The TS-5000Z
(Insent Inc., Atsugi-shi, Japan) was equipped with four lipid membrane
sensors and two corresponding reference electrodes (New Food Innovation
Ltd., UK). Positively charged membrane sensors included C00, responding
to acidic bitterness, and AE1, responding to astringency. Negatively
charged membrane sensors included AC0 and AN0, both responding to
basic bitterness at different sensitivity and selectivity levels.
The reference solution was prepared by dissolving 30 mmol/L potassium
chloride and 0.3 mmol/L tartaric acid in distilled water. The negatively
charged membrane washing solution was prepared by diluting absolute
ethanol to 30% v/v with distilled water, followed by the addition
of 100 mmol/L hydrochloric acid. The positively charged membrane washing
solution was prepared by diluting absolute ethanol to 30% v/v and
adding 100 mmol/L potassium chloride and 10 mmol/L potassium hydroxide
to the mixture. Tartaric acid, potassium chloride, and potassium hydroxide
were obtained from Sigma-Aldrich (UK). Iso-alpha acid was obtained
from Insent (Atsugi-shi, Japan). Hydrochloric acid was obtained from
Fisher Chemicals (Loughborough, UK). All substances were used as received.
A sensor check was conducted routinely before each measurement to
ensure that the sensors were working within the correct millivolt
range.
Each measurement cycle consisted of measuring reference
potential
(Vr) in reference solution, followed by
the measurement of electric potential (Vs) of the sample solution; Vs – Vr represented the initial taste.28 (link)The sensors were finally refreshed in
alcohol solutions before
measurement of the next sample.
(Insent Inc., Atsugi-shi, Japan) was equipped with four lipid membrane
sensors and two corresponding reference electrodes (New Food Innovation
Ltd., UK). Positively charged membrane sensors included C00, responding
to acidic bitterness, and AE1, responding to astringency. Negatively
charged membrane sensors included AC0 and AN0, both responding to
basic bitterness at different sensitivity and selectivity levels.
The reference solution was prepared by dissolving 30 mmol/L potassium
chloride and 0.3 mmol/L tartaric acid in distilled water. The negatively
charged membrane washing solution was prepared by diluting absolute
ethanol to 30% v/v with distilled water, followed by the addition
of 100 mmol/L hydrochloric acid. The positively charged membrane washing
solution was prepared by diluting absolute ethanol to 30% v/v and
adding 100 mmol/L potassium chloride and 10 mmol/L potassium hydroxide
to the mixture. Tartaric acid, potassium chloride, and potassium hydroxide
were obtained from Sigma-Aldrich (UK). Iso-alpha acid was obtained
from Insent (Atsugi-shi, Japan). Hydrochloric acid was obtained from
Fisher Chemicals (Loughborough, UK). All substances were used as received.
A sensor check was conducted routinely before each measurement to
ensure that the sensors were working within the correct millivolt
range.
Each measurement cycle consisted of measuring reference
potential
(Vr) in reference solution, followed by
the measurement of electric potential (Vs) of the sample solution; Vs – Vr represented the initial taste.28 (link)The sensors were finally refreshed in
alcohol solutions before
measurement of the next sample.
