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Research Article
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Minimally of Polyphenol Oxidase Activity and Controlling of Rotting and Browning of Longan Fruits cv. DAW by SO2 Treatment under Cold Storage Conditions
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Wilasinee Chitbanchong,
Vicha Sardsud,
Kanda Whangchai,
Rumphan Koslanund
and
Pitipong Thobunluepop
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ABSTRACT
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The effects of sulphur dioxide, in combination with, storage temperatures on postharvest decay, pericarp browning and physiological ultrastructure changed of the Longan fruit cv. daw were studied. The treatment of fresh the Longan fruit with SO2 fumigation combined with the suitable storage condition improved the overall the Longan fruit quality, especially on inner and outer peel tissue and aril color than no SO2 treatment, while no SO2 treatment showed the dark color of inner and outer peel of the Longan fruit was appeared, this was correlated with the increasing of polyphenol oxidase (PPO) activity. Moreover, the main factor affected Longan fruits quality was storage duration, the increasing of weight loss, pH value of both peel and aril, PPO activity, especially on the changing of dark-red color of peel was observed after long term of storage. However, the sulphite residues could detect immediately after SO2 treatment in all part of the Longan fruit, especially on peel tissue, but the residues was significantly decreased along the storage durations. On the other hand, Scanning Electron Microscope (SEM) evaluation found that the surface cracking was also impair the physiological function of the cuticle and increasing water permeability, which may cause water soaking at the inner side of the peel. The injured cell would accelerate the oxidation of phenolic substances and the oxidative products resulted in dark color of inner and outer peel. Therefore, the combination sulphur dioxide fumigation with controlling the optimum of storage temperature could control of postharvest decay and browning.
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How
to cite this article:
Wilasinee Chitbanchong, Vicha Sardsud, Kanda Whangchai, Rumphan Koslanund and Pitipong Thobunluepop, 2009. Minimally of Polyphenol Oxidase Activity and Controlling of Rotting and Browning of Longan Fruits cv. DAW by SO2 Treatment under Cold Storage Conditions. International Journal of Agricultural Research, 4: 349-361. DOI: 10.3923/ijar.2009.349.361 URL: https://scialert.net/abstract/?doi=ijar.2009.349.361
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INTRODUCTION
Longan (Dimocarpus longan Lour.) is a tropical fruit in the Spindaceae
family. In Thailand, the Longan is a most extensive production and one of the
most economically important fruits that has exported fresh Longan to China,
Hong Kong, Malaysia, Singapore, Indonesia and Canada (Tongdee,
1997). The cultivated areas are in the Northern region of Thailand. In the
year 2008, dried and especially fresh fruit of the Longan is mostly marketed
locally and export of the fruit has been increasing rapidly, the exported of
fresh Longan is about 168,286 tons and frozen Longan at 346 tons (Lin
el al., 2001). However, the quantity of domestic and export Longan
has been limited by its highly perishable nature, short storage life and susceptibility
to postharvest diseases, as a result of bacterial, yeast and fungal infections
(Tongdee, 1997). Color deterioration causes the fruit
to fetch a lower price at market and even be unmarketable (Smith
and McWilliams, 1978). Rapid pericarp browning during storage is the main
problem resulting in restrictions on the export of Longan to long-distant markets
(Sardsud et al., 1994). The fresh Longan fruit
could be stored for only 2-3 days at ambient temperature, which caused of discoloration
and disorder by postharvest disease including chilling injury and especially
on the pericarp browning (Martinez and Whitaker, 1995).
Pericarp browning has been attributed to oxidation of phenolics by PPO, producing
brown coloured by-products (Ferrar and Walker, 1996).
The PPO has been widely studied in various fruits such as apple, grape, litchi
and plum (Lin et al., 1994) but little is known
about the Longan.
For many years, the recommended method to control postharvest decay and prevent
pericarp browning in the Longan has been sulfur dioxide (SO2) treatment.
The use of SO2 fumigation has been the most effective practical postharvest
treatment for control of quality during storage (Deng et
al., 2005). It is currently commercially used in many countries. Recently,
importing countries such as China and Singapore have restricted the import of
Longan product and other fruits and reduced the maximum permitted residual level
of SO2. Longan consumers are becoming cautious regarding SO2
residues, due to allergenic symptoms and caused of off-tasted (Whangchai
et al., 2006).
The storage of Longan fruit under cold condition and the treatment of fresh
Longan by using sulfur dioxide is very effective application in browning prevention
on the pericarp of the fruits (Jiang et al., 2004).
However, due to the restriction of the import countries, sulfur dioxide is less
use due to allergic to humans (Underhill et al., 1997).
There is a need to find out the suitable of sulfur dioxide concentration and
the storage conditions which are the effective and could be prevented the browning
and prolonged the storage shelf life of fresh Longan. Thus, the aim of this
study was to evaluate the effect of sulfur dioxide treatment and storage conditions
on browning prevention and prolonged the storage shelf life of fresh the Longan
fruit to provide the better appearance and safe for consumers.
MATERIALS AND METHODS Longan (Dimocarpus longan Lour.) fruit cv. Daw was harvested from Chiang Mai province, Thailand in the year 2007. The fruits were then separated into bunches with selected homogenous size and grading. The fruit bunches without defects and spoilage was used for the experiments. The experimental design in this study was laid out in 2x2x5 Factorial in CRD with 4 replications. Treatments were including with and without SO2 treat Then, the treated fruits were store at 2±2 and 7±2°C. Finally, fruits were stored for 0, 2, 4, 6 and 8 weeks. The fruits were sampling immediately after SO2 treatment at the rate 4.50 tons per 2.5 kg SO2 and then every twice month after stored under various storage temperatures as discussed above.
Weight Loss Percentage
The fresh weight of the fruit was determined for all treatments as an index
of desiccation rate. Weight loss was calculated as following;
Weight loss = (Wf - Weight of sample)/Wf x 100
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where, Wf was weight of fresh fruit and Ws was weight of sample.
Polyphenol Oxidase Activity and Determination of Pericarp pH (unit)
Three fruits per treatment were thawed and peeled. And 2 g of pericarp tissue
was homogenized in 0.1 M phosphate buffer, pH 6.6 and 0.5 g of insoluble polyvinyl
pyrollidone (Merck) for 30 sec with a polytron homogenizer (Kinematica GmbH,
Kreins, Luzern, Switzerland; probe diameter, 20 mm). The homogenate was centrifuged
for 10 min at 8000x g in a Sorvall rotor SS-34 at 4°C. The supernatant was
collected and centrifuged repeated in 1.5 mL tubes at 20 000x g for 10 min at
4°C. The supernatant was collected into a fresh tube and 0.75 mL was used
for the PPO assay in duplicate. The PPO assay was conducted by adding 0.12 mL
4-methyl catechol (Sigma, St. Louis, MO, USA) freshly dissolved (0.25 g) in
2 mL of ethanol and 10 mL of distilled water (final concentration, 23 mM). A
contron spectrophotometer was used to follow changes in absorbance at 410 nm
over 2 min and the linear progress of the reactions was recorded between 30
and 90 sec. Protein content was determined according to Bradford with bovine
serum protein as the standard. Results were calculated as in Δactivity
mg-1 protein x1000. The change in the pH of the buffer was determined
in duplicate. To determine the pH of pericarp and aril tissue, extraction was
carried out as described, but without PVP and with distilled water instead of
phosphate buffer.
Peel and Aril Color
The pericarp (peel) and aril color of the Longan fruit were analyzed initially
and after various storage duration. The color was measured on opposite sides
of the fruit using (colourQuest XE, Hunter Associates Laboratory, Inc., New
York, USA) Minolta chromameter (model CR-200; Minolta, Ramsey, NJ) which provided
CIE L*, C*, H*, A* and B*
values.
Preparation of Longan Pericarp for Scanning Electron Microscope (SEM)
The Longan pericarps were cut into 5 mm squares for SEM evaluation. The
pericarps were cut in a dish of 0.1 M phosphate buffer pH 7.3. The pieces were
transferred immediately after they were cut into a primary fixative. The Longan
pericarp pieces were fixed in a fixative solution as described by Bozzola
and Russell (1999) with slight modification for anatomical study. The pericarp
specimens were fixed with a primary fixative containing 2.5% glutaraldehyde
in 0.1 M phosphate buffer pH 7.3 at 4°C for 2 h. After that the tissue was
usually washed in the same buffer vehicle used in the glutaraldehyde fixation
step. Next, the specimens were post-fixed in 1% osmium tetroxide in the same
buffer for 2 h. Then, the specimens were dehydrated stepwise by exposure to
ethanol-buffer mixture (30, 50, 70, 80, 90 and 100%) allowing 15 min in each
and critical point drying with liquid CO2. This is a critical drying
technique, as it achieves a phase change from liquid to dry gas without the
effects of surface tension and is, therefore, suitable for delicate biological
specimens for removal of water from the specimens. For SEM, the dried specimen
was mounted on specimen studs and sputter coated with gold. Finally, the specimens
were viewed with a scanning electron microscope (JEOL, JSM-5910LV, JEOL Ltd.,
Tokyo, Japan) at 15 kV.
Sulphite Residual (mg kg-1)
A sample of 50 g from the whole fruit, aril and peel was obtained from a
minimum of 30 fruits and stored overnight at -70°C. Sample were then examined
in duplicate for sulphite residual according to De Vries
et al. (1987).
Statistical Analysis
The statistical analysis was carried out using a statistical software Statistic
version released 8.0 and Least significant different test at 95% was used to
determine significant difference among the treatments.
RESULTS AND DISCUSSIONS
The ANOVA analysis indicated that SO2 treatment changed pH value
of peel tissue significantly (Table 2). The pH value of peel
tissue decreased significantly after treated the Longan fruit with SO2
(4.30), when compared with non SO2 treatment (5.36). However,
SO2 treatment did not affected on pH value of aril. The storage temperature
did not effect on pH value of peel and aril changed. On the other hand, the
storage duration was the main factor that affect on the change of peel and aril
pH. The pH value of both part of the Longan fruit increased significantly in
the long term of storage (Table 1). Additionally, ANOVA analysis
indicated that the storage duration did not affect only pH value of peel and
aril changed but also affected on weight loss of the Longan fruit (Table
2), while the weight loss increased significantly during the long term of
storage (Table 1). However, weight loss of the Longan fruit
did not affected by SO2 treatment and storage temperatures (Table
1). Table 1 and 2 indicated that all
treatments not affected on the change of PPO activity.
Table 1: | The
effects of sulphur dioxide treatments, storage temperatures and storage
durations on Longan cv. Daw fruit quality changes |
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The different letters indicate the statistically significant
difference by LSD at 5% level. *Polyphenol enzymatic activity (PPO) was
described in Δactivity mg-1 proteinx103 |
Table 2: | Effects
of sulphur dioxide treatment, storage temperatures and storage durations
on the changes of peel and aril pH and weight loss of Longan cv. Daw
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The different letters indicate the statistically significant
difference by LSD at 5% level. ns: not significantly different
*: Polyphenol enzymatic activity was described in Δactivity mg-1protein
x 103 |
The ANOVA analysis indicated that SO2 did not affect on aril color
changed. However, the storage duration was the main factor affected on the change
of aril color (Table 3) (Fig. 1a-d). The
aril was bright orange-yellow color after stored for 8 weeks (C*,
H*, L*, A* and B*were increased
significantly) (Table 1). Moreover, the storage temperature,
interaction between SO2 and storage duration and interaction between
all treatment significantly increased C* and B* values
(Table 3), which was indicated that the aril became dull yellow
color (Fig. 1g, h). The ANOVA results indicated that SO2
treatment, storage temperature and storage duration significantly affected
on H*, L* and A* values (Table
4). The SO2 treatment and storage temperature significantly increased
H* and L* values, while A* value significantly
decreased (Table 1). The results showed that inner part of
peel color of no SO2 treatment and stored under 7°C was more
darkened than that SO2 treatment and stored under 2°C (L*
value decreased), which was more bright green-yellow color (A* decreased)
(Table 4) (Fig. 1c, d). For the storage
duration, H* and A* values significantly increased, while
L* value decreased after stored for 8 weeks (Table
1). This results indicated that the inner part of peel color was became
orange-yellow darkness color after stored for 8 weeks (Fig. 1e-g).
Interestingly, all treatments were SO2 treatment, storage temperature
and duration was the main factors affected on the outer peel color (Table
5). The outer peel red color of no SO2 treatment were scarlet
than orange-red (H* decreased), became darkened (L* decreased),
less intensely red (C* decreased) and blue-yellowish (B*
decreased) color (Table 1).
Table 3: | Effects
of sulphur dioxide treatment, storage temperatures and storage durations
on the changes of aril color of Longan cv. Daw |
 |
The different letters indicate the statistically significant
difference by LSD at 5% level. ns: Not significantly different |
Moreover, under high storage temperature (7°C) and long term of storage
(8 weeks), the outer peel color became blue-yellowish (B* decreased),
darkened (L* decreased) and more scarlet than orange-red (hue angle;
H*, decreased) or changed to cloudy and dark or scarlet, which was
showed in browning (Table 1) (Fig. 1e, h).
Pericarp browning increased with increasing of storage period. Fruit fumigated
with SO2 did not show any pericarp browning throughout this investigation.
According to Duan et al. (2004) the major factors
reducing the storage life and marketability of the Longan fruit are microbial
decay and pericarp browning. Low temperature storage at 1-5°C is used to
reduce pathological decay, but has only a limited role in reducing pericarp
browning. In this study, the SO2 treatment inhibited browning and
decreased PPO activity of Longan pericarp during storage. Low PPO activity correlated
with low browning appearance. According to Jiang and Fu
(1998), the sulfur dioxide application gave better results in controlling
litchi browning and 80-85% inhibition of PPO (Jiang, 1999).
Moreover, the fruit deteriorates rapidly when removed from cold storage. It
was observed that under the refrigeration conditions Longan fruits have a storage
life of approximately 30 days. Pulp quality and disease development are generally
stable during cold storage until such time as fruits become visually unacceptable
from pericarp browning (Jiang and Li, 2001). Sulfur dioxide
fumigation has been the most effective postharvest treatment for control of
pericarp browning in the Longan fruit and is used extensively in commercial
situations at present. However, there is increasing consumer and regulatory
resistance to the use of this chemical (Jiang et al.,
2002).
| Fig. 1: |
The effects of SO2 treatments, storage temperature
and storage duration on the changing of inner and outer peel tissue and
aril color of Longan cv. daw. (a) No SO2 treatment at the initially
of storage, (b) SO2 treatment at the initially of storage, (c)
inner and outer peel tissue and aril color changing by no SO2
treatment at the initially of storage, (d) inner and outer peel tissue and
aril color changing by SO2 treatments at the initially of storage,
(e) and (f) the changing of inner and outer peel tissue and aril color by
no SO2 treatments stored at 2 and 7°C for 8 weeks, respectively,
(g) and (h) the changing of inner and outer peel tissue and aril color by
SO2 treatments stored at 2 and 7°C for 8 weeks, respectively |
The pearson correlation coefficients analysis showed that SO2 treatment
and storage temperature factors resulted weight loss, the changing of peel and
aril tissue pH and polyphenol enzymatic activity were had the positive correlation
between them (Table 6, 7). Moreover, the
effect of storage duration had positive correlation between peel tissue pH-PPO
enzymatic activity and weight loss-aril tissue pH but stated the negative correlation
between aril pH and peel tissue pH (Table 8). Meanwhile, the
experiment found that a lower pH in the peel kept in SO2 treatment
might be beneficial in preventing browning. The rapid increase in the browning
index of the Longan fruit stored in SO2 treatment after long term
of storage may be due to the senescence and fruit decay, indicated by increases
in pH value, which was agreed with Tian et al. (2002).
According to Solomon et al. (1992) reported that
PPO catalyzed browning of fruit could be prevented by several application such
as; heat inactivation of enzymes, exclusion or removal of one or both of the
substrates (O2 and phenols), adding compounds that inhibit PPO or
prevent melanin formation and especially on controlling the pH to be lowering
to 2 or more units below the pH optimum, by reaction-inactivation of the browning
enzyme.
Table 4: | Effects
of sulphur dioxide treatment, storage temperatures and storage durations
on the changes of inner part of peel color of Longan cv. Biewkaew |
 |
The different letters indicate the statistically significant
difference by LSD at 5% level. ns: not significantly different |
However, experimental results indicated that non-treated and treated Longans
fruit with SO2 provided the pH about 4.30-5.36 in peel and about
6 in arils tissue. This results congruence to Wong (1995)
reported that the pH optima to most PPOs activity are near 6. Under
this condition, PPO was activated and accelerated the browning of Longan fruits.
Moreover, Underhill and Critchley (1992) found that
the pericarp browning was correlated with moisture loss. Likewise, it is every
likely that the natural cracking of Longan peel facilitates rapid moisture loss
and cause surface browning during harvest and storage. The surface cracking
was also impair the physiological function of the cuticle and increasing water
permeability, which may cause water soaking at the inner side of the peel (Medeira
et al., 1999). The injured cell would accelerate the oxidation of
phenolic substances and the oxidative products resulted in dark color of inner
and outer peel (Abe, 1990). The PPO and peroxidase (POD)
catalyze the oxidation of phenolics to quinines and then condense tannins to
brown polymers. The initiation of the enzymatic browning depends largely on
the loss of compartmentation of enzymes and substrates. In this study, there
were high activities of PPO and POD in the Longan fruit at harvest, but no skin
browning occurred while high ATP production and low malondialdehyde (MDA) content
were observed, which further supports the hypothesis that the loss of compartmentation
of enzymes and substrates was the key factor for the enzymatic browning reaction
of plant tissues. Thus, reduced skin browning of the Longan fruit by pure oxygen
treatment could be accounted for maintenance of compartmentation of enzymes
and substrates by enhanced respiration and ATP production.
Table 5: | Effects
of sulphur dioxide treatment, storage temperatures and storage durations
on the changes of outer part of peel color of Longan cv. Daw |
 |
The different letters indicate the statistically significant
difference by LSD at 5% level. ns: Not significantly different |
Table 6: |
Pearson correlation coefficients of SO2 treatment
on the change of polyphenoloxidase enzymatic activity (PPO), Weight Loss
(WL) and pH value of peel and aril of Longan fruits cv. DAW |
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Table 7: |
Pearson correlation coefficients of storage temperatures on
the change of polyphenoloxidase enzymatic activity (PPO), Weight Loss (WL)
and pH value of peel and aril of Longan fruits cv. DAW |
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Table 8: |
Pearson correlation coefficients of storage duration on the
change of polyphenoloxidase enzymatic activity (PPO), Weight Loss (WL) and
pH value of peel and aril of Longan fruits cv. DAW |
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The result suggests that SO2 treatment may be suitable for keeping
of the Longans fruit over a relatively short period, which skin ultrastructure
played a role in its storability. However, the suitable concentration and fumigation
time is also necessary to point out. The Longan pericarp was thick about 630-700
μm and composed of three layers. The outer layer is exocarp consisted of
natural opening and cracking on the surface.
| Fig. 2: |
Transverse sectional micrographs of the Longan fruit pericarps
cv. Daw affected by SO2 treatment and various storage condition.
(a, b) Longan pericarps after no SO2 and SO2 treatment
at the initially of storage, (c, d) longan pericarps affected by no SO2
treatment after stored at 2 and 7°C for 8 weeks and (e, f) Longan
pericarps affected by SO2 treatment after stored at 2 and 7°C
for 8 weeks |
It was covered by thin discontinuous layer of cuticle and brown epidermal hair.
The mesocarp, main part of the pericarp consisted of about 70% of the pericarp
tissue. It contained elliptical in shape with thick cell walls (Fig.
2a, b). The vascular bundles were tubular and consisted of one layer cell.
When the fruit showed during SO2 treatment, increasing of storage
duration and temperatures, the dark color of inner and outer peel of the Longan
fruit was appeared. The SEM observation showed a layer of injured cell in the
pericarp was fibrous tissues disappeared (Fig. 2c, d). Wax
that covered the pericarp and epidermal hair also damaged. The mesocarp cell
were also damaged and had collapsed. The destruction of cell membrane was also
observed (Fig. 2e, f). Underhill and Critchley
(1992) found that the pericarp browning was correlated with moisture loss.
Likewise, it is every likely that the natural cracking of Longan peel facilitates
rapid moisture loss and cause surface browning during harvest and storage. The
surface cracking was also impair the physiological function of the cuticle and
increasing water permeability, which may cause water soaking at the inner side
of the peel (Medeira et al., 1999). The injured
cell would accelerate the oxidation of phenolic substances and the oxidative
products resulted in dark color of inner and outer peel (Abe,
1990).
| Fig. 3: | The
effect of storage duration on SO2 contamination in aril of
Longan cv. Daw |
| Fig. 4: | The
effect of storage duration on SO2 contamination in peel of
Longan cv. Daw |
At the prior of storage, the contamination of sulphite residue was found highest
in both aril and peel tissue. On the other hand, the contamination of sulphite
significantly decreased along the storage durations (Fig. 3,
4). However, sulphite contamination still high concentration
in peel tissue (350 mg kg-1) after stored for 8 weeks (Fig.
4), while sulphite contamination was not found in aril after stored for
4 weeks (Fig. 3). The fumigation time and concentration are
the most important factors affecting the SO2 residues. Higher concentration
and longer fumigation time resulted in higher SO2 residue (Ye
and Ge, 1996) which was mainly located in the peel and much less in the
aril and gradually decreased with prolonged storage (Lemmer
et al., 2000). Han et al. (2001) reported
that most of the SO2 residue was located in the pericarp. Appropriate
SO2 treatment lowered the SO2 residue level in the pulp
to as low as 10 μg g-1. The eating quality was maintained during
the early stage of storage and the shelf life was extended as compared with
the control fruit. If SO2 concentration and fumigation time were
strictly controlled, lower residue and longer storage life could be achieved.
CONCLUSIONS In conclusion, the combined application of SO2 treatment and cold storage temperature stored Longan fruits under the cold condition significantly prevented pericarp browning of harvested the Longan fruits. Exposure of the Longan fruits to those conditions enhanced high color quality, reduced weight loss percentage, prevented cell wall cracking and delayed the activity of PPO and the decompartmentation of PPO and POD and their substrates. ACKNOWLEDGMENTS The authors wish to thank for Ministry of Agriculture and Cooperation, Department of Agriculture, Royal Thai government for financial support provided is gratefully acknowledged, Assistant Prof Dr. Vicha Sardsud, Postharvest Technology Research Institute, Chiang Mai University and Dr. Pitipong Thobunluepop, Department of Agricultural Technology, Faculty of Technology, Maha Sarakham University for comment on the manuscript.
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REFERENCES |
1: Abe, K., 1990. Ultrastructural Changes During Chilling Stress. In: Chilling Injury of Horticultural Crops. Wang, C.Y., (Ed.). CRC Press Inc., Boca Raton, USA., pp: 71-84.
2: Bozzola, J.J. and L.D. Russell, 1999. Electron Microscopy: Principles and Techniques for Biologists. 2nd Edn., Jones and Bartlett Publishers, Massachusetts, Pages: 634.
3: De Vries, H.W., T. Patrick and H. Andreas, 1987. Molecular and atomic clouds associated with infrared cirrus in Ursa Major. Astrophys. J., 319: 723-729. Direct Link |
4: Deng, Y., W. Ying and L. Yuanfei, 2005. Effects of high O2 levels on post-harvest quality and shelf life of table grapes during long-term storage. Eur. Food Res. Technol., 221: 392-397. Direct Link |
5: Duan, X.W., Y.M. Jiang, X.G. Su, H. Liu and Y.B. Li et al., 2004. Role of pure oxygen treatment in browning of litchi fruit after harvest. Plant Sci., 167: 665-668. Direct Link |
6: Ferrar, P.H. and J.R.L. Walker, 1996. Inhibition of diphenol oxidases: A comparative study. J. Food Biochem., 20: 15-30. Direct Link |
7: Han, D.M., Z.X. Wu and Z.L. Ji, 2001. Effects of SO2 treatment on the overal quality of longan fruits (cv. Shixia) during cold storage. Acta Horticulturae, 558: 375-380. Direct Link |
8: Jiang, Y. and J. Fu, 1998. Inhibition of polyphenol oxidase and the browning control of litchi fruit by glutathione and citric acid. Food Chem., 62: 49-52. CrossRef | Direct Link |
9: Jiang, Y.M., 1999. Purification and some properties of polyphenol oxidase of longan fruit. Food Chem., 66: 75-79. CrossRef |
10: Jiang, Y. and Y. Li, 2001. Effect of chitosan coating on postharvest life and quality of longan fruit. Food Chem., 73: 139-143. CrossRef |
11: Jiang, Y., Z. Zhang, D.C. Joyce and S. Ketsa, 2002. Postharvest biology and handling of longan fruit (Dimocarpus longan Lour.). Postharvest Biol. Technol., 26: 241-252. CrossRef |
12: Jiang, Y., L. Yuebiao and L. Jianrong, 2004. Browing control, shelf life extension and quality maintenance of frozen litchi fruit by hydrochloric acid. J. Food Eng., 63: 147-151. CrossRef |
13: Lemmer, D., F.J. Kruger and I.J. Froneman, 2000. Evaluation of the postharvest characteristics of litchi fruit from the cultivar development programme. South Afr. Litchi Growers Assoc. Yearbook, 11: 33-36.
14: Lin, S.X., Y.M. Jiang, Y.B. Li, D.L. Zhang and F. Chen, 1994. Effect of GA3 on colour of plum fruit after harvest. Acta Hortic. Sin., 21: 320-322. Direct Link |
15: Lin, H.T., S.J. Chen, J.Q. Chen and Q.Z. Hong, 2001. Current situation and advances in postharvest storage and transportation technologies of longan fruit. Acta Hortic., 558: 343-351. Direct Link |
16: Martinez, M.V. and J.R. Whitaker, 1995. The biochemistry and control of enzymatic browning. Trends Food Sci. Technol., 6: 195-200. Direct Link |
17: Medeira, M.C., M.I. Maia and R.F. Vitor, 1999. The first stages of pre-harvest peel pitting development in Encore mandarin: An histological and ultrastructural study. Ann. Bot., 83: 667-673. Direct Link |
18: Sardsud, U., V. Sardsud, C. Sittigul and T. Chaiwangsri, 1994. Effect of Plant Extracts on the in vitro and in vivo Development of Fruit Pathogens. In: Development of Post-harvest Handling Technology for Tropical Tree Fruit, Jonhson, G. and I. Highley (Eds.). ACIAR, Canberra, Australia.
19: Smith, C.W. and E.L. McWilliams, 1978. Chilling, hardening and electrolyte loss in Scindapsus pictus and Maranta leuconeura. Hortscience, 13: 344-344.
20: Solomon, E.I., M.J. Baldwin and M.D. Lowrey, 1992. Electronic structures of active sites in copper proteins: Contributions to reactivity. Chem. Rev., 92: 521-542. Direct Link |
21: Tongdee, S.C., 1997. Postharvest Physiology and Storage of Tropical and Sub-Tropical Fruits. CAB International, USA., pp: 335-345.
22: Underhill, S.J.R. and C. Critchley, 1992. The physiology and anatomy of lychee (Litchi chinensis Sonn.) pericarp during fruit development. J. Hortic. Sci., 67: 437-444. CrossRef |
23: Underhill, S.J.R., L.M. Coates and Y. Saks, 1997. Litchi. In: Postharvest Physiology and Storage of tropical and Subtropical Fruits, Mitra, S.K. (Ed). CAB International, Wallingford, UK., pp: 191-208.
24: Whangchai, K., K. Saengnil and J. Uthaibuta, 2006. Effect of ozone in combination with some organic acids on the control of postharvest decay and pericarp browning of longan fruit. Crop Prot., 25: 821-825. CrossRef |
25: Wong, D.W.S., 1995. Food Enzymes, Structure and Mechanism. Chapman and Hall, New York pp: 284-320.
26: Ye, Q. and Y.Q. Ge, 1996. Several questions of grape postharvest diseases and SO2 treatment. Xinjiang Agric. Sci., 4: 184-184.
27: Tian, S.P., Y. Xu, Q.Q. Gong, A.L. Jiang, Y. Wang and Q. Fan, 2002. Effects of controlled atmospheres on physiological properties and storability of longan fruit. Acta Hortic. (ISHS), 575: 659-665. Direct Link |
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