Effects of cushioning materials on the firmness of Huanghua pears (Pyrus pyrifolia Nakai cv....

PACKAGING TECHNOLOGY AND SCIENCEPackag. Technol. Sci. 2008; 21: 1–11Published online 25 January 2007 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/pts.769

Effects of Cushioning Materials on theFirmness of Huanghua Pears (Pyrus pyrifoliaNakai cv. Huanghua) during Distribution and Storage

By Ran Zhou,1,2 Shuqiang Su2 and Yunfei Li2,*1 Institute of Refrigeration and Cryogenic Engineering, Shanghai Jiao Tong University, Shanghai, China

2 Department of Food Science and Technology, Shanghai Jiao Tong University, Shanghai, China

The type and quality of cushioning materials could significantly affect thevibration intensity and physical quality of fruits during transport. In the currentpaper, we evaluated the different cushioning materials (paper-wrap materials,foam-net packages) for their protective effect on the vibration levels, number ofbruises and mechanical damage to Huanghua pears (Pyrus pyrifolia Nakai cv.Huanghua) during transport. Changes in pear firmness, hydrolase activity and cellwall constituents were examined in fruits stored for up to 36 days after transport.Our data suggested that the choice of cushioning material significantly reduced thevibration intensity in transit, affecting the physical quality of fruits and theirsubsequent commercialization, and that foam-net packages provided a greaterprotective effect than paper-wrap packages. Copyright © 2007 John Wiley & Sons,Ltd.Received 15 May 2006; Revised 21 October 2006; Accepted 11 December 2006

KEY WORDS: cushioning materials; Huanghua pears; firmness

* Correspondence to: Y. F. Li, Department of Food Science and Technology, Shanghai Jiao Tong University, Shanghai, China.E-mail: [email protected]

Copyright © 2007 John Wiley & Sons, Ltd.

INTRODUCTION

The loss of the firmness and crispness in freshfruits and vegetables during transport and distrib-ution has been estimated to be above 30% inChina,1 particularly firm and crisp fruits, giventheir sensitivity to mechanical injury. The presenceof physical injuries results in the rejection of thesefruits, with consequent commercial and monetaryloss. This has led to increased research to developpackaging materials that reduce the mechanicaldamage to fruits and lengthen their post-harveststorage life.

The mechanical damage to fruits results mainlyfrom impacts, compression and vibration.2 It hasbeen well established that the primary reason forthe loss of fresh fruits is due to transport vibrationbetween farms and retail outlets.3,4 Damage due totransportation has been studied in a variety offruits and vegetables, such as tangerines,5 loquats,6

peaches7 and potatoes.8 Huanghua pears (P. pyrifolia Nakai cv. Huanghua) are widelyplanted in the south of China.9 Because of theirfirm, crisp and juicy nature when ripe, Huanghuapears are easily affected by mechanical damagefrom excessive vibration. Additionally, firmness, a

main index of quality changes, can be quickly lostwhen fruits are subject to mechanical damage,which typically includes darkened burnings of the skin, bruises with little or no penetrationinto the flesh and broken cuts. Severe vibrationdamage to fruits not only decreases consumeracceptance, but also leads to moisture loss andinvasion of decay organisms, further reducing thefruit quality.10,11 Previous studies suggested thatmechanical vibration induced physiologicalchanges associated with the deterioration anddecreased quality of fruits.12 Additionally, vibra-tion, even without obvious damage, resulted inchanges in the cell membrane and respiration offruits.12

Different methods have been developed toreduce the effects of transit damage on farmproduce. Wang et al.13 treated pears with 2-mercaptobenzothiazone (MBT) to inhibit frictiondiscoloration of the fruit skin. However, bruisesunder the epidermis still resulted in fruit qualitychanges during the storage after transport. Properpackaging of fruits is an alternative to relievemechanical damages as the choice of containerpacking configuration can greatly affect thebruising of sensitive fruits during shipping andhandling.2 The focus of much of the currentresearch has been to identify appropriate distribu-tion and storage conditions, such as utilizing themodified atmosphere package (MAP) methodwith plastic film.3 However, this kind of packageis not designed to reduce mechanical injuries intransit. Pear packers have attempted to reducetransit damage by wrapping the fruits with a‘tight-fill’ packing system, however, it has beensuggested that this method is not effective inreducing vibration damage.11 Although alternativepackaging systems have been investigated toreduce damage levels and post-harvest losses offruits during transport,11,14 little is known of theeffects of different kinds of cushioning materialson the vibration of Huanghua pears and thequality changes of the fruits in subsequentcommercialization.

The aim of the current study was to investigatethe vibration levels during transport and thedegree of vibration damage to Huanghua pearswith different kinds of cushioning materials.Changes in hydrolase activity and cell wall con-stituents were also assayed to measure the changes

in pear firmness during storage at room tempera-ture (23°C) after transport.

MATERIALS AND METHODS

Fruits and packages

Huanghua pears at commercial maturity, based onfruit skin colour and the harvest date, were hand-harvested from an orchard in Fengxian, Shanghai,China. The colour of the harvested pear was cyanwith a little yellow colour, according to the expe-rienced fruit grower’s advice. The harvest datewas corresponding to the optimum mature date.Each pear was verified to be without bruises beforepackaging. The pears were packaged in new,reusable plastic containers (RPCs), measuring 505mm × 350mm × 300mm and weighing approxi-mately 22.5kg. Two different cushion materialswere compared in this study. Pears wrapped withpaper package and with net package before beingplaced into the RPC are shown in Figure 1. The twocushioning materials were provided by theorchard, which are commonly used for packagingHuanghua pears. In order to compare the effects ofthe cushioning materials on mechanical damage,the fruits without cushioning materials were alsostudied. Each column consisted of six superposedRPCs (approximately 1.8m tall). All pear cushion-ing materials in one column were similar. The RPCcolumn of pears without cushioning materials,with paper-wrap packages and with foam-net

R. ZHOU, S. SU AND Y.F. LIPackaging Technologyand Science

Copyright © 2007 John Wiley & Sons, Ltd. 2 Packag. Technol. Sci. 2008; 21: 1–11DOI: 10.1002/pts

(a) (b)

Figure 1. A pear with paper-wrap package (a) and a pearwith foam-net package (b).

packages were placed side by side from left to righton the rear of the truck trailer as previous researchhad suggested that vertical acceleration can bemore severe at the rear of the truck trailer.4 Four-wheel Changchun truck with leaf-spring suspen-sion and 2ton payload capacity was used in thisstudy. In order to minimize research costs, theremainder of the truck was loaded with ballasts.Twenty pears at the top of the RPCs in the threecolumns were tagged on their stem to evaluatevibration damage to pears at the same relativeposition of the truck during transport. Some of theHuanghua pears were picked and transporteddirectly to the laboratory by a 15min drive. Thesefruits were used as control samples as they did notsuffer prolonged transit time.

Vibration levels in transit

Huanghua pears were transported from theorchard to the wholesale market then returned tothe laboratory over a variety of different road con-ditions. The driving distance was approximately500km, utilizing laterite roads (rutted, pothole-filled lanes on hardened clay, commonly used inChinese villages), tertiary, secondary and arterialroads and highways. A total of three accelerome-ters (JF-102, Xingcheng Corp., Shanghai, China)were connected by wire to a shock recorder (ModelVIB-30, Xingcheng Corp., Shanghai, China). Thevibration data were randomly recorded in realtime for 2s for every 3min of road travel. The totalrecording time was 320s during the entire route.Research has suggested that during transport, thetop container in a column suffers the most severevibration.15 Consequently, the three accelerometerswere embedded inside three pears at the top RPCin each of the three columns (Figure 2). Addition-ally, the pear accelerometer had the same kind ofcushioning materials as the pears and was locatedat the corner of the top RPC with the pears near itso as to keep it vertical. Accelerometer wires werealso fixed with clamps to prevent the detectorsfrom changing orientation during transport. Thevibration data were transferred to a computer foranalysis using VIB-30 software (Xingcheng Corp.,Shanghai, China). The data were presented aspower density (PD) spectra utilizing fast Fouriertransformation (FFT) algorithms.

Evaluation of vibration damage to pears

The tagged pears were unloaded and removedfrom their cushioning materials. The bruises of thepears without cushioning materials, with paper-wrap packages and with foam-net packages werecounted, respectively for three times after the pearswere stored at room temperature for 24h. The cat-egories of pear bruises were classified according tothe diameter of discoloration area as slight (<0.5cmdiameter), moderate (0.5–1.5cm diameter) andsevere (>1.5cm diameter).

To estimate the percentage of damaged skin ofHuanghua pears with different kinds of cushion-ing materials, the pears of each treatment werearrayed (four lines by five rows) with the side ofeach pear that is more severely hurt placed face-upon a table and then photographed (Canon power-shot A80, 4 megapixels of effective pixels, CanonInc., Tokyo, Japan). The pictures were transferredto a computer to calculate the percentage of bruisesutilizing Leica QWin software (Leica MicrosystemsImaging Solutions Ltd., Cambridge, UK) based onthe appearance difference between the damagedand undamaged regions of the pears. The testswere operated for three times.

Storage conditions

The pears were stored at room temperature (23°C)in approximately 80% relative humidity. The pearswithout cushioning materials, with paper-wrappackages and with foam-net packages wereassayed during the storage. Fruits not exposed tolong-time transit were used as controls.


EFFECTS OF CUSHIONING MATERIALS ON PEAR FIRMNESS Packaging Technologyand Science

Figure 2.An accelerometer inserted in the Huanghua pear.

The Huanghua pear (P. pyrifolia Nakai cv.Huanghua) is a climacteric fruit and easilybecomes soft after harvest.16 In the current study,the pears were analysed at five time points: 1, 9,18, 27 and 36 days after storage. The data of thefive fruits were averaged per each data point.

Firmness

Firmness was measured utilizing a TA-XT2itexture analyser (Stable Micro Systems Ltd.,Surrey, UK) with a 5kg load cell and a 2mm diam-eter cylinder probe. Each batch of five fruits wasrandomly chosen from the four packaging groupsand was peeled. The test was performed with apre-test and test speed of 5mm/s, a post-test speedof 10mm/s and auto-25g trigger force. Firmnesswas measured on four opposite sides of each fruitat the equatorial region, perpendicular to the stem-bottom axis.

Enzyme extraction and assay

The enzyme assay was adapted from Deng andcolleagues17, and all steps were performed at 4°C.Briefly, the flesh of the five pears was groundrapidly in an ice cold bath with mortar and pestle.The fruit flesh (10g) was homogenized with 10mlof 0.5M Tris-HCl (pH 8.0) containing 1mM CDTA,5% polyvinylpyrrolidone (w/v) and 2M NaCl forpectinesterase (PE) extraction, then centrifuged(8000 × g, 10min). PE in the supernatant wasassayed by acid–base titration according to Nageland Patterson.18 By definition, one unit of enzymeactivity was equivalent to the amount of enzymecatalyzing the formation of 1µmol ester hydrol-ysed per minute per gram of the original freshweight of the pear flesh.

The fruit flesh (10g) was homogenized with 10ml of 0.1M phosphate buffer [pH 7.0, 1mM CDTA,5% polyvinylpyrrolidone (w/v), 0.5M NaCl] forpolygalacturonase (PG) and cellulase, and cen-trifuged (8000 × g, 10min). PG activity was assayedin the supernatant by measuring the reducinggroups set free from citrus pectin (Sigma ChemicalCo., St. Louis, Mo.).17 One unit of enzyme wasdefined as 1µmol of reducing groups per hour per

gram of the original fresh weight of the pear flesh.Cellulase activity was assayed by measuring thereducing groups released from carboxymethyl cel-lulose.17 One unit of enzyme activity wasexpressed as 1µmol reducing groups per hour pergram of the original fresh flesh of the pears.

Pectin and cellulose content

Pectin quantitation in Huanghua pears wasassayed by m-hydroxydiphenyl,19,20 with galactur-onic acid (Fluka) as the standard. The flesh of thefive pears was ground rapidly in an ice cold bathwith mortar and pestle. The pear flesh (5g) washomogenized in 80% boiling ethanol (50ml, 10min) using a blender to eliminate saccharide andto inactivate enzymes, then filtered with filterpaper. The residue was then washed with 10ml96% ethanol and acetone, mixed with distilledwater (40°ml), heated in a water bath (50°C, 30min) and centrifuged (8000 × g, 10min). Thecontent of water-soluble pectin and protopectinwere measured in the supernatant and sediment,respectively. Total pectin content was obtained by the addition of protopectin and water-solublepectin.

Cellulose extract was obtained as previouslydescribed.21 Briefly, the pear flesh (10g) wasremoved from the mortar and stirred in 150ml of2% (v/v) hydrochloric acid. The suspension washeated with a reflux exchanger (3h) to remove thesaccharide, hemicellulose and starch. The residuewas consecutively washed with hot distilled water,absolute ethyl alcohol and ether to remove chlo-ride ions and other foreign substances, then air-dried. The cellulose content was determinedutilizing the anthrone method, with glucose as thestandard.

Statistical analysis

The statistical analyses utilized SAS 8.0 (StatisticalAnalysis Systems, Cary, NC, USA). Variance analy-sis was conducted for the root mean square (RMS)acceleration of the pears. Least significant differ-ence (LSD) was performed for the average numberof bruises with different cushioning materials,determined at the 5% level.



RESULTS AND DISCUSSION

Vibration levels in transit

The main characteristics of the vibration levels ofHuanghua pears in the top RPCs during the entireroute are shown in Figure 3 and Table 1. In thecurrent study, the PD spectra of pears with differ-ent cushioning materials were characterized bypeaks in the 2–5Hz and 15–20Hz range, with thehighest values noted for pears without cushioningmaterials and the lowest for pears with foam nets.These data were confirmed by the spectra of dif-ferent road conditions during transport.

According to Table 1, the frequency responsesfor the peak of PD spectra of the fruit withoutcushioning materials were the same as the fruitwith paper packages during the entire route.However, foam-net packages resulted in differentfrequency responses of peaks in PD spectra fromother samples nearly in the whole route except thesecondary road. This phenomenon could be due tothe texture of foam-net packages, which has moreelasticity and springiness than paper-wrap pack-ages. Slaughter et al.15 reported that pallet loads ofBartlett pears were most susceptible to vibrationbruising at frequencies below 40Hz. The data inFigure 3 indicate that the values of the PD spectra

attenuated above 40–50Hz relying on cushionmaterials and road conditions, which showed littleeffects of transport vibration in the damage tofruits because of their low energy for higher fre-quencies. Also, according to the results, there wasa very small difference between the different cush-ioning materials in the vibration levels at frequen-cies above 50Hz.

Global RMS acceleration values were signifi-cantly different (p < 0.05) for pears without cush-ioning materials (0.183g), pears with paper-wrappackages (0.179g) and pears with foam-net pack-ages (0.165g), demonstrating differences in thevibration levels depending on the type of cush-ioning materials. Our data suggest that foam-netpackages were the most efficient in alleviatingvibration intensity during transport.

Evaluation of vibration damage

In the current study, the pears were exposed tosevere vibration and extended transit time. Injuriesto pears included darkened burnings of the skinand bruises with little or no penetration into theflesh. Figure 4 gives the results of damage evalua-tion of the pears with different cushioning materi-als. The greatest damage was noted in the pears



Table 1. Main route characteristics and peak values of power density (PD) spectra of pears withdifferent kinds of cushioning materials, located at the top RPCs, at the rear of the truck floor

during transport

Peak value (g2/Hz) of PD spectra and itsSpeed, km/h frequency (Hz)

road Average Max hour Without package Paper package Net package

Highway 70 80 1 2.36E–3(16Hz) 2.23E–3(16Hz) 4.88E–4(3.5Hz)Asterial 70 75 2.5 3.35E–3(2.5Hz) 1.84E–3(2.5Hz) 1.80E–3(16.5Hz)

roadSecondary 60 70 2 1.36E–3(3Hz) 1.29E–3(3Hz) 1.28E–3(3Hz)

roadTertiary 50 55 2 4.15E–3(15.5Hz) 3.85E–3(15.5Hz) 1.46E–3(17.5Hz)

roadLaterite 20 25 1 2.91E–3(3Hz) 1.56E–3(3Hz) 1.32E–3(3.5Hz)

road

Type of Duration,



2 10 100 2001E-7

1E-6

1E-5

1E-4

1E-3

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ower

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sity

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FREQUENCY,Hz

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1E-6

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Without package Paper package Net package (e)

Figure 3. Power density (PD) spectra of the pears with different kinds of cushioning materials on highways (a); arterialroads (b); secondary roads (c); tertiary roads (d) and laterite roads (e).

without cushioning materials (p < 0.05). Similar towhat was seen with vibration levels, the use offoam-net packages was more efficient at reducingdamage to individual pears than paper-wrap pack-ages (p < 0.05). Both of the cushioning materialsefficaciously reduced severe and moderatedamages per fruit (Figure 4). However, the averagenumber of bruises in the slight range for pears withpaper-wrap packages was more than that for pearswithout packages. This was because the pears withpaper-wrap packages turned many severe andmoderate bruises into slight bruises for their pro-tective effects. Foam-net packages were still moreeffective at decreasing severe and moderatedamages than paper-wrap packages. This phe-nomenon was not solely due to the placement of alayer of cushioning materials between each fruit,but may also be related to their ability to decreasevibration levels during transport. Clearly, foam-net packages had more protective effect thanpaper-wrap packages.

The estimated percentage of the averagedamaged area of Huanghua pears was signifi-cantly different (p < 0.05) for pears without innerpackages (8.49%), pears with paper-wrap packages(3.59%) and pears with foam-net packages (1.91%).Gentry et al.10 reported that vibration bruisingaffected fruit appearance, provided a point ofentry for decay organisms and increased moistureloss from the fruit. According to the results, rela-tively lower damage area for pears with foam-netcontributed to keeping the quality of fruits betterduring the storage after transport.

Firmness

The firmness of Huanghua pears decreased signif-icantly during the storage after transport (Figure5). The highest and lowest levels of firmness werenoted with control samples and pears withoutcushioning materials, respectively. The use offoam-net packages was more effective in main-taining the firmness of pears than paper-wrappackages. By day 36, the firmness of controls was1.17–1.91 times higher than that of the transportedfruits. The fruits without cushioning materials hadthe fastest softening rate, losing about 64% of theirfirmness by day 36, while the softening rate offruits with paper-wrap and foam-net packages



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Net package Paper package Without package

Categories of bruises

Total Severe Moderate Slight

b

ab

a

a

bb

b

aba

a

aa

Figure 4.The average number of bruises of Huanghuapears with different kinds of cushioning materials aftertransport.Total is the average number of total bruises;

slight is the average number of bruises in the slight range;moderate is the average number of bruises in the

moderate range; severe is the average number of bruisesin the severe range.Values within the same figure with the

same letter are not significantly different (p < 0.05).

0 9 18 27 360

5

10

15

20 Control Net package Paper package Without package

Days after harvest

Firm

ness

,N

Figure 5. Changes in the firmness, after transport, ofHuanghua pears with different kinds of cushioning

materials during storage (23°C) after transport.The dataare means of 20 trials ±SD. Control is the control samples

as they did not suffer prolonged transit time.

was 52 and 47%, respectively. These data demon-strated that mechanically injured fruits had ahigher rate of softening than intact fruits duringstorage in ambient temperature.

Enzymatic activity

During the storage after transport, enzymaticactivity of Huanghua pears peaked then decreased(Figure 6). The pears undergoing severe transportvibration displayed increased PE, compared withcontrol samples. At day 27 of storage, PE activitypeaked in the pears without cushioning materials,

as well as in those with paper-wrap packages,albeit to a lesser extent. There were no significantdifferences in PE activity between the pears withpaper-wrap packages and those without cushion-ing materials, however, activity of control samplesand pears with net packages was relatively lowerduring the storage. PG activity is responsible forpectin depolymerization and solubilization.22 Inthe current study, no differences in PG activitywere noted between the four samples, with theexception of assays performed on days 9 and 18,in which pears that suffered heavier damages dis-played higher PG activity. Similarly, a positiverelationship was noted between cellulase activity



0 9 18 27 360

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0 9 18 27 360.0

0.5

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2.5

Cel

lula

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nits

/ g

Fru

it w

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t

Days after harvest

(c)


Figure 6. Changes in pectinesterase (a); polygalacturonase (b) and cellulase (c) activity of the Huanghua pears withdifferent kinds of cushioning materials during the storage (23°C) after transport.The data are means of three trials ±SD.

Control is the control samples as they did not suffer prolonged transit time.

and degree of damage to fruit, although no cleardifferences in enzyme activity were observedbetween the control samples and the pears withfoam-net packaging. This may have been due tothe relatively minor mechanical damage havinglittle effects on the enzymic activity during storage.

Fruit softening during ripening has been attrib-uted to the action of pectic enzymes and cellulaseon polysaccharides in the cell wall.23–25 Our datareveal that transport vibration affected hydrolaseactivity (Figure 6), suggesting that cushioningmaterials alleviated vibration intensity duringtransit, reducing visible damage to fruits andresulting in lower enzymatic activity. Additionally,the loss in firmness of all samples, during storage,has been found to vary consistently with the

increase in enzymatic activity (Figures 5 and 6),similar to what has been previously reported.17,26,27

Pectin and cellulose content

The content of total pectin, protopectin and cellu-lose decreased with the increased storage time(Figure 7). There was a rapid decline in protopectincontent, reaching 70–78%, for all samples, after 18days of storage. Protopectin levels were generallyhigher in the pears with net packages, comparedwith those with paper-wrap or without cushioningmaterials. The total pectin content of pearsexposed to long-transport transit times and longstorage time (36 days) was lower than the levels in



0 9 18 27 360.0

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ruit

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Days after harvest

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0 9 18 27 362.0

2.2

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Cel

lulo

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onte

nt,m

g/g

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it w

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t

Days after harvest

Control Net package Paper package Without package(c)

Figure 7. Changes in content of protopectin (a); total pectin (b) and cellulose (c) content of Huanghua pears withdifferent kinds of cushioning materials during the storage (23°C) after transport.The data are means of three trials ±SD.

Control is the control samples as they did not suffer prolonged transit time.

control samples. These data suggested thatextended vibration leads to changes in the qualityof Huanghua pears, even though the exteriordamage was not heavy, as was the case of the pearswith net packages. Additionally, there was aninverse relationship between pear cellulosecontent and intensity of vibration levels experi-enced by the pears during transport.

Softening during ripening in climacteric fruits,such as Huanghua pears, is generally attributed tothe degradation of the cell wall and the decompo-sition of pectin.16,25 Manrique and Lajolo reportedthe decreasing quantities of galacturonic acid andsome monosaccharides in cellulose residues, sug-gesting that polysaccharides may be involved inthe softening process of fruits during post-harvestripening.28 According to the results, the decrease infirmness of all samples was accompanied by dra-matic decreases in protopectin, total pectin and cel-lulose during storage.

In the current study, the influences of transportvibration on the activity of hydrolases were lessconvincing than their effects on the reduction incell wall contents during the storage after trans-port (Figures 3, 6 and 7). However, the relationshipbetween the vibration levels of fruits duringtransport and firmness changes is not clearlyunderstood. Ying and colleagues12 indicated thatmechanical vibration induced physiologicalchanges, which were related to the deterioration offruit quality. Visible bruises and invisible cell wallfractures caused by different degrees of transportvibration induced changes in the activity of hydro-lases, decomposing the supporting materials ofcell walls. Decreasing levels of depolymerizationand degradation of cell wall polysaccharides inthese fruits were accompanied by loss of firmnessduring the storage after transport.

Our data suggest that both the foam-net andpaper-wrap packages greatly decreased transportvibration intensity and damage to Huanghuapears, which was consistent with Chonhenchoband Singh, even though the type of paper-wrappackages used in this study differed from whatthey used.14 Our study also demonstrates thatenzymatic activity of pears with paper-based cush-ions was still relatively higher than that noted inthe pears with net packages, while firmness andcell wall material content of the pears with paperpackaging was dramatically lower than those with

net packages, even though differences in visibledamage was only about 1.6% between them, asdescribed earlier. This may have been due to thelack of ventilation of paper-based materials in con-junction with the accumulation of ethylene, whichleads to overripening and softening of fruitsduring storage.

CONCLUSION

The current study demonstrated that foam-netpackages reduced the transport vibration levels ofpears more effectively than paper-wrap packages(p < 0.05). The use of foam-net packages alsoreduced the mechanical damage to individualpears during transport, compared with paper-wrap packages (p < 0.05). Different levels of vibra-tion damage to pears influenced enzymaticactivity, which further affected the changes in pearfirmness and subsequent commercialization aftertransport. Given these data, we recommend theuse of foam-net cushioning materials to maintainHuanghua pears quality during transport anddistribution.

ACKNOWLEDGEMENTS

This work is the main part of the project ‘Research andDevelopment of Fresh Produce Modern Logistics Tech-nology and Trading Demonstration’ (2004BA527B)financed by the Ministry of Science and Technology ofChina. The authors thank L. P. Yan, L. Wang, J. Wangand T. T. Yin for their assistance in performing theexperiments.

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Effects of cushioning materials on the firmness of Huanghua pears (Pyrus pyrifolia Nakai cv....

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