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J Sci Food Agric 1998, 76, 427È434
Eþects of Type of Packaging Materials on
Physicochemical, Microbiological and Sensory
Characteristics of Durian Fruit Leather During
Storage
J Irwandi, Y B Che Man,* S Yusof, S Jinap and H Sugisawa
Faculty of Food Science and Biotechnology, Universiti Pertanian Malaysia, 43400 UPM Serdang Selangor
DE, Malaysia
(Received 9 September 1996 ; revised version received 1 April 1997 ; accepted 9 July 1997)
Abstract : A study on storage stability of durian leather was carried out at room
temperature using four types of packaging materialsÈlaminated aluminium foil
(LAF), high-density polyethylene (HDPE), low-density polyethylene (LDPE) and
polypropylene (PP) ÐlmsÈfor 12 weeks. Analyses on physicochemical, microbiological and sensory characteristics were conducted at weeks 0, 2, 4, 8 and 12.
Analyses for sugar, fat and caloric contents were conducted at the beginning and
the end of storage period. Moisture contents and water activity (A ) Ñuctuated
w browning
during storage but tended to decrease after week 8. Non-enzymatic
increased signiÐcantly (P \ 0É05) for all samples in packaging materials used ; the
highest increases were observed in LDPE-packed leather. The increases were
related to the changes in colour of samples during storage. The longer storage
time, the higher L and b values and the lower a value. The pH, although it
Ñuctuated in the Ðrst weeks, slightly increased at the end of the storage period,
while the hardness for each sample gradually increased during the storage.
Microbial analyses showed that total mesophilic bacteria (TMB) and total
moulds and yeast (TMY) counts were low, where after 12-week storage TMB
and TMY were less than 60 and 140 cfu g~1, respectively. Organoleptically, for
all attributes evaluated, all samples were acceptable by panelists during the
12-week storage period. ( 1998 SCI.
J Sci Food Agric 76, 427È434 (1998)
Key words : Durio zibethinus Murr ; clone D24 ; packaging materials ; organoleptic evaluation
INTRODUCTION
leather, as an alternative to diversify the uses of durian,
has been reported by Irwandi and Che Man (1996).
Like other fruit leathers, durian leather was prepared by
drying the aril after mixing with other ingredients into
leathery sheets. Che Man et al (1997) reported that the
additions of glucose syrup solid, sucrose, hydrogenated
palm oil and soy-lecithin into durian aril when mixing
resulted in an acceptable durian leather. Besides, both
oven and cabinet dryers were able to be used in the
preparation of the product.
Durian leather is an intermediate moisture food
(IMF), for which the market is presently growing
(Guilbert 1987). Brockmann (1973) stated that the
Durian (Durio zibethinus Murr), the most famous of the
popular seasonal fruit of South-East Asia, is usually
consumed fresh. The aril of the fruit can also be frozen
or processed into paste, processed into durian powder
or added into other products such as ice cream, cakes
and confectionary (Nantachai 1994). Fruit leather, a
product prepared by dehydration of fruit puree, is an
established product, particularly in the North-American
market (Raab and Oehler 1976). Development of durian
* To whom correspondence should be addressed.
427
( 1998 SCI.
J Sci Food Agric 0022È5142/98/$17.50.
Printed in Great Britain
J Irwandi et al
428
recent commercial success of IMF has stimulated interest in this area and in the development of new intermediate moisture product for human consumption. The
intermediate moisture products o†er the potential
advantage that can be eaten without preparation. They
can be consumed directly as fruit snacks or combination with nuts and breakfast cereal. They can also
be incorporated in various fabricated foods such as
biscuits, cookies and ice creams. Hence, for commercial
purposes, the use of suitable packaging materials of
durian leather is very important, particularly to prolong
the shelf-life of the product.
Brockmann (1973) stressed that there are three main
parameters normally related to stability of an IMF :
water activity, microbiological stability and physicochemical characteristics. The present study was
carried out to determine the e†ects of the type of packaging materials used and time of storage on quality of
durian leather, including physicochemical characteristics, microbial stability and sensory properties.
MATERIALS AND METHODS
Materials
Durian fruits from Clone D24 were obtained from the
Universiti Pertanian Malaysia farm. Glucose syrup
solid (GSS) (DE 12È15) and hydrogenated palm oil
(HPO) were kindly donated by Stamford Industry, Petaling Jaya, and Palm Oil Research Institute of Malaysia
(PORIM), respectively. Sucrose, soy-lecithin (SL), egg
yellow colour (Bush Boake Allen) and analytical grade
reagents were obtained from local suppliers in Sri
Serdang, Selangor DE. All packaging materials usedÈ
laminated aluminimum foil (LAF), high density polyethylene (HDPE), low density polyethylene (LDPE) and
polypropylene (PP)Èwere supplied by Malaysian Packaging Sdn Bhd, Selangor. The thickness of each packaging material was 0É10, 0É08, 0É05 and 0É10 mm for
LAF, HDPE, LDPE and PP, respectively.
enclosed water-bath container at 85È100¡C for 5 min
and blended. During blending, 10% GSS, 5% sucrose,
2É67% HPO, 0É45% SL, 30% water and 100 mg kg~1
egg yellow colour were added. Sorbic acid 200 mg kg~1
were also added as preservative. The mixture was then
formed into sheets of 1É2 mm thick and dried in both
oven and cabinet dryers. For the oven, drying was done
at 50¡C for 12É6 h ; for the cabinet, drying was done at
52É5¡C for 10 h. The leathers were then packed and
stored at ambient temperature (c 27¡C) for further
analyses.
Physicochemical analyses
Moisture and fat contents were determined according to
AOAC (1984) methods. Water activity (A ) was meaw
sured using chemical desiccation method described by
Rockland (1960). Non-enzymatic browning was determined using spectrophotometry method (Askar and
Treptow 1993). A 10-g sample was extracted with
100 ml 60% ethanol for 12 h and centrifugated at
1260 ] g for 5 min. The absorbance of the extract was
then measured with a spectrophotometer at 420 nm
with 60% ethanol as a blank. Total sugar was determined according to Hunt et al (1977). A HPLC (Waters
410 di†erential refractometer) was used with sucrose,
fructose, glucose and maltose as standards. pH was
measured using a pH meter (Corning 220) according to
Askar and Treptow (1993), while the caloric content
was determined using an oxygen bomb calorimeter
(Anon 1960).
The colour was determined using a Hunter lab colorimeter (Model D25-2). A yellow tile (L \ 77É5,
a \ [ 3É5, b \ 23) was used as a reference standard.
The texture was measured with Instron Universal
Testing Machine (model 1140). Chart and head speeds
were kept at 100 mm per min. The values were recorded
as the force (in kgf) required to penetrate a 1É2 mm
thick sample. The diameter of hole was 8 mm. Analyses
for physicochemical changes during storage were
carried out in triplicates.
Experimental design
Durian leather was prepared by using an oven and a
cabinet dryer. The durian leathers were then packed in
the four di†erent packaging materials. Storage study
was conducted for 12 weeks and all analyses were
carried out at weeks 0, 2, 4, 8 and 12, except for fat,
sugar and caloric contents, which were analysed only at
weeks 0 and 12.
Sample preparation
Durian leather was prepared according to Irwandi and
Che Man (1996). Durian aril was blanched in an
Microbiological tests
Total mesophilic bacteria (TMB) and total mould and
yeast (TMY) counts of fresh and stored durian leather
were conducted according to Anon (1982). A 10-g
sample was added with 90 ml sterile peptone water and
blended for 1 min. Aliquots were further diluted to
obtain 10~1È10~3 for both TMB and TMY. From each
dilution, 1É0 ml was transferred aseptically to Petri
dishes, poured with plate count agar (PCA) for TMB,
and acidiÐed potato dextrose agar (PDA) for TMY, and
incubated for 2È5 days at 37 and 30¡C for TMB and
TMY, respectively. Analyses were in triplicates.
E†ect of type of packaging materials on durian leather
Organoleptic evaluation
Sensory analyses for taste, texture, appearance, aroma
and overall acceptability were carried out using a
7-point hedonic scales (1 \ dislike extremely, 7 \ like
extremely) (Larmond 1977). All organoleptic attributes
were evaluated by 20 semi-trained panelists selected
from students of the Faculty of Food Science and Biotechnology, Universiti Pertanian Malaysia.
All data were assessed by analysis of variance
(ANOVA) and least signiÐcant di†erence (LSD) test
(Steel and Torrie 1980).
RESULTS AND DISCUSSION
Moisture content and water activity
Moisture content of both oven-dried and cabinet-dried
durian leathers Ñuctuated during storage, ranging from
13È17% (Table 1). This is due to di†erences in the moisture vapour permeability of the packaging Ðlms.
However, except for cabinet-dried leathers packed in
LAF, the moisture content of samples decreased signiÐcantly after week 4. The highest decrease was exhibited
by samples packed in LDPE. This was closely related to
the characteristics of the packaging materials as shown
by Che Man et al (1995). They reported that LDPE had
higher water vapour permeability (17É6 g m~1 d~1 at
38¡C, 90% RH), compared with PP (3É38) and HDPE
(7É88). The water vapour permeability for LAF is less
than 0É5 (Minakuchi and Nakamura 1990).
Early work on the stability of dried fruit also showed
the e†ects of tropical conditions on prunes, apricots,
peaches and pears. Nichols and Reed (1931) found that
deterioration at 25¡C took place twice as fast as at 0¡C.
They also found that drying to 10% moisture improved
the stability of apples, did not a†ect the stability of apricots, but made the pears less stable. They showed
further that quality of dried fruit was adversely a†ected
by increased time and temperature of storage and by
higher moisture content. The importance of moisture
content on stability of dried fruit product was also
reported by Schwarz (1943), who stressed that moisture
and equilibrium relative humidity of dried fruits were
very important in designing packages and selecting
storage conditions.
The initial moisture ranging from 15 to 16% in our
present study was suitable for storage purpose of durian
leather packed in di†erent packaging materials at
ambient temperature. Che Man and TauÐk (1995)
reported that jackfruit leather which contained 11È17%
moisture and packaged in polyethylene was still acceptable after 2 months storage, while Rao and Roy (1980)
reported that the ideal moisture to have storage stability of mango leather was found to be 15% or a little
more with a relative humidity between 63 and 70%.
429
However, lowering moisture contents to 10% or below
as suggested by Nichols and Reed (1931) might be
applied to improve the storage stability of dried fruit
product, but in the case of fruit leather it could greatly
inÑuence the product texture.
The changes in A of durian leather was relatively
w
similar to the moisture changes (Table 1). There was a
clear relationship between moisture content and A : the
w
higher the moisture content the higher the A . Similar
w
observations were made on kiwifruit leather by Lodge
(1981) and jackfruit leather by Che Man and TauÐk
(1995). The A changes were observed as early as the
w
fourth week of storage. During storage, for leathers
packed in LAF, HDPE and PP, the range of A Ñuctuw
ated from 0É57 to 0É63, with LAF and PP having a
lower Ñuctuation. However, for LDPE-packed leathers,
after achieving a maximum value in the fourth week, the
A drastically decreased until week 12, where the A
w
w
were even less than 0É55. Table 1 also shows that both
the type of packaging materials and storage time signiÐcantly (P \ 0É05) a†ected the A values of the samples.
w
The low A (0É5È0É65) of the durian leather product
w
helped to prolong their shelf-life, as most of microbial
activities occurs at A greater than 0É7 (Labuza et al
w
1970 ; Troller 1980). Che Man and Sanny (1996), who
conducted study on storage stability of jackfruit leather,
reported that A of 0É63 was well below the minimum
w
value needed to support microbiol growth. They also
found that, during storage, LAF has the lowest decrease
in A , and they recommended that this material could
w
maintain the desired textural characteristic of fruit
leather.
Non-enzymatic browning and colour
Table 1 shows that, for both dryers used, the type of
packaging materials and storage time had signiÐcant
(P \ 0É05) e†ects on non-enzymatic browning of durian
leather, with LDPE showing the highest degree of
browning. During storage, the degree of browning
shown by samples packed in LDPE was signiÐcantly
di†erent (P \ 0É05) from the samples in other packaging
materials. Results also indicated that the non-enzymatic
browning of LAF, HDPE and PP samples were not statistically di†erent until week 8. Table 1 also shows that,
during storage, the degree of browning gradually
increased for both dryers used, where absorbances (at
j \ 420 nm) of all samples increased from 0É2 at week 0
to 0É3È0É63 at week 12. The highest increase was
exhibited by LDPE-packed samples (absorbance \ 0É6È
0É62 after 12 weeks), compared with samples packed in
LAF, HDPE and PP (absorbance \ 0É35È0É45 after 12
weeks). Browning could also be due to oxygen e†ects on
other compounds in the fruit.
Moreover, lightness (L ), redness (a) and yellowness (b)
values of the leathers were also signiÐcantly (P \ 0É05)
430
TABLE 1
Physicochemical and microbiological changes of durian leather in di†erent packaging materials during storagea
T ype of packaging
Moisture (%)
Water activity
Non-enzymatic browning
(absorbance at 420 nm)
Texture (kgf )
pH
Lightness
Redness
Yellowness
Total mesophilic bacteria
(cfu/g)
Total moulds and yeast
(cfu/g)
Cabinet-dried leather, week
0
2
4
8
12
0
2
4
8
12
15É82aA
15É82aA
15É82aA
15É82aA
0É597bA
0É597aA
0É597bcA
0É597aA
0É204eA
0É204eA
0É204eA
0É204eA
0É347bA
0É347dA
0É347dA
0É347dA
6É87abA
6É87abA
6É87bA
6É87aA
66É01aA
66É01aA
66É01aA
66É01aA
[0É98aA
[0É98dA
[0É98dA
[0É98dA
35É64aA
35É64aA
35É64aA
35É64aA
16É57dA
16É57eA
16É57eA
16É57eA
16É7eA
16É7dA
16É7dA
16É7dA
15É48abB
16É85aA
15É77aA
17É17aB
0É593bcA
0É597aA
0É607abA
0É597aA
0É240dc
0É259dB
0É274dA
0É246dBc
0É390abB
0É447cAB
0É493cA
0É470cAB
6É60cA
6É67bA
6É60cA
6É68aA
64É55aA
62É89bB
62É88bB
62É81bB
[0É83cC
1É36cB
3É34cA
1É22cB
35É78aA
34É43aA
34É47aA
34É79aA
20É90cC
28É50dA
27É13dA
25É37dB
34É7dB
51É7cA
51É3cA
51É7cA
15É35abA
16É02aA
14É96abA
15É76bA
0É620aA
0É607aAB
0É617aA
0É593aB
0É272cB
0É288cB
0É348cA
0É275cB
0É400abB
0É513bcA
0É570bcA
0É533bcA
6É63bcB
6É63bB
6É97bA
7É07aA
61É71bA
61É85bcA
61É66bA
61É56bA
1É17bC
3É13bB
5É10bA
3É59bB
33É33aA
32É31bAB
30É72bB
32É65bAB
27É03bC
36É50cA
31É00cB
31É83cB
51É7bB
71É7bA
76É7bA
68É3bA
14É57abB
15É99aA
14É39bB
15É33bAB
0É597bA
0É580bA
0É580cA
0É587aA
0É354bB
0É370bB
0É428bA
0É377bB
0É460aB
0É583abA
0É647bA
0É600abA
7É07aA
6É83abA
7É00bA
7É10aA
59É61cA
59É85cA
57É14cA
59É11cA
3É49aC
4É13abBC
4É66bA
4É60abB
30É53bA
29É17cA
24É76cB
28É26cA
30É43aB
40É43bA
40É17bA
40É67bA
62É00aB
110É0aA
108É3aA
100É0aA
14É36bA
13É66bA
12É17cB
13É88cA
0É573cA
0É573bA
0É523dB
0É576aA
0É376aC
0É407aB
0É618aA
0É418aB
0É483aC
0É660aB
0É750aA
0É640aB
7É07aB
7É17aAB
7É23aA
7É17aAB
56É41dA
53É82dB
50É75dC
53É66dB
4É62aC
5É78aB
8É82aA
5É93aB
29É16bA
25É30dB
23É37cC
25É44dB
28É60abC
47É67aB
49É83aA
48É67aAB
41É7cC
105É0aB
116É0aA
101É0aB
15É29aA
15É29abA
15É29bA
15É29abA
0É603aA
0É603aA
0É603bA
0É603aA
0É192eA
0É192eA
0É192eA
0É192eA
0É387cA
0É387dA
0É387eA
0É387eA
7É00aA
7É00aA
7É00abA
7É00abA
66É66aA
66É66aA
66É66aA
66É66aA
[1É12dA
[1É12dA
[1É12eA
[1É12dA
35É15aA
35É15aA
35É15aA
35É15aA
19É27dA
19É27eA
19É27eA
19É27eA
19É3dA
19É3eA
19É3eA
19É3dA
14É90aB
16É22aA
17É07aA
16É08aA
0É613aA
0É613aA
0É603bA
0É603aA
0É218dC
0É235dB
0É251dA
0É243dAB
0É450bB
0É463cAB
0É487dA
0É470dAB
7É07aB
6É77bAB
6É80bA
6É87bAB
63É34bA
64É13bA
62É19bB
63É73bA
0É12cdB
1É95cA
2É02dA
1É83cA
34É97aA
34É96aA
33É62bB
34É89aA
24É23cB
26É43dA
27É50dA
26É33dA
35É7cB
40É7dB
56É7dA
41É7cB
15É37aA
15É54abA
15É81bA
15É30abA
0É617aAB
0É600aC
0É623aA
0É607aBC
0É255cC
0É282cC
0É379cA
0É308cB
0É417cC
0É587bA
0É600cA
0É517cB
6É93aA
6É83abA
6É93abA
6É83bA
62É84bA
62É86bA
61É34bB
61É88bAB
1É42bcB
3É10bA
3É60cA
2É93cA
33É47aA
31É23bBC
30É07cC
31É85bAB
28É83bB
28É93cB
31É23cA
30É83cA
56É7bC
63É3cBc
83É7cA
70É0bB
14É85aA
14É60bcA
12É05cA
14É96bcA
0É600abA
0É573bB
0É580cB
0É590abAB
0É303bB
0É361bB
0É433bA
0É364bB
0É500aC
0É607abB
0É683bA
0É623cB
7É13aA
6É93abB
7É00abB
6É90abB
60É24cA
59É33cAB
55É23cC
58É09cB
2É66bB
3É56bAB
6É03bA
4É25bB
30É53bA
29É17bAB
24É76dC
28É26cB
30É83aB
37É87bA
40É37bA
38É90bA
72É3aC
106É3aB
108É3bA
101É7aAB
15É27aA
13É75cB
12É05cC
13É96cB
0É583bA
0É577bA
0É517dB
0É580bA
0É345aB
0É414aB
0É603aA
0É419aB
0É513aC
0É650aB
0É817aA
0É717aB
7É03aA
7É03aA
7É17aA
7É10aA
56É51dA
53É71dB
50É41dC
53É41dB
4É53aC
5É59aB
8É33aA
5É76aB
28É32cA
24É96cB
21É76eC
25É47dB
27É87bC
48É90aA
50É53aA
43É83aB
49É0bC
93É3bB
124É3aA
98É3aB
a Mean of three replicates.
AhC Means within a column with di†erent letters are signiÐcantly di†erent (P \ 0É05).
ahe Means within a row with di†erent letters for each dryer are signiÐcantly di†erent (P \ 0É05).
J Irwandi et al
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
LAF
HDPE
LDPE
PP
Oven-dried leather, week
E†ect of type of packaging materials on durian leather
431
TABLE 2
Mean values (^SD) for sugar, fat and caloric content of fresh and 12-week stored durian
letters
Oven
Sugar (%)
Fat (%)
Caloric
(kcal per 100 g)
Cabinet
Sugar (%)
Fat (%)
Caloric
(kcal pers 100 g)
W eek
L AF
HDPE
L DPE
PP
0
12
0
12
0
12
45É5 ^ 1É6aA
42É2 ^ 1É3aA
4É1 ^ 0É3aA
3É6 ^ 0É1bA
638 ^ 13aA
499 ^ 7bAB
45É5 ^ 1É6aA
42É1 ^ 2É3aA
4É1 ^ 0É3aA
3É5 ^ 0É1bAB
638 ^ 13aA
477 ^ 7bB
45É5 ^ 1É6aA
41É4 ^ 0É9bA
4É1 ^ 0É3aA
3É4 ^ 0É2bB
638 ^ 13aA
492 ^ 5bAB
45É5 ^ 1É6aA
41É9 ^ 1É5bA
4É1 ^ 0É3aA
3É5 ^ 0É1bAB
638 ^ 13aA
466 ^ 5bB
0
12
0
12
0
12
43É7 ^ 1É2aA
42É1 ^ 1É5aA
4É2 ^ 0É2aA
3É7 ^ 0É1bA
643 ^ 17aA
492 ^ 5bA
43É7 ^ 1É2aA
41É6 ^ 1É4aA
4É2 ^ 0É2aA
3É5 ^ 0É1bAB
643 ^ 17aA
469 ^ 15bB
43É7 ^ 1É2aA
41É0 ^ 0É6bA
4É2 ^ 0É2aA
3É3 ^ 0É2bB
643 ^ 17aA
475 ^ 12bAB
43É7 ^ 1É2aA
41É1 ^ 1É1aA
4É2 ^ 0É2aA
3É5 ^ 0É1bAB
643 ^ 17aA
488 ^ 7bAB
ahb Means with a column with di†erent letters are signiÐcantly di†erent (P \ 0É05).
AhB Means within a row with di†erent letters are signiÐcantly di†erent (P \ 0É05).
a†ected by the type of packaging materials and time of
storage (Table 1). L values decreased signiÐcantly
(P \ 0É05) during storage, and the decrease was greatest
for the leathers packed in LDPE, followed by PP,
HDPE and LAF. A similar decrease was also seen in
the b values. However, unlike L values, the b values for
leathers packed in HDPE and PP were not signiÐcantly
di†erent. Inversely, the a values increased signiÐcantly
(P \ 0É05) for leathers packed in all materials used. It
could be concluded that, as the L and b values
decreased, the a value increased. The means of a values
at week 0 for the two types of dryer used were negative
(Table 1), indicating that the samples were more green.
The changes in L , a and b values during storage were
related to non-enzymatic browning reaction, as mentioned above.
E†ect of processing and storage on colour quality of
fruit product has been reported by Askar and Treptow
(1993). According to them, heat processing and subsequent storage of fruit products is often accompanied
by an unattractive discolouration, perhaps due to nonenzymatic browning or oxygen e†ects on other compounds in the fruit. Three factorsÈprocessing
condition, storage time and temperatureÈinÑuence the
colour of the product ; non-enzymatic browning is considered one of the major causes of quality loss of fruit
products.
Discolouration of fruit leather during processing and
storage were also reported by almost every researcher
who conducted studies on fruit leather (Chan and Cavaletto 1978 ; Rao and Roy 1980 ; Che Man and Sanny
1996 ; Che Man and TauÐk 1996 ; Irwandi and Che
Man 1996). In the case of durian, Suyitno (1984) also
reported the similar phenomenon in durian powder
product.
Texture
Both the type of packaging materials and time of
storage had signiÐcant (P \ 0É05) e†ects on the texture
(Table 1). Generally, the hardness increased during
storage, as shown by the increase in texture unit (kgf).
However, for both dryers used, LAF seemed to be the
best material for maintaining the desired texture of
durian leather, while samples packed in LDPE had the
greatest increase in hardness until week 8. For the ovendried product, there was no signiÐcant di†erence
between LDPE, PP and HDPE. Meanwhile, for the
cabinet-dried product, HDPE and PP were not signiÐcantly di†erent, except for samples at week 4. The
results showed that the textural characteristic of durian
leather was closely related to moisture content of the
sample and water vapour permeability of the packaging
material. These changes in water content resulted in signiÐcant changes in the texture, as shown by the measured shear forces.
pH
The acidity level, indicated by pH, of durian leathers
tended to Ñuctuate during storage (Table 1). In the Ðrst
2 weeks of storage, except for the cabinet-dried leather
packed in LAF, the pH values of samples decreased ;
however, the pH then increased gradually until week 12.
At the end of the storage time, the pH values ranged
from 7 to 7É25, with LDPE having the highest pH. The
mean pH value during storage for oven-dried leathers
packed in PP was 7É01, while the leathers in LDPE,
HDPE and LAF were 6É93, 6É84 and 6É85, respectively.
However, for cabinet-dried leathers, the highest mean
pH value during storage was exhibited by the leathers
J Irwandi et al
432
packed in LDPE (6É97), followed by PP (6É94), HDPE
(6É91) and LAF (6É91). Che Man and Sanny (1996) also
showed the Ñuctuation of pH values of jackfruit leather
during 3 months storage. Similar observations, where
the pH tended to increase at the end of the storage time,
was also reported (Che Man and Sanny 1996).
Sugar, fat and caloric contents
Table 2 shows mean values for sugar, fat and caloric
contents for oven-dried and cabinet-dried durian
leathers packed in LAF, HDPE, LDPE and PP,
analysed at weeks 0 and 12. There was no signiÐcant
e†ect of the type of packaging material for each time of
storage on the sugar content of durian leather. The
sugar contents of all samples seemed to decrease during
12 weeks storage, due to the dilution e†ect as the moisture increased. However, for oven-dried leathers, only
samples packed in LDPE and PP had a signiÐcant
(P \ 0É05) decrease ; for cabinet-dried leathers, a signiÐcant (P \ 0É05) decrease was only exhibited by samples
in LDPE. The results also showed that the decrease was
exhibited by all four types of sugar found in durian of
D24 : sucrose, fructose, glucose and maltose. The
decrease was also closely related to the browning and
the colour changes discussed before. The similar trend
of total sugars was also observed by Rao and Roy
(1980).
The 12 weeks of storage also had a signiÐcant
(P \ 0É05) e†ect on fat and caloric content for samples
in all packaging materials used, those dried by both
oven and cabinet. Samples packed in LDPE had the
greatest decrease (P \ 0É05) in fat content during
storage, but no signiÐcant di†erence among the other
materials. In term of caloric content, LAF was seen to
have the lowest decrease during storage. The fresh
durian leather in this study was 638 kcal per 100 g for
oven-dried leathers and 643 kcal per 100 g for cabinetdried leathers. At the end of the storage time, the caloric
contents of the samples dried by oven were 499, 477,
492 and 466 for LAF, HDPE, LDPE and PP, respectively ; for samples dried by cabinet, the values were 492,
469, 475 and 488, respectively. Although there was a signiÐcant decrease of durian leather during 12 weeks of
storage, the “statusÏ of durian leather as a rich-caloric
snack food (Irwandi and Che Man 1996) was still maintained, even at the end of the storage time. As a comparison, the caloric content of fresh jackfruit leather as
reported by the Che Man and TauÐk (1995) was only
348 kcal per 100 g.
Microbial analyses
Results from Table 1 indicate that the type of packaging
materials and time of storage both signiÐcantly
(P \ 0É05) a†ected the microbial growth during storage.
From the results, LAF seemed to be the Ðnest material
to inhibit the growth of the mesophilic bacteria, mould
and yeast. Table 1 also shows that, apart from LAF,
TMB gradually increased from less than 20 cfu g~1 at
week 0 to 40È50 cfu g~1 at week 12, with the highest
TMB exhibited by leathers packed in LDPE, followed
by PP and HDPE for oven-dried leather and HDPE
and PP for cabinet-dried leather. The TMB for LAF
showed a di†erent pattern, where the highest TMB was
reached at week 8, and decreased thereafter. The
turning points at week 8 were also showed by TMY for
both oven-dried and cabinet-dried leathers. It seamed
that only LDPE-packed leathers had increasing TMY
up to 12 weeks of storage. This indicated that, for
durian leather, week 8 could be considered as a
maximum point for moulds and yeast growth. The
decrease in TMY counts after week 8 could be caused
by the decrease in the nutrients supporting the microbial growth or unsuitable environment due to production of some toxic compounds by the microbe itself
(Fardiaz 1989). In the case of TMB counts, during 12
weeks of storage, the maximum points could be
detected only for samples packed in LAF, while samples
packed in HDPE, LDPE and PP may be reached their
optimum points after week 12. Jayaraman (1987)
reported that the maximum points for total plate counts
(TPC) and total moulds count of stored mango leather
was also reached at week 8 ; for banana leather, the
highest TPC and yeast counts were achieved after 6
months storage. However, no moulds were found in this
study.
Overall, both TPC and TMY of samples kept for 12
weeks in all packaging materials were very low (less
than 60 cfu g~1 for TPC and 140 cfu g~1 for TMY).
This indicated that the durian leathers were resistant to
bacteria, mould and yeast growths and microbiologically safe for direct consumption. The low counts of
TMB and TMY in this study was closely related to the
low A of the samples. According to Christian (1963),
w
foods with A lower than 0É6 are essentially free from
w
microbial growth. The low counts was also due to presence of sorbic acid. Moulds are more e†ectively inhibited by mycostatic agents such as sorbic acid (Christian
1963).
Sensory characteristics during storage
Table 3 shows the sensory characteristics of durian
leather during storage. In terms of taste, there was no
signiÐcant di†erence for the four types of packaging
materials used, but the type of material had signiÐcant
(P \ 0É05) e†ects on texture, appearance, aroma and
overall acceptability. For both oven-dried and cabinetdried leathers, results also showed that panelists gave
the lowest score of texture, appearance, aroma and
T ype of packaging
Oven-dried leather, week
Cabinet-dried leather, week
0
2
4
8
12
0
2
4
8
12
Taste
LAF
HDPE
LDPE
PP
5É75aA
5É75aA
5É75aA
5É75aA
5É85aA
5É80aA
5É60abA
5É70abA
5É60abA
5É51aA
5É30abA
5É39abcA
5É29bA
5É25abA
5É18bA
5É22bcA
5É12bA
4É98bA
4É51cA
5É05cA
5É82aA
5É82aA
5É82aA
5É82aA
5É80aA
5É75aA
5É70abA
5É77abA
5É69aA
5É47abA
5É50abA
5É52abA
5É41aA
5É29abA
5É14bA
5É22bA
5É20aA
5É00bA
4É64cA
4É99bA
Texture
LAF
HDPE
LDPE
PP
5É91aA
5É91aA
5É91aA
5É91aA
5É77aA
5É65abA
5É60abA
5É70abA
5É60aA
5É47abcA
5É18bcA
5É39bcA
5É54aA
5É20bcAB
4É77cB
5É18cAB
5É47aA
4É96cA
3É98dB
4É88cA
6É00aA
6É00aA
6É00aA
6É00aA
5É75aA
5É73aA
5É66aA
5É70abA
5É80aA
5É42abA
5É28aA
5É45abA
5É62aA
5É28bA
4É51bA
5É20abB
5É55aA
5É00bA
4É05bB
4É98bA
Appearance
LAF
HDPE
LDPE
PP
6É51aA
6É51aA
6É51aA
6É51aA
6É50aA
6É45aA
6É30aA
6É39aA
6É25abA
6É18abA
5É95aA
6É10abA
6É05abA
5É77bA
5É10bB
5É65bAB
5É76bA
5É17cB
4É12cC
5É20cB
6É54aA
6É54aA
6É54aA
6É54aA
6É50abA
6É33abA
6É20abA
6É40abA
6É10abcA
6É10bcA
5É85bA
6É05bcA
6É02bcA
5É62cdAB
5É21cB
5É70cdAB
5É92cA
5É25dB
4É21dC
5É31dB
Aroma
LAF
HDPE
LDPE
PP
5É60aA
5É60aA
5É60aA
5É60aA
5É64aA
5É50aA
5É55abA
5É55aA
5É58aA
5É25aA
5É10abcA
5É35abA
5É45aA
5É00abAB
4É85bcB
4É90bAB
5É25aA
4É75bA
4É55cA
4É70bA
6É00aA
6É00aA
6É00aA
6É00aA
5É90aA
5É80aA
5É80abA
5É85abA
5É90aA
5É70aA
5É50bA
5É75abA
5É70aA
5É20bB
5É10cB
5É33bAB
5É50aA
4É95bA
4É75dA
4É80bA
Overall acceptability
LAF
HDPE
LDPE
PP
6É05aA
6É05aA
6É05aA
6É05aA
5É97abA
5É83abA
5É27abB
5É77abAB
5É90abA
5É48bcAB
5É05abcB
5É60abAB
5É48bcA
5É22cdA
4É65bcB
5É31bcA
5É25cA
4É90dA
4É08cB
4É92cA
6É10aA
6É10aA
6É10aA
6É10aA
6É00abA
5É80abA
5É33aB
5É65abAB
5É80abA
5É55abAB
5É02abB
5É60abAB
5É40abA
5É16bB
4É51bcC
5É10bB
5É20bA
5É00bA
4É12cB
4É97bA
E†ect of type of packaging materials on durian leather
TABLE 3
Sensory characteristics changes of durian leather in di†erent packaging materials during storagea
a Mean of 20 panelists.
AhC Means within a column with di†erent letters are signiÐcantly di†erent (P \ 0É05).
ahd Means within a row with di†erent letters for each dryer are signiÐcantly di†erent (P \ 0É05).
433
J Irwandi et al
434
overall acceptability to LDPE-packed samples and the
highest scores to samples packed in LAF. On the other
hand, for several attributes, the use of HDPE and PP
did not give a signiÐcant e†ect.
There was a signiÐcant e†ect (P \ 0É05) of storage
time on the sensory qualities of durian leather.
However, for almost every attribute evaluated, there
was no signiÐcant di†erence for the Ðrst 2 weeks. Only
overall acceptability of oven-dried leather had a signiÐcant di†erence after 2 weeks of storage. In fact, for taste
and aroma of oven-dried leathers, and taste, texture and
overall acceptability of cabinet-dried leathers, no signiÐcant di†erences were observed up to week 4. Besides,
the scores of all sensory attributes signiÐcantly
(P \ 0É05) decreased, with the highest decrease found
for leathers packed in LDPE and the lowest changes for
LAF-packed leathers. Overall, all samples were acceptable (score more than 4), even after 12 weeks of storage.
CONCLUSIONS
Out of four types of packaging materials used, LAF was
found to be the best material to maintain the stability of
durian leather during storage. During 12 weeks of
storage, LAF had the lowest changes in moisture
content and A , a lowest decrease in colour quality and
w
a lowest increase in microbiol counts. Inversely, LDPE
had a highest changes in moisture and water activity, a
highest decrease in colour quality and a greatest
increase in microbial counts. This was closely related to
the water vapour characteristics of the packaging
materials. However, organoleptically, all four packaging
materials were acceptable.
ACKNOWLEDGEMENTS
The authors wish to thank Universiti Pertanian Malaysia for providing the research grant No. 50218-96-17 to
carry out this study.
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