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Impact damage in mangosteens(Garcinia Mangostana L.)S. Prasertsan a , C. Peeraprasompong b & P. Thamaratwasik ba Department of Mechanical Engineering , Prince of SongklaUniversity , Hat Yai, Thailand, 90110b Department of Food Technology , Prince of SongklaUniversity , Hat Yai, Thailand , 90110Published online: 02 Sep 2009.

To cite this article: S. Prasertsan , C. Peeraprasompong & P. Thamaratwasik (1998) Impactdamage in mangosteens (Garcinia Mangostana L.), International Journal of Food Properties, 1:3,243-254, DOI: 10.1080/10942919809524580

To link to this article: http://dx.doi.org/10.1080/10942919809524580

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INTERNATIONAL JOURNAL OF-[ FOOD PROPERTIES, 1(3), 243-254(1998)

IMPACT DAMAGE IN MANGOSTEENS ( GARCINIA MANGOSTANA L.)

S. Prasertsan1,*, C. Peeraprasompong2, P. Thamaratwasik2

1Department of Mechanical Engineering, Prince of Songkla University,Hat Yai, Thailand 90110

2Department of Food Technology, Prince of Songkla University,Hat Yai, Thailand 90110; *Corresponding author

ABSTRACT

Mangosteen pericarp is very susceptible to mechanical force. The damaged pericarpreleases latex which causes pericarp hardening, spoils the flesh and shortens the shelflife. In order to maintain good quality, the mangosteens require careful handling inevery step from the orchards to the consumer. It is essential to establish the limit ofmechanical force or energy allowed in the handling processes. In this study, impactdamage in mangosteens was investigated. It was found that the degree of damage canbe related to the impact velocity, impact energy and energy absorbed by the fruit. Thedegree of damage was presented in the terms of the mass of hardened pericarp, damagedepth ratio of the pericarp, weight loss and withering of the aril. Two types ofpackaging materials, the polystyrene foam and card board, were tested for theirprotective abilities. It was found that the packaging material for the mangosteensshould be soft and have low stiffness. Deterioration of damaged mangosteens withstorage time was also presented. Empirical equations describing the impact damagebehaviour and the allowable impact energy were established.

INTRODUCTION

An understanding of mechanical property of fruit is essential for reducing mechanicaldamage in the produce handling. Mechanical damage provides the entrance formicroorganisms to spoil the produces. Consequently, the loss was reported as high as30% (Dalai, 1988).

243

Copyright © 1998 by Marcel Dekker, Inc. www.dekker.com

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244 PRASERTSAN, PEERAPRASOMPONG, AND THAMARATWASIK

Mangosteen (Garcinia mmgostana L.) is often referred as the "Queen of theFruits" because of its pleasant odor, delicate taste and soft texture. Mangosteen wasranked second after durian in the list of export fruit of Thailand (Department ofCommercial Economics, 1994). In stead of having thick-soft pericarp, the mangosteenflesh is easily perishable. The soft pericarp releases yellow latex if the cells aredamaged, mostly by mechanical force. The damaged pericarp develops hard core, thenucleus from which the hardening keeps expanding. If the latex spreads into the flesh,which often occurs, the fruit is not acceptable by the market. Unfortunately, suchdamage is unnoticeable from the external appearance, but can be sensed only by fingersqueezing for the hard spot. However, squeezing is usually not permitted since, if thefruit is good, it will cause the damage.

Mangosteen is very susceptible to mechanical force, which presents in almostevery step of the fruit handling, e.g., harvesting, cleaning, grading, packaging anddistribution. Although the postharvest management is a critical factor for the marketquality, yet very few works on the mechanical-damage resistance of mangosteen werecarried out. Theerapawa et. al. (1986) reported that the harvesting by a speciallydesigned detaching bag could reduce the damage by a factor of three compared to theconventional method which detaches the fruits dropping on the ground. Tongdee andSuwanakul (1989) found that the pericarp could not withstand a drop on concrete floorfrom 10 cm height. At 20 cm drop tests the damage progressed to the flesh. Thedamage threshold in the quasi-static compression was 5 kg.

The experiment by Tongdee and Suwanakul (1989) did not give the damage-resistant property of mangosteen directly. It has been shown that the degree of damagedepended on the energy absorbed by the fruit (Holt and Schoorl, 1977). Therefore, it isappropriate to determine the amount of damage with respect to the mechanical energyabsorbed by the fruit. The term specific damaged mass (or volume) is commonly usedto define the fruit susceptibility to mechanical force. Specific damaged mass (SDM) isdefined as the ratio of the mass of damaged pericarp to the energy absorbed by themangosteen.

In order to set a guide line for postharvest management, fundamentalknowledge of the mangosteen damage resistance must be clearly understood. Thispaper reports the susceptibility of the mangosteens subjected to impact. Two types ofpackaging materials, polystyrene foam and card board, used for protecting the fruitagainst impact damage were also studied.

MATERIALS AND METHODS

The Fruit

The mangosteens were hand-picked from an orchard. The fruit maturity, according toTongdee and Suwanakul (1989) classification method, was stage 2. The pericarp waslight greenish yellow or yellowish pink with distinct irregular pink spots covering theentire fruit. The newly picked fruit was packed in plastic bags, not more than three kgper bag, and transported to an air conditioned laboratory where the fruit was cleanedand kept for experiment when its maturity reached stage 4. The maturity stage 4, the

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IMPACT DAMAGE IN MANGOSTEENS 245

^ H „ ..••••' 2 laser sources and photo^ H ^--^A ••ii-*"—" receivers

EEx° „• 1 — Granite

Figure 1. Principle of impact testing apparatus

stage recommended for export, was identified by the red or reddish brown pericarpwith some purple tinge. The fruit was divided into three groups according to theweight. Mangosteens of groups 1, 2 and 3 weigh 60-80g, 80-100g and 100-130 g,respectively.

The Apparatus

In an attempt to evaluate the true property of the fruit, the energy absorbed by the fruitmust be measurable. The test rig must be devised to measure the velocities of the fruitright before and after the impact. An apparatus employing the pendulum principle,Figure 1, set the fruit at an adjustable height. The fruit was tied at the calyx andreleased from the holder. By the gravity, the fruit swang, hit the granite slab andbounced back. Two laser light sources and photo receivers together with a signalanalyzer detected the inbound and outbound laser beam crossing times of the fruit (tjand to). The corresponding velocities of the fruit can be determined as following,

V,2 = 2gr (1)

Alternatively, V2 = v? + 2gh (2)

Therefore, 2gh = 2gr- \y\

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246 PRASERTSAN, PEERAPRASOMPONG, AND THAMARATWASIK

Similarly, Vo2 = vj+ 2gh

The energy immediately before and after impact (Eh Eo) are,

E, = mgr (4)

Eo = \mVo2 (5)

Substitute equation (3) into (5),

ms2(\ 0Eo = mgr-—\jj-7jj (6)

Energy absorbed by the fruit, Eab, is the difference of £,and Eo,

E,= f fe-3 (7)All parameters on the right hand side of equation (7) can be determined from theexperiment. The distance s, mass m and time t were measured with resolutions of 0.25mm, 0.01 g and onefis, respectively.

Experiments

There were two experiments in the study namely the damage resistant property ofmangosteens and the damage under the protection of packaging materials.

In the determination of damage resistance of the mangosteens, the fruit wasreleased at the heights of 10 to 40 cm with an increment of five cm. At each droppingheight, 25 mangosteens were tested. Thus, for the seven drop heights, the experimentwas conducted on 175 mangosteens and 25 untreated as the control. Two duplicateswere carried out (altogether 400 mangosteens). The fruit was kept for three days until itreached maturity stage 5 (darken to reddish purple), the best eating stage, after whichthe hardened pericarp was fully developed. The hardened pericarp was carefullyremoved, weighed and the subsequent specific damaged mass (SDM) was determined.The damage depth ratio (DDR), which is the thickness of the hardened portion of thepericarp divided by the total thickness at the damage spot, was determined. The SDMdetermines the damage susceptibility of the pericarp while the DDR indicates theseverity of damage (through which mechanical force advances to injure the flesh).Weight loss was determined and used to indicate the degree of damage. However, thequality of the mangosteen is preferably evaluated by the level of withering of the aril.There were five levels of withered aril. Level zero means no injury to the aril. Level 1was identified if the aril damage was noticeable but the flesh (at the impact spot) was

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IMPACT DAMAGE IN MANGOSTEENS 247

not flattened. Levels 2, 3 and 4 were defined as the flesh was flattened byapproximately one, two and three mm, respectively. Normally the withered aril ofdamage levels 2, 3 and 4 developed yellowish brown color.

Packaging materials under investigation were polystyrene foam of three mmthickness and card board. The card board was obtained from those used to pack layersof apples in the cartons. It has an array of curve-formed setting for individual apple.The polystyrene foam and the card board are characterized by mass-to-area ratio as0.0069 g/cm2 and 0.0533 g/cm2, respectively. The packaging material was fixed to thegranite slab at the striking point. The mangosteens of maturity stage 3 were obtained.They were sorted for uniform size and weight of 100 ± 10 g and kept in the laboratoryfor the experiment at maturity stage 4. The fruit was released from the drop heights of20 cm, 40 cm and 60 cm. The fruit struck the granite slab with and without thepackaging material protection. The specimens were kept for 3, 8, 13, 18 and 23 daysthe time at which the damage was evaluated. There were Five fruits for each treatmentand two duplicates were carried out. Therefore, altogether 500 mangosteens were usedin this experiment.

RESULTS AND DISCUSSION

Damage Resistance of Mangosteens

The impact damage of mangosteen was evaluated as functions of impact velocity andabsorbed energy. The impact velocity depends on the drop height but not the mass,hence different sizes (masses) of the fruit may hit the granite slab at the same velocity.Drop height or impact velocity was often used as a variable in damage study of fruitand vegetable (Tongdee and Suwanakul, 1989 ; Holt and Schoorl, 1980). However, fora particular impact velocity, the impact energy might be different if different masses offruit are used. Absorbed energy-related damage, such as SDM, is a more general termas it directly relates to the energy that damages the pericarp tissue.

After 3 days of impact, the hardened pericarp was removed, measured andweighed. Figure 2 showed that the amount of hardened mass increased with the impactvelocity (drop height).' For all three sizes of the mangosteens, the highest impactvelocity of 2.8 m/s (drop height of 40 cm) gave hardened pericarp up to 2.5-3.0 timesof those caused by the lowest impact velocity (1.4 m/s or drop height of 10 cm). It wasnoticed that there was impact velocity threshold, which depended on the size of thefruit, for the pericarp damage. At impact velocity beyond 2.20 m/s, the damage interms of hardened pericarp of the small size mangosteens increased distinctively. Thecorresponding thresholds for the medium and large mangosteens were 2.00 m/s and1.40 m/s, respectively. This observation, in fact, indicated the role of impact energysince energy depends on both mass and velocity.

As the impact velocity increased, the DDR increased nonlinearly as shown inFigure 3. The DDR of the small fruit notably varied with the impact velocity, becauseits pericarp was relatively thin. However, the impact velocities that gave unity DDR ofthe large and medium fruit were 2.43 m/s and 2.80 m/s, which are lower than that ofthe small fruit. In other words, the smaller the fruit, the higher is the tolerable drop

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248 PRASERTSAN, PEERAPRASOMPONG, AND THAMARATWASK

6.00 . . . • 1 1 — np—

5.00 J-/ ^ ^ _ x - small

| 4.00 / J^a S / -A_ medium

g. 3.00 r J- _^S•g ^ - ° ^ ^ S ^P^ -o-laige

I 2.oo L = ^ : ^ ^ — ^ ^ ? ^ l z ^a %• —• *——^ \f

1.00 i~r--~

0 . 0 0 -I 1 1 1 I I I1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80

Impact velocity (m/s)

Figure 2. Effect of impact velocity on the damage of pericarp (three days afterimpact)

1.05 -, . . . . . .

I- I.OO ~Z^° 1^^\ 1«3 ^ ^ - ° y/ y/\ —x— small

2 0 9 0 y ^^•'^ / I -^ -medium

| 0 . 8 5 l _ _ Y 1 ^_laise

i / |l I

0.75 \ 1 1 I | | |1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80

Impact velocity (m/s)

Figure 3. Effect of impact velocity on the damage depth ratio (three days afterimpact)

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IMPACT DAMAGE IN MANGOSTEENS 249

Table 1. Weight loss of damaged mangosteens three days after impact

Drop height(cm)Control

1.401.721.982.212.432.622.80

Percentage of weightSmall

4.32 ax4.37 b x4.50 b x5.10 ex5.50 d x5.32 e x4.99 b x5.42 d x

Medium3.474.485.084.394.895.214.484.80

a xb xd yb y

cdyd yb xcy

lossLarge

3.39 a x3.48 a y3.71 b z3.77 b z4.29 c z4.35 c z3.69 aby3.91 b z

Note: a, b, c, d indicate significant difference at 95% confidence levelin column; and x, y, z indicate significant difference at 95%confidence level in row.

height. Statistical analysis showed that the difference of DDRs between 0.97 and 1.00was insignificant (p < 0.01). If DDR 0.97 is the limit, it is recommended that theallowable drop heights of the large, medium and small size mangosteens are 20 cm, 35cm and 40 cm, respectively. The small size mangosteen, while the mass is 61% of thelarge mangosteen, can withstand a drop height two times of the large one. In otherwords, the small mangsteen can tolerate impact energy 20% higher than the largemangosteen can.

Weight loss at day 3 after the impact is presented in Table 1. The larger fruithad lower percentage of weight loss. However, the average weight loss of the largefruit was 4.95 g which was higher than 3.85 g of the small fruit. Itxan be explained bythe fact that the large fruit was hit with higher impact energy; hence bigger damagedpericarp as shown previously in Figure 2. Thus, apart from the higher surface area forweight (water) loss due to respiration, the cell liquid released from the damagedpericarp was also responsible for the higher weight loss.

Aril damage was evaluated as shown in Figure 4. Aril damage of degree 1occurred at impact velocities of 1.98 m/s, 2.33 m/s and 2.40 m/s for the large, mediumand small fruits, respectively which are less than those cause unity DDR (see Figure 3).This implies that the impact force (or energy) can travel through the pericarp to injurethe flesh but the whole thickness of the pericarp is not necessary be damaged. Thevery soft and juicy tissue of the aril is responsible for its lower damage threshold incomparison to the pericarp (at the innermost layer).

The impact energy of every fruit (350 samples) can be plotted together,regardless the size and drop height, and related to the damage of pericarp as shown inFigure 5. The experiment enabled the evaluation of the energy absorbed by the fruitduring the impact. The energy absorbed by the fruit increased nonlinearly with theimpact energy as appeared in Figure 6. Data plotted in Figure 6 are the average energyof the mongosteens in the same group, two duplicates. Statistic analysis revealed thatthe experiment is reproducable (Peeraprasompong, 1996 ). The energy absorbed by the

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250 PRASERTSAN, PEERAPRASOMPONG, AND THAMARATWASIK

3.50 .

3.00 U-

_ 2.50 / j

j> / j -x-small"w 2.00 / ^,—-4-A-medium

| ,.50 ^—/^A^^_

1 i.oo z^° /y — -

o.5o ^L ^iF- I

1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80

Impact velocity (m/s)

Figure 4. Effect of impact velocity on the aril withering level (three days afterimpact)

7.00 ,

6.00 . . /l !

y=19.962x2 + 2.7238x +0.9941 \ / j

@ 5 0 0 - - R2 = 0.9422 T/

J 4.00 .. J/

1 3 . 0 0 . . I J P ^ I I

£ 2.00.. j f j^T I

1.00 .. j ^ ^ ^ I

0.00 J 1 1 1 1 10.00 0.10 0.20 0.30 0.40 0.50

Impact energy (J)

Figure 5. Effect of impact energy on the damage of pericarp (three days afterimpact)

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IMPACT DAMAGE IN MANGOSTEENS 251

0.40 .

0.35 _.y = 0.6742x2 + 0.5311x S\. . . R2 = 0.9603 Y

& 0.25 -- %/^

«3 0.20 .- T l l ^ ^

1 0.15 .. \JkT^I o.io .. &$-

0.05 .- _ ^ 1 ^

0.00 ti+l 1 1 1-0.05 J

0.00 0.10 0.20 0.30 0.40 0.50

Impact energy (J)

Figure 6. Energy absorbed by mangosteens as function of impact energy

mangosteens can be written as:

Eab = 0.6742 E,2 + 0.5311 E, (8)

The mass of the damaged pericarp, Md (g), related to the absorbed energy can bederived from Figure 5 and equation (8) as:

Md = 34.702 Eab2 + 1.2496 Eab+ 1.4467 (9)

The SDM (g/J) is obtained by differentiating equation (9):

SDM = 69.404 Eah + 1.2496 (10)

Equation (10) gives the true damage resistant property of the mangosteen. Usually, Eab

has to be determined from the experiment for a particular material. Dropping the fruitat the same height but striking on different floor materials will yield different Eab

because the floor material itself also absorbs impact energy. It is commonlyunderstandable that concrete floor can easily injure the mangosteen but sand pitprobably cannot. The polished granite slab used in this experiment is very hard andmassive. It is, therefore, reasonable to assume that the energy absorbed by the graniteslab is negligible and equation (7) is valid for this experiment.

It is, sometimes, desirable to write the SDM as a function of impact energybecause the impact energy can be easily determined from the mass m (kg) and drop

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252 PRASERTSAN, PEERAPRASOMPONG, AND THAMARATWASIK

height r (m). This can be achieved by substituting equations (8) and (4) into equation(10):

SDM= 4503.1 (mrf + 361.6mr + 1.250 (11)

However, equation (11) is valid only when the mangosteen is dropped on a granitefloor. For other floor materials, the relation similar to equation (8) is required.

Damage under Protection of Packaging Materials

Table 2, where the average data of 400 mangosteens are presented, gives a clear pictureof the role of the two packaging materials on the damage protection ability for thefruit. The packaging material, when placed at an impact interface, reduced the damageby the self absorbing of the impact energy; thus allowed less energy getting to thefruit. It is evident that the polystyrene foam is preferable in comparison to the cardboard. The energy absorbed by the fruit was reduced by 22.7-64.0% and 3.0-8.3%when the foam and card board were employed, respectively. The card board is toodense and too hard to protect the mangosteens. In other words, it can be concluded thatsoft and low stiffness material is recommended for packing of the mangosteens.Therefore, only damage characteristic under the protection of polystyrene foam will befurther discussed.

Energy absorbed by the 100 g mangosteen protected by three mm thickpolystyrene foam is:

Eah = 0.8861 E, - 0.1236 (12)

Substitute equations (12) and (4) into (9), obtain the Md (g) of the mangosteen mass m(kg) wrapped by three mm polystyrene foam and dropped at height r (m) on a hardfloor as:

Md =2622.15 3(mr)2-73.705mr+1.8232 (13)

Equation (13) is only a guide line to evaluate the pericarp damage of the mangosteen.Alternatively, if the allowable Md is set by the market, the allowable impact energy(Eia) must not exceed,

Eia = 0.1379+(0.0367Md-0.0479)OJ (14)

Equation (14) is a criteria for the design of mangosteen handling system if Md canreflect the quality of the produce.

The mangosteens were evaluated for the damage at day 3, 8, 13, 18 and 23after the impact and the results were tabulated in Table 3. The control specimens (zeroimpact energy) could be stored up to 23 days without any sign of damage. It is clearthat the severity of damage increased with the impact energy and storage time. At thehigh impact energy and long storage time, the damage was not measurable since thesamples were totally perished.

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IMPACT DAMAGE IN MANGOSTEENS 253

Table 2. Energy absorbed by mangosteens tested with and without packagingmaterial protection

Drop height(cm)

control204060

Impact energy

(J)0.0000.1960.3920.589

Without0.000 ax0.149 bz0.334 cz0.539 dz

Packaging materialsPolystyrene

0.000 ax0.090 by0.187 ex0.239 dx

Card board0.000 a x0.046 b x0.324 c y0.494 d y

Note: a, b, c, d indicate significant difference at 95% confidence level in column;and x, y, z. indicate significant difference at 95% confidence level in row

Table 3. Damage development under three mm polystyrene protection (values inparentheses are the damage when tested without packaging material)

Damage

Hardenedpericarp

(g)

DDR

Level ofwitheredaril

Time(day)

381318233813182338131823

00(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)0(0)

Impact energy (J)0.2181.59(3.29)0.79(3.40)2.31(4.09)9.54(35.00)7.99(na)0.85(0.93)0.85(0.95)0.86(1.00)1.00(1.00)1.00(na)0.50(1.40)0.33(1.40)0.50(2.00)1.20(2.33)1.87(na)

0.3972.43(5.62)3.46(5.74)3.75(6.53)32.33(na)38.93(na)0.96(1.00)0.97(1.00)0.97(1.00)1.00(1.00)na(na)0.70(2.40)2.10(2.60)2.29(2.80)2.50(3.00)3.33(na)

0.6514.63(6.72)3.30(5.42)4.79(5.67)na (na)na(na)1.00(1.00)1.00(1.00)1.00(1.00)1.00(na)na(na)2.60(3.20)2.75(3.20)2.60(3.25)4.00(na)na(na)

Note: na means not available because the fruits were rotten

Naturally, the fruit lost its weight due to the respiration. It is anticipated that thepericarp density decreases with time. However, as the mass of the hardened pericarpincreased with time, it implied that the hardening effect spread into the nearby pericarp.This coincides with the observation that the size of the hardened pericarp increasedwith the storage time. The damaged pericarp lost its cell sap and desiccated. It furtherdeveloped into a dry-hard core which osmotically drew liquid from the adjacent cells.Phytoalexin, which is an antibacterial chemical substance, was developed in the near-by cells. In addition, the fruit reacts to the damage by developing lignin in the cell wall

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254 PRASERTSAN, PEERAPRASOMPONG, AND THAMARATWASIK

adjacent to the damaged cells to protect itself from bacteria attack. These mechanismscaused the expanding of the hardened pericarp. Since the DDRs were about 1.00, thehardening spread radially and finally, as the time elapsed, the damaged pericarp wasperished beyond the measurable DDR. It was found that even though the withered arilwas less than one at day 3, which means the aril was in good condition, the level ofwithering advanced with time. For example, the withering of level 0.5 at day'3 after theimpact has developed to level 1.87 after 20-day storage. By comparing the results ofthe experiments tested with and without protection of the packaging material, it isobvious that the packaging material effectively protected the mangosteens.

CONCLUSION

The damage of mangosteens and protective ability of some packaging materials werestudied. The true damage resistant property of the mangosteen was obtained bymeasuring the energy actually absorbed by the fruit and the amount of damage. Thedamage was identified by the mass of hardened pericarp, the damage depth ratio ofpericarp, weight loss and the level of aril withering. Once the fruit was injured, thedegree of damage progressed with the storage time. A soft packaging material likepolystyrene foam can substantially reduce damage and increase shelf life of themangosteens. Empirical equations describing impact damage of the mangosteens wereestablished. The findings from this work are the fundamental knowledge for thedevelopment of code of practice for mangosteen handling to reduce loss.

REFERENCES

Dalai, V. B. 1988. Losses in fresh fruits and vegetable and their remedial measures.Indian Food Industry. 7: 1-13.

Department of Commercial Economics. 1994. Report: Fruit and Vegetable Export.Planning Division, Ministry of Agriculture and Cooperatives, Bangkok (inThai).

Holt, J. E., and Schoorl, D. 1977. Bruising and energy dissipation in apple. Journal ofTexture Studies. 7: 421-432.

Holt, J. E., and Schoorl, D. 1980. Bruise resistance measurements in apple. Journal ofTexture Studies. 11:389-394.

Peeraprasompong, C. 1996. Impact Damage in Mangosteens. Master of Science (FoodTech) thesis. Prince of Songkla University, Thailand (in Thai).

Theerapawa, V., Preemanot, V., Kratureog, C , and Pungsuwan, D. 1986. Report: AStudy on Quality Improvement of Mangosteens for Export. Department ofAgricultural, Ministry of Agriculture and Cooperatives, Bangkok (in Thai).

Tongdee, S. C , and Suwanagul, A. 1989. Postharvest mechanical damage inmangosteens. ASEANFood Journal. 4(4): 151-155.

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