Consumer preference data for black coffee

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.