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 ApplicationThis 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.
Acidity is a highly prized attribute in coffee, but there is little understanding of the brewing conditions under which acidity contributes favorable sensory attributes versus unfavorable sourness. Here, we examine the effect of titratable acidity and pH on the perception of sourness and consumer acceptance in drip brew coffee. Sour perception and acidity liking were assessed over a wide range of brew strengths and extraction yields at three different roast levels (light, medium, dark) and three different brewing temperatures (87 °C, 90 °C, and 93 °C). We find that perceived sour intensity correlates weakly with pH, but strongly with titratable acidity. Increases in titratable acidity also yielded increases in consumer perception of "too much acidity" and also impacted consumer liking and consumer preference segmentation with one cluster of consumers preferring more acidic coffee. Importantly, our data show that titratable acidity is linearly correlated with total dissolved solids (TDS) under all conditions studied, indicating that TDS is a good proxy for titratable acidity. The results presented here will provide the coffee industry with insight toward controlling perceived acidity or sourness, a key sensory attribute that substantially impacts consumer acceptance.
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.
We recently performed a systematic investigation of consumer preferences for black coffee versus key brewing parameters, including total dissolved solids, extraction yield, and brewing temperature (Cotter et al., Journal of Food Science, 2021). An experimental goal in that work was for participants to taste the coffee at a beverage temperature of 65°C, but the large sample size of more than 3,000 individual tastings, combined with natural variations in the brewing and cooling processes, meant that coffees were assessed over a normally distributed range of temperatures between 56 and 71°C. Here we use those data to provide a more detailed analysis of the impact of beverage temperature on consumer acceptance of the coffee. Using a 5-point just-about-right (JAR) scale, we find that a majority of consumers (>50%) assessed the temperature as JAR at all temperatures tested up to 70°C. A substantial fraction of consumers, approximately 6 to 12%, assessed the coffee as too cold over the range 56 to 68°C. Only above 70°C did a majority of consumers assess the coffee as too hot and none assessed it as too cold, albeit with 40% still assessing it as JAR. Complementary analyses indicate that beverage temperature over this range had little impact on assessments of the adequacy of flavor intensity, acidity, and mouthfeel, but did correlate slightly with overall liking and purchase intent. Overall, the results suggest that temperatures over the range of 58 to 66°C maximize consumer acceptance, and that 68 to 70°C is the minimum temperature range at which no consumers will assess black coffee as too cold.
We recently performed a systematic investigation of consumer preferences for black coffee versus key brewing parameters, including total dissolved solids, extraction yield, and brewing temperature (Cotter et al. in J Food Sci 86(1):194–205, 2021. https://doi.org/10.1111/1750-3841.15561). An experimental goal in that work was for participants to taste the coffee at a beverage temperature of 65 °C, but the large sample size of more than 3000 individual tastings, combined with natural variations in the brewing and cooling processes, meant that coffees were assessed over a normally distributed range of temperatures between 56 and 71 °C. Here we use those data to provide a more detailed analysis of the impact of beverage temperature on consumer acceptance of the coffee, with a key objective of identifying beverage temperatures at which no consumers assess the coffee either as too hot or too cold. Using a 5-point just-about-right (JAR) scale, we find that a majority of consumers (> 50%) assessed the temperature as JAR at all temperatures tested up to 70 °C. A substantial fraction of consumers, approximately 6–12%, assessed the coffee as too cold over the range 56–68 °C. Only above 70 °C did a majority of consumers assess the coffee as too hot and none assessed it as too cold, albeit with 40% still assessing it as JAR. Complementary analyses indicate that beverage temperature over this range had little impact on assessments of the adequacy of flavor intensity, acidity, and mouthfeel, but did correlate slightly with overall liking and purchase intent. Overall, the results suggest that temperatures over the range of 58–66 °C maximize consumer acceptance, and that 68–70 °C is the minimum temperature range at which no consumers will assess black coffee as too cold.
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