Hedonic scaling is a sensory method that asks participants to rate their level of liking for a product on a scale, usually ranging from dislike very much to like very much. When using this method to verify the effect of grind-size uniformity, it's important to distinguish clearly between what the method measures — liking — and what it doesn't measure — the actual physical uniformity of the ground beans themselves.

Hedonic scaling measures liking

The result of a hedonic-scaling test is a score reflecting the subjective impression of the person tasting the cup offered, under the conditions of that specific test. This score is influenced by personal taste, expectations set before tasting, and even factors unrelated to the grind itself, such as serving temperature or presentation.

Grind uniformity needs a physical measurement

To know whether a batch of ground coffee is uniform, you need a physical measurement method such as particle size distribution (PSD) analysis — it can't be inferred from a taster's liking score. Research on using ground-coffee particle size and distribution to model beverage properties shows these are two separate types of data that need to be measured with two different methods.

Separating PSD, extraction efficiency, and perception

A rigorous study design needs to measure three layers of data separately: particle size distribution using a physical measuring device, extraction efficiency using a chemical method or refractometer, and level of liking using hedonic scaling. Research by Smrke, Eiermann, and Yeretzian on the role of fine particles in espresso extraction dynamics is an example of separating physical and extraction data before relating them to perception.

Higher extraction doesn't mean more liked

A higher chemical extraction efficiency doesn't automatically lead to a higher hedonic score. People can prefer a moderate extraction level over a maximum one, depending on taste and beverage type. So you shouldn't use a liking score to infer a specific extraction efficiency, or vice versa.

Designing the sensory test

A reliable hedonic-scaling test needs to control serving temperature, sample presentation order, the number of samples each taster evaluates, and prevent tasters from knowing in advance which sample corresponds to which grind configuration. Without this control, results can be influenced by expectation rather than reflecting genuine perception.

Don't use liking score as a substitute for PSD

If the goal is controlling grinder quality or assessing grind uniformity, particle-size-distribution measurement remains the direct and necessary tool. Liking score should only be used as a supplementary layer of data to understand the effect of uniformity on the drinker's experience, not as a substitute for physical measurement.

When this research has value

Combining PSD, extraction efficiency, and hedonic scaling has value when the goal is understanding whether a change in grind-size uniformity creates a perceptible difference, which then informs how much investment in grinder control is justified. If all you need is physical uniformity, measuring PSD alone is enough without needing a sensory test.

Practical conclusion

Hedonic scaling is a tool for measuring liking, not a tool for measuring grind-size uniformity. To fully verify the relationship between grind uniformity, extraction efficiency, and drinker perception, all three layers of data need to be measured separately using methods appropriate to each, then cross-referenced against each other.

References

• Lim, J. (2011). Hedonic scaling: A review of methods and theory. Food Quality and Preference.
• Smrke, S., Eiermann, A. & Yeretzian, C. (2024). Scientific Reports, 14, 5612. DOI 10.1038/s41598-024-55831-x.
• Using ground coffee particle size and distribution to remodel beverage properties (2023). European Food Research and Technology. DOI 10.1007/s00217-023-04210-3.