Post on 23-Feb-2022
ISSN 1226-8763
Kor. J. Hort. Sci. Technol. 33(3):364-374, 2015 http://dx.doi.org/10.7235/hort.2015.14042
Research Report
Effects of a Combined Treatment of Hot Water with Green Tea Extract and
NaCl on the Postharvest Quality of Fresh-cut Burdocks
Min-Sun Chang and Gun-Hee Kim*
Department of Food and Nutrition, Duksung Women’s University, Seoul 132-714, Korea
Abstract: This study investigated quality changes in fresh-cut burdocks treated with hot water and anti-browning agents. The
combined treatment using both heat treatment and anti-browning agents delayed the browning of burdocks, especially for those
dipped in hot water and a solution of green tea extract plus NaCl. This treatment reduced the respiration rate and inhibited
the growth of microorganisms more than heat treatment alone. The organoleptic quality of burdocks treated with the combined
method proved to be the best according to sensory evaluation. Hence, this combined treatment using heat and anti-browning
agents can enhance overall quality of processed fresh-cut root vegetables by browning inhibition and shelf-life extension.
Additional key words: antioxidant, browning, heat treatment, shelf life
*Corresponding author: ghkim@duksung.ac.kr
※ Received 10 March 2014; Revised 26 August 2014; Accepted 5 September 2014. This work was carried out with the support of “Cooperative
Research Program for Agriculture Science and Technology Development (PJ0074812012)” Rural Development Administration, Republic of
Korea and in part from the Priority Research Centers Program through the National Research Foundation of Korea (NRF) funded by the
Ministry of Education Science and Technology (2009-0094017).
Ⓒ 2015 Korean Society for Horticultural Science
Introduction
The popularity of minimally-processed vegetables has
been increased due to not only their health benefits as
the fresh produce, but also the consumer demand as the
convenience fresh-cut products. Fruits and vegetables are living
organisms showing quick quality losses due to physiological
aging, biochemical changes, increase in respiration rate,
and the proliferation of microorganisms during processing
and distribution (Martin-Belloso et al., 2007). In particular,
the browning on the surface from cutting and peeling causes
the quality loss for fruits and vegetables (Lunadel et al.,
2011; Pristijono et al., 2006). It has been variously approached
to prevent the browning of fresh-cut fruits and vegetables,
such as citric acid, ascorbic acid (Sapers and Miller, 1998;
Dong et al., 2000), and oxalic acid (Son et al., 2001) as the
reducing agent, and calcium. In addition, sulfite-containing
additives have been extensively used as anti-browning
agents to keep vegetables and fruits looking fresh. However,
consumer awareness of the risks associated with sulfites
and increased regulatory scrutiny has created the urgent
need for substituting those chemical treatments (Iyengar
and McEvily, 1992).
Green tea (Camellia sinensis L.) is a popular beverage
exerting the beneficial effects on several diseases due to
their antioxidant, anticancer, and antimicrobial activities
(Si et al., 2006; Rietveld and Wiseman, 2003; Cooper et
al., 2005). Green tea is an excellent source of polyphenols,
natural antioxidants used as alternatives to synthetic anti-
oxidants (Martín-Diana et al., 2008). These antioxidants,
which inhibit the oxidation of organic molecules, are very
important for food preservation (Masuda et al., 2003).
Green tea has been used to extend the shelf-life of candy
jellies (Gramza-Michalowska and Regula, 2007) and cooked
pork patties (Nissen et al., 2004). However, only a few
studies can be found on the use of green tea in fresh-cut
fruits or vegetables. NaCl is a food preservative and commonly
used in most culinary habits. It binds water satisfactorily,
thus rendering it unavailable for microbial growth on food
products (Ehabe et al., 2006). In addition, it has been used
Min-Sun Chang and Gun-Hee Kim 365
to inhibit the browning of fruits and vegetables at home.
The heat treatment is able to inhibit the browning of
plants after harvest without using chemicals (Zuo et al.,
2004), and can be easily applied to fruits and vegetables
by using either hot water dips, vapor heat, or hot dry air.
Moreover, it costs less, and is easily able to be scaled-up
for commercialization (Silveira et al., 2011; Hofman et al.,
2002). The heat treatment can be positively applied for
fruits to improve the storability and marketability as it
can inhibit the ripening of fruits (Dea et al., 2010; Lurie
1998). They have been successfully used in the Amarillo
melon (Aguayo et al., 2008), mangoes (Djioua et al., 2009),
rocket leaves (Koukounaras et al., 2009) and shredded
carrots (Alegria et al., 2010). This method was also reported
to reduce growth phenomena, including sprout development
in potatoes (Ranganna et al., 1998), and has been considered
as an environmentally-friendly method for prolonging the
shelf life of minimally processed products (Hong et al.,
2000; Luna-Guzmán et al., 1999).
Burdock (Arctium lappa L.) is a root vegetable used as
a folk medicine, diuretic, and antipyretic (Kan, 1981; Chen
et al., 2004). Several studies have reported that the root
of burdock possesses various pharmaceutical activities,
including antibacterial activity (Chow et al., 1997), antioxidant
activity (Duh, 1998), and anti-inflammatory activity (Lin
et al., 1996). Hence, its demands have been increased, but
more considered processed ones due to its inconvenience
in handling. In addition, little is known about burdock
physiology and its shelf life when processed into fresh-cut
burdock slices in order to commercialize a high quality
product with an acceptable shelf life as the marketable
standard.
This study aimed to evaluate the effect of combined
treatment applying heat, green tea extract, and salt for
preventing browning and remaining the quality of fresh-cut
burdocks while storing at low temperature.
Materials and Methods
Plant Materials
Burdocks (Arctium lappa L.) were harvested from Bongwha-
gun, Gyeongsangbuk-do, Korea, transported to the laboratory,
and stored at 4°C overnight before processing. Burdocks
were selected based on their uniformity of size, color, and
defects-free.
Green Tea Extract Preparation
Dried green tea (Camellia sinensis) was purchased from
the medicine market in Seoul. Fifty-gram of the powdered
sample was then extracted three times with 80% ethanol
at 60°C for 6 h. After combining all extracts and evaporating
(Rotary Vacuum Evaporator, EYELA, Japan), the freeze-dried
powder was used in the experiment.
PPO Inhibitory Activity of Green Tea Extract
The assay was carried out by reacting 1.7 mL of phosphate
buffer (pH 6.5, 50 mM), 0.1 mL of substrate (1%) and 0.2
mL of polyphenol oxidase (PPO) (500 units/mg). The increase
in absorbance at 420 nm was monitored at 30 s intervals
for 5 min, using a microplate reader (M2, Molecular Device,
Canada) and the average change in absorbance per min was
calculated. One unit of enzymatic activity was defined as the
amount of enzyme causing a change of 0.1 in absorbance/min
(Dennis and Miller, 1998).
PPO inhibition activity (%) = (1-A/B) × 100
(A: absorbance of sample, B: absorbance of blank)
DPPH Radical Scavenging Activity of Green Tea Extract
1,1-diphenyl-2-picryhydrazyl (DPPH) radical scavenging
activity was analyzed by using a modification of the method
by Loizzo et al. (2010). Using 96-well microtitre plate,
reaction mixtures containing 50 µL of 0.1% sample and
150 µL of 0.3 mM DPPH were placed for 10 min at room
temperature. The reacted mixtures were recorded at 517
nm.
DPPH radical scavenging activity (%) = (1-A/B) × 100
(A: absorbance of sample, B: absorbance of blank)
Copper Chelating Activity of Green Tea Extract
The copper binding capacity of extracts was determined
according to the method of Wettasinghe and Shahidi (2002)
with a slight modification. Tetramethylmurexide (1 mM・L-1
)
and CuSO4 solutions (5 mM・L-1
) were prepared in 10 mM・L-1
hexamine-HCl buffer (pH 5.0) containing KCl (5 mM・L-1
).
Absorbance of the reaction mixtures was record at 460
and 530 nm and the ratio of A460 to A530 nm was calculated.
These absorbance ratios were then converted to corresponding
free Cu2+
concentrations using a standard curve of free Cu2+
concentration vs absorbance ratio. The difference between
the total Cu2+
and the free Cu2+
concentrations indicated
the concentration of chelated Cu2+
. Copper chelating activity
was calculated using the following equation :
Chelating capacity activity (%) = (1-A/B) × 100
(A: absorbance of sample, B: absorbance of blank)
Kor. J. Hort. Sci. Technol. 33(3), June 2015366
Treatments
Burdocks were washed with running tap water to remove
the soil. Then they were peeled and cut into about 3 mm
thick slices using a sharp ceramic knife. Each burdocks
slice was dipped in the following solutions for 45 sec at
55°C (the selected heat treatment condition through the
preliminary experiment) : 0.5% green tea extract, 1% NaCl
(sodium chloride, > 99.5%, Sigma-Aldrich Corp., St. Louis,
Mo., USA), and 0.5% green tea extract + 1% NaCl. Dipping
in water (without browning inhibitors) at 55°C for 45 sec
was used as a control treatment. After dipping, each burdock
slice was kept over a plastic sieve and dried. 80 ± 5 g
of untreated and treated burdock slices were packaged
in polyethylene film bags (150 × 200 mm) of 30 µm and
sealed. The samples were stored at 4°C for 8 days and
weight loss, color, respiration rate, microorganisms, and
sensory characteristics were measured.
Weight Loss Rate
Bags were weighed at 0 day and each sampling day
during the storage period. Results were expressed as
percentage of weight loss relative to the initial weight at
0 day, and the weight loss rate (%) was calculated using
the following equation.
Weight loss rate (%) = [(W1 - W2) / W1] × 100
(W1: Initial weight, W2: Weight after storage)
Color
Color measurements were taken with a reflectance Chroma
Meter (CR-400, Minolta Co., Japan) on the cut surface of
burdock slices. There were ten measurements made per
treatment and color determined by measuring Hunter L,
a, and b values. The chromaticity difference of each treatment
was analyzed using color difference (△E) with the calculation
shown below. The Chroma Meter was calibrated on a
standard white tile (L = 97.40, a = -0.49 and b = 1.96)
before each series of measurements.
△E = (△L2 + △a
2 + △b
2)
1/2
Respiration Rate Measurement
Respiration rates of the burdocks were measured using
a closed system method (Hong et al., 2007). The 80 ±
5 g of burdock slices were taken at random from each
treatment, placed into airtight glass jars (1 L) with silicon
samplings ports and tightly sealed. Jars were stored at
4°C and a 1 mL gas sample from the headspace was taken
periodically through an airtight septum and analyzed by
an Oxygen Carbon Dioxide Headspace Analyzer (Model 6,600,
Illinois Instrument Inc., USA). The mean value was calculated
from the samples for each treatment.
Microbiological Analysis
To determine microbial load, a 10 g sample was mixed
with 90 mL saline solution in a sterile stomacher bag and
shaken for 1 min. Dilutions were made in 0.85% saline
solution as needed for plating. Plate count agar (PCA, Difco
Lab., USA) was used as the media for mesophilic aerobic
counts and Chromocult agar (CM, Merck Co., Germany)
was used as the media for coliform group counts. Prepared
dishes were incubated at 35°C for 48 h. The microbial
counts were expressed as log10 CFU/g. All measurements
were performed in three replicates.
Sensory Evaluation
A panel of ten people was trained to recognize and score
the quality attributes of the treated burdock slices. Appearance,
odor and texture were scored on a nine-point scale, where
1 = complete lacking or soft and 9 = fully characteristic of
fresh. On a similar scale for evaluating overall acceptability,
1 = inedible, 3 = poor, 5 = fair (limit of marketability),
7 = good and 9 = excellent.
Statistical Analysis
Statistical analysis of the data was performed using the
SPSS Win program (Version 12.0, SPSS Inc., Chicago, USA).
Analysis of variance (ANOVA) with Duncan’s multiple range
test was used to test the significance of differences among
means. Significance was accepted at p < 0.05. Three inde-
pendent trials were carried out.
Results and Discussion
Inhibition of Enzyme Activity and Antioxidant Activity of Green Tea Extract
Green tea extract showed high PPO inhibitory activity
(79.88%) (Table 1). The flavonoids present in green tea
is mainly catechins (flavan-3-ols) (Cabrera et al., 2006).
Catechin was probably acted as a competitive inhibitor
for PPO because of its structural similarity, which was able
to substrate for PPO (Nirmal and Benjakul, 2009). Green
tea extract, containing phenolic compound could be used
as the natural inhibitor against PPO.
DPPH is used as a free radical to evaluate antioxidant
activity of some natural sources, and the degree of its
Min-Sun Chang and Gun-Hee Kim 367
Table 1. PPO inhibitory activity, DPPH radical scavenging activity, and copper chelating activity of green tea extract.
Green tea extractzy
Ascorbic acidy
PPO inhibitory activity (%) 79.88 ± 1.73 19.35 ± 0.95
DPPH radical scavenging activity (%) 78.68 ± 0.89 95.12 ± 0.23
Copper chelating activity (%) 45.93 ± 2.25 90.64 ± 0.51zFifty-grams of dried green tea was extracted three times with 80% ethanol at 60°C for 6 h.yThe concentration was 0.1%.
Fig. 1. Weight loss rate of fresh-cut burdocks dipped in hot
water and browning inhibitors at 4°C (CT, control; HW, hot
water at 55°C; HW + GT, hot water at 55°C + 0.5% green
tea extract; HW + N, hot water at 55°C + 1% NaCl; HW
+ GT + N, hot water at 55°C + 0.5% green tea extract +
1% NaCl). Vertical bars represent ± SE of the means (n
= 5).
discoloration is attributed to hydrogen donating ability
of test compounds, indicating their scavenging potentials
(Shimada et al., 1992). DPPH radical scavenging activity
of green tea extract was 78.68% (Table 1). Green tea extract
was the potential free radical scavengers, as donating their
hydrogens and acted as primary antioxidants.
Green tea extract exhibited high copper chelating activity
(45.93%) (Table 1). Commercial catechin had the lowest
copper chelating activity. Due to copper chelating activity
of extracts, they could inhibit PPO by chelating Cu (II)
in the active site of PPO, thus leading to the lowered PPO
activity (Nirmal and Benjakul, 2011). The capacity of phenolic
compounds for chelating metals is strongly dependent on
the number of hydroxyl groups in ortho position (Maqsood
and Benjakul, 2010). PPO is one of the metalloproteins
with two copper atoms in the active site (Jang et al., 2003).
The copper chelating activity of extracts was in accordance
with PPO inhibitory activity.
Weight Loss Rate
The weight loss is a crucial quality parameter in the
economic stand point of view. In addition, the weight loss
strongly impacts appearance as it causes the shrinkage. The
weight loss of non-heat treated burdocks was compared
to burdock dipped in green tea extract and NaCl with heat
treatment during the storage period (Fig. 1). The use of heat
treatment with green tea extract and NaCl as anti-browning
agents induced to slow down the weight loss during the
storage period. For non-heat-treated samples, the weight
loss was 0.14% at 8 days of storage period in comparison
with the initial weight. Throughout storage, the weight
loss of non-heat-treated burdock slices was significantly
(p < 0.05) higher than heat-treated burdock slices (2-3.5
times higher). It was reported that the increased weight
loss is potentially associated with transpiration rate through
the microscopic cracking occurring on the fruit and vegetable
surface (Hong et al., 2007). If too much water is transported
from the fruit and vegetable turgidity is able to be reduced,
and even appeared slightly shriveled. The heat treatment
had a significant effect on reducing weight loss during
the storage period, compared to non-heat-treated samples.
Similar results have been reported for hot water treatments
applying to grapefruit (Porat et al., 2000) and minimally
processed leeks (Tsouvaltzis et al., 2006). In hot water
with the 0.5% green tea extract and 1% NaCl combination
solution, samples showed the lowest weight loss (0.04%)
at day 8 of storage period, whereas hot water with 0.5%
green tea extract or 1% NaCl reached 0.05%. The presence
of hydrophobic ingredients in the green tea extract and
NaCl as edible coating could be the potential reasons
decreasing the water vapor permeability of the surface,
thus restricting water transfer.
Color
Color is a critical quality of fresh-cut fruits and vegetables,
since cutting operations often lead to enzymatic browning
(Oms-Oliu et al., 2010). Color changes are also caused from
the wound-induced response due to the peeling and slicing
(Siomos et al., 2010). The L value, generally depending
Kor. J. Hort. Sci. Technol. 33(3), June 2015368
A
B
C
Fig. 2. Changes in the Hunter L (a), a (b), and b (c) value
of fresh-cut burdocks dipped in hot water and browning
inhibitors at 4°C (CT, control; HW, hot water at 55°C; HW
+ GT, hot water at 55°C + 0.5% green tea extract; HW +
N, hot water at 55°C + 1% NaCl; HW + GT + N, hot water
at 55°C + 0.5% green tea extract + 1% NaCl). Vertical bars
represent ± SE of the means (n = 15).
on the surface reflectivity, is used to express the luminosity
of the sample surface, and the a and b values indicate
chromaticity on a green (-) to red (+) axis and blue (-)
to yellow (+) axis, respectively (Du et al., 2009).
Changes in surface color of non-heat-treated were compared
with heat-treated burdock slices, with and without treatments
of anti-browning agents, during the storage period. The
L and b values were decreased with extending the storage
period (Fig. 2a and 2c), which can be related to the appearance
of browning. The higher the L value of burdock slices,
the brighter the surface. The L value of the hot water
+ 1% NaCl sample and non-hot water-treated sample were
73.67 and 67.13, respectively, at 8 days of storage period (Fig.
2a). It is believed that the NaCl is interacted with the copper
at the active center of the enzyme (Iyengar and McEvily,
1992; Sapers, 1993). Several works have been reported
the effect of NaCl on PPO activity. Luh and Phithakpol
(1972) claimed that a 3% sodium chloride solution (0.51
M) is used as an inhibitor to hinder enzymatic browning
in cling peaches. Therefore, the combined treatment of hot
water with anti-browning agents was effective for inhibiting
the browning on the surface of burdock slices. In addition,
the darkening effect associated with decreased L values
may have been linked to fruit and vegetable dehydration
(Lydakis and Aked, 2003).
Generally the a value of burdock slices increased during
the storage period, and the a value of the controls was
highly increased in comparison with other treatments (Fig.
2b). The dipping hot water + adding 0.5% green tea extract
+ adding 1% NaCl treatment samples reported the slowest
trend during storage. As a result, the combined treatment
contributed to a slower accumulation of red color on the
burdock slices and delayed the browning of burdocks,
especially when slices were dipped in a hot water and 1%
NaCl combination solution. Polyphenol oxidase (PPO), a
key enzyme responsible for browning in fruits and vegetables
by catalyzing the oxidation of phenolic compounds, results
in this formation of colored melanins (Budu and Joyce,
2003). Green tea extract had a very high PPO inhibitory
activity and it seemed to help for the reduction of color
changes of burdocks.
The color difference (△E) was calculated with the collected
L, a, and b values. According to the measurement results,
the △E value was generally higher in the non-heat-treated
burdocks than the heat-treated burdocks (Fig. 3). In addition,
the △E value was 3.28 for the burdock slices that were
treated with combined heat, green tea extract, and NaCl,
showing the smallest change in color. The discoloration
was effectively prevented in the sample treated at 45 or
55°C optimally inhibiting PPO (Zuo et al., 2004). Moreover,
the combined effect of heat treatment and anti-browning
agents on the activities of PPO, POD, and pectin methylesterase
(PME) was better than control and thermal treatments
under the experiment conditions of this study. The burdock
slices that were heat-treated with browning inhibitors
showed the smallest change in color during the storage
period.
Min-Sun Chang and Gun-Hee Kim 369
Fig. 3. Changes in the color difference (△E) of fresh-cut burdocks
dipped in hot water and browning inhibitors at 4°C (CT,
control; HW, hot water at 55°C; HW + GT, hot water at
55°C + 0.5% green tea extract; HW + N, hot water at 55°C
+ 1% NaCl; HW + GT + N, hot water at 55°C + 0.5% green
tea extract + 1% NaCl).
Fig. 4. Changes in the respiration rate of fresh-cut burdocks
dipped in hot water and browning inhibitors at 4°C (CT,
control; HW, hot water at 55°C; HW + GT, hot water at
55°C + 0.5% green tea extract; HW + N, hot water at 55°C
+ 1% NaCl; HW + GT + N, hot water at 55°C + 0.5% green
tea extract + 1% NaCl). Vertical bars represent ± SE of the
means (n = 5).
Respiration Rate
Fresh-cut fruits and vegetables are living tissues, even
after treatment. Damaged plant tissues exhibit an increase in
respiratory rate (Rico et al., 2007). The respiration rate of
slices untreated and treated with hot water + anti-browning
agents is shown in Fig. 4. It was shown that all treatments
were increased in relation to the microbial growth and
general tissue deterioration. Especially, the respiration rates
in the non-heat-treated burdock slices were significantly
higher than that in heat-treated burdock slices (5 times
higher). Fallik et al. (1999) observed that the respiration
rate on bell peppers dipped in hot water (55°C for 12 s)
was significantly lower than that in untreated ones during
15 days of storage period at 7°C followed by 4 days at
16-18°C. This effect could be a physiological response to
heat shock. The samples treated with the hot water and
NaCl combination solution showed the lowest respiration
rates (5.09 mL CO2/kg・hr) at day 8 days of storage period,
while hot water-treated samples reached values of 6.97
mL C02/kg・hr. Similarly, Lamikanra and Watson (2004)
and Luna-Guzmán and Barrett (2000) found a reduction
in respiratory rates in fresh-cut cantaloupe melon treated
with CaCl2 and lactate, in terms of ripening, which delayed
the senescence as a result of the combined additive effects of
hot water dipping and calcium salts. Hence, the combination
of heat and anti-browning agents were very effective in
markedly reducing the respiration rate of burdocks.
Microbiological Analysis
The evolution of total microbial load during the storage
period of burdocks treated with green tea extract and NaCl
with hot water treatment is shown in Table 2. Initial
mesophilic aerobic count of 7.05 × 104 CFU/g was found
in the untreated control. When compared to non-treated
controls, the combination solution of hot water and anti-
browning agents detected mesophilic aerobic counts of 4.54
× 102
- 2.38 × 103 CFU/g. The decrease in the microbial load
produced by the heat treatment (by 3 logs) is in agreement
with Alegria et al. (2009) and Aguayo et al. (2008) where
total aerobic bacterial growth on fresh-cut Amarllo melon
pieces was reduced by dipping in hot water (60°C for 1
min). Heat treatment was effective for reducing microbial
count; furthermore, the heat treatment and anti-browning
agent combinations inhibited the growth of microorganisms
more effectively than heat treatment alone. In samples
from hot water supplemented with anti-browning agents,
there were low mesophilic aerobic counts (1.84-6.25 × 105
CFU/g) at 8 days of storage period, whereas samples with
hot water treatment alone were detected with 7.18 × 107
CFU/g. According to our results, heat treatment, followed
by adding green tea extract and NaCl, was successful for
controlling bacterial growth.
Similar results were observed in the reduction of coliform
group count on burdock slices (Table 3). Initial coliform
group count of 1.88 × 103 CFU/g was found in the untreated
control. When compared to non-treated controls, 4.79 ×
102 CFU/g were found in the hot water-treated sample,
and 1.13-2.57 × 101 CFU/g were found in samples that were
treated with hot water and anti-browning agents. Heat
treatment is an effective method for reducing microbial
Kor. J. Hort. Sci. Technol. 33(3), June 2015370
Table 2. Changes in the mesophilic aerobic counts of fresh-cut burdocks dipped in hot water and browning inhibitors at 4°C.
Values are given in CFU/g
Treatmentz
Storage period (days)
0 2 4 6 8
CT 7.05 × 104 Aa
yx2.49 × 10
5 Bc 8.08 × 10
5 Ba 7.85 × 10
6 Bab 7.18 × 10
7 Cc
HW 5.16 × 103 Aa 2.19 × 10
4 Bbc 2.98 × 10
5 Ba 2.86 × 10
5 Cb 8.12 × 10
6 Cb
HW + GT 2.38 × 103 Aa 1.19 × 10
4 Ba 1.32 × 10
4 BCa 3.52 × 10
4 BCa 1.84 × 10
5 Cab
HW + N 8.10 × 102 Aa 1.31 × 10
3 Bb 2.68 × 10
3 BCa 7.31 × 10
4 Db 2.12 × 10
5 CDc
HW + GT + N 4.54 × 102 Aa 8.05 × 10
3 Bb 2.84 × 10
3 BCa 1.59 × 10
5 Cab 6.25 × 10
5 Da
zTreatment: CT, control; HW, hot water at 55°C; HW + GT, hot water at 55°C + 0.5% green tea extract; HW + N, hot water
at 55°C + 1% NaCl; HW + GT + N, hot water at 55°C + 0.5% green tea extract + 1% NaCl. Burdocks were harvested in September.yValues with different capital letters (A-D) among burdocks of the same treatment are significantly different at p < 0.05 based
on Duncan’s multiple range test.xValues with different small letters (a-c) among burdocks on the same storage day are significantly different at p < 0.05 based
on Duncan’s multiple range test.
Table 3. Changes in the coliform group counts of fresh-cut burdocks dipped in hot water and browning inhibitors at 4°C.
Values are given in CFU/g
Treatmentz
Storage period (days)
0 2 4 6 8
CT 1.88 × 103 Aa
yx3.01 × 10
3 Ba 9.72 × 10
4 Ba 1.70 × 10
4 BCa 7.10 × 10
5 Ca
HW 4.79 × 102 Aa 3.85 × 10
2 Ba 6.59 × 10
3 Ba 7.74 × 10
3 Ca 1.40 × 10
3 Ca
HW + GT 2.57 × 101 Aa 4.41 × 10
2 ABa 1.17 × 10
3 BCa 1.83 × 10
3 CDa 1.00 × 10
3 Da
HW + N 2.19 × 101 Aa 1.31 × 10
1 ABa 1.87 × 10
2 Ba 1.44 × 10
3 Ca 1.42 × 10
3 Ca
HW + GT + N 1.13 × 101 Aa 1.07 × 10
2 Ba 3.66 × 10
2 BCa 1.89 × 10
3 BCa 6.56 × 10
3 Ca
zTreatment: CT, control; HW, hot water at 55°C; HW + GT, hot water at 55°C + 0.5% green tea extract; HW + N, hot water
at 55°C + 1% NaCl; HW + GT + N, hot water at 55°C + 0.5% green tea extract + 1% NaCl. Burdocks were harvested in September. yValues with different capital letters (A-D) among burdocks of the same treatment are significantly different at p < 0.05 based
on Duncan’s multiple range test.xValues with different small letters (a-c) among burdocks on the same storage day are significantly different at p < 0.05 based
on Duncan’s multiple range test.
counts and effectively inhibits the growth of microorganisms.
Heat treatment with green tea extract and NaCl seemed
to have a synergistic effect for controlling the microbial
growth of fresh-cut burdocks.
Sensory Evaluation
The overall quality and shelf life of fruits and vegetables
are reduced by several factors, including water loss, enzymatic
browning, texture deterioration, senescence processes, and
microbial growth (Rojas-Graü et al., 2008). Sensorial results
for appearance, odor, texture, and overall acceptability are
shown in Table 4. Ranking scores of all sensory attributes
were significantly different among samples (p < 0.05).
Untreated samples suffered from poor overall visual quality
and surface edge browning.
Appearance scores were decreased during the storage
period. At 8 days, burdock slices treated with hot water
+ green tea extract + NaCl scored the highest (5.5 score).
The odor of burdock slices was improved with heat treatment.
Moreover, heat treatment with green tea extract and NaCl
still was scored within the limit of marketability (5.0 score),
and they were no significant differences. Texture decreased
during the storage period, showing a similar trend with
appearance values. Texture also did not differ between
treatments at the beginning of the experiment, however,
other treatments had unacceptable scores for consumption
except of hot water + green tea extract + NaCl at 8 days
of storage period. The lowest texture score was scored (2.0)
Min-Sun Chang and Gun-Hee Kim 371
Table 4. Sensory evaluation of fresh-cut burdocks dipped in hot water and browning inhibitors at 4°C.
Attributesz
Treatmenty
Storage period (days)
0 2 4 6 8
Appearance CT 8.3 Aaxw
5.0 Ba 3.7 Ba 2.0 Bb 1.0 Ba
HW 8.7 Aa 7.0 ABa 6.0 ABa 5.3 Bab 3.0 BCa
HW + GT 8.7 Aa 7.5 ABa 7.0 Ba 6.0 ABa 4.0 Ba
HW + N 8.7 Aa 8.5 Ba 7.3 Ba 8.0 Bab 5.5 Ba
HW + GT + N 8.7 Aa 9.0 Ba 8.3 ABa 6.0 Bab 4.0 Ba
Odor CT 8.3 Aa 6.5 Aa 6.3 Ba 3.0 Ba 3.5 Ba
HW 8.0 Aa 6.5 ABa 7.0 Ca 3.7 BCa 4.0 Ca
HW + GT 8.7 Aa 6.5 ABa 7.0 BCa 4.3 BCa 5.0 Ca
HW + N 8.7 Aa 6.5 Aa 7.0 Ba 4.7 Ba 5.0 Ba
HW + GT + N 8.7 Aa 6.5 Aa 7.0 Ba 4.7 Ba 5.0 Ba
Texture CT 9.0 Aa 6.5 ABa 5.0 BCa 4.3 Ca 2.0 Ca
HW 9.0 Aa 8.0 ABa 6.0 BCa 5.7 Ca 4.0 Ca
HW + GT 9.0 Aa 8.0 ABa 6.3 ABa 6.3 Ca 3.5 Ca
HW + N 9.0 Aa 8.5 ABa 6.7 ABa 7.3 BCa 5.0 BCa
HW + GT + N 9.0 Aa 8.5 ABa 7.0 ABa 7.3 BCa 4.5 CDa
Overall acceptability CT 9.0 Aa 3.5 Bb 4.0 BCa 1.7 Ca 1.0 Ca
HW 9.0 Aa 7.0 ABab 5.3 BCa 4.5 Ca 3.0 BCa
HW + GT 9.0 Aa 8.0 ABa 7.0 BCa 5.3 Ca 4.5 Ca
HW + N 9.0 Aa 8.5 Bb 7.3 Ba 7.7 Ba 6.0 BCa
HW + GT + N 9.0 Aa 9.0 ABab 8.0 Ba 5.3 Ba 4.5 BazAppearance, odor and texture were scored on a nine-point scale, where 1 = complete lacking or soft and 9 = fully characteristic
of fresh. On a similar scale for evaluating overall acceptability, 1 = inedible, 3 = poor, 5 = fair (limit of marketability), 7
= good and 9 = excellent.yTreatment: CT, control; HW, hot water at 55°C; HW + GT, hot water at 55°C + 0.5% green tea extract; HW + N, hot water
at 55°C + 1% NaCl; HW + GT + N, hot water at 55°C + 0.5% green tea extract + 1% NaCl. Burdocks were harvested in September. xValues with different capital letters (A-D) among burdocks of the same treatments are significantly different at p < 0.05 based
on Duncan’s multiple range test.w
Values with different small letters (a-c) among burdocks on the same storage day are significantly different at p < 0.05 based
on Duncan’s multiple range test.
for the non-heat-treated sample. Texture is a critical quality
for consumer acceptability of fresh vegetables. Weigh loss
has a key role in stem texture, since tissue dehydration is
accompanied by increasing elasticity and fibrous structure
(Serrano et al., 2006). At the end of storage, general accep-
tability scored similar values for samples treated with hot
water + 0.5% green tea extract and hot water + 1% NaCl
(4.5 score). The hot water + 0.5% green tea extract + 1%
NaCl treated samples generated high overall acceptability
values (> 6.0). Browning is one of the main factors causing
these changes during the storage period, and it strongly
affects the extension of shelf life and consumer purchase
decisions in fresh-cut fruit (Oms-Oliu et al., 2010). The
organoleptic quality of burdocks treated hot water + green
tea extract + NaCl were the best in sensory evaluations.
There was a significant difference in appearance score
between non heat-treated and heat-treated burdocks (Fig.
3 and 5). Sample treated with hot water showed less change
in appearance than the non-heat-treated burdocks. Changes
in color and browning were especially found on the surface
of the non-heat-treated burdocks. Browning was present
mainly in the control sample (without the heat treatment),
and reduced in samples with a previous heat treatment.
Enzymatic browning was mainly present in control samples
Kor. J. Hort. Sci. Technol. 33(3), June 2015372
Fig. 5. Appearance after storage at 4°C of fresh-cut burdocks dipped in hot water and browning inhibitors (CT, control; HW,
hot water at 55°C; HW + GT, hot water at 55°C + 0.5% green tea extract; HW + N, hot water at 55°C + 1% NaCl; HW
+ GT + N, hot water at 55°C + 0.5% green tea extract + 1% NaCl).
without a thermal treatment. Thermal treatment at 50°C
probably inhibited the activity of phenylalanine ammonialyase
(PAL), the enzyme involved in the first step of the phenyl-
propanoid pathway leading to the production of the major
phenolic compounds and causing the browning (Pereyra
et al., 2005).
Conclusion
Hot water + 0.5% green extract + 1% NaCl treatment
could be used as natural postharvest treatments in fresh-cut
burdocks to delay postharvest browning and maintain quality.
Hot water treatment at 55°C lowered the increase in weight
loss rate of fresh-cut burdocks. The burdock slices with
heat treatment in green tea extract and NaCl also showed
a higher L value and lower △E value than the non-heat-
treated burdocks in storage. In addition, the heat-treated
burdocks had a lower respiration rate and showed a more
gradual speed of microorganism proliferation. The hot water
+ 0.5% green extract + 1% NaCl solution was effective
in reducing the browning of burdock slices. The use of
heat treatment and anti-browning agent combinations for
processing fresh-cut root vegetables may improve quality
through the inhibition of browning, extending the shelf
life for the products through an environmentally-friendly
technique.
Literature Cited
Aguayo, E., V.H. Escalona, and F. Artés. 2008. Effect of hot
water treatment and various calcium salts on quality of fresh-cut
‘Amarillo’ melon. Postharvest Biol. Technol. 47:397-406.
Alegria, C., J. Pinheiro, E.M. Goncalves, I. Fernandes, M. Moldão,
and M. Abreu. 2010. Evaluation of a pre-cut heat treatment
as an alternative to chlorine in minimally processed shredded
carrot. Innovative Food Sci. Emerg. Technol. 11:155-161.
Alegria, C., J. Pinheiro, E.M. Goncalves, I. Fernandes, M. Moldão,
and M. Abreu. 2009. Quality attributes of shredded carrot (Daucus
carota L, cv. Nantes) as affected by alternative decontamination
processes to chlorine. Innovative Food Sci. Emerg. Technol.
10:61-69.
Budu, A.S. and D.C. Joyce. 2003. Effect of 1-methylcyclopropene
on the quality of minimally processed pineapple fruit. Austral.
J. Exp. Agric. 43:177-184.
Cabrera, C., R. Artacho, and R. Giménez. 2006. Beneficial effects
of green tea-a review. J. Am. College Nutr. 25:79-99.
Chen, F.A., A.B. Wu, and C.Y. Chen. 2004. The influence of
different treatments on the free radical scavenging activity of
burdock and variations of its active components. Food Chem.
86:479-484.
Chow, L.W., S.J. Wang, and P.D. Duh. 1997. Antibacterial activity
of burdock. Food Sci. 24:195-202.
Cooper, R., D.J. Morré, and D.M. Morré. 2005. Medicinal benefits
of green tea: Part II. Review of anticancer properties. J. Altern.
Complement. Med. 11:639-652.
Dea, S., J.K. Brecht, M.C.N. Nunes, E.A. Baldwin. 2010. Quality
Min-Sun Chang and Gun-Hee Kim 373
of fresh-cut ‘Kent’ mango slices prepared from hot water or
non-hot water-treated fruit. Postharvest Biol. Technol. 56:171-180.
Dennis, D. and J.W. Miller. 1998. Enzymatic browning. In: Kinetics
of tyrosinase. J. Agric. Food Chem. 30:44-49.
Djioua, T., F. Charles, F. Lopez-Lauri, H. Filgueiras, A. Coudret,
M. Freire, M.N. Ducamp-Collin, and H. Sallanon. 2009. Improving
the storage of minimally processed mangoes (Mangifera indica
L.) by hot water treatments. Postharvest Biol. Technol. 52:221-226.
Dong, X., R.E. Wrolstad, and D. Sugar. 2000. Extending shelf
life of fresh-cut pears. J. Food Sci. 65:181-186.
Du, J., Y. Fu, and N. Wang. 2009. Effects of aqueous chlorine
dioxide treatment on browning of fresh-cut lotus root. LWT-
Food Sci. Technol. 42:654-659.
Duh, P.D. 1998. Antioxidant activity of burdock (Arctium lappa
Linne): Its scavenging effect on free-radical and active oxygen.
J. Am. Oil Chem. Soc. 75:455-461.
Ehabe, E.E., G.D. Eyabi Eyabi, and F.A. Numfor. 2006. Effect
of sugar and NaCl soaking treatments on the quality of sweet
banana figs. J. Food Eng. 76:573-578.
Fallik, E., S. Grinberg, S. Alkalai, O. Yekutieli, A. Wiseblum, R.
Regev, H. Beres, and E. Bar-Lev. 1999. A unique rapid hot
water treatment to improve storage quality of sweet pepper.
Postharvest Biol. Technol. 15:25-32.
Gramza-Michalowska, A. and J. Regula. 2007. Use of tea extracts
(Camellia sinensis) in jelly candies as polyphenols sources in
human diet. Asian Pacific J. Clinical Nutr. 16:43-46.
Hofman, P.J., B.A. Stubbings, M.F. Adkins, G.F. Meiburg, and
A.B. Woolf. 2002. Hot water treatments improve ‘Hass’ avocado
fruit quality after cold disinfestation. Postharvest Biol. Technol.
24:183-192.
Hong, G., G. Peiser, and M.I. Cantwell. 2000. Use of controlled
atmospheres and heat treatment to maintain quality of intact
and minimally processed green onions. Postharvest Biol. Technol.
20:53-61.
Hong, S.I., H.H. Lee, and D.M. Kim. 2007. Effects of hot water
treatment on the storage stability of Satsuma mandarin as a
postharvest decay control. Postharvest Biol. Technol. 43:271-279.
Iyengar, R. and A.J. McEvily. 1992. Anti-browning agents: Alternative
to the use of sulfites in foods. Trends Food Sci.Technol. 3:
60-64.
Jang, M.S., A. Sanada, H. Ushio, M. Tanaka, and T. Ohshima.
2003. Inhibitory effect of enokitake extract on melanosis of
shrimp. Fisheries Sci. 69:379-384.
Kan, W.S. 1981. Pharmaceutical botany. Natl. Res. Inst. Chinese
Med., Taiwan. p. 549.
Koukounaras, A., A.S. Siomos, and E. Sfakiotakis. 2009. Impact
of heat treatment on ethylene production and yellowing of
modified atmosphere packaged rocket leaves. Postharvest Biol.
Technol. 54:172-176.
Lamikanra, O. and M.A. Watson. 2004. Effect of calcium treatment
temperature on fresh-cut Cantaloupe melon during storage. J.
Food Sci. 69:468-472.
Lin, C.C., J.M. Lu, J.J. Yang, S.C. Chuang, and T. Ujiie. 1996.
Anti-inflammatory and radical scavenging effects of Arctium
lappa. Am. J. Chinese Med. 24:127-137.
Loizzo, M.R., R. Tundis, U.G. Chandrika, A.M. Abeysekera, F.
Menichini, and N.G. Frega. 2010. Antioxidant and antibacterial
activities on foodborne pathogens of Artocarpus heterophyllus
Lam. (Moraceae) leaves extracts. J. Food Sci. 75:291-295.
Luh, B.S. and B. Phithakpol. 1972. Characteristics of polyphenol
oxidase related to browning in cling peaches. J. Food Sci.
37:264-268.
Lunadel, L., P. Galleguillos, B. Diezma, L. Lleó, and L. Ruiz-Garcia.
2011. A multispectral vision system to evaluate enzymatic
browning in fresh-cut apple slices. Postharvest Biol. Technol.
60:225-234.
Luna-Guzmán, I. and D.M. Barrett. 2000. Comparison of calcium
chloride and calcium lactate effectiveness in maintaining shelf
stability and quality of fresh-cut cantaloupes. Postharvest Biol.
Technol. 19:61-72.
Luna-Guzmán, I., M. Cantwell, and D.M. Barrett. 1999. Fresh-cut
cantaloupe: effects of CaCl2 dips and heat treatments on firmness
and metabolic activity. Postharvest Biol. Technol. 17:201-213.
Lurie, S. 1998. Postharvest heat treatments. Postharvest Biol. Technol.
14:257-269.
Lydakis, D. and J. Aked. 2003. Vapour heat treatment of Sultanina
table grapes. II: Effects on postharvest quality. Postharvest Biol.
Technol. 27:117-126.
Maqsood, S. and S. Benjakul. 2010. Comparative studies of four
different phenolic compounds on in vitro antioxidative activity
and the preventive effect on lipid oxidation of fish oil emulsion
and fish mince. Food Chem. 119:123-132.
Martin-belloso, O., R. Soliva-fortuny, and G. Oms-oliu. 2007.
Fresh-cut fruits. In: Hui YH (Ed.), Handbook of Food Products
Manufacturing, p. 879-899. In: John Wiley and Sons (eds.).
Principles, Bakery, Beverages, Cereals, Cheese, Confectionary,
Fats, Fruits, and Functional Foods. New Jersey.
Martín-Diana, A.B., D. Rico, and C. Barry-Ryan. 2008. Green
tea extract as a natural antioxidant to extend the shelf-life of
fresh-cut lettuce. Innovative Food Sci. Emerg. Technol. 9:593-603.
Masuda, T., Y. Inaba, T. Maekawa, Y. Takeda, H. Yamaguchi,
K. Nakamoto, H. Kuninaga, S. Nishizato, and A. Nonaka. 2003.
Simple detection method of powerful antiradical compounds
in the raw extract of plants and its application for the identification
of antiradical plant constituents. J. Agric. Food Chem. 51:1831-
1838.
Nirmal, N.P. and S. Benjakul. 2011. Use of tea extracts for inhibition
of polyphenoloxidase and retardation of quality loss of Pacific
white shrimp during iced storage. LWT-Food Sci. Technol.
44:924-932.
Nirmal, N.P. and S. Benjakul. 2009. Melanosis and quality changes
of Pacific white shrimp (Litopenaeus vannamei) treated with
catechin during iced storage. J. Agric. Food Chem. 57:3578-3586.
Nissen, L.R., D.V. Byrne, G. Bertelsen, and L.H. Skibsted. 2004.
Kor. J. Hort. Sci. Technol. 33(3), June 2015374
The antioxidative activity of plant extracts in cooked pork
patties as evaluated by descriptive sensory profiling and chemical
analysis. Meat Sci. 68:485-495.
Oms-Oliu, G., M.A. Rojas-Graü, L.A. González, P. Varela, R.
Soliva-Fortuny, M.I.H. Hernando, I. Pérez Munuera, S. Fiszman,
O. Martín-Belloso. 2010. Recent approaches using chemical
treatments to preserve quality of fresh-cut fruit: A review.
Postharvest Biol. Technol. 57:139-148.
Pereyra, L., S.I. Roura, and C.E. del Valle. 2005. Phenylalanine
ammonia lyase activity in minimally processed Romaine lettuce.
LWT–Food Sci. Technol. 38:67-72.
Porat, R., D. Pavoncello, J. Peretz, S. Ben-Yehoshua, and S. Lurie.
2000. Effects of various heat treatments on the induction of
cold tolerance and on the postharvest qualities of ‘Star Ruby’
grapefruit. Postharvest Biol. Technol. 18:159-165.
Pristijono, P., R.B.H. Wills, and J.B. Golding. 2006. Inhibition of
browning on the surface of apple slices by short term exposure
to nitric oxide (NO) gas. Postharvest Biol. Technol. 42:256-259.
Ranganna, B., G.S.V. Raghavan, and A.C. Kushalappa. 1998. Hot
water dipping to enhance storability of potatoes. Postharvest
Biol. Technol. 13:215-223.
Rico, D., A.B. Martín-Diana, J.M. Barat, and C. Barry-Ryan. 2007.
Extending and measuring the quality of fresh-cut fruit and
vegetables: a review. Trends in Food Sci. Technol. 18:373-386.
Rietveld, A. and S. Wiseman. 2003. Antioxidant effects of tea:
Evidence from human clinical trials. J. Nutr. 133:3285S-3292 S.
Rojas-Graü, M.A., M.S. Tapia, and O. Martín-Belloso. 2008. Using
polysaccharide-based edible coatings to maintain quality of
fresh-cut Fuji apples. LWT-Food Sci. Technol. 41:139-147.
Sapers, G.M. 1993. Browning of foods: Control by sulfites,
antioxidants and other means. Food Technol. 47:75-84.
Sapers, G.M. and R.L. Miller. 1998. Browning inhibition in fresh-
cut pears. J. Food Sci. 63:342-346.
Serrano, M., D. Martinez-Romero, F. Guillén, S. Castillo, and
D. Valero. 2006. Maintenance of broccoli quality and functional
properties during cold storage as affected by modified atmosphere
packaging. Postharvest Biol. Technol. 39:61-68.
Shimada, K., K. Fujikawa, K. Yahara, and T. Nakamura. 1992.
Antioxidative properties of xanthan on the autoxidation of
soybean oil in cyclodextrin emulsion. J. Agric. Food Chem.
40:945-948.
Si, W., J. Gong, R. Tsao, M. Kalab, R. Yang, and Y. Yin. 2006.
Bioassay-guided purification and identification of antimicrobial
components in Chinese green tea extract. J. Chromatography
A, 1125:204-210.
Silveira, A.C., E. Aguayo, V.H. Escalona, and F. Artés. 2011.
Hot water treatment and peracetic acid to maintain fresh-cut
Galia melon quality. Innovative Food Sci. Emerg. Technol.
12:569-576.
Siomos, A.S., D. Gerasopoulos, P. Tsouvaltzis, and A. Koukounaras.
2010. Effects of heat treatment on atmospheric composition
and color of peeled white asparagus in modified atmosphere
packaging. Innovative Food Sci. Emerg. Technol. 11:118-122.
Son, S.M., K.D. Moon, and C.Y. Lee. 2001. Inhibitory effects
of various antibrowning agents on apple slices. Food Chem.
73:23-30.
Tsouvaltzis, P., A.S. Siomos, and D. Gerasopoulos. 2006. Effect
of hot water treatment on leaf extension growth, fresh weight
loss and color of stored minimally processed leeks. Postharvest
Biol. Technol. 39:56-60.
Wettasinghe, M. and F. Shahidi. 2002. Iron (II) chelation activity
of extracts of borage and evening primrose meals. Food Res.
Intl. 35:65-71.
Zuo, L., E.J. Lee, and J.H. Lee. 2004. Effect of hot water treatment
on quality of fresh-cut apple cubes. Food Sci. Biotechnol.
13:821-825.