3.5. Sensory evaluation
In order to combine the structural studies performed so far with
the sweet taste of our proteins we also performed a sensory characterisation.
The average differences from the reference for each
concentration at pH equal to 6.8, both for Y63R and MNEI, are illustrated
in Fig. 5A. Experimental data show that by increasing concentrations
of both proteins, the differences from the reference
increased too, Y65R being sweeter than MNEI in all the investigated
concentrations, with the exception of the highest one, where
no differences are found among sweetness intensities. The first
significantly (p < 0.05) different concentration of Y65R from the
reference was 0.84 mg/l, whereas the first such difference was
observed at a MNEI concentration of 1.86 mg/l (p < 0.05). Then,
the DT, i.e. the geometric mean between the highest undetected
and lowest detected concentration, were 0.665 mg/l for Y65R and
1.645 mg/l for MNEI. Furthermore, the recognition threshold (RT)
of Y65R was 1.43 mg/l, a concentration at which 62% of assessors
correctly recognised the sweet taste; whereas for MNEI the RT
was 1.86 mg/l, a concentration correctly recognised as sweet by
the 55% of assessors (Fig. 3S, panel A). In the Fig. 5B sensory data
acquired at the pH equal to 5.1 are shown. The average differences
from the reference for both proteins increased with increasing
concentrations, in this experimental condition as well. The first
significantly (p < 0.05) different concentration of Y65R from the
reference is 1.43 mg/l, whereas the first such difference is observed
for the concentration of MNEI equal to 1.86 mg/l (p < 0.05). Then, in
this pH conditions the DT of Y65R was 1.265 mg/l and that of MNEI
1.645 mg/l, whilst the RT of Y65R was 1.43 mg/l and RT of MNEI
was 1.86 mg/l, with the percentage of corrected responses of 70%
and 65%, respectively (Fig. 3S, panel B).