The physical 'functional' properties typically are derived from the chemical structure and interactions of the constituents. Instrumental measurements may or may not relate well to human perceptions due to the generally poorer reproducibility of sensory assessments and to differences between the perceptions of people and instruments.
Humans are often more sensitive for olfaction and less sensitive for appearance factors.
They can also discern relationships between instrumental and sensory measurements. S.A. Ramus, C.A. Witt, and K.J. Siebert. 1989. Correlation of sensory and instrumental data in elucidating the effect of varietal differences on hop flavor in beer. The sensory and chemical basis of beer flavor. In Monograph XXII E.B.C. Symposium on Hops, European Brewery Convention, Zoeterwoude, The Netherlands.