effect of packaging and modified atmosphere on the shelf ... papers/pert vol... · effect of...

Pertanika 11(2), 217-228 (1988)

Effect of Packaging and Modified Atmosphere on the Shelf Lifeof Rambutan (Nephelium lappaceum) I

SUHAILA MOHAMED and ESHAH OTHMANDepartment of Food Science

Faculty of Food Science and BiotechnologyUniversiti Pertanian Malaysia

43400 Serdang, Selangor, Malaysia,

Key Words: Rambutans; low temperature storage; modified atmosphere storage and packaging.

ABSTRAKRambutan menjadi hitam dan keringdi bahagian kulit, dalam masa 72 jam bila ianya disimpan pada

suhu bilik tanpa bungkusan. Warna kulit, kemantapan dan berat rambutan dapat dikekalkan dengan me-nyimpan rambutan-dalam bungkusan tidak telap, pada suhu rendah (8°C) dan dalam udara 7% karbondioksid. Penyimpan rambutan pada suhu 8?C, dapat melanjutkan kesegaran rambutan sehingga 6 hari tan-pa bungkusan. Simpanan pada suhu rendah dalam bungkusan tidak telap (bekas polyethyelen) dapatmelanjutkan usia penyimpanan kepada 18 hari. Peningkatan kandungan karbon dioksid ketahap optima7% (kandungan awal) pada !fc dapat menekan pernafasan rambutan segar dan memanjangkan masasimpanan rambutan segar sehingga hampir sebulan. Dalam keadaan ini kesegaran rambutan dapat dikekal-kan hampir sebulan. Kesegaran rambutan tidak dapat dikekalkan lama tanpa oksigen kerana pernafasan-nya terencat. Satu kaitan rapat ujud antara kehilangan kelembapan rambutan, kegelapan kulit dan keman-tapan buah. Kerosakan rambutan lepas tuai adalah disebabkan perubahan-perubahan fisiologi.

ABSTRACTRambutans undergo rapid darkening and dehydration of the skin in 72 hours or less when stored

unwrapped at ambient temperature. Skin colour, firmness and weight of rambutans could be effectivelypreserved by low temperature storage, packagings and modifying the storage atmosphere. Low tempera-ture storage at 8° C prolonged the shelf life of fresh unwrapped rambutans to 6 days. Low permeabilitypackaging (polyethylene rigid containers) together with low temperature storage extended the shelf lifefurther to 18 days. Increasing the initial concentration of carbon dioxide to an optimum level of 7%at £°C effectively suppressed respiration of fresh rambutan and prolonged the shelf life to nearly a month.Total absence of oxygen (as with vacuum packages) was detrimental to the shelf life of fresh rambutan,since the fruit was unable to respire normally. A good correlationship was found between weight loss oframbutan, darkening of skin and frimness of the fruit. The post harvest deterioration of rambutans wasfound to be mostly physiological

related to the litchi {Nephelium litchi), longanINTRODUCTION ^ longana) and Pulasan (N. mutabile) and

The rambutan is a seasonal tropical fruit, so consists of a seed, surrounded by edible whitecalled because of its hairy skin. The skin is pulp enclosed in the skin. The size of the seed,green when young and ripens to red or yellow, the thickness of the pulp and skin depend ondepending on the variety. The fruit is closely variety. The planting area of rambutan in Malaysia

EFFECT OF PACKAGING & MODIFIED ATMOSPHERE ON SHELF LIFE OF RAMBUTAN

was 15,548 hectares in 1980 and is projectedto increase to 24,241 hectares by 1990 (Malay-sian Agricultural Directory and Index, 1986).

Tests carried out to gauge acceptance andperception to rambutan by 100 Hong Kongvisitors to the ASEAN Fruit and Vegetable Ex-position in September 1986 resulted in a "degreeof liking" score of 4.21 on a 1 to 5 scale where1 • dislike a lot and 5 = like a lot. Most of themindicated a willingness to purchase these fruitsif they were available in the market. (ASEANFood Handling Newsletter, No. 24, 1987).

The main problem with rambutan is therapid loss of moisture and physiological browningof the skin after harvest. This is normally followedcracking of the skin and exposure of the juicyflesh to pathological damage. This researchattempts to prolong the storage life of fresh ram-butans in order to reduce wastage and increase itsmarket potential by packaging and modifiedatmosphere (MA) storage.

Films with different permeabilities to 02

and CO2 are available (Anon, 1971). In a sealedpackage, most of the free O2 is used in a shorttime and CO2 are produced. At room temperature,injurious CO2 concentrations above 20% can buildup. Film packages can be used to develop benefi-cial MA through product respiration which isgreatly affected by temperature, humidity andtime the fruits remain in the package. Type andthickness of package affect the O2 and CO2 levels;and each fruit has a different tolerance for low0 2 or increased CO2 (Hall et al, 1973). Thistherefore merits the investigation on the packagingof rambutan. MA storage implies addition or remo-val of gases resulting in an atmospheric composi-tion substantially different from that of normalair. Modified Atmosphere storage, when combinedwith refrigeration, markedly retards respiratoryactivity and may delay softening, yellowing,quality changes and other breakdown process bymaintaining an atmosphere with more CO2 andless O2 than in normal air (Do and Salunkhe.1975).

MATERIALS AND METHODS

Rambutans of the red variety (R7) were harvestedin bulk from the University Orchards (Ladang 5).They were sorted, weighed and subjected tovarious treatment and storage conditions on the

same day. Each result is an average reading froman analysis of 6 fruits.

Low Temperature Storage StudiesGroups of fruits were sorted and stored at 8°C,20°C and at ambient temperature (27 ± 3°C).

Different PackagingFruits were packed in groups of 6 in (i) 0.05 mmthickness low density polyethylene bags (LDPE);(ii) vacuum (suction pressure 5.93 kN/m); sealedin 0.05 mm LDPE; (iii) perforated 0.02 mm LDPEbags (4 mm diameter hole per square cm); and(iv) polystyrene tray (CP10) with PVC cling filmoverwrap. All the bags had a dimension of 15.5cm x 22 cm. Unwrapped fruits were used ascontrol for both temperatures of storage.

Modified A tmosphere StorageFruits were stored in 6-litre air tight plastic con-tainers. Carbon dioxide was generated from abeaker containing weighed amounts of Na2CO3

and excess acid to produce an initial concentrationof 3.5%, 7.0% and 10.0% carbon dioxide in thecontainer. Fruits stored in normal atmosphere insimilar air tight plastic containers were used ascontrol.

Assessment of the Stored FruitsFruits were assessed for weight loss, skin colour,texture, % unacceptability and storage life. Colourwas determined using the Hunter Lab tristimuluscolorimeter, expressed as lightness (L), redness(a), and yellowness (b values), with the pink tileNo. C2-22952 as reference (L = 68.8, a = 21.2,b = 12.2). Texture of the skin and pulp weredetermined using the Instron Universal Testingmachine with the Kramer Shear cell attachmenton samples of dimensions 1 x 1 cm (skin) and2 x 2 cm (pulp). A drive speed of 50 mm/minand a chartspeed of 200 mm/min were used todetermine the yield force. The % unacceptablefruits were assessed based on the appearance ofthe skin and not to the taste of the flesh. Inmost circumstances, under the low temperaturestorage, the flesh was still very fresh and accep-table even if the skin had turned dark. The shelflife of the fruits was taken as the number ofdays when 90% of the skin had discoloured.

218 PERTANIKA VOL. 11 NO. 2, 1988

SUHAILA MOHAMED AND ESHAH OTHMAN

Microbiological AssaysPeeled rambutan was immersed in 100 ml steri-lized 0.1% peptone water in a beaker, followedby contimous shaking using an automatic shakerfor 1 hour at ambient temperature. 0.1 ml of theabove solution was spread plated onto variousmedia as follows;

i) Plate Count Agar (pH 7)— for estimation of total aerobic

bacteria.ii) Czapek Dox Agar (pH 6.8)

for estimation of mold,iii) Malt extract, yeast extract, glucose,

peptone agar (pH 5.4)- for estimation of yeast.

The plates, done in duplicates, were thenincubated for 1 - 5 days at 30°C. Microbialcounts were made and stated in terms of numberof colonies per gram (colonies/g).

RESULTS AND DISCUSSION

The shelf life of rambutans under various storageconditions and permeability of the various pac-kaging material are summarised in Table 1. Un-wrapped fruits stored at ambient temperatures,20°C and 8°C had a shelf life of 3, 4 and 6 days

respectively. On the 4th day, fruits stored atambient temperature showed skin dehydration,which leads to skin browning and shrinking. Theedible pulp became soft and had a fermentedsmell. By the 5th day, fungal growth was present.Although fruits stored at 8°C were shrivelled anddarkened after 6 days storage, the flesh was stilledible.

Storage of fresh rambutans in sealed LDPEat 8°C prolonged the shelf life to 16 days byreducing the amount of unacceptable fruits up to90% (Figure 7). Storage of fruits in perforatedLDPE at 8°C was less effective and resulted in ashelf life of 9 days, where the rate of browningand dehydration (% weight loss) was greatercompared to unperforated LDPE package (Figure2). At ambient temperatures, LDPE packagingmanaged to extend the shelf life of the fruits to5 days (Figure 3). Vacuum packed fruits at 8°Chad a shelf life of only 10 days. The absence ofoxygen interfered with normal fruit respirationand resulted in increased injury or browningcompared to normal LDPE packed fruits. Howeverdehydration, which relates to respiration, wassignificantly reduced in vacuum packed fruits(Figure 2).

Fruits packed in polystyrene trays andover wrapped with cling film, had a shelf lifeof 12 days at 8°C. Moisture loss from expanded

TABLE 1Storage life of fruits under different conditions and types of packaging materials.

Storage Life (Days) ± 1

Treatment 8°C 20°C Ambienttemperature

Packaging materials:

a) Control 6b) LDPE bag (0.05 mm thickness) 16c) Perforated LDPE bag (0.02 mm thickness) 9d) Vacuum pack (0.05 mm thick LDPE bag) 10

e) Polystyrene tray with cling film wrap 12

Modified atmosphere:

a) Control 18b) 3.5% CO 19c) 7.0% CO 26d) 10.0% CO 20

35454

4465

PERTAN1KA VOL. 11 NO. 2, 1988 219

SUHAILA. MOHAMED AND ESHAH OTHMAN

polystyrene with cling film wrap was highercompared to fruits wrapped in LDPE (Figure 2),thus explaining the shorter shelf life compared toLDPE packed fruits. Polystyrene is more per-meable than LDPE but less permeable than per-forated LDPE.

A: ControlA: LDPE bag (0.05 mm)o: Perforated LDPE bag

(0.02 mm)• : Polystyrene tray with

cling film wrap—: PE rigid containers0 : Vaccum pack

unacceptable level

Days

Fig. 1: % Unacceptable fruits with time storedat $Pc (Various packaging)

This experiment indicates that the shelflife of rambutans stored at 8°C is related to thepermeability of the packaging material. The lesspermeable, the packaging materials, the longerwill the rambutans remain attractive, providedoxygen is present for the normal respiration of thefruits. The permeability of the packaging materialaffected the storage life in 2 ways: (i) by reducingdehydration of the fruits, (ii) by causing theaccumulations of carbon dioxide and reductionin oxygen since gaseous exchange between theatmosphere inside and outside the package isreduced. The accumulated carbon dioxide in thepackage suppressed the respiration and sloweddown the physiological changes to the fruits.

Work by Mendoza et al (1972) on Seemat-jan and Maharlika rambutans showed that themost effective storage procedure was wrappingin sealed polyethylene bags and holding at 50°F(10°C) and 95% RH; by this mean a marketinglife of 12 days was achieved. However, sealedpolyethylene bags were ineffective at high, roomtemperature and ventilated bags were found tobe preferable. Chilling injury was observed at 7°C(45 °F). The most satisfactory material for reduc-ing weight loss during transport and stroragewas sawdust.

Modified Atmosphere StorageFruits stored in air tight polyethylene rigid con-tainers had a shelf life of 18 days at 8°C. Storageof rambutan under 7.0% carbon dioxide extendedthe shelf life to 26 days at 8°C (Figure 4). At thistime, when 90% of the fruits had discoloured skin,a slight alcoholic smell could be detected althoughthe flesh was still acceptable. Rambutans stored at8°C under 10.0% and 3,5% carbon dioxide had a

Ambient temperature10 °CControlLDPE bag (0.05 mm)Perforated LDPE bag(0.02 mm)

Polystyrene tray withcling film wrapVacuum pack

^ Days0 1 3 5 7 9 i t 13 15 17

Fig, 2: % Weight loss with time (variouspackaging)

220 PERTANIKA VOL. 11 NO, 2, 1988


© : ControlO: 3.5% CO2

• : 7.0<7o CO,• 10.0% CO

unacceptable level

10

Days0 1 3 5

Fig, 5: % Unacceptable fruits with time stored atambient temperature (Modified Atms.)

ColourObjective colour measurements using the HunterLab colorimeter showed that modified atmos-pheric (MA) storage retained the colour of fruitsstored at 8°C best (Table 2). The retention of thered colour (a values) was highest under MA storageespecially at 7.0% carbon dioxide level, followedclosely by 3.5% carbon dioxide level.

8.0-

6.0

4.0

2-0;

I 1 0

$ 0.8

0.6

0.4

0.2

Polythylene rigid containers and LDPEbags were effective in slowing down the darkeningof the skin colour compared to other packagingmaterials tested, at 8°C. However, fruit in per-forated bags or vacuum packed bags showed rapidskin browning (drop in a and b values). At ambienttemperature, fruits stored in LDPE bags and clingfilm showed better red colour retention comparedto the other kinds of packaging, even if the storagelife was not very much prolonged.

TextureTexture changes of fruits stored under differentpackaging are shown in Figure 7. Rambutansstored unwrapped showed an increase in toughnesson storage; the skin of those stored at ambienttemperature being tougher than those stored at8°C. The increase in toughness of the skin was dueto hardening of the skin with moisture loss.However, the texture of the pulp at both tem-peratures of storage showed decrease in firm-ness (Figure 8). This may be due to senescenceof the fruit on storage causing breakdown oftissues and fibres by autolytic enzymes. Onthe other hand, fruits packed in various pac-kaging materials showed decreased firmness inskin and pulp shearing test on storage.

During storage of rambutans, dehydrationof the skin resulted in increasing toughness;while senescene, resulted in a decrease in firm-ness. When dehydration is inhibited or sloweddown, the skin firmness was better maintained.

Increasing the initial level of carbon dioxidein the storage atmosphere, appeared to increasethe firmness of rambutan skins (Figure 9). 10%

Ambient temperature10°CControl

0 ] 3 5 7 9 II 1} 15 17 19 21 23 25 27 29

Fig. 6: % Weight loss with time (CO2 treatments)

PERTANIKA VOL. 11 NO. 2, 1988

- > Days

221


100-

A: CdntrolA: LDPE bag (0.5 mm)o: Perforated LDPE bag (0.02 mm)• : Polystyrene tray with ding

film wrapO: Vacuum pack

_. unacceptable level

(Days0 1 3 5 7

Fig. 3: % Unacceptable fruits with time storedat ambient temperature (Variouspackaging)

shelf life of 20 and 19 days respectively. Fruitsstored at ambient temperature under 3.5%, 7%and 10% carbon dioxide, had a shelf life of 4, 6and 5 days respectively {Figure 5), after which afermented smell was observed and the flesh wasacidic. The increased level of carbon dioxide retar-ded the respiration of the fruit as well as anyaerobic microorganism which may be present.However, the optimum carbon dioxide levelappeared to be around 7%; a very much furtherincrease in carbon dioxide level, depressed aerobicrespiration and resulted in a higher % of anaerobicrespiration in the fruit, causing the fermentedsmell, and a decreased shelf life of the fruit.

Weight LossGenerally, the weight loss in fruits stored at8°C was much lower than in fruits stored atambient temperatures (Figures 2 &6). Among thevarious types of packaging, sealed LDPE bagswithout vacuum at 8°C showed the lowest weightloss of about 0.5%, followed by vacuum packaging

(1%), expanded polystyrene with cling film wrap(3.5%), perforated LDPE bags (19%) and control(unwrapped fruits, 24%) at the end of their shelflife (Figure 2).

Under modified atmospheric storage at8°C, 7.0% carbon dioxide showed the minimumweight loss, compared to the control, 3.5% and10.0% carbon dioxide. However, at ambienttemperatures 10.0% carbon dioxide atmosphereresulted in a higher weight loss than that of thecontrol (Figure 6). The weight loss at 3.5% and7.0% carbon dioxide was not significantly diffe-rent from each other (at 5% level) at ambienttemperatures.

The amount of dehydration in rambutanstherefore(1) increases with increasing premeability of the

packaging;(2) increases with increasing respiratory injury

in the fruits when the permeability of-thepackaging material is kept constant. This isseen in vacuum, packed fruits and 10.0%carbon dioxide MA stored fruits at ambienttemperatures.

O: ControlO: 3.5% CO2

: 7.0%10.0%

O2

CO,

100-

222

0 3 ]"l |'S 19 23 27

Fig. 4: % Unacceptable fruits with time storedat 8°*C (Modified Atmosphere)



TABLE 2

Day

8°C

13579

1115171921232529

ControlL

26.425.923.719.915.916.415.817.012.5

Ambient

125

24.719.012.9

a

6.07.78.29.510.9.48.57.74.8

2.13.74.0

Various packaging8C

13579

11131517

Control

17.715.014.113.4

Ambient

135

16.115.213.4

8.36.55.14.9

6.55.73.7

b

2.43.04.14.55.56.35.63.93.3

3.63.12.7

6.95.74.03.4

4.23.53.1

Effect of packaging and MA storage on rambutan skin color

3L

22.32U920.017.915.915.514.314.214.113.5

25.019.314.5

LDPE

19.918.218.517.716.715.9

15.013.5

20.118.615.5

J%CCa

10.411.413.715.712.59.38.78.47.97.4

7.26.54.2

13.010.910.49.88.57.8

7.06.2

11.911.39.7

nb

2.93.24.44.65.17.15.85.33.53.5

2.83.52.9

6.96.46.05.75.45.2

4.13.9

7.05.83.9

L

23.923.822.719.616.714.613.513.112.912.712.612.312.0

24.718.413.0

7.0% CO2a

9.89.59.1

15.015.311.99.89.08.38.17.46.56.9

3.94.55.9

b

4.04.24.34.84.94.64.14.03.73.43.33.22.8

1.42.33.3

L

23.022.921.020.017.016.015.414.76.2

12.011.8

24.120.914.7

10.0% CO2a

10.310.510.711.412.312.79.17.74.15.85.4

7.97.15.9

Perforated LDPE Polystyrene

18.517.815.314.914.5

18.316.814.7

10.19.07.36.16.1

8.56.94.0

7.76.55.84.84.2

6.14.73.4

22.220.219.117.015.914.714.3

21.718.215.0

14.213.311.09.48.47.56.8

11.19.47.6

b

2.22.42.52.83.53.95.35.5

3.22.9

3.63.33.3

6.96.55.85.34.13.43.3

4.84.13.5

L aVacuum

18.717.917.616.015.613.5

19.517.416.5

9.27.66.84.34.03.7

7.45.44.9

b

6.96.35.95.03.83.5

6.95.74.3

S.D. between 0.1 - 0.3 units

carbon dioxide gave a firmer skin texture than7.0% carbon dioxide, and 7.0% carbon dioxidegave a firmer texture than 3.5% carbon dioxide.The high carbon dioxide levels may have sup-pressed respiration which in turn may have re-duced the production of enzyme responsiblefor the pectin degradation in the fruits, henceretarding softening. However, fruits stored in10% carbon dioxide also showed greater weightloss and shorter shelf life, indicating carbondioxide injury.


Packaging and modified atmospheric sto-rage appeared to benefit pulp firmness (Figures8 and 10). The pulp was firmest under vacuumpackaging followed by LDPE packaging. Thevacuum packaging appeared to retard cell struc-ture breakdown, but on prolonged storage (afterthe 11th day) caused fruit injury. In modifiedatmospheric storage, the pulp firmness followedan almost similar trend to skin firmness, i.e. 10%carbon dioxide gave the best response, but pro-longed storage in 10% carbon dioxide resulted in

223


38.0

—r 1 1 rM 13 15 17

I1

\ir

I0 1

Ii//

v (

it

3

fii

tii

\

»

5

Ambient temperature10°C

ControlLDPE bag (0.05 mm)Perforated LDPE (0.02 mm)Polystyrene tray withcling f i lm wrapVaccum pack

Days1 3 5 7 9

Fig. 7: Skin firmness with time (Various packaging).

a shorter shelf life compared to 7% carbon dioxidestorage, because of carbon dioxide injury.

Correlationship between Weight Loss, Texture andColourThere appears to be a good correlationshipbetween skin firmness and L value for all thetreatments both at 8°C and ambient temperature.Under the packaging experiments a good corre-lationship could be seen between texture and allthe tristimulus values, L, a and b (Table 3) forskin colour.

Table 4 shows the close correlationshipbetween skin texture and weight loss (dehydra-tion), or pulp texture and weight loss both at8°C and ambient temperature. This indicates that

37.0

36.0

34.0-

32.0'

30.0

28.0-

26.0-

24.0

22.0 .

20.0

18.0-1

16.0

224

the loss in turgidity of cells is the major cause ofthe reduction in skin and pulp firmness.

The existence of a correlationship betweenfirmness with lightness (L value) and firmness withdehydration indicates' the presence of a corre-lationship between fruit darkening with dehydra-tion. Theoretically therefore, fruit darkening canbe prevented by preventing dehydration. However,there appear to be no strong correlation betweena values (redness) or b values (yellowness) totexture of dehydration. Therefore the overallskin colour could not be preserved by merelypreventing dehydration. Dehydration triggersphysiological changes in the fruit and causescell injury which would trigger the enzymicbrowning in the skin.

Ambient temperature10 °CControlLDPE bag (0.05 mm)Perforated LDPE bag((0.02 mm)Polystyrene tray with clingfilm wrapVacuum

-i r-—i ] 1 1 1 1 1—1 3 5 7 9 11 12 15 19

Days

Fig. 8: Pulp firmness with time (Various packaging).


TABLE 3Correlationship between skin firmness with colour

s<or:p

-00

l reatments

MODIFIED ATMOSPHERE (CO*)(8°C)

a) Controlb) 3.5%c) 7.0%d) 10.0%

PACKAGING MATERIAL(8°Q

a) Controlb) LDPE bags (0.05 mm)c) Perforated LDPE bags (0.02 mm)d) Polystyrene tray with cling filme) Vacuum pack

MODIFIED ATMOSPHERE (CO2)(Ambient)

a) Controlb) 3.5%c) 7.0%d) 10.0%

PACKAGING MATERIALS(Ambient)

a) Controlb) LDPE bags (0.05 mm)c) Perforated LDPE bags (0.02 mm)d) Polystryene tray with cling flhne) Vacuum pack

N

18202622

816101412

6666

66666

Correlation CoefficientTexture vs Colour

L

0.9480.9970.9830.970

-0.9010.8930.8850.9830.857

0.9880.9980.9820.990

-0.9990.9190.9990.9750.960

a

-0.0340.5800.5140.606

-0.8950.9480.9010.9680.932

-0.8520.961

-0.8950.978

-0.9960.8940.9990.9650.925

b

-0.507-0.520

0.6310.690

-0.9470.9220.9170.9890.875

0.972-0.115-0.9650.661

-0.9510.8410.9870.9790,999

y =y =y =y =

y =y =y =y -y =

y =y =y =y -

y =y -y =y -y =

L

0.729 x+ 9.6011.564 x+ 0.6191.10 x+ 12.4571.077 x+13.357

-2.411 x+59.8411.815 x-0.4420.554 x +9.8271.239 x +0.2681.029 x+13.152

0.760 x+21.0090.317 x+20.2930.982 x +26.0281.399 x+ 4.229

-6.251 x+122.3430.996 x+11.5020.368 x+18.7410.874 x+ 8.0692.212 x -7 .817

Best Fitted LineTexture vs Colour

a

y = - 0.07 x + 24.226y= 1.116 x+15.391y= 0.962 x+20.894y= 1.061 x+21.827

y=-2.873 x+41.372y= 1.778 x+ 13.925y= 0.576 x+ 14.364y= 1.287 x+ 9.180y= 0.941 x + 24.609

y =-3.786 x+47.713y = 1.022 x +20.407y = -16.589 x +39.900y = 6.562 x-13.647

y = -5.940 x+60.690y= 2.000 x+ 7.568y= 0.292 x+22.965y= 1.655 x+ 8.555y= 2.480 x+16.921

yyyy

y

yyyy

y

yyy

yyyyy

b

= _ 1.477 x +29.993= -2.074 x+36.570= 5.118 x+10.067= 12.828 x+41.521

= -2.985 x +38.487= 3.716 x+10.03= 0.755 x +14.427= 2.567 x+ 9.217= 1.451 x+22.59

= 9.780 x+ 4.702= 0.507 x+28.061 J

=-19.314 x+36.500= 25.767 x-55.540

= -14.684 x +82.069= .0.983 x+15.017= 0.487 x +22.547= 5.519x+ 5.382= 2.724 x+16.20

mmnHO*nP

AC

K

C2c

2Sa

2

mrn

zc/>Xm>nrmO

1H

•z

N: Number of readings for calculation of correlationship.

TABLE 4Correlationships between skin firmness with weight loss and pulp firmness with weight loss

m?o

^.

r-

ZO

3030

Treatments

MODIFIED ATMOSPHERE (C0 2 ) (8°C)

a) Controlb) 3.5%c) 7.0%d) 10.0%

PACKAGING MATERIALS (8°Q

a) Controlb) LDPE bags (0.05 mm)c) Perforated LDPE (0.02 mm)d) Polystryene tray with cling filme) Vacuum pack

MODIFIED ATMOSPHERE (CO2> (ambient)

a) Controlb) 3.5%c) 7.0%d) 10.0%

PACKAGING MATERIALS (ambient)

a) Controlb) LDPE bags (0.05 mm)c) Perforated LDPE (0.02 mm)d) Polystryene tray with cling filme) Vacuum pack

N

18182626

816121412

6666

66666

Correlation Coefficient Best Fitted LineSkin Texture vs Wt. Loss Pulp Texture vs. Wt. Loss Skin Texture v<vs. Wt. Loss

-0 .941-0 .901-0 .829-0 .929

0.992-0 .903-0 .922-0 .978-0 .662

-0.987-0 .999-0 .840-0 .904

0.982-0 .943-0 .983-0.966-0 .944

-0 .947 -•* 0.914

-0.932-0.923 '

-0.970-0.918-0.827-0.991-0.610

-0.968-0.993-0.940-0.973

-0.992-0.880-0.999-0.895-0.936

y =y =y =

;• y =

y =y -y =y =y =

y =y =y =y =

y -y =y =y =y =

-23.078 x+32.045-38.285 x+40.412-27.178 x+40.446-31.800 x+43.920

0.614 x+14.77623.261 x + 36.502-0.136 x+20.451-3.142 x+28.614-3.178 x+31.249

-2.078 x+41.640- 3 242 x+30.646-2.957 x+35.503-1.810 x+39.871

0.588 x+14.310-6.0969 x+32.433-0.094 x+25.984-0.538 x+28.142

-10.718 x 38.200

yyyy

yyyyy

yyyy

yyyyy

>. Wt. Loss Pulp Texture

--16 .62 x+25.402= -44.491 x +37.319=-17.238 x+29.448=-13.563 x+28.548

= -0.334 x+27.210= -15.137 x+30.149= -0.405 x+23.437= -4.845 x +33.027= -5.677 x+31.999

= -1.762 x+36.447= -6.636 x+32.432= -2.521 x+29.411= -1.255 x+34.727

= -0.210 x+29.567= -8.395 x+32.069= -0.381 x+28.827= -0.589 x+27.378= -6.467 x+32.336

C

XILAM

OI

X

1ITI

mO>

zDmXX

|

• ' * •

J

N: Number of readings for calculation of correlationship.


18X)

: Ambient temperature: 8°C

O ContFOl0 : 3.5% CO2

7.0% CO,

9 11 13 15 P 19 21 23 25 27 29Days

Fig. 9: Skin firmness with time (CO2 treatments)

Microbiology AssaysStorage of fruits at 8°C with respect to typesof packaging showed low levels of microbialcount. Only yeasts were found in each packagingtreatment in the range of 1.0 x 102 to 11 x 103

colonies/g. Vacuum packed treatment showed thehighest yeast count of 1.1 x 103 colonies/g. Am-bient temperature storage treatments showed aslightly higher amount of yeast count, in the rangeof 1.0 x 103 to 2.45 x 103 colonies/g.

The results obtained showed that spoilageof rambutans was not due to microbes, sincestorage at both temperatures of 8°C and ambienttemperature only showed a slight difference inthe microbial counts. The counts obtained may be

due to contamination through handling during theexperiment or may be due to insect infection onfruits before hand. Another factor which may bethe cause of spoilage is through skin injury of thefruits.

Tongdee et al (1982) observed that the ini-tial browning during storage of tissue at the stemend adjacent to the seed of litchi fruits appearedto be a senescent process and not related to micro-bial deterioration. No fungal growth was obtainedwhen isolations were made from the browntissue early in storage but as browning progressed,positive isolations resulted.

The rambutan skin which is firm and thickhelps to keep the flesh sterile for a period of time.

- : Ambient temperature- : 10°CQ : ControlO : 3.5% CO2

• : 7.0% CO2

$ : 10.0% CO,

9 11 13 15 17 19 21 23 25 27 29

Fig. 10: Pulp firmness with time (CO2 treatments)

PERTANIKA VOL. 11 NO. 2, 1988 227


The fact that fruits stored in various packagingmaterials were still edible at the end of the storagelife at 8°C (26 days), even though dehydrationand browning of the skin occurred, proved thispoint.

ACKNOWLEDGEMENT

The authors thank the Universiti farm per-sonel for making available the fruits for research(especially Wan Jaharah Wan Ngah and Haji Mah-mood Jaafar), Encik Abdullah Hassan (BTM,MARDI) for useful suggestions at the start of theresearch, and Norhayati Salamuddin for typing themanuscript.

REFERENCES

ANON (1971): Properties of basic packaging films.Modern Packaging Encyclopedia 44 (7A): 144.

ASEAN FOOD HANDLING NEWSLETTER (1987):No. 24.

DO J.Y. and D.K. SALUNKHE (1975): ControlledAtmosphere Storage in Postharvest physiology,handling and utilization of tropical and subtro-pical fruits and vegetables. Ed. Pantastico E.B.AVI Publishing Co.

HALL C.W., K.E. HARDENBURG and E.B. PANTAS-TICO (1973). Consumer packaging with plasticsin Postharvest Physiology, Handling and Utili-zation of Tropical and Subtropical Fruits andVegetables. Ed. Pantastico E.B. AVI PublishingCo.

MALAYSIAN AGRICULTURAL DIRECTORY & IN-DEX (1986). 84/85 : 91:

MENDOZA D.B. Jr., E.B. PANTASTICO and F.B. JA-VIER (1972): Storage and handling of rambutan(Nephelium lappacum L.) Philippine agric. 55:322.

TONGDFE S.C. (1982): Packaging and cold storage ofLitchi fruit. CSIRO Food Research, 42 : 25.

(Received 17 June, 1987)

228 PERTANIKA VOL. 11 NO. 2, 1988

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