DOI: 10.25338/b8993h
title: Consumer preference data for black coffee

description: 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. 
description: 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.
description: 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.