Extending the shelf life of lychee using different CO2:O2 ratios and an ethylene absorbent in polyethylene bags

Journal of Agricultural Technology
Extending the shelf life of lychee using different CO2:O2 ratios
and an ethylene absorbent in polyethylene bags



S. Glahan1?

1Department of Horticulture, Faculty of Agricultural Technology, King Mongkut’s Institute of
Technology Ladkrabang, Bangkok 10520, Thailand

Glahan, S. (2006). Extending the shelf life of lychee using different CO2:O2 ratios and an
ethylene absorbent in polyethylene bags. Journal of Agricultural Technology 2(1): 121-135.

The extension of the shelf life and quality of lychee was examined by using CO2:O2 ratios plus
an ethylene absorbent in polyethylene bags. The weight loss of lychee increased according to
storage time. Lychee stored in 3% ethylene absorbent with CO2:O2 flow rates of 0:0 PSI lost
the most weight with a mean of 1.44%. The total soluble solid content (17.10-17.9 brix) and
titratable acidity (0.25-0.31%) of lychee slightly decreased in all treatments according to
storage time. Lychee stored in 4% ethylene absorbent with CO2:O2 flow rates of 5:5 PSI
resulted in the best acceptable quality and longest storage life of 18 days. Lychee stored in
LDPE bags with CO O2 flow rates of 0:0 PSI lost the most weight with a mean of 1.70%. Total
soluble solid content (15.73-17.2 brix) and titratable acidity (0.18-0.22%) in all lychee
treatments decreased slightly according to storage time. Lychee stored in PE bags with CO2:O2
flow rates of 5:5 PSI had the best performance and longest storage life of 18 days with
acceptable quality.

Key words: CO2:O2, ethylene absorbent, fruit quality, lychee, shelf-life

Introduction


Lychee is a worldwide economic fruit and roughly 18,412 tons are
exported from Thailand each year with an estimated value of more than 600
million Baht. Future demand of lychee is likely to increase in the future.
Lychee is a perishable fruit with a short shelf-life and fungal spoilage may
cause serious losses over long distance transportation and during marketing.
The optimum storage time for lychee is only 2-3 days. Over longer periods
weight loss and browning of peal occurs resulting in a very short shelf-life (Lin
and Chiang, 1981; Chang, 1983) Modified control packaging is an of
alternative to extension storage life of lychee. Lee (1996) stated that increasing
CO2 content and lowering O2 content would reduce chilling injury and
decrease ethylene synthesis. Glahan (2000) found that a combination of plastic

?Corresponding author: S. Glahan ; e-mail : somchai_glahan@yahoo.com

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bags and ethylene absorbent could lengthen the storage life of Gros Michel,
mangosteen and asparagus spear. In this study we assess the affect of storage
bags and CO2:O2 content to increase the shelf-like of lychee.

Materials and methods

Influence of ethylene absorbent (EA), and CO2:O2 flow rates on quality and
storage life of lychee

The statistical model was a 5 × 5 factorial completely randomised design
comprising 5 levels of ethylene absorbent at 0, 1, 2, 3 and 4% by fresh weight
of lychee (gm), and 5 levels of CO2:O2 at: 0:0, 5:5, 10:5, 15:10 and 20:10 PSI.
Lychees were selected, placed in polyethylene bags (PE) and filled with
CO2:O2 and ethylene absorbent (EA) according to treatment combinations +
moisture absorbent (MA) 0.5 percent (by fresh weight of lychee), and stored at
14°C in a refrigerator.

Influence of packaging materials and CO2:O2 flow rates on quality and
storage of lychee

The statistical model was a 3 × 5 factorial completely randomized design
coomprising three types of plastic bags: polyethylene (PE) bags; low density
polyethylene (LDPE) bags and; polypropylene (PP) bags; and ratios of CO2:O2
of 0:0, 5:5, 10:5, 15:10 and 20:10 PSI. Lychees were placed in the plastic bags
and ethylene absorbent 1% (by fresh weight of lychee) + moisture absorbent
(MA) 0.5% (by fresh weight of lychee) and filled with various CO2:O2 ratios
and stored at 14°C in a refrigerator

Results

Influence of ethylene absorbent (EA), and CO2:O2 flow rates on quality and
storage life of lychee

Percentage fresh weight loss

The weight loss of lychee in storage increased with time (Table 1.1, Fig
1.1). After 3 days storage the weight loss was 0.31-0.88%. Lychee stored with
2% ethylene absorbent + 0:0 PSI CO2:O2 for 18 days had the lowest weight
loss of 1.25%, while lychee stored with 3% ethylene absorbent + 0:0 PSI
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CO2:O2 had the greatest weight loss of 1.44%. Weight loss however, had no
impact on shriveling of the peel (Fig. 7).

Total soluble solids

During lychee storage the total soluble solids slightly decreased with
time (Fig. 2). At the start of the experiment total soluble solids was 17-08.2
brix while after 18 days of storage lychee with 3% ethylene absorbent + 0:0
PSI CO2:O2 the lowest soluble solids content of 17.00 brix was recorded.
Lychee fruit stored with 2% ethylene absorbent + 5:5 PSI CO2:O2 had the
highest total soluble solids content of 17.90 brix (Table 1).



2.0


1.5


1.0
h weight loss


0.5


percent fres

0.0

3
6
9
12
15
18

day after storage (days)

a1b1
a1b2
a1b3
a1b4
a1b5
a2b1
a2b2

a2b3
a2b4
a2b5
a3b1
a3b2
a3b3
a3b4

a3b5
a4b1
a4b2
a4b3
a4b4
a4b5
a5b1
a5b2
a5b3
a5b4
a5b5


Fig. 1. Percentage weight loss of lychee after storage in ethylene absorbent with various
CO2:O2 flow rates.

Titratable acidity

Titratable acidity in lychee decreased with storage time (Fig. 3) from
0.27-0.47% at the start of the experiment, whereas after 18 days storage in 4%
ethylene absorbent + 5:5 PSI CO2:O2 titratable acidity was the lowest (0.25%).
When stored in 2% ethylene absorbent + 0:0 PSI CO2:O2 titratable acidity
content was highest at 0.31% (Table 2).

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19.0

18.5

r
i
x)
b 18.0

( 17.5

o
lid

17.0
l
e
s
b

16.5
o
lu

16.0

o
t
a
l s
t 15.5


15.0

0
3
6
9
12
15
18
day after storage (days)

a1b1
a1b2
a1b3
a1b4
a1b5
a2b1
a2b2

a2b3
a2b4
a2b5
a3b1
a3b2
a3b3
a3b4

a3b5
a4b1
a4b2
a4b3
a4b4
a4b5
a5b1

a5b2
a5b3
a5b4
a5b5

Fig. 2. Total soluble solids in lychee after storage in ethylene absorbent with various CO2:O2
flow rates.

Peel and pulp colour


The outer peel of lychee before storage was red (Red Group 47A-C).
After 3-9 days of storage the outer and inner peel colour had not changed,
whereas after 12-18 days the inner and outer peel had more intensity (Red
Group 46C-47C). Pulp was greyish-white (Group 156C) before storage and
retained the original colour throughout the experiment (Figs 4-7).

Palatability

The palatability of lychee decreased with storage time (Table 2). Before
storage palatability ranged from 4.64-4.94, while after 18 days of storage
lychee stored in 4% ethylene absorbent + 5:5 PSI CO2:O2 showed the highest
palatability score of 2.08 and was barely acceptable for consumption.

Storage life


Lychee stored without ethylene absorbent + 0:0, 5:5, 10:5 and 20:10 PSI
CO2:O2, 1% ethylene absorbent + 0:0 and 20:10 PSI CO2:O2, 2% ethylene
absorbent + 10:5 PSI CO2:O2, 3% ethylene absorbent + 5:5, 10:5 and 20:10
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Journal of Agricultural Technology
PSI CO2:O2, 4% ethylene absorbent + 15:10 and 10:5 PSI CO2:O2 resulted in
the shortest storage times of up to of 12 days. Lychee stored with 2% ethylene
absorbent + 0:0 PSI CO2:O2, 3% ethylene absorbent + 0:0 PSI CO2:O2 and 4%
ethylene absorbent + 5:5 PSI CO2:O2 resulted in the longest storage life of 18
days (Table 2).



0.50


) 0.40


ity (%

0.30

l
e
acid

t
ab
0.20

titra


0.10

0
3
6
9
12
15
18

day after storage (days)

a1b1
a1b2
a1b3
a1b4
a1b5
a2b1
a2b2

a2b3
a2b4
a2b5
a3b1
a3b2
a3b3
a3b4
a3b5
a4b1
a4b2
a4b3
a4b4
a4b5
a5b1

a5b2
a5b3
a5b4
a5b5

Fig. 3. Titratable acidity of lychee after storage in ethylene absorbent with various CO2:O2 flow
rates.


Influence of packaging materials and CO2:O2 flow rates on quality and
storage life of lychee

Percent fresh weight loss

According to the behavior of fresh Weight loss in lychee during storage
increased with time (Table 3 and Fig. 8). After 3 days of storage weight loss
was 0.23-0.46%. After 18 days of storage in PP bags + 0:0 PSI CO2:O2 weight
loss was lowest at 1.14% and in LDPE bags + 0:0 PSI CO2:O2 was 1.7%.
Weight had no impact on shriveling of the peel (Fig 2.1).

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Fig. 4. Lychee before storage. Fig.
5.
Lychee after 12 days storage in ethylene
absorbent with various CO2:O2 flow rates.




















Fig. 6. Lychee after 15 days storage. Fig.
7.
Lychee after 18 days storage in ethylene
absorbent with various CO2:O2.flow rates.
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Journal of Agricultural Technology


19.50

19.00


18.50

18.00


17.50

17.00

16.50


16.00

total soluble solid (brix) 15.50

15.00


0
3
6
9
12
15
18


day after storage (days)

a1b1
a1b2
a1b3
a1b4
a1b5
a2b1

a2b2
a2b3
a2b4
a2b5
a3b1
a3b2

a3b3
a3b4
a3b5

Fig. 8. Weight loss in lychee after storage in plastic bags with various CO2:O2 flow rates.


Total soluble solid


During storage period for 3-9 days in PE and PP bags the total soluble
solids of lychee fruit slightly increased after which this decreased slightly (Fig.
2). Before storage total soluble solids in lychee was 16.40-18.90 brix. After 18
days of storage in LDPE bags + 5:5 PSI CO2:O2 the lowest total soluble solids
content of 15.73 brix was recorded and those stored in PP bags + 0:0 PSI
CO2:O2 had the highest total soluble solids content of 17.20 brix (Table 3).

Titratable acidity (TA)


Titratable acidity decreased with storage time (Fig. 10). Before storage
titratable acidity was 0.23-0.46%, whereas after 18 days storage in LDPE bags
+ 0:0 PSI CO2:O2 it was lowest at 0.18%, while those stored in LDPE bags +
5:5 PSI CO2:O2 and PP bags + 0:0 PSI CO2:O2 had the highest titratable acidity
0.31% (Table 3).


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