expectations and attitudes, selection process (preferences, habit), in-
dividual preparation (chewing, saliva), attention, perception (psycho-
physics), integration (peripheral, cognitive access), affective involve-
ment, recognition, verbalization, quantification.All of these steps have been discussed several places in detail (An-
dani and MacFie, 1999; Cardello and Sawyer, 1992; Brown et al., 1996;
McBride and Anderson, 1990; Kroeze, 1990; Pangborn, 1981; Schutz,
1993; Conner, 1994). There does not seem to exist a comprehensive
model integrating the theoretical background of the different disciplines
involved. Although some of the above aspects are covered elsewhere in
this book, I will describe some processes closely related to sensory con-
sumer acceptance testing.
THE PERCEPTION PROCESS
To lead to any human sensation a perception process of a physical or
chemical or combined stimulus must take place. To produce a sensation
the stimulus has to be present for a certain length of time and to be above
the absolute threshold. Identification of the specific stimulus usually re-
quires a further increase of the stimulus level to reach the recognition
threshold. Above the terminal threshold, no further increase in the in-
tensity of the stimulus is perceived. A stimulus intensity difference above
the difference threshold is necessary to produce a just noticeable differ-
ence (JND). This noticeable difference increases at higher stimulus
levels (Weber’s law), thus being usable as “natural” scaling units for
sensory intensity.
All of these threshold values are not constant, but vary considerably
from person to person and from time to time (Land, 1983; Meilgaard et
al., 1991). Therefore care must be taken when threshold values are used
to calculate flavor intensity. To use the absolute threshold as the yard-
stick of intensity is recommended only for 0.5–3-fold concentrations
(Meilgaard et al., 1991). For practical levels of stimuli, there seems to
exist no relation between threshold and suprathreshold sensitivity in the-
ory or observation (Booth, 1990).
The sensory perception of a single stimulus has been described by
psychophysical laws. The strength of a perceived sensation is calculated
as a function of the magnitude of the stimulus. Fechner’s law uses JNDs
in a logarithmic, Steven’s law uses a power form. The Beidler Model
shows a sigmoidal structure (Meilgaard et al., 1991). All of them can be