Food Chemistry xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Food Chemistry
journal homepage: www.elsevier.com/locate/foodchem
Effect of different drying methods on moisture ratio and rehydration of
pumpkin slices
Liliana Seremet (Ceclu) ⇑, Elisabeta Botez, Oana-Viorela Nistor, Doina Georgeta Andronoiu,
Gabriel-Danut Mocanu
Food Science and Engineering Faculty, ‘‘Dunarea de Jos’’ University of Galati, 111 Domneasca Street, 800201, Romania
a r t i c l e
i n f o
Article history:
Received 24 July 2014
Received in revised form 9 March 2015
Accepted 12 March 2015
Available online xxxx
Keywords:
Moisture
Drying combined method
Microwave
Pumpkin
a b s t r a c t
This study was carried to determine the influence of hot air drying process and combined methods on
physicochemical properties of pumpkin (Cucurbita moschata) samples. The experiments in hot air chamber were lead at 50, 60 and 70 °C.
The combined method consists of a triple combination of the main drying techniques. Thus, in first
stage the samples were dried in hot air convection at 60 °C followed by hot air ventilation at 40 °C
simultaneous with microwave.
The time required to reduce the moisture content to any given level was highly dependent on the drying conditions. So, the highest value of drying time in hot air has been 540 min at 50 °C, while the lowest
time has been 189 min in hot air combined by microwave at 40 °C and a power of 315 W.
The samples dried by hot air shows a higher rehydration capacity than samples dried by combined
method.
Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
Pumpkin (Cucurbita moschata) is one of the most important fruit
grown in the world because of its nutritional qualities and health
protective value of the seeds (especially oil) (Yang, Zhao, & Lv,
2007), but also by fleshy shell.
Pumpkin (C. moschata) is one of the vegetables that meet the
requirements of healthy nutrition. It is a tasty and valuable vegetable crop, containing a lot of biologically active substances and
distinguished for dietary qualities (Gajewski, Radzanowska,
Danilcenko, Jariene, & Cerniauskiene, 2008). It is a good source of
carotene and water soluble vitamins (Arévalo-Pinedo & Murr,
2006). It is rich in phenolics, flavonoids (Que, Mao, Fang, & Wu,
2008), polysaccharides, mineral salts, vitamins, and other substances beneficial to health (Yang et al., 2007).
Abbreviations: MW, microwave drying; HA, hot air drying; MR, moisture ratio,
dimensionless; DR, drying rate, (g water/g dry matter)/min; RR, rehydration ratio,
dimensionless; RC, rehydration capacity, %; Wi, initial weight of pumpkin samples,
g; Wd, weight of pumpkin samples after drying, g; Wr, weight of rehydrated
pumpkin samples, g; M, moisture content, g water/g dry matter; M0, initial moisture
content, g water/g dry matter; Me, equilibrium moisture content, g water/g dry
matter; RH, relative humidity, %; t, drying time, min.
⇑ Corresponding author. Tel./fax: +40 236 460165.
E-mail address: florika05@mail.ru (L. Seremet (Ceclu)).
Because of the high level of water (96%) from pumpkin the product can be easily spoiled (Perez & Schmalko, 2009). Drying is used
to remove water from foods. As a consequence, it prevents (or inhibits) development of microorganisms, improves food preserving
and reduces the weight and bulk of food for cheaper transport
and storage. As well, the reduction in moisture content below certain level can reduce the microbial damages of dried food materials
and accompanied by proper treatment (Jangam, Law, & Mujumdar,
2010). So, drying is an excellent way to preserve pumpkin flesh
that can add variety to meals and provide delicious and nutritious
snacks. Dried and rehydrated fruits and vegetables, as pumpkin,
are key ingredients in dairy products, breakfast cereals, dietetic
foods formulated for people suffering from physiological disorders
or for healthy people with additional needs and traditional foods
such as puddings, desserts, cakes, biscuits. Product rehydration
behavior must be known as total or partial reconstitution of water
(Contreras, Martín-Esparza, & Martínez-Navarrete, 2012).
Therefore, dried pumpkin may be a finished product or a halffinished product, subject to further processing. Properly selected
drying method of the raw material may increase the quality of
the finished product (Sojak, & Głowacki, 2010). Hot air drying of
agricultural products is one of the most popular preservation
methods because of its simplicity and low cost (Diamante, Ihns,
Savage, & Leo Vanhanen, 2010). However, it causes the degradation
of sensitive components leading to the losses of sensorial and other
http://dx.doi.org/10.1016/j.foodchem.2015.03.125
0308-8146/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Seremet (Ceclu), L., et al. Effect of different drying methods on moisture ratio and rehydration of pumpkin slices. Food
Chemistry (2015), http://dx.doi.org/10.1016/j.foodchem.2015.03.125
2
L. Seremet (Ceclu) et al. / Food Chemistry xxx (2015) xxx–xxx
important properties of the dried products. For improving drying
conditions combined drying techniques can be used, such as vacuum or convective drying using high frequency radiations like
microwave, radio frequency, and infrared heating (Contreras,
Martín-Esparza, Chiralt & Martínez-Navarrete, 2008; Kassem,
Shokr, El-Mahdy, Aboukarima, & Hamed, 2011).
Microwave drying has several advantages over conventional hot
air drying, such as high drying rate and short drying time (Sharma
& Prasad, 2004; Wang, Wang, & Yu, 2007).
Heat is generated when microwave interacts with the polar
water molecules in fruits and vegetables and significantly high
drying rate was achieved compared to air drying (Workneh,
Raghavan, & Gariepy, 2011). Heating is immediate due to irradiative energy transfer; hence the surface-to-center conduction stage
is largely eliminated due to gradual vapor pressure differences.
Under microwave drying, internal heat generation leads to an
increase in internal temperature and vapor pressure, both of which
help liquid flow towards the surface, thus increasing the drying
rate. MW drying offers opportunities to shorten the drying time
and improves the final quality of the dried products (Zhang,
Tang, Mujumdar, & Wang, 2006).
The variance of moisture content in pumpkin is important for
process design and conditions. This was calculated using mathematical models, empirical, semi-empirical or theoretical, which
can optimally describe the drying mechanism (Akgun & Doymaz,
2005). Heat and moisture transfer, induce stresses inside food
materials, which consequently lead to many physical changes such
as cell wall collapse and shrinkage. Such deformations are the main
determinant of textural properties in foods (Prachayawarakorn,
Tia, Plyto, & Soponronnarit, 2008). Some parameters are related
to the properties of the sample such as thickness, shape, particle
size, drying air temperature and relative humidity. Therefore, modeling of a drying process is a complex task, because pumpkin exhibits a capillary porous structure and kinetics of this liquid removal
depends on the material properties of the solid phase as well as on
cellular structure. The principle of modeling is based on a set of
mathematical equations which can satisfactorily explain the drying system.
The aim of the present study was to determine the influence of
different drying methods, convective drying and combined drying
methods on the drying curves and rehydration capacity, due to its
highest technological efficiency. The experimental results were
interpreted by statistical analysis.
2. Materials and methods
2.1. Raw material
Pumpkin (C. moschata) is cultivated all over the Romanian territory. This pumpkin variety is characterized by some specific issues
like: pear shape, thin peel and flesh colored in yellow to dark
orange, which varies due to the carotenes percentage content.
The pumpkin is well known for the main characteristics of flesh,
an important source of b-carotene, vitamins and minerals. This
crop is also valuable for seeds and flowers.
Pumpkins were purchased from the local market, from Galati,
Romania hand peeled and washed in running tap water. The
pumpkins were cut into cylinders with 5 mm thickness and diameter 25 mm, weighting 50 ± 1 g. The zone near the peel (<10 mm)
was removed because of its different texture.
2.2. Equipments
The drying process was carried in a convection microwave oven
(SHARP R-94ST Inverter Germany).
Humidity/Temperature Transmitter for High Humidity and
Chemical Applications (EE33 Series) was used for measurement
of the temperature (°C) and RH (%) inside the drying oven.
2.3. Drying process
In this study two different drying methods were analyzed as
follows:
2.3.1. Hot air drying
Pumpkin drying kinetics was examined for a hot-air dryer using
air with temperature ranging between 50 and 70 °C and RH
between 30.6% and 47.1%. Pumpkin samples were dried from moisture content (M0) of 90.06 ± 0.3% until (Me) 8.40 ± 0.11%. The final
moisture content of each sample was measured in order to calculate the moisture content at each weighing interval. Drying tests
were replicated three times at each inlet air temperature and
averages are reported.
2.3.2. Combined method
The combined method consists of a triple combination of the
main drying techniques. Thus, in first stage the samples were dried
in hot air convection at 60 °C, 180 min, followed by hot air ventilation at 40 °C simultaneous with microwave at different powers
(105 W – 30 min, 210 W – 15 min and 315 W – 9 min). From the
starting of the drying the change in the sample weight was
recorded at the time intervals of 30 min for hot air drying and
3 min for microwave drying. The drying method labels for these
set are (60 °C/C40 °C + MW105 W), (60 °C/C40 °C + MW1210 W),
(60 °C/C40 °C + MW315 W).
2.4. Mathematical modeling of drying
Drying curves obtained under controlled conditions provide
important information regarding the water transportation mechanisms, and they are used in the determination of the effective diffusion coefficient (Corrêa et al., 2011).
The moisture content (M) at any time of drying (%), was calculated according to Eq. (1):
M¼
Wi Wd
100; %
Wi
ð1Þ
The reduction of moisture ratio with drying time was used to
analyze the experimental drying data. Moisture ratio (MR) represents the amount of moisture remaining in the pumpkin samples
reported to the initial moisture content. It was calculated using
Eq. (2):
MR ¼
M Me
M0 Me
ð2Þ
The equilibrium moisture contents (Me) were determined by
drying until no further change in weight was observed for the
pumpkin samples in each treatment and drying conditions
(Tunde-Akintunde & Ogunlakin, 2013).
The drying rate (DR) of pumpkin samples can be determined by
Eq. (3):
DR ¼
Mtþdt Mt
dt
ð3Þ
where dt is a time dependent derivative and varies depending on
the nature of the heat treatment, such as: the time interval for convection drying is 30 min, while for MW using the treatment time is
3 min.
Please cite this article in press as: Seremet (Ceclu), L., et al. Effect of different drying methods on moisture ratio and rehydration of pumpkin slices. Food
Chemistry (2015), http://dx.doi.org/10.1016/j.foodchem.2015.03.125
3
L. Seremet (Ceclu) et al. / Food Chemistry xxx (2015) xxx–xxx
2.5. Rehydration analysis
(a)
1
Hot Air 50°C
Hot Air 60°C
Hot Air 70°C
0.8
Moisture ratio, MR
The rehydration characteristics of dried products are known as
quality parameters and indicate if physical and chemical changes
occurred during the drying process due to process conditions,
pre-treatments and sample composition (Apati, Furlan, &
Laurindo, 2010). Rehydration means refreshing the dehydrated or
dried products in water. Dried samples were put into 50 ml of cold
water in Petri dishes. Samples were out into a dish, after their surface was covered with a piece of filter paper to soak the excess
water. The samples’ weight was recorded and the rehydration ratio
was calculated according to Eq. (4):
0.6
0.4
0.2
0
Wr
Wd
The rehydration capacity, described as percentage water gain,
was calculated from the samples weight difference before and after
the rehydration (Maskan, 2001) as follows (Eq. (5)):
Mr
RC ¼
100; %
M0 Me
0
ð4Þ
ð5Þ
2.6. Scanning electron microscopy (SEM) analysis
(b)
60
120
180
240
300
360
1
420
480
540
Time, min
Hot Air 60˚C
60˚C/C40˚C+MW105W
0.8
Moisture ratio, MR
RR ¼
60˚C/C40˚C+MW210W
60˚C/C40˚C+MW315W
0.6
0.4
0.2
The structure of the dried pumpkin slices was examined using a
scanning electron microscope SEM Quanta 250 FEI with X-ray and
WetSTEM detector. To analyze the changes produced by the drying
temperatures which can affect the cellular structure of dried products, the samples were identically prepared (same size). Thin slices
of about 1 mm thick were cut from the dried samples, fixed on the
SEM stub and studied under the same conditions: High Vacuum
mode at a pressure 100 kPa, mag 600.
2.7. Statistical analysis and evaluation
Empirical modeling of the drying behavior of agricultural products often requires the statistical methods of regression and
correlation analysis. Linear and nonlinear regression models are
important tools to find the relationship between different variables, especially those for which no established empirical relationship exists (Omid, Baharlooei, & Ahmadi, 2009).
A non-linear multiple regression analysis was performed using
the drying mathematical models and the experimental data. The
experimental data were interpreted by means of a non-linear
regression and statistical analysis modeled with the DataFit
9.0.59 – program. The drying models which are expressing the best
the experimental data were selected based on the mean relative
error (MRE), the standard error of estimate (SEE) and coefficient
of multiple determinations (R2).
Time series analyses are forecasted by including an automatic
selection model procedure. Models include exponential smoothing,
moving averages, random walks, linear and nonlinear trends.
3. Results and discussions
3.1. Drying data
Fig. 1 provides information on the hot air drying curves for
pumpkin samples and the combined methods curves. These figures
contain the experimental results of pumpkin having an average
initial moisture content of 90.06 ± 0.3%. The drying process is
characterized by a progressive decrease in moisture content versus
time.
The necessary time to achieve the moisture equilibrium content
(8.40 ± 0.11%) for pumpkin samples dried by hot air was 540 min
0
0
60
120
180
240
300
360
420
Time, min
Fig. 1. Effect of drying air temperature and drying time on the moisture ratio of
pumpkin samples: (a) hot air drying; (b) combined method drying.
(50 °C), 420 min (60 °C) and 330 min (70 °C). Regarding the combined method, the drying time was 210 min (60 °C/
40 °C + 105 W), 195 min (60°/40 °C + 210 W) and 189 min (60 °C/
40 °C + 315 W).
Drying curves (Fig. 1.) were experimentally obtained by plotting
the moisture content versus drying time. Eq. (3) is a derivative time
and has the role of calculating the drying rate from the curves
determined by process kinetics.
Drying curves describe two distinct stages with a short constant
drying rate time for hot air drying (hot air 50 °C and hot air 60 °C)
(Fig. 2(a)).
In first stage, when moisture content was high (0.8200–
0.9085 g water/g dry matter), drying rate increased with drying
temperature, reaching the highest value at 70 °C – 0.483 (g
water/g dry matter)/min, in which the unbound water is removed.
Water evaporates as if there is no solid present, and its rate of
evaporation is not dependent on the material being dried. In the
second stage, the drying rate is decreasing, up to 0.0083–0.0056
due to water linkage. In the first stage, the drying rate reached
its maximum level, 0.3476–0.483 (g water/g dry matter)/min.
Then falling drying rate period occurred after 30 min. It can be
noticed, from the curves that the drying temperature had a significant effect on the DR.
These results are in agreement with the observation of earlier
researchers (Akpinar, 2006; Therdthai & Zhou, 2009; Workneh
et al., 2011).
For the combined method the classical shape of the drying
curves can be observed as a variance of drying rate with a constant
drying rate stage (Fig. 2(b)) (Mujumdar, 2006).
Drying rate increased with high power level (from 0.2123 g
water/g dry matter/min for 105 W to 0.4057 g water/g dry matter/min for 315 W) at the same moisture content, 0.3247 (g
water/g dry matter). The result indicated that mass transfer within
Please cite this article in press as: Seremet (Ceclu), L., et al. Effect of different drying methods on moisture ratio and rehydration of pumpkin slices. Food
Chemistry (2015), http://dx.doi.org/10.1016/j.foodchem.2015.03.125
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L. Seremet (Ceclu) et al. / Food Chemistry xxx (2015) xxx–xxx
(a)
Hot Air 50°C
0.5
DR, (g water/g dry matter)/ min
Hot Air 60°C
Hot Air 70°C
0.4
0.3
0.2
0.1
0
0
DR, (g water/g dry matter)/min
(b)
100
200
300
400
500
Time, min
0.45
0.3
0.15
60°C/C40°C+MW105W
60°C/C40°C+MW210W
60°C/C40°C+MW315W
0
0
30
60
90
120
150
180
210
Time, min
Fig. 2. Drying rate of pumpkin samples changes with drying time. (a) Hot air
drying; (b) combined method drying.
the sample is rapid for greater microwave power heating, 315 W/
9 min, because more heat is generated within the sample, creating
a larger vapor pressure differential between the center and the surface of products (Soysal, Öztekin, & Eren, 2006; Therdthai & Zhou,
2009; Wang et al., 2007; Workneh et al., 2011; Özbek & Dadali,
2007).
3.2. Rehydration
Removal of water from a cellular structure induced variations in
the physico-chemical properties of the system. The rehydration
characteristics of pumpkin samples dried at different temperatures
and combined method are shown in Fig 3. Rehydration is a complex process and indicates the physical and chemical changes
induced by drying treatments. It can be also observed from Fig. 3
that the rehydration ratio of pumpkin samples is increasing with
the decrease of temperature and microwave power (hot air drying
– 79.81 ± 0.3% at 70 °C, 88.97 ± 0.3% at 60 °C, 92.92 ± 0.3% at 50 °C,
combined method – 77.68% at 315 W, 85.44% at 210 W, 87.05% at
105 W).
The lower rehydration values (77.68–79.81%) are evidence of
higher temperature (70 °C) and microwave power (315 W), which
have the capacity to break the cellular structure (Fig. 4). Such a
behavior is reported in a few similar studies regarding microwave
assisted air drying of apple and mushrooms (Singh & Pandey,
2011).
When placing the dried samples into water, the cell walls
absorb water. Then due to the natural elasticity of the cellular
structure, the cells returned to their original shape by drawing
water into inner cavities. The volume of absorbed water increased
with increasing rehydration time, 77.6 ± 0.3–93.0 ± 0.3% in
210 min in water at 25 °C irrespective of the air temperature/microwave power. This was manifested in a relatively rapid rate of
reconstitution (half from total moisture content) during the early
stages – in first 30 min increased up to 40.5 ± 0.3–54.2 ± 0.3%, followed by a more gradual increase in rate, tended towards a maximal rehydration ratio, 79.81–92.92% for pumpkin samples dried by
hot air and 77.6 ± 0.3–87.1 ± 0.3% for pumpkin samples dried by
combined method. This rapid moisture uptake is very likely due
to surface and capillary suction (Singh & Pandey, 2011; Souzaa,
Pimentela, Pradob, Marquesb, & Naraina, 2011).
3.3. Scanning electron microscopy (SEM) results
Effects of different drying methods and conditions on the structure of dried pumpkin samples was observed under scanning electron microscopy. From the obtained images (Fig. 5) can be
observed temperature effects on tissue structure by comparing
fresh sample with dried samples. At fresh sample can be seen a
fraction of cell where vacuoles are well defined by cell walls
(lighter areas to a pale white) as well as parts similar to pockets
filled with cellular juice (darker areas). More noticeable are the
results for the dried samples, which are no longer indicating these
vacuoles inside cell due to water evaporation and merge cell walls
or even to breakage the cell walls, enlightening some severe contraction of tissue. Thus, it is obvious that the increasing of tissue
dehydration is accompanied by heightened deformation of cell texture and it is related to collapse as a result of loss of cell turgor.
3.4. Statistical analysis and evaluation
Response Surface Methodology (RSM) was used to investigate
the main effects of drying methods. DataFit was used to fit
response surfaces and optimize the drying process. From the 79
9
Hot Air
1
100
Rehydration ratio, RR
I
II
3
6
75
RC, %
Hot Air 50˚C
50
Hot Air 60˚C
3
Combined method
2
III
1 - Hot Air 50°C
2 - Hot Air 60°C
3 - Hot Air 70°C
I - 60°C/40°C+105W
II - 60°C/40°C+210W
III - 60°C/40°C+315W
Hot Air 70˚C
60˚C/C40˚C+MW105W
25
60˚C/C40˚C+MW210W
60˚C/C40˚C+MW315W
0
0
50
100
150
200
Time, min
Fig. 3. Influence of drying temperature/drying treatments on rehydration ratio.
0
Fig. 4. Influence of drying temperature/drying treatments on rehydration capacity.
Please cite this article in press as: Seremet (Ceclu), L., et al. Effect of different drying methods on moisture ratio and rehydration of pumpkin slices. Food
Chemistry (2015), http://dx.doi.org/10.1016/j.foodchem.2015.03.125
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L. Seremet (Ceclu) et al. / Food Chemistry xxx (2015) xxx–xxx
Fresh samples
HA 50°C
HA 60°C
HA 70°C
60°C/40°C+105W
60°C/40°C+210W
60°C/40°C+315W
Fig. 5. SEM micrographs for pumpkin fresh and dried samples.
models which were generated by Data Fit program, for moisture
ratio (MR) and drying rate (DR), the equation which gave the best
fitting curve was of the dried samples of pumpkin compared with
the other equations (Figs. 6 and 7).
Moisture ratio data
3
5
Y ¼ a þ bX 1 þ cX 21 þ dX 2 þ eX 22 þ fX 2 þ gX 42 þ hX 2
Equations of regression represent the prediction of a dependent
variable (moisture content) based on independent variables (drying temperature and drying conditions).
The moisture content values for both simple and combined drying are folded on 4 different mathematical models (Newton’s and
Page’s exponential models, a logarithmic model, Pabis and
Handerson modified model).
Prediction is done by fitting a surface to the experimental data
points that minimizes the standard error of estimation (Table 1).
The standard error of estimated values is the sum of the differences between each obtained value and its value as predicted by
the regression equation.
From Table 1 it can be observed that the coefficient of multiple
determinations for moisture content variation during time and
temperature evolution are strongly positive reaching values of
0.97–0.98.
The strong correlation indicates that more than 97% of the total
variation in Y can be explained by the linear relationship between
X and Y (as it was described by the regression equation). As
expected, the other 3% or less of the total variation in Y remains
unexplained (Abraham & Ledolter, 2006).
The mathematical formula or the analytical expression pattern
was chosen from a set of non linear approximation models offered
by the soft DataFit 9.0.59:
Table 1
Fit information.
Coefficient of multiple determination (R2)
Adjusted coefficient of multiple
determination (Ra2)
Standard error of the estimate
Proportion of variance explained
MR hot
air
MR combined
method
0.9831
0.9799
0.9773
0.9722
4.6828
98.31%
0.0566
97.74%
3
5
Y ¼ a þ bX 1 þ cX 21 þ dX 2 þ eX 22 þ fX 2 þ gX 42 þ hX 2
where: Y is the value predicted for the moisture content (dependent
variable); X1 represents a time-dependent vector; X2 is temperature/drying period dependent vector; a is the constant term of the
regression line (when the value for X = 0) – the independent variable; b, c, d, e, f, g, h are coefficients which are indicating the amount
by which the Y value is decreasing/increasing when X value is modified by one unit.
The prediction of the dependent variable Y, can be mathematically formulated by determining the quantities a, b, c, d, e, f, g, h
from the equation generated by the program in order to describe
the mathematical model.
Multiple non linear regression equations describes the prediction of the dependent variable (moisture content), depending on
the independent variables (temperature of drying/the combination
of drying conditions and time).
From the graphs (Figs. 6 and 7) it can be seen that the multiple
non linear regression equation has the same form for both cases
(drying in hot air convection and convection combined with
microwave).
3.6. Drying rate data
3
5
Y ¼ a þ bX 1 þ cX 21 þ dX 2 þ eX 22 þ fX 2 þ gX 42 þ hX 2
Prediction of drying rate was based on a range of process
parameters that were determined in the preliminary investigations
including the optimum values. For both methods, the graphs have
a linear behavior which means that the experimental data for drying rate are similar to the predicted ones (Fig. 8(a) and (b)). The
graphic is based on the residual probability, which is obtained as
a difference between the predicted and the experimental data.
The differences of the values have a negligible level of significance
and arranged after a linear model. (Abraham & Ledolter, 2006;
Wang, 2011).
Following the obtained results, it can be concluded that by combined method with microwaves, the drying time is reduced with
almost 50% relative to classical convection. But, due to the thermal
shock, a profound destruction of cell walls occurs, leading to a
lower capacity of hydration compared to the samples dried by
convection.
Please cite this article in press as: Seremet (Ceclu), L., et al. Effect of different drying methods on moisture ratio and rehydration of pumpkin slices. Food
Chemistry (2015), http://dx.doi.org/10.1016/j.foodchem.2015.03.125
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L. Seremet (Ceclu) et al. / Food Chemistry xxx (2015) xxx–xxx
4. Conclusions
Water removal during drying of the pumpkin slabs occurs in the
falling rate period. The reconstitution attributes are indicative of
the degree of structural modification occurred during drying. The
rehydration characteristic is correlated positively with the air temperature and drying treatment.
The methodology we have proposed, can give a good reason to
be used in case of new experimental drying ovens and/or drying
products or exploratory drying processes, when the most advantageous drying schedule must be selected from a number of variants.
Since the drying results can be obtained by simulation of a large
number of factor combinations and the outcomes processed by
using a multifactor experiment, the experimental work can be
reduced, the presence and magnitude of factors interactions can
be estimated and recommendations over a large variety of conditions can be outlined.
Acknowledgements
The morphological analyses were supported by the Laboratory
of Instrumental Analysis and Analytical Chemistry (LAICA),
Research Center from Alexandru Ioan Cuza University of Iasi,
Romania. Data Fit 9.0.59 – program is acknowledged for providing
technical support for mathematical modeling.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.foodchem.2015.
03.125.
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Please cite this article in press as: Seremet (Ceclu), L., et al. Effect of different drying methods on moisture ratio and rehydration of pumpkin slices. Food
Chemistry (2015), http://dx.doi.org/10.1016/j.foodchem.2015.03.125