Abstract |
- Acids contribute important flavor characteristics to
many foods and beverages. They occur naturally in these
products, arise from fermentation processes, or can be
added. Most acids taste sour. However, little is known
about their time-intensity characteristics of sourness.
This project was set forth to see if selected acids could be
characterized, then differentiated according to their time-intensity
parameters of sourness. Astringency was also
evaluated since it seemed to be another common
characteristic of the acids. Power functions were
determined for the sourness to investigate the slopes of the
individual acids and also to calculate equi-sour
concentrations for the time-intensity study. It was found
that the slopes of the acids: acetic, lactic, fumaric,
fumaric-QD, citric, tartaric, and malic were not
significantly different. However, hydrochloric acid with a
slope value of 2.02 was significantly different than all of
the other acids that had slope values of about 1.25. This
study also showed that some panelists consistently responded
differently to the sourness of the acids. The time-intensity
studies showed that fumaric-QD and lactic acid
differed from each other in maximum intensity, area under
the curve, perimeter, and duration. Although hydrochloric
acid was strong in its overall impact parameters, it
elicited a short duration of sourness. The fruit acids -
tartaric, malic, and citric - were not very different from
one another in their sourness characteristics. For
astringency, hydrochloric acid was the most different from
all of the other acids mostly in the overall impact
parameters. For the time-intensity studies, the acids were
never significantly different in time to initial response
and time to maximum intensity. However, these two
parameters tended to be longer for the astringency response
as compared to the sourness response which suggests that
astringency occurs after sourness in the taste of acids.
Astringency/sourness ratios were calculated based on area
under the curve measurements and showed that hydrochloric
and lactic acid has significantly higher ratios than all of
the other acids indicating that lactic acid may also be an
astringent acid. Correlation among the time-intensity
parameters showed that the overall impact parameters correlated frequently with one another and occasionally with
duration. Peak area and peak time also correlated often.
Correlation between the sensory responses and the chemical
indices showed that the maximum intensity, area under the
curve, and perimeter correlated well with normality and PK[subscript a]
for sourness. For astringency, high correlations were found
between maximum intensity, area under the curve, and
perimeter with pK[subscript a], number of carboxyl groups, and molarity.
At level two, a strong relationship between pH and all other
time-intensity parameters except time to maximum intensity
and peak time is apparent. The principal component analysis
for sourness showed significant separation of lactic and
fumaric-QD in principal component one, and for astringency,
hydrochloric acid was significantly separated from the other
acids. Principal components two and three were not able to
significantly differentiate the acids.
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