Bruising injury of persimmon (Diospyros kaki cv. Fuyu) fruits

Scientia Horticulturae 103 (2005) 179–185

Bruising injury of persimmon (Diospyroskaki cv. Fuyu) fruits

Hee Jae Leea,∗, Tae-Choon Kimb, Su Jin Kima, Seung Je Parkca School of Plant Science, Seoul National University, Seoul 151-742, Republic of Koreab Department of Horticulture, Wonkwang University, Iksan 570-749, Republic of Korea

c Department of Agricultural Machinery Engineering, Chonbuk National University,Jeonju 561-756, Republic of Korea

Accepted 16 April 2004

Abstract

This study was performed to monitor the deterioration of bruised persimmon (Diospyros kaki cv.Fuyu) fruits. Freshly harvested fruits were bruised by dropping them from a height of 50 cm onto a steelboard and then stored at 0 or 20◦C in temperature controlled chambers for up to 4 weeks. Immediatelyafter the bruising, no visible injury on the fruits was evident, but the fruits deteriorated rapidly duringstorage. The skin tissues of the fruits stored at 20◦C became more reddish with the duration of thestorage, but no such changes were found with the fruits stored at 0◦C. The increase in redness of theskin tissues appeared to be associated with storage temperature, but not with the bruising. The skintissues also became darker when stored at 20◦C than at 0◦C and this tendency was more obvious withthe bruised fruits. Flesh firmness decreased rapidly during storage except for the non-bruised fruitsstored at 0◦C. Even the non-bruised fruits rapidly lost their flesh firmness at 20◦C. No significantchanges in lipid peroxidation, as expressed by malondialdehyde production, were found between thebruised and the non-bruised fruits during the storage either at 0◦C or at 20◦C. This implies that thefruit deterioration caused by bruising is not due to the consequences of lipid peroxidation. Polyphenoloxidase activity increased more rapidly in the bruised fruits than in the non-bruised fruits duringstorage. The bruising had more effect on increasing polyphenol oxidase activity than did the storagetemperature. Although the increase in polyphenol oxidase activity appeared to be associated with thevisual deterioration of the bruised fruits, it did not exactly correspond to the physical deterioration.These results indicate that polyphenol oxidase is not the only factor influencing the deteriorationassociated with bruising. Cell wall hydrolases are currently being assayed to determine if they alsocontribute the deterioration following bruising.© 2004 Elsevier B.V. All rights reserved.

Keywords: Bruising;Diospyros kaki; Lipid peroxidation; Mechanical injury; Polyphenol oxidase

∗ Corresponding author. Tel.:+82-2-880-4566; fax:+82-2-873-2056.E-mail address: [email protected] (H.J. Lee).

0304-4238/$ – see front matter © 2004 Elsevier B.V. All rights reserved.doi:10.1016/j.scienta.2004.04.016

180 H.J. Lee et al. / Scientia Horticulturae 103 (2005) 179–185

1. Introduction

With the increasing use of mechanical equipments for the harvesting and packing offruits, the mechanical injury on fruits has become a very important problem (Brusewitz andBartsch, 1989; Marshall and Brook, 1999). Mechanical injury, such as bruises, cuts, andabrasions, causes marked deterioration in fruit quality (Quintana and Paull, 1993; Shewfelt,1993). Bruising can occur when the fruit is carelessly dropped onto hard surfaces or sub-jected to harsh impacts during harvesting and packing. The bruising is initiated by thebreakage of cell membranes, allowing cytoplasmic enzymes to act on sequestered sub-strates (Rouet-Mayer et al., 1990; Shewfelt, 1993). The resultant browning is caused by theenzyme action on phenolic substrates.

Polyphenol oxidase (PPO) is well known enzyme responsible for tissue browning inmechanically injured fruits (Van Lelyveld and Bower, 1984; Sciancalepore, 1985; Nicolaset al., 1994). PPO catalyzes the oxidation of phenolic compounds too-quinones whichsubsequently polymerize to form dark-colored pigments (Rouet-Mayer et al., 1990).

During harvesting, grading, and transport of persimmon fruits, the fruits often deterio-rate due to bruising and subsequent storage. However, no comprehensive study has beenpublished on bruising injury of persimmon fruits. In the present study, the deterioration ofbruised persimmon (Diospyros kaki cv. Fuyu) fruits were monitored with respect to fruitdiscoloration, firmness decrease, and lipid peroxidation during storage. PPO activity wasalso monitored to determine if it is associated with the deterioration of the bruised fruits.

2. Materials and methods

Unblemished persimmon fruits of ‘Fuyu’ cultivar were purchased from an orchard inJinyoung county, Korea at their commercial harvest. The fruits were dropped from heightof 50 cm onto a steel board and caught after one bounce. The impact area was marked withblack indelible ink. Control fruits were not dropped. The fruits were then placed in cuppedplastic trays and stored at 0 or 20◦C in temperature controlled chambers for up to 4 weeks.

One hour prior to sampling, the fruits to be examined were removed from the chambersand equilibrated to room temperature. The discoloration of the skin and the flesh wasdetermined as changes ina∗ andL∗ values by using a chromameter (model CR-300, MinoltaCo., Ltd., Japan) as suggested bySapers and Douglas (1987). Thea∗ value is negative forbluish-green and positive for red-purple. TheL∗ value represents the lightness of colorsfrom 0 to 100, being small for dark colors and large for bright colors (McGuire, 1992). Thefirmness of fruit skin and flesh was measured using a Rheometer (model TA.XT2, StableMicro Systems) with an 8 mm tip.

For extracting PPO, fruit skin and flesh samples were separately homogenized with apolytron twice for 10 s at maximum speed using a fresh weight to volume ratio of 1:4. The ho-mogenization buffer consisted of 50 mMN-2-hydroxyethylpiperazine-N′-2-ethanesulfonicacid (HEPES, pH 7.6), 2 mM ethylenediaminetetraacetic acid, 1 mM MgCl2, 1 mM MnCl2,330 mM sucrose, and 5 mM dithiothreitol (McConchie et al., 1994). The homogenate wasfiltered through one layer of Miracloth (Calbiochem, La Jolla, CA, USA) and centrifugedat 6000× g for 5 min. The pellet was resuspended in a solubilization buffer consisting of

H.J. Lee et al. / Scientia Horticulturae 103 (2005) 179–185 181

50 mM HEPES (pH 7.6), 2% (w/v) sodium dodecyl sulfate, 3% (w/v) polyvinylpyrrolidone,and 50 mM CaCl2, and the suspension was then incubated on ice in the dark for 30 minwith periodic mixing (Valero et al., 1988). The suspension was centrifuged at 25,000× gfor 20 min and the resulting supernatant was used as a crude enzyme extract.

PPO activity was assayed by monitoring absorbance change at 420 nm in 100 mM sodiumcitrate buffer (pH 5.0) and 50 mM catechol with the crude enzyme extract (Coseteng and Lee,1987). The PPO activity was expressed as�A420h−1 mg−1 protein, because the productshave unknown extinction coefficients. Protein was determined by the method ofBradford(1976)with bovine serum albumin as a standard.

Lipid peroxidation was estimated by the level of malondialdehyde (MDA) productionusing a slight modification of the thiobarbituric acid (TBA) method as previously described(Du and Bramlage, 1992). The separate samples of fruit skin and flesh were completelyhomogenized in a solution of 0.5% TBA in 20% trichloroacetic acid with a polytron at max-imum speed using a fresh weight to volume ratio of 1:10 and 1:5 for fruit skin and flesh,respectively. The homogenate was centrifuged at 20,000× g for 15 min and the supernatantcollected. The supernatants were heated in a boiling water bath for 25 min and allowed tocool in an ice bath. Following centrifugation at 20,000× g for 15 min, the resulting super-natants were used for spectrophotometric determination of MDA. Absorbance at 532 nmfor each sample was recorded and corrected for non-specific turbidity at 600 nm and forsoluble sugars at 440 nm (Du and Bramlage, 1992). MDA concentration was calculatedusing a molar extinction coefficient of 156 mM−1 cm−1 (Buege and Aust, 1978).

3. Results and discussion

Freshly harvested fruits were bruised by dropping them from a height of 50 cm onto asteel board and then stored at 0 or 20◦C in temperature controlled chambers for up to 4weeks. Immediately after the bruising, no visible injury of split or puncture on the fruitswas evident, but the fruits deteriorated rapidly during storage. The first bruising symptom,color change of fruit tissues, could be observed after 2 or 3 days of storage at 20◦C, andthe injury became more apparent with increasing the storage duration.

When the non-bruised and the bruised fruits were stored at 20◦C, their skin and fleshbecame more reddish with increased duration of storage (Fig. 1A and B). The increase inredness was more apparent in the flesh than in the skin. However, when the fruits werestored at 0◦C, no such changes were found neither in the skin nor in the flesh (Fig. 1A andB). Since the redness change was not affected by the bruising at any storage temperatures,the redness increase appeared to be associated with storage temperature, not with bruising.

Both skin and flesh of the fruits stored at 20◦C also became darker with increasingthe storage duration (Fig. 1C and D). A higher magnitude of the decrease in lightnesswas observed in the flesh than in the skin and the bruising accelerated the decrease. Thelightness of the skin decreased almost linearly with increasing the storage duration (Fig. 1C),whereas that of the flesh decreased rapidly during the first week of the storage and thenremained relatively constant thereafter (Fig. 1D). The lightness decrease was found to bemore associated with the bruising than with storage temperature. For example, the fleshtissues of the bruised fruits stored at 0◦C became darker more rapidly than those of the


Fig. 1. Changes of chromaticity in skin and flesh tissues of non-bruised and bruised persimmon fruits stored at 0or 20◦C. (A) �a∗ in skin tissue; (B)�a∗ in flesh tissue; (C)�L∗ in skin tissue; (D)�L∗ in flesh tissue. Valuesare the mean± S.E. of five replicates. In some cases error bars are obscured by the symbol.

non-bruised fruits stored at 20◦C (Fig. 1D). However, the lightness of the skin and fleshdid not change in the non-bruised fruits stored at 0◦C (Fig. 1C and D).

Skin and flesh firmness decreased rapidly during storage except for the non-bruised fruitsstored at 0◦C (Fig. 2). The decrease in firmness was more obvious in the flesh than in the skinand it was dependent on both storage temperature and bruising. The fruits stored at 20◦C losttheir skin and flesh firmness more rapidly than those at 0◦C and the bruising acceleratedthe decrease in firmness. In skin tissues, the bruising had more effect on decreasing thefirmness that the storage temperature (Fig. 2A). In flesh tissues, however, higher magnitudeof firmness decrease was observed in the non-bruised fruits stored at 20◦C than in thebruised fruits stored at 0◦C (Fig. 2B). The firmness decrease of the bruised fruits did notappear to correspond to the lightness decrease. The flesh tissues of the bruised fruits losttheir lightness rapidly during the first week of storage at 20◦C (Fig. 1D), but their firmnessgradually decreased up to 3 weeks (Fig. 2B).

The flesh deterioration of the bruised fruits appeared to be associated with the increasedactivity of PPO. With increasing the storage duration, PPO activity of the flesh increasedmore rapidly in the bruised fruits than in the non-bruised fruits (Fig. 3). The PPO activityalso increased even in the non-bruised fruits stored at 0◦C. During the first week of storage,however, the PPO activities did not change except for the flesh of the bruised fruits storedat 20◦C. The increase in PPO activity was higher in the fruits stored at 20◦C than inthose at 0◦C. Even in the non-bruised fruits, PPO activity significantly increased when the


Fig. 2. Changes of firmness in skin (A) and flesh tissues (B) of non-bruised and bruised persimmon fruits storedat 0 or 20◦C. Values are the mean± S.E. of five replicates.

Fig. 3. Changes of PPO activity in flesh tissues of non-bruised and bruised persimmon fruits stored at 0 or 20◦C.Values are the mean± S.E. of five replicates.


fruits were stored at 20◦C. The bruising had more effect on increasing PPO activity thanstorage temperature. However, PPO activities in the skin of the non-bruised and the bruisedfruits were found to be negligible and changed insignificantly at any storage duration andtemperatures (data not shown).

PPO activity has been well known to have the enzymatic browning potential in fresh fruits(Lee et al., 1990; Gradziel and Wang, 1993) and to be responsible for tissue browning inbruised fruits (Van Lelyveld and Bower, 1984; Sciancalepore, 1985; Nicolas et al., 1994).The tissue browning following bruising is primarily due to phenolic oxidation resultingfrom the mixing of phenolics and PPO upon the collapse of cellular compartmentalization(Rouet-Mayer et al., 1990; Shewfelt, 1993). In our study, mechanical impacts resulting fromthe dropping may cause unseen physical damage below the surface of the persimmon fruits.These impacts may cause damage to the cellular membranes.

Senescence also results in decompartmentalization of PPO and its substrates. Thus, thebrowning of olives (Sciancalepore and Longone, 1984) and other fruits (Vamos-Vigyazo andNadudvari-Markus, 1983) is dependent on PPO activity, although the functional significanceof PPO in senescence is not obvious.

Considering that the tissue browning is both qualitatively and quantitatively substratedependent (Coseteng and Lee, 1987), strict correlation between PPO activity and tissuebrowning potential may not exist. In the present study, the PPO activity change did notexactly correspond to the lightness and the firmness decrease. These results indicate thatPPO is not the only factor influencing the deterioration associated with bruising.

No significant changes in lipid peroxidation, as expressed by MDA production, werefound between the bruised and the non-bruised fruits during storage either at 0 or 20◦C(data not shown). Thus, the possibility that lipid peroxidation is associated with the fruitdeterioration can be excluded. By contrast, increased lipid peroxidation has been observedduring the development of chilling injury in many harvested fruits and vegetables and ofsuperficial scald in apples (Shewfelt and del Rosario, 2000). We are currently assaying cellwall hydrolases to determine if they also contribute the deterioration following bruising.

Acknowledgements

This work was supported by Wonkwang University in 2001 and Agricultural Plant StressResearch Center (grant no. R11-2001-9203003) funded by Korea Science and EngineeringFoundation.

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Bruising injury of persimmon (Diospyros kaki cv. Fuyu) fruits

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