Journal of Sensory Studies - 2012 - Torre - Search and Validation of Acidity References in Sensory Evaluation of Pepper

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Journal of Sensory Studies ISSN 0887-8250
SEARCH AND VALIDATION OF ACIDITY REFERENCES IN
SENSORY EVALUATION OF PEPPER
PALOMA TORRE1, INÉS ARANA, MARÍA ORTIGOSA and FRANCISCO C. IBÁÑEZ
Department of Environmental Sciences, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Navarra, Spain
1
Corresponding author.
TEL.: 00-34-948169145;
FAX: 00-34-948168930;
EMAIL: paloma@unavarra.es
Accepted for Publication August 16, 2012
doi:10.1111/joss.12003
ABSTRACT
The accreditation of sensory methods for quality control of specific products
requires the fulfillment of interlaboratory tests. These tests are one of the requirements to guarantee the technical competence of the laboratories in an independent way. In order to compare the laboratory results, it is convenient to use
references in judge training. This investigation shows the efficiency of the references for evaluating the intensity of the acidity during sensory quality control of
peppers with protected designation of origin (PDO). Such references are prepared
from a vegetable food matrix. Three references have been obtained for the acidity
intensity and they have been tested with three sensory panels from different laboratories. The samples used belonged to a PDO. It also compared the use of two
response scales in a trained panel. The results show a high correlation between
both response scales and it can be considered as a preliminary study of the development of acidity references to be used for improvement of sensory quality
control procedures of some type of pepper.
PRACTICAL APPLICATIONS
This study provides the guidelines for development of acid references in a vegetable food. These references are relevant to minimize the variability in sensory
evaluation for quality control of protected designation of origin.
The use of a reference standard for intensity is helpful in intercomparison
testing studies.
INTRODUCTION
The Piquillo de Lodosa Pepper with protected designation
of origin (PDO) is a canned vegetable that is produced in
Navarra (Spain). They are distinguished from other processed peppers in that they are hand peeled without introducing them in water or chemical solutions. Before being
autoclaved, a pill that is composed of citric acid and salt is
added in order to prevent the development of Clostridium
botulinum. Its entire process, including cultivation, produce
reception, canning and final product certification, is controlled by the Regulatory Council, which has implemented
its own quality system in accordance with the ISO/IEC
Guide 65 (ISO 1996).
Sensory testing on the finished product is performed in
the Sensory Analysis Laboratory of the Universidad Pública
de Navarra, accredited by the Entidad Nacional de Acreditación (National Accreditation Entity) in compliance with
Standard ISO/IEC 17025 (ISO 2005a). This accreditation
384
requires, when possible, the fulfillment of intercomparison
testing with other laboratories. The members of the sensory
panel for Piquillo de Lodosa with PDO pepper receive
training before the official tasting (ISO 2008) in each campaign. This regulation recommends using references for
evaluating the intensity of the different parameters, such as
acid taste. A reference standard plays an important role in
developing appropriate terminology and establishing intensity ranges (Drobna et al. 2004).
The natural acidity of the pepper is due to the set of
organic acids, mainly citric acid and ascorbic acid (Serrano
et al. 2010). The references for the acid taste (ISO 1993) are
prepared using citric acid dissolved with water. These references are useful for the selection of new judges, but, in our
experience, they are not efficient for their training when
intensity scales are used.
Many papers have identified sourness as a key attribute of
flavor quality in several foodstuffs. Citric acid diluted in
water, but not a food matrix, was used as reference for sour
Journal of Sensory Studies 27 (2012) 384–391 © 2012 Wiley Periodicals, Inc.
P. TORRE ET AL.
taste. For example, in fresh and processed tomatoes
(Baldwin et al. 2008; Hongsoongnern and Chambers 2008),
pomegranate juice (Koppel and Chambers 2010), wholegrain rice (Bett-Garber et al. 2012), sweet potato cultivars
(Leksrisompong et al. 2012), strawberry jam (Koppel et al.
2011), and fresh leafy vegetables (Talavera-Bianchi et al.
2010). However, different emulsions were developed to
evaluate the near-threshold taste intensities of sourness.
These emulsions were formulated with different lipid
chemical compositions plus citric acid addition (Thurgood
and Martini 2010).
Our objective was to obtain the sensation desired in that
reference that is the closest possible to the perception of that
sensation in the food itself. Some references prepared on a
similar matrix to the food are being evaluated in other
studies. For instance, in order to evaluate the acidity in
cheese, a milk product made with yoghurt combined with
curd is used as reference (Pérez-Elortondo et al. 2007).
However, in the analysis of peppers there are no adequate
references for the training of judges or for performing
sensory analysis intercomparison tests between laboratories.
Contextual shifting in the use of rating scales is a potential problem for sensory evaluations. It is even more problematic when the data from different sessions are to be
compared (Diamond and Lawless 2001). For this reason, in
the present study, we have developed some acid references
on a matrix food similar to the pepper itself.
In preliminary tests, the intention was to prepare references with acidified peppers by keeping the samples several
hours in their own covering liquid enriched with citric acid,
but the acid intensity achieved in the pepper samples turned
out to be heterogeneous. So it was decided to prepare references with pepper purée and added citric acid for the
purpose of properly homogenizing the acidity.
In sensory analysis, the perception of a property, not the
property itself, is evaluated, and different types of measurement scales can be used (ordinal, interval, proportion) as
well as different models of response scales. The response
scale (i.e., numerical, verbal or graphic), is the tool the judge
uses to register the quantitative response. Thus, a scale of
continuous response (linear) gives the judges the opportunity to express minor differences in their judgments, but it
may result as harder to use than a numerical scale of categories (ISO 2003). On the other hand, it is hard to maintain
the equality of the intervals proposed in an interval scale
with numerical category response. The judges with low
training consider that a 9-point category scale is easier to
use than the continuous 15 cm scale (Lawless and Malone
1986), but the smaller the number of categories the higher
is the effect of the extremes, which lessens the discriminatory power of the scale (Park et al. 2004, 2007). For the
purpose of comparing the use of both types of response
scales in a trained panel, in this study the tasters have used a
Journal of Sensory Studies 27 (2012) 384–391 © 2012 Wiley Periodicals, Inc.
ACIDITY REFERENCES IN PEPPER
6-category numerical scale as well as a continuous 10 cm
scale simultaneously (ISO 2003). In both cases, point zero
(absence of acidity) was located at one end of the scale
(unipolar scale).
The main objective of this study has been to develop
some valid acidity references for the purpose of improving
the results of a sensory panel that has been trained in
sensory analysis of the acidity in Piquillo de Lodosa peppers
with PDO and to verify its usefulness in other less trained
panels. A secondary objective has been to compare the use
of two response scales in a trained panel.
MATERIAL AND METHODS
Three consecutive tests were conducted:
• Preliminary selection of references: Six tasting sessions
were held and in each session three acidity references with
different concentrations of citric acid were evaluated, in
order to associate them to the intensity scores of the sensory
scale. This test is also useful to measure the acidity intensity
of roasted natural PDO pepper and the acidity provided by
adding the pill in its processing.
• Final selection of references for the acidity intensity: Two
new acidity references associated to the high and midpoint
of the sensory scale were selected and the intensities
assigned were compared three times by means of a numerical scale of categories and a continuous scale (ISO 2003).
• Verification of the efficiency of the acidity references: An
intercomparative test was carried out so as to verify the efficiency of the above-mentioned references developed, using
three tasting panels from three different sensory analysis
laboratories (1, 2 and 3) with different degrees of training.
Initial Selection of References
Preparation of References. Pepper natural acidity,
expressed as citric acid, is approximately 0.33% (w/w)
(Serrano et al. 2010). But it may range between 0.19 and
0.61% (w/w) fresh weight depending on the different genotypes (Eggink et al. 2012). In this study, acidity was considered as a constant for all the samples, and for practical
purposes, it was established as 0.0% (w/w), namely without
acid citric added. This natural acidity of the peppers has not
been taken into account when calculating the final concentrations in the references. Most of the production of
Piquillo peppers is canned. During its processing, a pill of
Diapim containing 16% citric acid and 84% salt is added in
each can.
For an accurate sensory evaluation, it is necessary to find
a reference standard that is low in secondary tastes. An
expert judge with a qualification of over 10 years for the
sensory analysis of Piquillo de Lodosa PDO peppers always
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ACIDITY REFERENCES IN PEPPER
tasted the samples of PDO peppers and eliminated the ones
that had more acidity than normal, as well as those that
were hot/spicy, so as to eliminate possible interferences. Any
remaining seeds and burnt peel had been removed from the
peppers and then they were crushed.
Paste with 0.0% (w/w) Citric Acid. From the selected
samples, a homogeneous paste was made with Piquillo de
Lodosa PDO peppers that were roasted but not canned.
These peppers were purchased on the market at the
time when they are in season. The peppers were made
into a puree with a homogeneous texture using a
blender.
Paste with 0.12% (w/w) Citric Acid. Purée was made with
canned Piquillo de Lodosa PDO peppers.
Pastes between 0.17 and 0.23% (w/w) Citric Acid. They
were obtained by weighing 225 g of the canned pepper
paste above and adding the quantity of citric acid necessary to reach the corresponding final concentration. Citric
acid was previously solubilized in 45 mL of deionized
water.
Sensory Panel. The panel was composed of 14 expert
sensory assessors belonging to the sensory panel of
Piquillo de Lodosa PDO pepper. This panel was first
selected according to the guidelines of the standard (ISO
1993) and it has a periodic control and performance
evaluation in compliance with standard ISO 8586-2 (ISO
2008).
Procedure. The study was performed in tasting booths
with properly controlled environment conditions (ISO
2007). Six tasting sessions on different days were held in
which the references were presented to the tasters in plastic
cups labeled with a three-digit code in random order. They
were tasted at room temperature. Tasters were instructed to
take a comfortable amount of the sample into their mouth
and swish it around for approximately 5 s. The evaluation of
the acidity intensity of the pepper pastes was requested by
means of a 6-category numerical response scale (0: absence,
1: very weak, 2: weak, 3: medium, 4: intense and 5: very
intense) (ISO 2003). The tasters had available water and
unsalted breadsticks as palate cleansers between references.
The tasters were allowed to taste the references again and
review and change their scores, for it has been proven that
this reduces discriminative errors (Lee et al. 2001; Jeon et al.
2004).
Statistics. A model of one-way analysis of variance
(ANOVA) on the data of acidity concentration was performed. Afterwards, multiple post hoc comparisons were
done by means of the Bonferroni test. All of the analyses
were done with the help of the statistical package SPSS
v.18 (Windows version, SPSS, Inc., Chicago, IL).
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P. TORRE ET AL.
Final Selection of References
Preparation of References. New references were made
with a food matrix of pepper, using the same methodology
as in the section “Initial Selection of References.” In order to
achieve references with greater acidity intensities, pepper
pastes were prepared with Piquillo PDO peppers canned
with a concentration of 0.12, 0.5 and 1% citric acid, the
latter two adding the grams of citric acid necessary to reach
the corresponding concentration.
Sensory Panel. The panel was composed of the same 14
expert sensory assessors of the tasting panel of Piquillo de
Lodosa PDO peppers.
Procedure. Each assessor tasted the same three references
in three consecutive sessions. The sessions were conducted
in 1 day, with 10-min breaks between replicates to reduce
sensory fatigue. In each session, the three concentrations
(0.12, 0.5 and 1% [w/w] citric acid) were tasted in random
order in three-digit coded cups. The assessors were
instructed to wait for 1 min between samples. In each
session, the intensity of the acidity of the pepper pastes was
evaluated simultaneously through the use of two types of
response scales: the numerical scale of categories and a continuous 10 cm line unstructured scale (ISO 2003) with
anchors in the extremes: not acid and very acid. The position marked by the assessors on this scale was converted to a
number between 0 and 100.
Statistics. With the data of acidity concentration,
one-way ANOVA was used and afterwards multiple post
hoc comparisons were done by means of the Bonferroni test. A box plot was made as well. A regression analysis was performed on the acidity intensities obtained
through the two types of response scales used (numerical
of categories and continuous) in order to study the correlation between them. All of the analyses were done with
the statistical package SPSS v.18 (Windows version, SPSS,
Inc.).
Verification of the Utility of the References
Preparation of References. The three confirmed references from previous section for categories – 2: weak acidity,
3: medium acidity and 5: very intense acidity – were prepared in Laboratory 1 and were transported refrigerated to
Laboratories 2 and 3. A person from Laboratory 1 moved to
Laboratories 2 and 3 to do this test.
Samples. Three different samples from different peppers,
two samples Piquillo de Lodosa PDO peppers (coded as A
and C) and another sample of Piquillo peppers without
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P. TORRE ET AL.
ACIDITY REFERENCES IN PEPPER
PDO (coded as B), were used. For this purpose, three cans
of the same production batch for each sample were acquired
and distributed to the three laboratories.
Although the samples of each panel came from cans of
the same lot, certain variability between samples is
common. In order to reduce such variability, a pepper was
carefully cut in equal pieces for all the tasters of the same
panel, so that all the panelists tasted a portion of the same
pepper, with or without references.
Sensory Panel. Three laboratories with sensory panels
with different degrees of training took part in this study.
The first panel was from the Universidad Pública de
Navarra (Laboratory 1), with seven expert sensory assessors
of Piquillo de Lodosa PDO peppers. Laboratory 2, with
eight tasters, is in charge of quality control board of Roasted
IGP peppers from el Bierzo (León, Spain). Laboratory 3 was
composed of nine tasters trained in the laboratory of the
Instituto Tecnológico Agrario de Castilla y León (Valladolid,
Spain). Hereinafter, these panels will be referred to as 1, 2
and 3. Panel 1 is the most highly trained in the evaluation of
Piquillo de Lodosa PDO pepper. Panel 3 is very experienced
in the sensory analysis of a great variety of vegetable
samples, and Panel 2 is the one with the lowest degree of
training.
Procedure. The sessions were held in the tasting rooms of
each laboratory. In each laboratory, two sessions were held.
In the first session, each panelist was presented three portions in random order according to a random pattern of
distribution of the samples (ISO 2005b). The acidity was
evaluated by means of the 6-category numerical scale. The
tasters had to evaluate the acidity of the three pepper
samples without the help of references. Tasters chewed the
sample in order to evaluate its acid intensity. They waited
for 2 min before tasting each portion.
In the second session, after a 5-min break, they tasted the
weak, medium and very intense acid references. The references were distributed in small cups with a spoon. The cups
were coded with the numbers 2, 3 and 5 depending on the
acid intensity of the reference. Next, each taster was given,
in the same order as in the first presentation, portions of the
same peppers so that they could rate the acidity again. The
tasters were allowed to taste the references again.
Statistics. In addition to the descriptive statistics of the
data, box plots were done. For the inferential analysis, a
TABLE 1. AVERAGE VALUES AND STANDARD
DEVIATIONS IN THE INTENSITY OF THE ACID
TASTE IN THE PEPPER PASTE REFERENCES
PREPARED WITH NATURAL ROASTED PEPPER
(NP); ROASTED, CANNED PEPPER (CP) AND
CP PLUS CITRIC ACID (CPC). (N = 14 TASTERS)
three-factor ANOVA was used (panel, sample and references), including the interaction terms of three and two
factors. Likewise, the acidity intensities were compared in
accordance with whether or not references were used. The
differences between the intensities were analyzed by means
of a Student’s t-test for depending samples. The contrast in
the hypotheses in all of the tests was done through a bilateral test establishing the significance level at 5%.
All of the analyses were done with the help of the statistical package SPSS v.18 (Windows version, SPSS, Inc.).
RESULTS AND DISCUSSION
Initial Selection of References
The paste of the natural roasted, not canned pepper (NP),
was perceived by the tasters with a very weak acidity intensity, a 1 on the scale (Table 1). The tasters classified the paste
from canned PDO peppers (CPs) whose citric acid concentration was 0.12% (w/w) around the category of weak
acidity, a 2 on the scale. Initially, the hypothesis suggested
was that in doubling the initial concentration (0.23%
[w/w]), a reference around 5 (very intense) would be
achieved. For this reason, the references prepared had a
citric acid concentration of 0.17, 0.20 and 0.23% (w/w)
citric acid, in the attempt to achieve acidity intensities that
were medium, intense and very intense. However, the results
(Table 1) showed that although the average values are
slightly higher, there were no important differences in
acidity between the three concentrations tested and the
0.12% (w/w) citric acid concentration. It is important to
note that a reference standard establishes relative rather
than absolute intensity.
Final Selection of References
The result of the tests performed with citric acid concentrations of 0.12, 0.5 and 1% (w/w) citric acid is shown on
Table 2. The concentrations 0.5% (w/w) citric acid
(medium acidity) and 1% (w/w) citric acid (very intense
acidity) were used as references for the category numerical
and the continuous scales. It is confirmed that the CP paste
serves as reference for the category of weak intensity.
Figure 1 shows the box plots of the three sessions held.
There is lower variability in the results of the first session,
Sample
NP
CP
CPC-1
CPC-2
CPC-3
Citric acid %
Acidity intensity
0.00
0.9 ⫾ 1.0a
0.12
2.0 ⫾ 0.8b
0.17
2.2 ⫾ 1.0b
0.20
2.3 ⫾ 1.1b
0.23
2.4 ⫾ 1.1b
***
*** P < 0.001.
Different letters in the same row indicate significant differences between the average values.
Journal of Sensory Studies 27 (2012) 384–391 © 2012 Wiley Periodicals, Inc.
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ACIDITY REFERENCES IN PEPPER
P. TORRE ET AL.
Citric acid %
0.12
0.50
1.00
P
Acidity intensity (EE)
Acidity intensity (EC) (mm)
1.9 ⫾ 1.0a
29.6 ⫾ 19.6a
3.1 ⫾ 1.1b
56.3 ⫾ 25.5b
4.6 ⫾ 0.7c
88.4 ⫾ 15.3c
***
***
*** P < 0.001.
EE: 6-category numerical scale: 0: absence, 1: very weak, 2: weak, 3: medium, 4: intense and 5:
very intense.
EC: 100 mm continuous line unstructured scale (with anchors from not acid to very acid).
Different letters in the same row indicate significant differences between the average values.
which could indicate sensory fatigue of the tasters in the
next sessions: It is known that citric acid produces selfdesensitization caused by repeated stimulation (Dessirier
et al. 2000). Nevertheless, the same average values were
obtained in the three sessions, which confirms the consistency of data provided by the panel.
In the second test, a regression analysis of the acid intensities obtained by both types of scales, continuous and
numerical categories, was performed. The result (Fig. 2)
evidences that there is a high correlation (R2 = 0.922).
According to Stevens (1969), the relation between both
types of scales must be linear as occurs in this case. It must
be pointed out that some assessors assigned intensities 0,
with the numerical category scale evaluating samples with
0.12% citric acid in the second and third sessions. On
the other hand, the use of the continuous scale enabled
higher scores when estimating the intensity of the highest
concentration.
The linear relation between the citric acid concentration
and the estimation of the intensity is a little better with the
numerical category scale. Perhaps this could be attributed to
the fact that the tasters are more familiar with this scale.
This result indicates that the quality of the measurements
TABLE 2. AVERAGE VALUES AND STANDARD
DEVIATIONS OF THE SCORES GIVEN FOR THE
ACID INTENSITIES IN THE REFERENCES OF
PASTE OF CANNED PEPPER WITH ADDED
CITRIC ACID (N = 14 TASTERS AND THREE
REPEATED SAMPLES FOR EACH
CONCENTRATION)
depends on the manner in which they have been obtained,
for example on the level of training of the judges (ISO
2003). It is important to note that in order for the acidity
references to be as uniform as possible throughout the successive training campaigns, it is recommended to always use
peppers belonging to PDO and of the same brand as the
one used in this study.
Verification of the Usefulness of
the References
The results of the scores assigned to the three samples by
juries 1, 2 and 3 are summarized in Table 3. The interaction
term of the three factors in the ANOVA was not statistically
significant (P = 0.197). Therefore, there is no combined
effect of these factors. However, one interaction term of two
factors was statistically significant (P = 0.03), in particular
the combined effect “laboratory ¥ sample.” It can be
deduced that the evaluation of the acidity can be conditioned by a “psychological emotional” component in relation with the type of pepper each panelist is accustomed to
analyzing.
Session 1
Session 2
Session 3
Acidity intensity
5
4
3
2
1
Acidity intensity (continuous scale)
100
80
60
40
20
0
0.12
0.50
1.00
0.12 0.50 1.00
Citric acid (%)
0.12
0.50
1.00
0
0
1
2
3
4
5
Acidity intensity (structured scale)
FIG. 1. BOX PLOT OF THE ACIDITY INTENSITIES OBTAINED BY PANEL
1 WITH THE NUMERICAL SCALE OF CATEGORIES IN THREE SESSIONS
WITH THREE CITRIC ACID CONCENTRATIONS
Data are expressed as percentage of citric acid (n = 14 Tasters).
388
FIG. 2. CORRELATION OF THE ACID INTENSITIES OBTAINED BY
MEANS OF THE CONTINUOUS AND NUMERICAL CATEGORY SCALES
(N = 14)
Journal of Sensory Studies 27 (2012) 384–391 © 2012 Wiley Periodicals, Inc.
P. TORRE ET AL.
ACIDITY REFERENCES IN PEPPER
TABLE 3. AVERAGE VALUES OF THE ACIDITY SCORES AND THEIR
STANDARD DEVIATIONS FOR THE SAMPLES OF PEPPER A (PDO), B
(NOT PDO) AND C (PDO), EVALUATED WITHOUT AND WITH
REFERENCES IN THE PANELS 1 (N = 7), 2 (N = 8) AND 3 (N = 9)
Sample
Panel
Without references
With references
P
A
1
2
3
1
2
3
1
2
3
2.1 ⫾ 1.1
2.5 ⫾ 1.4
2.1 ⫾ 0.9
1.1 ⫾ 0.9
2.4 ⫾ 0.9
0.9 ⫾ 0.8
1.9 ⫾ 0.9
3.4 ⫾ 0.7
2.6 ⫾ 1.0
1.7 ⫾ 0.5
2.8 ⫾ 0.7
2.6 ⫾ 0.9
0.7 ⫾ 0.5
1.8 ⫾ 0.7
1.2 ⫾ 1.0
2.0 ⫾ 0.6
4.6 ⫾ 0.5
2.7 ⫾ 1.4
NS
NS
*
NS
*
NS
NS
*
NS
B
C
* P < 0.05.
NS, not significant.
Comparing the scores given for the acid intensity in each
sample (A, B and C) within each of the sensory panels and
depending on whether or not the references were used
(Table 3), the following can be seen:
• In Panel 1, the acid taste intensity score does not change
significantly after the use of references.
• In Panel 2 (the one with the lowest degree of training), the
score of the acid taste intensity changed significantly in
samples B where the score was reduced, getting closer to the
score given by other juries. However, the case of sample C
increased unexpectedly.
PANEL 1
• In Panel 3, the acid taste intensity score does not change
significantly after the use of references except for sample A,
which slightly increases its score.
As can be seen in Fig. 3, in the case of Panel 1, there is a
reduction of dispersion in the scores of the three samples
after using the acid references. Panel 2 has also reduced the
dispersion in the scores after using the acidity references,
although perhaps not as sharply as Panel 1. Panel 2 (the one
with the lowest degree of training) is the one registering the
highest variability in the scores. In the case of Panel 3, after
using the acid references, it increased its dispersion in the
scores for samples A and B, but decreased the variability in
evaluating sample C.
The results obtained differ for each panel. In the case of
Panel 1, the average score does not vary between before and
after the use of references; however, the dispersion is
reduced after using the references. This panel had already
worked and been trained with these references.
Regarding the other two sensory panels, Panel 2 corrected
its acidity score after using the references with sample B, so
it seems that the use of references improved its response; the
Piquillo without PDO peppers hardly had acidity. However,
with sample C, it started with a high acidity intensity and
after tasting the references, it has increased acidity. Possibly,
there was an interference from some other taste not discriminated by the panel; e.g., that the sample was slightly
hot/spicy, for it is known that citric acid has sensory properties similar to those exhibited by capsaicin (sensitization at
short intervals, self- and cross-desensitization) (Dessirier
et al. 2000). Nevertheless, after the use of references, the
PANEL 2
PANEL 3
5
Acidity intensity
4
3
2
1
0
sample A
sample B
sample C
sample A
sample B
sample C
sample A
sample B
sample C
FIG. 3. COMPARISON OF THE AVERAGE VALUES AND DISPERSIONS OF THE SCORES FOR ACIDITY INTENSITY WITHOUT (䊐) AND WITH (䊏)
THE USE OF REFERENCES IN THE THREE PANELS
Journal of Sensory Studies 27 (2012) 384–391 © 2012 Wiley Periodicals, Inc.
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ACIDITY REFERENCES IN PEPPER
dispersion of intensities attributed to this sample is reduced.
Panel 3 only changed the score of sample A after tasting the
references and, in this case, its scores are somewhat higher.
In this panel, contrary to what was expected, the use of references did not contribute to control data dispersion, and
instead it increased.
CONCLUSIONS
• The measurement of the acidity of Piquillo de Lodosa
PDO pepper pastes using an interval measurement scale
with a six-category numerical response scale (0: absence, 1:
very weak, 2: weak, 3: medium, 4: intense and 5: very
intense) gives the following values: NP Piquillo de Lodosa
PDO pepper paste intensity 1, very weak, attributable to its
own natural acidity; Roasted, canned Piquillo de Lodosa
PDO pepper paste: intensity 2, weak, due to the combination of pepper’s own acidity and the acidity from the pill
added during elaboration. The addition of citric acid up to
concentrations between 0.17 and 0.23% (considering 0.0%
citric acid as natural acidity) does not manage to increase
significantly the perception of acidity intensity. It is necessary to reach concentrations between 0.5 and 1% citric acid
in order for the perception to increase up to medium and
very intense acidity, respectively. These references are appropriate for categories 3 and 5 of the scale.
• In a trained panel, both the numerical scale of categories
and the continuous scale are equally valid for correctly
evaluating the acidity intensity.
• The use of references of acid taste, prepared on a paste of
the same food matrix that the tasting panel uses normally,
reduces the dispersion in the acid intensity scores and therefore is useful for the training and formation of tasters. These
references have proven valid for the pimiento Piquillo PDO
panel. The results are not conclusive when these acid taste
references are used for the first time, with panels that are
used to different food. It should be confirmed with new
tests whether the use of acidity references, whose basis is
other than the product that is usually evaluated by a panel,
has an influence on the assignment of the acid intensity. The
use of panels that are not familiarized with the product to
validate references may be successful, but we think it would
require prior training sessions with the references in order
to evaluate their validity.
ACKNOWLEDGMENTS
All judges from three sensory panels are thanked for their
participation.
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