for the coffee industry.

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

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 min. We used trained sensory panels to evaluate the flavor profiles of light, medium, and dark roast coffees held in three different carafe types (glass on hot plate, thermal jacket, and vacuum insulated) for times ranging from 15 min to 3 h. 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 increasing over time (i.e., higher titratable acidity, lower pH), but only for the light and medium roasts. Dark roasted coffee became significantly more acidic over 3 h post-brew but was not perceived as more sour over time by the sensory panel. Variations were observed between the thermal jacket and vacuum carafes for the light and dark roast, but few differences were observed with storage type in the medium roast. Surprisingly, the panel of coffee industry professionals showed no preference for fresh over held.

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. © 2022 Society of Chemical Industry.

Sensory Analysis of Full Immersion Coffee: Cold Brew Is More Floral, and Less Bitter, Sour, and Rubbery Than Hot Brew

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.

Effects of Total Dissolved Solids, Extraction Yield, Grinding, and Method of Preparation on Antioxidant Activity in Fermented Specialty Coffee

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.

Does Coffee Have Terroir and How Should It Be Assessed?

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.

Consumer Perception of Milk and Plant-Based Alternatives Added to 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.

From Plantation to Cup: Changes in Bioactive Compounds during Coffee Processing

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.

Effect of three post-harvest methods and roasting degree on sensory profile of Turkish coffee assessed by Turkish and Brazilian panelists

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.

Acids in coffee: A review of sensory measurements and meta-analysis of chemical composition

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.

Chemical and sensory evaluation of cold brew coffees using different roasting profiles and brewing methods

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.

Consumer preferences for black coffee are spread over a wide range of brew strengths and extraction yields

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.

Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee

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.

Effects of brew strength, brew yield, and roast on the sensory quality of drip brewed coffee

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.

Coffee Flavor: A Review

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.

Dulce de leche submitted to ohmic heating treatment: Consumer sensory profile using preferred attribute elicitation (PAE) and temporal check-all-that-apply (TCATA)

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.

Sensory and monosaccharide analysis of drip brew coffee fractions versus brewing time

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 s during the brew. Using a trained sensory descriptive panel, we found that most taste and flavor attributes decreased with brew time; for example, the earlier fractions were systematically more bitter and more sour than later fractions. Surprisingly, however, several flavor and taste attributes increased in time; for example, later fractions were systematically sweeter and more floral than earlier fractions. Since later fractions had lower 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. © 2020 Society of Chemical Industry.