Postharvest Biology and Technology 40 (2006) 149–154
Fresh-cut radish using different cut types and storage temperatures
Juan Saavedra del Aguila a,∗,1 , Fabiana Fumi Sasaki b,2 , Lilia Sichmann Heiffig a,1 ,
Edwin Moisés Marcos Ortega c , Angelo Pedro Jacomino a,1 ,
Ricardo Alfredo Kluge b,1
a
b
Department of Crop Production, Escola Superior de Agricultura “Luiz de Queiroz”, University of São Paulo, C.P. 9, 13418-900, Piracicaba, SP, Brazil
Department of Biological Science, Escola Superior de Agricultura “Luiz de Queiroz”, University of São Paulo, C.P. 9, 13418-900, Piracicaba, SP, Brazil
c Department of Basic Science, Escola Superior de Agricultura “Luiz de Queiroz”, University of São Paulo, C.P. 9, 13418-900, Piracicaba, SP, Brazil
Received 30 March 2005; accepted 31 December 2005
Abstract
This project studied the effects of different types of cuts and storage temperatures on the quality of stored, fresh-cut radish. Two types of
cuts (sliced and shredded), and three storage temperatures (1, 5 and 10 ◦ C), were studied during 10 d. Whole radish was used as the control.
Respiration rate and ethylene production were evaluated daily, while physicochemical parameters (soluble solids, weight loss, titratable acidity,
ascorbic acid content, and color) were evaluated every second day. Twelve hours after processing, shredded roots had produced 0.04, 0.11
and 0.17 ng kg−1 s−1 of C2 H4 at 1, 5 and 10 ◦ C, respectively. On the 10th day, whole roots stored at 1 ◦ C showed the lowest respiration rate
(1.59 ␮g kg−1 s−1 of CO2 ) while the highest rate was observed in shredded roots stored at 10 ◦ C (7.42 ␮g kg−1 s−1 ). Shredded radishes had
lower soluble solids during storage compared to other cut types. Loss of fresh matter increased with storage time and temperature. The content
of ascorbic acid decreased in shredded roots stored at 10 ◦ C. The value of lightness (L* ) of shredded roots decreased during storage at the
three studied temperatures. Temperatures of 1 and 5 ◦ C are recommended for maintenance of quality in fresh-cut radishes.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Raphanus sativus L.; Fresh-cut; Respiration rate; Ethylene; Postharvest; Cold storage
1. Introduction
The demand for fresh-cut products is growing rapidly in
the foodservice and retail markets. Fresh-cut business has
been experiencing exponential increases in many countries,
particularly in large metropolitan areas such as São Paulo, one
of the biggest cities in Brazil, where supermarkets sell around
US$ 4 million of fresh-cut products per month, including both
fruit (54%) and vegetables (46%) (Rojo and Saabor, 2002).
Minimal processing (fresh-cut) comprises selection,
washing, peeling and cutting procedures aimed at producing
a product that is fresh and convenient to prepare or consume (Burns, 1995). In general, fresh-cut products have a
∗
1
2
Corresponding author. Tel.: +55 19 34294115; fax: +55 19 34344460.
E-mail address: [email protected] (J.S. del Aguila).
CNPq fellow.
FAPESP fellow.
0925-5214/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.postharvbio.2005.12.010
shorter shelf life, which is mainly due to mechanical stresses
(Watada, 1997). At the cut surface, cells and membranes
are damaged leading to alterations in tissue metabolism.
Although these alterations are different, many authors have
observed increase in carbon dioxide and ethylene evolution,
water loss, alterations in flavor and aroma, in volatile profiles,
and increase in the activity of enzymes related to enzymatic
browning (Rolle and Chism, 1987; Brecht, 1995; Artés et al.,
1998; Saltveit, 2003).
Temperature control is the most common and important
technology to minimize the effects of cutting in fruit and vegetables (Brecht, 1995; Cantwell, 1996; Watada et al., 1996).
Whole and sliced carrots kept at 0 and 10 ◦ C demonstrate the
importance of low temperatures for the reduction of respiration, and consequently metabolism. Whole carrots produced
1.0 and 1.4 ␮g kg−1 s−1 of CO2 at 0 and 10 ◦ C, respectively,
which represents an increase of 40.54% in respiration at
10 ◦ C, while carrot slices produced 1.7 and 3.0 ␮g kg−1 s−1
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J.S. del Aguila et al. / Postharvest Biology and Technology 40 (2006) 149–154
of CO2 at 0 and 10 ◦ C, respectively, which represents an
increase of 66.67% in respiration at 10 ◦ C. Sliced carrots
showed an increase of 62.2 and 92.3% in respiration rate compared to whole carrots, at 0 and 10 ◦ C, respectively (Cantwell,
1992). Furthermore, Vitti et al. (2004) have observed that respiration rate of fresh-cut beets stored at 15 ◦ C was two times
higher than that observed at 5 ◦ C.
Among many fruit and vegetable crops processed in
Brazil, radish is increasing in importance, being an important component of many mixed salads, and a relatively good
source of vitamin C. Fresh-cut radish has had little study with
respect to storage and preparation mode. In this study, different cut types and storage temperatures were investigated
in an attempt to maintain the quality and enhance the storage
period of radish minimally processed.
2. Materials and methods
2.1. Plant material
Bunched radishes (Raphanus sativus L., CV. Crimson
Gigante) obtained from a producer in Piracicaba, SP, Brazil,
were use for this study. The above-ground foliage was
removed from the bunched radishes, thus obtaining topped
radishes. The product was sorted for uniform appearance,
size and absence of physical and pathological damage.
2.2. Minimal processing
Whole, topped radishes were pre-washed in running water
to remove impurities, and after drying, were stored at 10 ◦ C
for 12 h before minimal processing.
Radishes were submitted to the following cut types: shred
cut (approximately 2 mm for 20 mm), slice cut (2 mm thick)
and without cut (whole radish). The radishes were cut with an
industrial processor (Robot Coupe CL50 version D). Minimal processing was carried out at 15 ◦ C. Treatments were
washed in a 200 mg L−1 chlorine solution for 3 min, rinsed
for 1 min to remove the excess chlorine and, finally, centrifuged at 800 × g for 1 min to remove excess water.
Fresh-cut and whole radishes were placed in expanded
polystyrene trays (130 g in each 14 cm × 20 cm tray),
wrapped in 14-␮m thick polyvinyl chloride (PVC) film and
stored in cold chambers at 1 ± 1, 5 ± 1 or 10 ± 1 ◦ C and
90 ± 5% RH for 10 d.
lids to allow the collection of a 1 mL of internal atmosphere.
Gas samples were analyzed in a gas chromatograph (Thermoffinigan, model Trace 2000 GC). Results in % CO2 were
used in the calculation of the respiration rate, which considered the flask volume, the radish mass and the time the flask
was closed. The respiration rate was determined within 5 h
after minimal processing, by means of four readings, the first
of which (time zero) was carried out 1 h after processing.
Subsequent readings were conducted daily for 10 d. Results
were expressed as the production rate of CO2 in ␮g kg−1 s−1 .
The procedures to determine ethylene production were the
similar to those used for respiration rate analysis. Internal
atmosphere readings were analyzed with a gas chromatograph (Thermoffinigan, model Trace 2000 GC) equipped with
flame ionization detector (FID) with column Porapack N, of
2 m of length. The injector, column, and detector temperatures were 100, 100 and 250 ◦ C, respectively, and with H2
carrier gas flow of 0.40 mL s−1 . The production rate of C2 H4
was expressed in ng kg−1 s−1 .
The soluble solids concentration (SSC) was determined
by direct reading of centrifuged fresh-cut in a digital refractometer (Atago PR-101, Atago Co. Ltd., Tokyo, Japan) with
the results expressed in percentage (%). Titratable acidity
(TA) was determined from 10 g of puree diluted with 90 mL
of water, titrated with 0.1N NaOH to pH 8.1 and expressed
in percentage of malic acid (Carvalho et al., 1990), once this
acid represents approximately 80% of the total organic acids
presents in radish (Wang, 1998). Ascorbic acid content was
determined by titration (Carvalho et al., 1990) and the results
expressed in mg kg−1 . The weight loss was the difference
between the initial and the final mass of each replicate and
the results were expressed in %. Lightness (L* ), was determined using a colorimeter (Minolta CR-300, Osaka, Japan).
A decrease of L* value indicated a loss of whiteness (brightness). Readings were conducted directly on the minimally
processed products and on the whole radish just after cutting.
2.4. Data analysis
The data were subjected to analysis of variance and the
least significant differences were calculated using SAS software for the completely randomized experimental design
with five replicates for each day of analysis. Differences
between any two treatments greater than the sum of two standard deviations were always significant (P > 0.05).
2.3. Assessments
3. Results and discussion
The evaluations of respiration rate and ethylene production were carried out daily, while for the other variables the
evaluations were carried out every second day. To determine
respiration rate, 130 g of minimally processed or whole radish
were placed in 580 mL glass flasks and hermetically sealed
for 1 h at different temperatures (1 ± 1, 5 ± 1 or 10 ± 1 ◦ C
and 90 ± 5% RH). A silicone septum was fitted in the flask
At all temperatures used the maximum respiration rate
was observed just 1 h after processing (Fig. 1) with subsequent decrease through the final evaluation (4 h). This initial
increase of respiration was due to the stress caused by cutting, which promotes the uncontrolled mixing of cellular
components, or through controlled cellular repair mechanism
(Saltveit, 2003). The subsequent decrease in the respiration
J.S. del Aguila et al. / Postharvest Biology and Technology 40 (2006) 149–154
Fig. 1. Respiration rate of evolved CO2 (␮g kg−1 s−1 ) in whole, shredded
and sliced radish just after processing, during cold storage at 1 ◦ C (A), 5 ◦ C
(B) and 10 ◦ C (C). Vertical bars represent ±S.D. (n = 5).
rate after 1 h is probably due to the self-regulation of the
tissue respiratory activity caused by the great production of
ATP (Purvis, 1997). It is also possible that such reduction
in the respiration rate happens because respiratory substrates
stop reacting with the enzymes of the cells present in the cut
surface. Therefore, the respiration rate observed after 1 h, is
probably caused by cells injured by the cut lying below the
surface. Preliminary tests had verified this statement.
Significant differences in respiration rate between shredded and sliced cut were obtained at the temperatures of 1 and
5 ◦ C 1 h after processing (Fig. 1A and B). Also, shredded
radish showed higher respiration than whole radish throughout the 4-h period. At 10 ◦ C whole radish showed lower
respiration rate than minimally processed radish throughout
the 4-h period of evaluation (Fig. 1C). The response of tis-
151
Fig. 2. Respiration rate of evolved CO2 (␮g kg−1 s−1 ) of whole, shredded
and sliced radish during cold storage at 1 ◦ C (A), 5 ◦ C (B) and 10 ◦ C (C).
Vertical bars represent ±S.D. (n = 5).
sue to processing wounds usually increases as the severity
of the injury increases (Brecht, 1995; Saltveit, 2003). This
can explain the differences observed in the respiration rate
between whole and shredded radish and between shredded
and sliced radish. During cold storage the respiration rate of
whole radish remained stabile, while oscillations in fresh-cut
radishes were observed. Respiration was generally higher in
shredded radish (Fig. 2).
There was no detectable ethylene production up to 9 h
after processing. After 9 h, ethylene production was higher in
shredded and sliced radish compared to whole radish (Fig. 3).
No ethylene was detected 12 h after processing. Ethylene
production is another response of vegetables to wounding
(Abeles et al., 1992; Sakr et al., 1997). Thus, the increase
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Fig. 3. Ethylene production rate (ng kg−1 s−1 ) in whole, shredded and sliced
radish after 9–12 h at 1 ◦ C (A), 5 ◦ C (B) and 10 ◦ C (C). Vertical bars represent
±S.D. (n = 5).
in ethylene production may be attributed to the biosynthesis of wound ethylene (Abeles et al., 1992). In radish, the
ethylene production response to injury appears to be retarded
if compared to other fresh-cut underground storage organs.
For example, in shredded beets ethylene (0.22 ng kg−1 s−1 )
was detected after 1 h of processing (Vitti et al., 2004). In
relation to storage temperature it was verified that ethylene
production was higher with increase of temperature. Freshcut radish produced C2 H4 at 0.03–0.08 ng kg−1 s−1 at 1 ◦ C,
0.10–0.13 ng kg−1 s−1 at 5 ◦ C and 0.17–0.22 ng kg−1 s−1 at
10 ◦ C.
Weight loss increased as a function of storage time and
temperature (Fig. 4), but it did not increase as a function of
cut type. At 1 and 5 ◦ C, weight loss was 2–3% at the end of
10 d of storage, while at 10 ◦ C the weight loss was about 5%.
Shredded radish lost more soluble solids than sliced and
whole radish (Fig. 5). Shredded radish lost 2.2% during 10 d
Fig. 4. Weight loss (%) of whole, shredded and sliced radish during cold
storage at 1 ◦ C (A), 5 ◦ C (B) and 10 ◦ C (C). Vertical bars represent ±S.D.
(n = 5).
of cold storage, while the loss observed in whole and sliced
was 0.43 and 1.1%, respectively. This decrease in soluble
solids can be attributed, partially, to the consumption of carbohydrates in respiration related to the repair of injury. In
addition, the higher injured area of shredded radish may have
caused an amplification of the response to the injury.
There were no differences in acidity among cut types and
storage temperatures. The values of malic acid have varied
from 0.05 to 0.06% (data not shown).
Ascorbic acid content decreased in shredded radish stored
at 10 ◦ C (Fig. 6) from 220.45 to 30.01 mg kg−1 after 10 d
of storage. Whole and sliced radish showed essentially no
reduction of ascorbic acid during storage at both temperatures. Ascorbate is the most important antioxidant molecule
J.S. del Aguila et al. / Postharvest Biology and Technology 40 (2006) 149–154
Fig. 5. Soluble solids (SS) of whole, shredded and sliced radish during cold
storage at 1 ◦ C (A), 5 ◦ C (B) and 10 ◦ C (C). Vertical bars represent ±S.D.
(n = 5).
in plants, having a vital role in the removal of H2 O2 through
the glutathione–ascorbate cycle (Noctor and Foyer, 1998).
The content of ascorbic acid in most vegetables decreases
when bruising, trimming and cutting occurs (Lee and Kader,
2000). In the present study, the severity of injury has contributed to the large decrease of this antioxidant. The content of ascorbic acid in fresh-cut produced during storage
is affected by both biosynthesis and degradation reactions.
Thus, the decrease in ascorbic acid in the shredded radish does
not necessarily mean a lack of ascorbic acid biosynthesis, but
concomitant consumption of this antioxidant by browning
reactions.
The last explanation can be related to the values of L*
verified in shredded radish (Fig. 7). At all temperatures there
was a decrease of L* , which indicated a loss of whiteness of
shredded radish just after 2 d of storage. No difference was
observed in the L* value between whole and sliced radish
during cold storage at the temperatures studied.
Processing injury induces many physical and physiological responses. Most of these changes are unwanted and contribute to decreasing product quality. Temperature is the main
153
Fig. 6. Ascorbic acid of whole, shredded and sliced radish during cold storage at 1 ◦ C (A), 5 ◦ C (B) and 10 ◦ C (C). Vertical bars represent ±S.D. (n = 5).
technique postharvest to preserve the quality of fruit and vegetables. In fresh-cut commodities, the use of low temperature
from preparation to the marketing is essential, considering
that several reactions are triggered by the processing injury
and many of these reactions are amplified by an increase in
temperature. Temperature of 5 ◦ C has been indicated for cold
storage of fresh-cut produce. Shredded and sliced are the
main forms of commercial fresh-cut radish in Brazil. However, in many cases the product is marketed at temperature
of 10–15 ◦ C. In this trial, quality differences were observed
between these cut types, mainly when the storage temperature
was 10 ◦ C.
In this study, few quality differences were observed
between 1 and 5 ◦ C in minimally processed radish, while
10 ◦ C contributed to the loss of quality of the product. At this
temperature, the loss of ascorbic acid (vitamin C) was high in
shredded radish compared to the lowest temperatures. Respiration and ethylene were also higher at 10 ◦ C, denoting a
higher metabolism and, consequently, higher consumption
of reserves. On the other hand lower temperature (1 or 5 ◦ C)
showed decreases in metabolism, thus preserving fresh-cut
radish quality.
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