1. S:Sensory&Food
Quality
Pasta Fortified with Potato Juice: Structure,
Quality, and Consumer Acceptance
Przemysław Kowalczewski, Gra˙zyna Lewandowicz, Agnieszka Makowska, Ismena Knoll, Wioletta Błaszczak, Wojciech Białas,
and Piotr Kubiak
Abstract: The potential of potato juice in relieving gastrointestinal disorders has already been proven. Work continues
on implementation of this active component into products that are widely consumed. In this article, results of an attempt
to fortify pasta with potato juice are presented and discussed. Fortification is performed using fresh and dried juice. The
influence of the addition on culinary properties of the final product, such as cooking weight and cooking loss, as well as
microstructure, color, texture, and consumer acceptance were evaluated. It was found that potato juice can be used for
fortification of pasta both in its fresh and dried forms, however the effects on different responses depend on the potato
juice form used. The addition of potato juice influenced the color of the product reducing its lightness and shifting color
balances from green to red, yellow color saturation was decreased as well. Changes in color were more significant in the
case of fresh juice addition. The firmness and microstructure of pasta was also influenced. The surface microstructure of
pasta containing fresh potato juice was different from that of the other 2 products being a likely explanation of the lower
cooking loss observed in its case. In contrast, the consistency of dough was strengthened by addition of dried potato juice.
Principal components analysis indicated that the color change had the most pronounced effect on consumer acceptance.
Other physicochemical changes were slightly less significant. Nevertheless, sensory evaluation proved that functional pasta
produced with fresh potato juice finds consumer acceptance comparable with that of classic pasta.
Keywords: functional food, microstructure, pasta, potato juice
Introduction
The interest in inflammatory bowel disease (IBD) is growing
along with its worldwide occurrence rate. Alike Crohn’s disease
(CD) and ulcerative colitis (UC), its etiology is still unknown. The
causes appear to lie in disregulated immune response to proper
commensal microflora of the gut of affected individuals (Burisch
and other 2013). Novel approaches have been introduced to IBD
therapy, their impact, however, is still uncertain (Burisch and
Munkholm 2013). Chronic and relapsing inflammatory condition
of the gastrointestinal tract leads to malnutrition as a result of
impaired absorption of nutrients. Thus, combining therapy
and diet have been paid increasing attention in IBD treatment
(Andersen and other 2012).
The antacid and spasmolytic properties of freshly squeezed
potato juice have made it a traditional remedy for stomach com-
plaints, long present in medicine of European folk (Vlachojannis
and other 2010). Current research on medicinal use of potato
juice proved its applicability for the treatment of gastrointestinal
tract diseases (Chrubasik and other 2006; Vlachojannis and other
2010). However, it is well known that potato juice contains toxic
glycoalkaloids, and a lot of effort was made to avoid the supply
of these substances in the human diet (Korpan and other 2004).
Generally, it is believed that medicinal, mainly anti-inflammatory,
properties of potato juice are related to proteins it contains, thus
they are considered its most valuable fraction (Pouvreau and other
MS 20141933 Submitted 11/24/2014, Accepted 4/16/2015. Authors Kowal-
czewski, Lewandowicz, Knoll, Białas, Kubiak are with Dept. of Biotechnology and
Food Microbiology, Pozna´n Univ. of Life Sciences, Pozna´n, Poland. Author Makowska
is with Dept. of Cereal Science and Technology, Inst. of Food Technology of Plant Ori-
gin, Pozna´n Univ. of Life Sciences, Pozna´n, Poland. Author Błaszczak is with Dept.
of Chemical and Physical Properties of Food, Inst. of Animal Reproduction and Food
Research of Polish Academy of Sciences, Olsztyn, Poland. Direct inquiries to author
Kowalczewski (E-mail: przemyslaw.kowalczewski@up.poznan.pl)
2001; Ruseler-van Embden and other 2004). However, there still
is little awareness that glycolalkaloids show activity against cancer
cells (Kuo and other 2000). Our previous work proved that the
ingredients of potato juice not only show antioxidant activity,
but are cytotoxic against cancer cells of gastrointestinal tract
(Olejnik and other 2011; Kowalczewski and other 2012) and have
anti-inflammatory properties (Lewandowicz and other 2014).
This activity does not disappear even after high-temperature
treatment, for example by spray drying (Lewandowicz and other
2012). The properties indicated above suggest that potato juice
could serve as a functional ingredient of food addressed to people
suffering from IBD.
Pasta is popular worldwide and considered staple food of many
nations. Traditionally, the primary ingredient of pasta is wheat
semolina. However, it is often enriched with different functional
components, such as antioxidants, proteins, or even seafood, in
order to introduce health promoting properties (Kadam and Prab-
hasankar 2010; Khan and other 2013; Sun-Waterhouse and other
2013). Unlike most starchy foods, eating pasta does not induce
high glycemic and insulinemic responses (Foster-Powell and other
2002; Khan and other 2013). Moreover pasta is cheap, versatile,
and convenient, and therefore it is an almost ideal carrier of bioac-
tive components.
An attempt at design of health-oriented food product containing
potato juice and addressed to patients with IDB was undertaken in
this work. The effects of fresh and dried potato juice addition on
physicochemical properties, structure, and consumer acceptance
of pasta were examined.
Materials and Methods
Materials
Commercially available semolina of Triticum durum was pur-
chased from a commercial mill (Radzy´n Podlaski, Poland). Fresh
C 2015 Institute of Food Technologists R
doi: 10.1111/1750-3841.12906 Vol. 0, Nr. 0, 2015 r Journal of Food Science S1
Further reproduction without permission is prohibited

2. S:Sensory&Food
Quality
Pasta fortified with potato juice . . .
potato juice, a by-product of potato starch production, was col-
lected from starch production plant (WPPZ Lubo´n, Poland) dur-
ing potato processing season. Directly following its production,
the juice was cooled to 4 °C and transported to the laboratory.
The dry matter content was 5.2 ± 0.3% in this raw material.
Drying was carried out in a pilot scale P-dryer Niro Atomizer
6.3 (Denmark) using air temperatures: 170 °C at the inlet to the
drying chamber, 95 °C at the outlet, and the feed rate of juice 12
l/h. The dry matter in the obtained product was 90.1 ± 0.5%. De-
tailed characteristics of the potato juice used in the experiments in
dry matter: protein content: 49.22 ± 0.40 %; ash 16.34 ± 0.09 %.
Macro- and microelements: Ca 135.04 ± 4.62 mg/100g; Mg
551.50 ± 21.92 mg/100g; Mn 3.27 ± 0.01 mg/100g; Fe 158.01
± 1.28 mg/100g; Zn 7.964 ± 0.131 mg/100g; K 8354 ± 17
mg/100g; Cu 1.846 ± 0.248 mg/100g; Pb 0.336 ± 0.054 mg/kg;
Cd 0.697 ± 0.024 mg/kg.
Pasta manufacturing
Pasta was prepared with a lab-scale pasta extruder Polo-5 (G¨otz
GmbH, Heiligkreuztal, Germany). The semolina was hydrated to
obtain 33% content of water then mixed for 20 min and extruded.
The potato juice was introduced in 2 forms—fresh and dried. Pasta
without potato juice was used as control. The amount of the juice
in the formulation was based in the dry mass of the added juice;
in both cases 1.3 g dry mass of potato juice was added per 100
g of moist final pasta. This amount was found to be maximum
if dough of ɸ = 33% was to be prepared (moisture suitable for
correct course of the production process).
With respect to the water content in the raw materials used
pasta samples were prepared using the following recipes: Control:
semolina 77.90 g, water 22.10 g; Pasta with fresh potato juice:
semolina 76.46 g, fresh potato juice 23.54 g; Pasta with dried
potato juice: semolina 76.58 g, water 22.10 g, dried potato juice
1.32 g.
Pasta was dried in a humidity chamber TH-TG-180 (Jeiotech,
Korea) using the following parameters: 45 °C, ɸ = 75% for 3 h;
63 °C ɸ = 85% for 12 h; 40 °C ɸ = 60% for 4 h. After drying,
the pasta was stabilized for 10 h in at room temperature and 70%
relative humidity. Thus prepared pasta was packed into PE bags.
Protein content was as follows in the obtained pasta samples. The
protein content of manufactured pasta:
Control 13.80b
± 0.24% d.m.; Pasta with fresh potato juice:
14.49a
± 0.30% d.m.; Pasta with dried potato juice: 14.53a
±
0.21% d.m.
Before texture and organoleptic analyses, the pasta was cooked
in tap water (water/pasta ratio of 20, 10 min).
Firmness test
Textural properties of pasta were determined for cooked samples
using a TA.XT2i texture analyzer (Stable Micro System, Surrey,
U.K.), according to AACC Approved Method 66-50 (2000). The
texture analyzer was equipped with a plexiglas straight probe and
the measurements were carried out at room temperature using a
5 kg compression cell. Dimensions of pasta samples were 2 mm
height, 10 mm width, and 100 mm length. Three samples of
pasta (cut into pieces of 10 cm length) were placed in parallel
position onto the measurement plate of the texture analyzer. The
probe was moved perpendicularly to the plate and the force was
recorded with acquisition rate equal to 200 points per seconds and
plotted by a computer in a force–time plot. The measurement
assay parameters were: pretest speed: 0.5 mm/s; test speed: 0.2
mm/s; posttest speed: 10 mm/s. Down stroke distance was: 4.5
mm, so the sample was cut completely. Maximum force to cut the
sample (maximum shearing force, firmness) and the work needed
to move the blade thought the sample (work of shearing) were
calculated.
Cooking Properties
Cooking weight (CW)
Water absorption was measured and calculated according to
Zardetto and other (2002). About 30 g of pasta was weighted and
cooked in 500 mL of distilled water. After that, the whole pasta
sample was removed, drained, and weighed after 5 min. The result
was calculated as mass ratio of cooked and raw pasta (g/g).
Cooking loss (CL)
Loss of dry matter during cooking was determined according
to Zardetto and other (2002). The cooking and drain water were
combined and collected in a tarred beaker, placed in an air oven at
105 °C and evaporated to dryness. The residue was weighed and
reported as a percentage of dry pasta.
Color measurements
Color of cooked pasta was measured using a Chroma Meter
CR-410 (Konica Minolta Sensing Inc., Osaka, Japan) color meter.
Differences were recorded in CIE L∗
a∗
b∗
scale in terms of lightness
(L) and color (+a – red; -a – green; +b – yellow; -b – blue).
Total color difference (TCD) were calculated using the following
formula:
E = L2 + a2 + b2 (1)
Scanning electron microscopy (SEM)
Small pieces of dried pasta were cross-sectioned, mounted on
an aluminium disc using silver paste, and coated with gold in a
JEE-400 vacuum dryer (Jeol, Japan). Specimens were observed
with a JSM-5200 scanning electron microscope (Jeol, Japan) at
accelerating voltage of 10 kV.
Consumer acceptance
Consumer acceptance assessment was carried out using a ques-
tionnaire with a line acceptance scale (Szymandera-Buszka and
other 2013). The scale, alike the typical unstructured line scale,
was anchored with “dislike extremely” and “like extremely” on
opposing ends of the scale (Hein and other 2008). Moreover, it
was divided (structured) into 10 segments (Baryłko-Pikielna and
Matuszewska 2009). Following categories were used for evalua-
tion: appearance, color, taste, smell, and texture. Overall rating of
the product was also recorded. The study involved 45 volunteers
suffering from IBD, aged between 21 and 25 years.
Statistical analysis
All measurements were made in 6 repetition and studied using
one-way analysis of variance independently for each dependent
variable. A post-hoc Tukey HSD (honest significant difference)
multiple comparison tests were used to identify statistically ho-
mogeneous subsets at α = 0.05. Statistical analysis of the data
was performed with Statistica 10 (StatSoft, Inc., Tulsa, Oklahoma,
USA 2011) software.
Principal component analysis (PCA) was performed using the
data obtained through consumer acceptance survey. Covariance
matrices were composed. All the data obtained in the survey were
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3. S:Sensory&Food
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Pasta fortified with potato juice . . .
Table 1–Properties of manufactured pasta.
Fresh potato Dried potato
Parameter Control juice addition juice addition
Cooking weight and cooking loss values of pasta samples
Cooking weight (g/g) 2.4 ± 0.1a 2.6 ± 0.2a 2.9 ± 0.3a
Cooking loss (%) 4.5 ± 1.2a 0.6 ± 0.2b 5.8 ± 0.8a
Color parameters of pasta enriched with potato juice
L∗ 78.57 ± 0.14a 66.24 ± 0.10b 66.58 ± 0.11b
a∗ –2.02 ± 0.01c 2.56 ± 0.01b 2.68 ± 0.04a
b∗ 22.95 ± 0.02a 14.04 ± 0.03c 17.12 ± 0.10b
࢞E – 15.89 14.14
Texture of pasta
Firmness (N/mm) 1.10 ± 0.11c 1.22 ± 0.05b 1.42 ± 0.12a
Total work of shear
(N/mm × s)
4.65 ± 0.32c 5.19 ± 0.20b 6.33 ± 0.27a
Consumer sensory scores of tested pasta
Appearance 7.36 ± 0.49a 6.98 ± 0.52a 5.36 ± 0.59b
Color 7.44 ± 0.50a 6.65 ± 0.48a 5.46 ± 0.47b
Taste 7.26 ± 0.36a 6.97 ± 0.41a 6.04 ± 0.22b
Flavor 7.12 ± 0.51a 7.03 ± 0.44a 6.34 ± 0.36b
Texture 6.80 ± 0.22a 6.51 ± 0.28a 5.97 ± 0.33b
Overall rating 7.00 ± 0.24a 6.80 ± 0.32a 5.70 ± 0.33b
The means in rows with different superscripts are significantly different (P < 0.05).
used to form the axes. The result is presented in a 2-dimensional
system (biplot) obtained by plotting the observations and variables
on the plane formed by the calculated principal components. Ad-
ditionally, correlation matrix was constructed for the variables used
in PCA.
Results and Discussion
Cooking properties
Cooking properties are considered important indicators of pasta
quality. Functional ingredients introduced into the recipe of the
product, especially proteins or fiber, are known to significantly
influence its properties (Prabhasankar and other 2007; Fradique
and other 2013; Khan and other 2013). Protein fraction makes for
about 50% of the total dry mass content of potato juice (Zwij-
nenberg and other 2002; Kowalczewski and other 2012), thus it
can be assumed that the properties of pasta will be changed by its
addition.
Addition of potato juice in any of its tested forms did not im-
pact cooking weight (Table 1). However, cooking loss was affected
by the addition. The value of this parameter was significantly
decreased by fresh juice addition. Dissolution of loosely bound
molecules of gelatinized starch form the surface seems to be the
main reason for losses during cooking of gluten-free pasta. The ex-
tent of starch gelatinization and the resilience of the matrix formed
by retrograded starch around the gelatinized starch molecules in-
fluence this process (Marti and other 2010). The presence of pro-
tein itself as well as their properties have significant influence on
the binding mechanism between macromolecules that form the
structure of pasta, thus changing its culinary properties (Khan and
other 2013). Potato proteins present in their native form in fresh
juice seem to facilitate formation of strong matrix that binds the
starch fraction and in turn lead to decreased loss of dry mass dur-
ing cooking. The proteins denatured during spray drying does not
exert such an effect.
Color
The difference in color between the control and pasta enriched
with potato juice was visible already in raw products. This was true
for pasta with both fresh and dried juice. The fortified products
were darker, their color resembled commercially available whole-
meal pastas. The dark shade was retained during cooking. The
color parameters measured are given in Table 1.
The value of L∗
, a parameter related directly with the lightness
of the samples, was reduced in pasta containing both fresh and
dried potato juice. Also, the green/red color balance (a∗
) was
shifted toward red in both tested cases, and the blue/yellow (b∗
)
balance shifted toward blue. In the case of pasta fortified with fresh
potato juice, the saturation with yellow was decreased by almost a
half compared to control. This difference was not as pronounced
for pasta with dried juice.
Such color changes can be explained by nonenzymatic and
enzymatic browning reactions that occur during exposition to el-
evated temperatures when the dough undergoes drying. Potato
juice contains 1.8% protein, most of molecular mass below 50
kDa, about 1.8% free amino acids, and carbohydrates (Burlingame
and other 2009). Some of the proteins possess oxidative enzy-
matic activity. As a consequence, it is possible that free aromatic
amino acids and polyphenols that may be present in potato juice
are oxidized to derivatives that change the color of the product.
Peroxidase (POD) and polyphenol oxidase (PPO) are catalysts of
such reactions. The latter protein facilitates biochemical transfor-
mation of phenolic compounds to quinones in the presence of
oxygen. Quinones are further polymerized to form dark colored
melanins (Feillet and other 2000). Enzymatic color changes in case
of semolina are insignificant as native POD and PPO activity are
negligible and the raw material lacks substrates for such reactions.
Moreover, the shift in b∗
value was a likely result of the activity
of lipooxygenase (LOX), an enzyme that catalyzes decomposition
of carotenoids (De Simone and other 2010).
The overall color difference (࢞E) value determined for pasta
prepared with fresh potato juice was slightly higher than for pasta
with dried juice. According to Mokrzycki and Tatol (2011), an
experienced observer may visually detect color deviation when
E is greater than 3.5 between 2 objects. Thus, the results of
measurements obtained hereby ( E > 14) allow a statement that
samples of pasta fortified with both fresh and spray-dried juice
deviated from control samples to such an extent that made it
visible to naked eye.
This facilitates the statement that enzymatic reactions play an
important role in shaping the color of the final product. It can
be assumed that although the chemical composition of potato
juice in both of its forms utilized hereby was identical, the spray-
drying process inactivated a part of the enzymes that catalyze redox
reactions leading to differences in color between the tested pastas.
Texture analysis of cooked pasta
Two textural parameters were determined in the pasta samples:
firmness and total work of shear. As is well known, the firmness
of pasta decreases with cooking duration (Dziki and other 2012),
all the samples were cooked for identical periods before analysis.
The addition of potato juice resulted in increased firmness of pasta
compared to control (Table 1). This effect was stronger in samples
fortified with dried juice then with fresh juice.
As firmness, the total work of shear determined during cutting
of pasta samples was increased by addition of potato juice. These
results indicate that not only potato juice addition itself, but also
the form in which it is added influence the quality of the final
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4. S:Sensory&Food
Quality
Pasta fortified with potato juice . . .
Table 2–Correlations matrix for investigated variables.
Cooking Cooking Firmness Total work of Overall
weight (g/g) loss (%) L∗ a∗ b∗ (N/mm) shear (N/mm × s) Appearance Color Taste Flavor Texture rating
1.000 0.808 −0.664 0.687 −0.376 0.995 0.988 −0.999 −0.981 −1.000 −0.994 −0.990 −0.998
0.808 1.000 −0.096 0.127 0.242 0.746 0.709 −0.827 −0.679 −0.799 −0.867 −0.719 −0.847
−0.664 −0.096 1.000 −1.000 0.943 −0.735 −0.770 0.638 0.796 0.676 0.580 0.761 0.610
0.687 0.127 −1.000 1.000 −0.932 0.755 0.789 −0.662 −0.814 −0.698 −0.605 −0.780 −0.634
−0.376 0.242 0.943 −0.932 1.000 −0.466 −0.513 0.345 0.548 0.391 0.274 0.500 0.310
0.995 0.746 −0.735 0.755 −0.466 1.000 0.999 −0.991 −0.995 −0.997 −0.979 −0.999 −0.986
0.988 0.709 −0.770 0.789 −0.513 0.999 1.000 −0.983 −0.999 −0.991 −0.966 −1.000 −0.975
−0.999 −0.827 0.638 −0.662 0.345 −0.991 −0.983 1.000 0.974 0.999 0.997 0.985 0.999
−0.981 −0.679 0.796 −0.814 0.548 −0.995 −0.999 0.974 1.000 0.984 0.955 0.998 0.965
−1.000 −0.799 0.676 −0.698 0.391 −0.997 −0.991 0.999 0.984 1.000 0.992 0.993 0.996
−0.994 −0.867 0.580 −0.605 0.274 −0.979 −0.966 0.997 0.955 0.992 1.000 0.970 0.999
−0.990 −0.719 0.761 −0.780 0.500 −0.999 −1.000 0.985 0.998 0.993 0.970 1.000 0.978
−0.998 −0.847 0.610 −0.634 0.310 −0.986 −0.975 0.999 0.965 0.996 0.999 0.978 1.000
product. Thermal exposition during drying results in a variety
of changes in potato juice. The influence on conformation of
protein should be considered one of the most important thermal
effects. Its consequences are inactivation of enzymes as well as
changes to water holding capability and association with other
biopolymers of semolina. All these factors have potential effects
on the microstructure of pasta.
Microstructure of pasta
The microstructure of pasta samples depends on several factors
of which the interaction between starch and the protein fraction
is considered the most important (Lucisano and other 2008). The
results of SEM analyses (Fig. 1 and 2) explain the differences ob-
served in textural parameters of tested pasta samples that were
presented in Table 1. The images taken at 35-fold magnification
factor (Fig. 1A, C, and E) show different amounts of empty spaces
filled with air throughout the structure of pasta sample. The pres-
ence of these pores itself is related to the process of extrusion.
Their amount and size, however, are determined by the rheology
of dough that undergoes extrusion, and rheological properties of
dough are a result of its composition. Protein and amino acids that
amount to 50% total dry mass of potato juice (Burlingame and
other 2009) may influence the rheology of dough. Moreover, it
can also be modified, although through different mechanisms, by
the presence of salts which make for 30% of total dry mass of potato
juice and are mainly salts with potassium cation (Burlingame and
other 2009).
As determined for other properties, the effects of fortification on
the microstructure were dependent on the form in which potato
juice was introduced. When dried juice was added, the pores were
round-shaped and their size was more even. The micrographs
taken at 1000-fold magnification factor (Fig. 1B, D, and F) show
that the microstructure of the control sample was the most loose
of all. Fortification with potato juice, especially dried, resulted in
stronger consistency of pasta.
Surface studies with SEM (Fig. 2) explained the differences
observed in texture and culinary properties of the tested pastas.
The pasta fortified with fresh potato juice had different surface
Figure 1–Scanning Electron Microphotographs
of cross-sections of pasta by different
magnifications: A & B – Control pasta, C & D –
pasta fortified with fresh juice, E & F – pasta
fortified with dried juice.
Figure 2–Scanning Electron Microphotographs
of pasta layer: A – Control pasta, B – pasta
fortified with fresh juice, C – pasta fortified
with dried juice.
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5. S:Sensory&Food
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Pasta fortified with potato juice . . .
microstructure than the control and the pasta with dried juice.
As clearly visible, the surface of 2 samples (Fig. 2A and C) was
smoother than that of the pasta containing fresh juice (Fig. 2 B).
This smoothness is a likely result of amylose release from starch
granules that occurred during formation of dough. This phe-
nomenon could have resulted in higher cooking loss values
noted for the control and the pasta containing dried juice, when
compared to the result obtained for samples with fresh potato
juice.
Consumer acceptance
As fortification of conventional food with functional ingre-
dients is often accompanied by changes in sensory properties,
newly designed products may not always meet expectations of
consumers who demand proven health benefits but will not sac-
rifice the pleasures of consumption. If a functional food product
is be a commercial success, nutritional value and health promot-
ing functionality must be accompanied by desirable sensory fea-
tures (Sun-Waterhouse and Wadhwa 2013). Most recent studies on
comparison of different scaling methods, that is unstructured line
scale, 9-point category scale, LAM scale, paired preference, and
best–worst scaling, indicate that similar conclusions are reached
despite different methodologies. Therefore, structured line scale
was used in our study. It is essentially a slight modification of the
unstructured line scale, and is the most common method used in
consumer testing in Poland (Baryłko-Pikielna and Matuszewska
2009; Szymandera-Buszka and other 2013). Moreover, our study
involved only people suffering from IBD, representing the target
group of consumers of the bioactive pasta. Therefore, only 45
people have been questioned. This could be considered a rather
small group, however, it is an acceptable number of examined
consumers (Hough and other 2006). The restriction concerning
test participants was introduced based on the results of research
on taste sensitivity of different groups of consumers suffering from
diseases of affluence (Nesterowicz and Nowak 2010).
Data presented in Table 1 show that the product with addition
of dried potato juice found lower consumer acceptance than both
the control pasta and the pasta containing fresh juice, which did
not differ significantly in terms of any score of the evaluation.
The participants of consumer acceptance study pointed out that
pasta fortified with potato juice resembles wholemeal pasta that
is commercially available. These products differ significantly from
classic pastas, not only in appearance, but also in taste, smell, and
texture. Thus, it is possible that among consumers who usually
choose health promoting food the pasta with dried juice would
have found better acceptance.
To facilitate the interpretation of the influence of technological
factors and physicochemical properties of pasta on consumer ac-
ceptance, PCA was performed. Two principal components were
obtained, based on calculations, that allowed to explain 99.78%
of the total variance of the 13 variables analyzed. The 1st and
the 2nd principal component carries 85.54% and 14.24% of in-
formation about the tested products represented by the variables,
respectively. The relation between the data input and the princi-
pal components are plotted in Figure 3. Every vector represents
one variable, its magnitude and direction indicates the influence
it has on the principal components. Moreover, the magnitude
of the vector is dependent on the ability of a variable to dif-
ferentiate tested samples (pasta types) from each other. The 1st
primary component compiles variables related to sensory vari-
ables (Appearance, Color, Taste, Flavor, Texture, Overall rating)
and instrumental texture analysis (Firmness, Total work of shear).
The vectors associated with texture have direction opposite to
sensory analysis related vectors. This indicates negative correlation
between these 2 groups of variables and means that potato juice
addition triggers increment in Firmness and Total work of shear
that result in deterioration of sensory quality. These results com-
ply with SEM analysis where samples of increased firmness were
shown to have modified surface and cross-section microstructure.
Details concerning correlations between the variables are included
in Table 2.
Figure 3–Projection of the variables on the component-plane (1×2).
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6. S:Sensory&Food
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Pasta fortified with potato juice . . .
The 2nd principal component is compiled mainly of parameters
that describe the color of pasta (L∗
, a∗
, and b∗
) and cooking
loss. Vectors representing these variables are relatively long, which
indicates greatest power to differentiate the tested pasta. It is in
accordance with the fact that the color differences were noticeable
to naked eye and were responsible for low rating of pasta fortified
with potato juice. The magnitudes of vectors representing other
variables (sensory and texture analyzes) were similar, indicating
similar discriminatory power of these variables.
In addition, to the vectors described above, the plot includes
points that represent each row of the analyzed table (pasta types).
The distance between these points clearly indicates differences
between the profile composed by the 13 variables used in the
PCA and correspond with the Overall rating values given in Table
1. A general conclusion can be drawn that color difference is the
main factor influencing consumer perception of pasta. It indicates
that marketing strategy for such products, similarly to wholegrain
pasta considered health-promoting food, should target consumers
affected with bowel disorders who are aware of specific dietary
recommendations.
Conclusion
Taking into account the slight change in consumer acceptance,
potato juice can be used for fortification of pasta both in its fresh
and dried forms. However the effects on different responses varied
depending on the potato juice form used. Generally, the observed
changes were more extensive when dried potato juice was intro-
duced, especially in the case of textural properties and consumer
sensory scores. In contrast, more significant changes in color were
in case of fresh juice addition. Fortification with potato juice
caused reduction in lightness of pasta and shift in color balance
from green to red and reduction in yellow color saturation. Simi-
larly, decreased cooking loss accompanied by increased roughness
of surface was observed in pasta samples containing fresh potato
juice. Microscopic analysis of internal microstructure of pasta with
potato juice showed decreased porosity in fortified samples. PCA
proved that the color of the tested pasta had decisive effect on
consumer acceptance of these products. Other parameters were
somewhat less significant. Nevertheless, consumer acceptance of
pasta fortified with fresh juice was similar to that observed for the
control sample.
Acknowledgments
This paper was financially supported by the grant POIG
01.01.02-00-061/09 “Bioactive food” implemented within the
Programme Innovative Economy 2007–2013.
Authors’ Contributions
P. Kowalczewski—designing of the experiment, collection of
some test data and participation in drafting of the manuscript.
G. Lewandowicz—idea of the study, research supervision and
participation in drafting of the manuscript.
A. Makowska—texture analyses.
I. Knoll—collection of some test data.
W. Błaszczak—SEM experiment performance.
W. Białas—statistical analyses of obtained data.
P. Kubiak—participation in interpretation of the results and in
drafting of the manuscript.
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