Consumer preference data for black coffee
Cite this dataset
Ristenpart, William; Cotter, Andrew R.; Guinard, Jean-Xavier (2023). Consumer preference data for black coffee [Dataset]. Dryad. https://doi.org/10.25338/B8993H
The dataset provided here contains physical, chemical, and consumer preference data for 118 individual consumers who each tasted 27 distinct coffees prepared with precisely controlled brewing conditions, yielding a total of 3,186 individual tastings of black coffee. Physical measurements include the temperature, total dissolved solids, and percent extraction of the brewed coffee; chemical measurements include the pH and titratable acidity of the brewed coffee; and the consumer preference measurements include hedonic liking, just-about-right assessments of beverage temperature, flavor intensity, mouthfeel, and acidity, and purchase intent. A total of 48 variables are quantified in a spreadsheet with 3,168 rows representing each individual consumer's assessment of each coffee. The dataset is associated with two papers: (1) "Consumer Preferences for Black Coffee are Spread Over a Wide Range of Brew Strengths and Extraction yields," by Cotter, Ristenpart, & Guinard, Journal of Food Science, 2021, and (2) "Impact of Beverage Temperature on Consumer Preferences for Black Coffee" by Ristenpart, Cotter, & Guinard, Scientific Reports, 2022.
The data presented here are drawn from a large study that afforded an opportunity to assess consumer preferences for coffee-tasting temperature. Specifically, we used a 3x3x3 factorial design to determine how the brew strength, extraction yield, and brew temperature affected the sensory attributes and consumer preferences for drip-brewed black coffee. Three specific brew temperatures of 87, 90, and 93°C were tested, with great care taken to adjust the grind size and flow rate such that the final brew strength and extraction yield were held constant despite the different brew temperatures.
Full details regarding the type of coffee, water chemistry, and brewing protocols are available in Cotter et al., Journal of Food Science, 2021. In brief, a medium-roast washed coffee from Honduras was used for all trials, using water with mineral content and pH recommended by the Specialty Coffee Association. Coffees were brewed using Curtis ThermoPro Single 1 Gallon Coffee Brewers, using one of three different set points for brew temperature (87, 90, or 93°C), with the flow rate or grind size varied as necessary to achieve desired values for the TDS and extraction yield. The brewed coffee was immediately transferred into 1.0-L stainless steel insulated carafes for service to the consumers.
All tasting sessions were conducted in the Silverado Vineyards Sensory Theater at UC Davis, a room designed for food and beverage sensory testing. Dividers placed between consumers help maintain the independence of evaluations. The number of consumers served in each session ranged from 12 to 26. Once a panelist was ready for their first/next sample, approximately 30 mL of coffee was poured from the appropriate carafe into a 120 mL paper hot cup (Solo Cup Co., Highland Park, IL, USA). To allow the coffee to cool, as well as to minimize tasting temperature differences resulting from differences in brew temperature, consumers were instructed, via a timer programmed into the survey, to wait 90 seconds after receiving the sample before taking their first sip and starting the evaluation. Consumers were provided with water and crackers to cleanse their palates between samples, and a cup to expectorate if they wished to do so. Each consumer was served single-blind and in random order; they were provided no information about the temperature or any other aspect of the coffee.
For every tasting session, a research assistant sat in the Sensory Theater and was served coffees in exactly the same manner as the actual participants, but instead of tasting the coffees, the research assistant measured the post-pour temperature and 90 seconds later measured the tasting temperature. In this fashion representative temperature data was obtained for all coffees as actually served.
A total of 118 consumers each tasted 27 coffees, yielding a total of 3,186 individual tastings. The tastings were split over 18 separate sessions, meaning a total of 162 separate brews were prepared. The tasting temperatures had an overall mean of 64°C, but with a wide range of 56 to 71°C.
The tasting study was approved by the UC Davis Institutional Review Board (IRB# 1082568), and all research was performed in accordance with relevant guidelines and regulations. Participants gave informed consent, had the freedom to withdraw at any time, and were compensated with a $25 gift card. We used RedJade (RedJade Sensory Software Solutions, Redwood City, CA, USA) to design and administer the questionnaire presented to the consumers. Each consumer filled out the questionnaire using their personal electronic device such as a smartphone, tablet, or laptop.
For each coffee sample, consumers first rated the adequacy of tasting temperature using a 5-point just-about-right (JAR) scale. They then evaluated overall liking using the 9-point hedonic scale. From there, they evaluated the adequacy of flavor intensity, acidity, and mouthfeel using JAR scales. Then, they described the coffees by checking applicable descriptors from a check-all-that-apply (CATA) list. Finally, consumers indicated purchase intent ($3 for a 12 oz cup) using a 5-point bipolar scale.
The dataset consists of one large excel spreadsheet, which may be opened with Microsoft Excel or Google Sheets. Each row represents the data collected for one individual tasting by a panelist; all personal identifiers have been removed. The first row contains the 48 variable names. The variables are defined as follows:
- Judge: numerical identifier of an individual person. Ranges from 1 to 118.
- Cluster: numerical identifier for which consumer preference segmentation cluster the individual judge was identified as belonging to. Either 1 or 2. (See Cotter et al. 2021).
- Week: identifies which week the tasting of that coffee occurred. Either 1, 2, or 3 for first, second, or third weeks respectively.
- Session Number: identifies which of the 18 unique tasting sessions this tasting occurred at. Ranges from 1 to 18 (with six tastings per week over three weeks).
- Position: identifies the order in which this specific coffee was sampled within a session. Range from 1 to 10 (for first to last coffees sampled).
- Brew: denotes the target brew conditions. The first number identifies the target brew temperature, the second number identified the target total dissolved solids (TDS), and the third number identifies the target percent extraction (PE). For example, 87-1.0-16 denotes 87 degrees Celsius, 1% TDS, and 16% PE.
- Temp.x: identifies whether the target brew temperature was “low”, “medium”, or “high,” referring to 87, 90, or 93 degrees Celsius, respectively.
- TDS.x: identifies whether the target total dissolved solids was “low”, “medium”, or “high,” referring to 1%, 1.25%, or 1.5%, respectively.
- PE.x: identifies whether the target percent extraction was “low”, “medium”, or “high,” referring to 16%, 20%, or 24%, respectively.
- Dose: the mass, in grams, of coffee grounds added to the brewer.
- Setting: the equipment-specific programming code used to brew the coffee in the Curtis brewer.
- Grind: the equipment-specific setting used to grind the coffee in the Mahlkönig grinder.
- Empty Carafe: the mass, in grams, of the empty carafe.
- Full Carafe: the mass, in grams, of the full carafe after brewing.
- Brew Mass: the mass, in grams, of the brewed coffee.
- TDS_1: the total dissolved solids, expressed as a percentage, of the brewed coffee as measured with a digital refractometer.
- Percent Extraction: the percent extraction from the coffee grounds, expressed as a percentage, as calculated using the TDS and the brew mass (cf. Cotter et al. 2021).
- pH: the pH of the brewed coffee.
- Initial NaOH: the volume, in milliliters, of 0.1 molar NaOH prior to adding to 50 mL of brewed coffee to determine the titratable acidity.
- Final NaOH: the volume, in milliliters, of 0.1 molar NaOH after adding to 50 mL of brewed coffee to determine the titratable acidity. The difference between initial and final represents that volume added.
- Titration pH: the final pH of the solution after adding the NaOH.
- Volume: the actual volume, in milliliters, of 0.1 molar NaOH added to titrate 50 mL of brewed coffee to a target pH of 8.2.
- Brew Temperature: the temperature, in degrees Celsius, of the brew in the carafe after completion of the brewing cycle.
- Pour Temperature: the temperature, in degrees Celsius, of the brew in the paper cup immediately after pouring.
- 90Sec Temperature: the temperature, in degrees Celsius, of the brew in the paper cup after a 90-second wait to allow cooling.
- Liking: the consumer assessment of hedonic liking, on the classic 9-point scale with values ranging from 1 to 9.
- Temp: the consumer assessment of the adequacy of the beverage temperature, using the just-about-right (JAR) scale, where 1 denotes “much too cold”, 2 denotes “somewhat too cold”, 3 denotes “just-about-right”, 4 denotes “somewhat too hot”, and 5 denotes “much too hot.”
- Flavor Intensity: the consumer assessment of the adequacy of the overall flavor intensity, using the just-about-right (JAR) scale, where 1 denotes “too little”, 2 denotes “somewhat too little”, 3 denotes “just-about-right”, 4 denotes “somewhat too much”, and 5 denotes “too much.”
- Acidity: the consumer assessment of the adequacy of the overall acidity, using the just-about-right (JAR) scale, where 1 denotes “too little”, 2 denotes “somewhat too little”, 3 denotes “just-about-right”, 4 denotes “somewhat too much”, and 5 denotes “too much.”
- Mouthfeel: the consumer assessment of the adequacy of the overall mouthfeel, using the just-about-right (JAR) scale, where 1 denotes “much too thin”, 2 denotes “somewhat too thin”, 3 denotes “just-about-right”, 4 denotes “somewhat too thick”, and 5 denotes “much too thick.”
- Tea.floral, Fruit, Citrus, Green.veg, Paper.wood, Burnt, Cereal, Nutty, Dark.chocolate, Caramel, Bitter, Astringent, Roasted, Sour, Thick.viscous, Sweet, & Rubber: binary values indicating whether or not the consumer detected the respective sensory attribute in the coffee, where 0 denotes “not detected” and 1 denotes “detected.”
- Purchase.intent: the consumer assessment of whether they would purchase this coffee at a $3 price point, using a 5-point bipolar scale where 1 is very unlikely and 5 is very likely.
Coffee Science Foundation