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LWT - Food Science and Technology 59 (2014) 1146e1151

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LWT - Food Science and Technology

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Efficacy of some antimicrobial treatments compared to sodiumhypochlorite on physical, physiological and microbial quality offresh-cut melons (Cucumis melo L. var. inodorus)

Tuba Dilmaçünal a, *, Derya Erbas a, Mehmet Ali Koyuncu a, Cemile Ebru Onursal b,Hakan Kuleasan c

a Suleyman Demirel University, Faculty of Agriculture, Department of Horticulture, 32260, Isparta, Turkeyb E�girdir Horticultural Research Institute, 32500, Isparta, Turkeyc Suleyman Demirel University, Faculty of Engineering, Department of Food Technology, 32260, Isparta, Turkey

a r t i c l e i n f o

Article history:Received 5 April 2013Received in revised form30 June 2014Accepted 24 July 2014Available online 2 August 2014

Keywords:Cold storageGaseous ozoneHazelnut oilKırka�gaçSodium hypochlorite

* Corresponding author. Tel.: þ90 246 2113923; faxE-mail addresses: tubadilmacunal@sdu.edu.tr,

(T. Dilmaçünal).

http://dx.doi.org/10.1016/j.lwt.2014.07.0330023-6438/© 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

Turkish-type ‘Kırka�gaç’ melons (Cucumis melo L. var. inodorus cv. ‘Kırka�gaç’) were hand-harvested at acommercial harvest maturity stage from a greenhouse in Turkey (Antalya). Fruits were divided into fourgroups for the experiments: 1. Control (C), 2. Hazelnut oil (HO), 3. Gaseous Ozone (GO), and 4. NaClO.After the treatments, slices were placed immediately to lidded plastic boxes (500 g capacity) and storedin a cold room at 5 �C and 90 ± 5% relative humidity for 12 days. Fruits were evaluated at three-dayintervals for microbial enumeration, firmness, flesh color, titratable acidity (TA), pH, soluble solid con-tent (SSC), weight loss, sensorial attributes (external appearance, taste-flavor and translucency), respi-ration rate and ethylene production. The integrity of the slices treated with GO was preserved better thanthose of the others and no juice leakage was observed during storage. According to the results, especiallyfor microbial and sensorial attributes, control, NaClO and HO treated melon slices were preserved theirquality for six days, whereas GO treated samples were stored for nine days with good quality.

© 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The melon is one of the most economically important andwidely cultivated crops in the world, and Turkey is the secondlargest producer after China, producing 1,708,415 million t annually(Anonymous, 2014a). The European and American melon marketsare dominated by two major cultivar types differing in quality at-tributes and postharvest behavior. Cantaloupensis and Reticulatusgroups include the very aromatic, climacteric, and fast senescingcantaloupes and muskmelons; Inodorus group includes the lessaromatic, non-climacteric, slow senescing melons (Amaro,Beaulieu, Grimm, Stein, & Almeida, 2012).

Kırka�gaç (Cucumis melo L. var. inodorus) is one of the commonlygrown melon cultivars, particularly in the Aegean and the CentralAnatolia regions of Turkey (Yıldırım, Halloran, Çavuso�glu,& Sengül,2009). It has generally light green skin color with dark green spotsat first, yellow at maturity (Sensoy, Büyükalaca, & Abak, 2007). Its

: þ90 246 2118696.tuba.dilmacunal@gmail.com

fruit flesh is sweet and delicious and they are more resistant totransportation and postharvest resting than many other cultivars(Yıldırım et al., 2009). Exportation value of Kırka�gaç melons hasgained importance in recent years thanks to its high quality char-acteristics (Anonymous, 2014b).

Fresh-cut processing of fruit and vegetables is well known topromote faster deterioration in comparison with their intactcounterparts. In particular, microbial growth and development ofbiochemical reactions onwounded plant tissues are responsible forsafety and quality degradation of the product, which translate notonly in food spoilage but also in risk for foodborn illness (Manzocco,Pieve, & Maifreni, 2011). Safe production methods and properdisinfection/decontamination procedures are therefore criticalsteps in ensuring the safety of ready-to-eat fresh fruit and vege-tables (Abadias, Alegre, Usall, Torres, & Vi�nas, 2011).

Chlorine is the most common sanitizer used in fresh-cut fruitand vegetable production (Anonymous, 2014c). The common formof chlorine used in the fresh production industry is sodium hypo-chlorite (NaClO). The use of hypochlorite-based systems for freshproduct washing is already prohibited in various European Unioncountries because of the risk of a range of cancers (Silveira, Conesa,

Table 1Microbial counts (log cfu/g) of fresh-cut Kırka�gaç melon slices stored for 12 days at5 �C.

Days Control GOb HOc NaClOd

Aerobic bacteria0 3.32 ± 0.03 aAa 3.23 ± 0.10 aA 3.35 ± 0.10 aAB 3.63 ± 0.08 aB3 4.39 ± 0.07 bA 3.71 ± 0.12 bB 4.87 ± 0.23 bA 4.40 ± 0.26 bA6 4.73 ± 0.13 cA 4.51 ± 0.23 cA 5.24 ± 0.08 bcB 4.84 ± 0.03 cA9 6.61 ± 0.36 dA 4.78 ± 0.10 cdB 5.42 ± 0.30 cdC 6.22 ± 0.06 dAC12 7.08 ± 0.17 eA 5.06 ± 0.06 dB 5.83 ± 0.11 dC 6.84 ± 0.12 eA

Yeast and molds0 2.56 ± 0.23 aA 0 aB 2.10 ± 0.17 aC 0 aB3 2.74 ± 0.13 aA 0 aB 2.40 ± 0.17 abAC 2.15 ± 0.28 bC6 3.16 ± 0.09 aA 0 aB 2.69 ± 0.09 bcC 3.21 ± 0.16 bcA9 4.36 ± 0.31 bA 0 aB 3.01 ± 0.11 cdC 3.32 ± 0.50 cC12 4.92 ± 0.06 bA 0 aB 3.31 ± 0.08 dC 4.13 ± 0.09 cD

GO: Gaseous ozone, HO: Hazelnut oil, NaClO: Sodium hypochlorite.a Capital letters in lines show comparisons between applications and small letters

in columns show comparisons between storage periods. Same letters in lines orcolumns indicates no significance at p < 0.05, n ¼ 3, Tukey.

b GO: Gaseous ozone.c HO: Hazelnut oil.d NaClO: Sodium hypochlorite.

T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151 1147

Aguayo, & Art�es, 2008). Additionally, on fresh-cut melon cubes,chlorine resulted in less than a 90% reduction in viable cells ofseveral strains of Salmonella (Selma, Ib�a�nez, Cantwell, & Suslow,2008). The concept of using multiple intervention methods orvarious preservation technologies that are healthier for consumersis increasing in their importance (Selma, Ib�a�nez, Allende, Cantwell,& Suslow, 2008). Therefore, there is much interest in developingsafer and more effective sanitizers for fruit and vegetable (Abadiaset al., 2011). The use of ozone gaseous has been suggested as analternative to reduce microbial populations on melon before cut-ting (Selma, Ib�a�nez, Cantwell, et al., 2008). Hazelnut oil (OleumCoryli) is an edible oil extracted from hazelnut (Corylus avellana L.)fruit seeds without heat treatment and chemical application,naturally by cold pressing method by a firm operating in Turkey. Itcontains essential fatty acids (Omega-3, 6 and 9) as well as vitaminE. Vitamin E is a good antioxidant and has beneficial impacts inlowering cholesterol and protecting cardiovascular health and itcan be used as an alternative in reducing microbial populations andquality losses.

The aim of this work was to evaluate the efficacy of sometreatments compared to NaClO in reducing microbial populationsand remaining the quality of cold stored fresh-cut ‘Kırka�gaç’melons.

2. Materials and methods

2.1. Plant material

Turkish-type melons cv. ‘Kırka�gaç’ (Cucumis melo L. var. inodoruscv. ‘Kırka�gaç’), grown under greenhouse conditions in the Medi-terranean region of Turkey (Antalya), were hand-harvested in Juneat the commercial harvest maturity stage and transported imme-diately to the laboratory. Melons were inspected carefully and fruitwith no visual defects and uniform in shape and size were selected.Fruit skin color was yellow on green spotted, wrinkled andmedium-thick and resistant to transporting and have a long shelflife. Fruit flesh color was white-cream, juicy, delicious and sweet.The average weight of fruits was 3350 g, average fruit diameter was23.5 cm and average fruit length was 23.25 cm.

2.2. Storage conditions

Fruits were transported immediately to the laboratory and allfruits and dipping water were chilled to 5 �C overnight beforeprocessing on the following morning. Disposable gloves were wornduring preparation of the fruits. Chopping boards and knives weredisinfected with sodium hypochlorite (NaClO), washed with tapwater, sanitized with ethyl alcohol and air-dried immediatelybefore use. Also workbench and boxes were sanitized with ethylalcohol. In a clean cold room, at 5 �C, whole unprocessed melons(12 melons for each treatment, totally 48 melons for all experi-ments) were washed with tap water at 5 �C, drained and dried withblotting paper before the treatments. All unprocessed melons weredipped into distilled water (DW) at 5 �C for 2 min, drained anddried with blotting paper, peeled, halved, cored and hand cut toobtain trapezoidal sections (3.0 ± 0.4 cm of wide, 4.0 ± 0.5 oflength) before the treatments except NaClO treatment. Unpro-cessed melons, prepared for NaClO treatment, were dipped intoNaClO solution (200 mL/L, pH 6.5) at 5 �C for 2 min drained anddried with blotting paper, peeled, halved, cored and hand cut toobtain trapezoidal sections (3.0 ± 0.4 cm of wide, 4.0 ± 0.5 oflength). After dipping, fruits were prepared for the experiments: 1.Control (C): Slices were dipped into DW for thirty seconds. 2.Hazelnut oil (HO): HO was put into a sprayer and sprayed on melonslices. HO was extracted from hazelnut (Corylus avellana L.) fruit

seeds without heat treatment and chemical application, naturallyby cold pressing method by a firm operating in Turkey. HO containsessential fatty acids (Omega-3, 6 and 9) and also, vitamin E. HO is agood antioxidant and has positive impacts in lowering cholesteroland protecting cardiovascular health. 3. Gaseous Ozone (GO): Sliceswere treated with 6.34 mg/m3 gaseous ozone by an ozone gener-ator (OPAL, OGHe03, Turkey) in a glass gas tight cabinet for 3 h 4.Sodium hypochlorite (NaClO): Slices were dipped into NaClO so-lution (150 mL/L, pH 6.5) at 5 �C for thirty seconds.

After the treatments, slices (22 ± 2 slices per each boxes) wereplaced immediately to lidded plastic boxes (500 g capacity) andstored in a cold room at 5 �C temperature and 90 ± 5% relativehumidity for 12 days. The experiment was set up with 3 replication,each package was regarded as a replication, and totally 60 boxes ofmelon slices were used during analyzing periods. Melon slices wereanalyzed initially (initial analyses were made after the treatments)and at three-day intervals for microbial enumeration, flesh firm-ness, flesh color, titratable acidity (TA), pH, soluble solid content(SSC), weight loss, sensorial attributes (external appearance, taste-flavor and translucency), respiration rate and ethylene productionduring storage.

2.3. Physical and chemical analyses

Analyses were made initially and at three-day intervals duringcold storage. Fruit firmness was determined using a digital texturemachine (AMETEK LLOYD Instruments LF-Plus Tensile Tester, En-gland) and measured via compression using a 50 N load cell and astainless steel, 5.1 mm diameter cylindrical probe with a constantspeed of 100 mm/min at harvest date and during storage period.The maximum force (N) generated during the probe travel wasused for data analysis. Fruit flesh color was determined using achromameter (Minolta CR-300, Minolta Ramsey, NJ, USA). The di-mensions L*, a*, and b* were obtained, and the L*, C* and h� valueswere used to determine the color of melon slices. L* indicateslightness and is the same as the L*a*b* color space, C* is chroma, andh� is the hue angle. The value of C* is 0 at the center and increasesaccording to the distance from the center. Hue angle is defined asstarting at theþa* axis and is expresses in degrees; 0� would beþa*

(red), 90� would be þb* (yellow), 180� would be �a*(green) and270� would be �b* (blue). The hue angle was calculated(h� ¼ arctan b*/a*) and expressed in degrees (�). Saturation index, or

Table 2The quality attributes (weight loss, firmness, soluble solid contents (SSC), titratable acidity (TA), pH, ethylene production, respiration rate, taste- flavor, external appearance,color (L*, C*, h

�and DE*)) of fresh-cut Kırka�gaç melon slices stored for 12 days at 5

�C.

Treatments Storageperiod(days)

Weightloss

Firmness SSC TA pH Ethyleneproduction

Respirationrate

Taste-flavor(1e5 scale)

Externalappearance(1e9 scale)

L*

(lightness)C*

(chroma)h

�

(hue angle)DE(Delta E)

Control 0 e 5.88 6.25 0.090 5.44 0.801 0.017 5.00 9.00 76.32 11.77 111.93 e

3 0.003 3.73 7.32 0.100 5.55 1.733 1.797 4.93 8.73 73.25 10.64 110.96 3.376 0.034 4.87 7.92 0.127 5.41 1.397 1.351 4.21 8.46 74.71 10.27 110.27 3.129 0.027 4.54 7.35 0.125 5.40 2.619 1.323 1.92 4.75 74.33 9.23 111.39 3.65

12 0.028 3.15 7.27 0.121 5.40 1.207 1.991 1.00 1.00 69.34 8.52 109.66 10.55NaClOd 0 e 5.21 6.83 0.100 5.44 0.955 0.020 5.00 9.00 73.13 10.35 112.28 e

3 0.163 4.11 6.25 0.097 5.48 1.841 1.540 3.17 8.80 70.32 10.07 112.09 1.926 0.051 4.09 6.43 0.101 5.44 1.057 1.455 3.13 8.46 72.00 10.63 112.89 1.359 0.038 4.38 5.63 0.098 5.45 0.759 1.131 1.83 5.83 75.02 9.74 111.66 2.01

12 0.204 4.07 6.33 0.134 5.08 0.278 0.976 1.33 3.38 70.37 9.38 110.87 1.05HOe 0 e 4.94 7.35 0.090 5.66 2.354 0.019 5.00 9.00 73.12 12.75 112.18 e

3 0.000 3.89 6.45 0.107 5.47 1.072 2.414 3.39 8.33 73.51 12.32 111.55 1.696 0.015 3.38 7.82 0.108 5.49 1.108 2.105 2.93 7.39 74.04 11.26 111.16 4.159 0.042 2.36 8.32 0.120 5.82 1.455 2.573 2.33 4.83 70.82 12.06 109.39 1.66

12 0.417 2.97 8.5 0.113 5.61 0.642 1.078 1.89 4.72 73.22 10.73 110.42 1.55GOf 0 e 4.02 7.45 0.080 5.60 1.022 0.020 5.00 9.00 71.36 10.39 111.51 e

3 0.482 4.09 6.73 0.113 5.38 0.650 0.560 4.13 8.87 73.86 10.63 111.41 2.136 0.391 4.35 7.58 0.110 5.40 1.016 1.198 2.92 8.54 70.25 11.43 112.39 2.039 0.417 4.06 6.68 0.114 5.56 1.274 1.258 2.87 5.75 72.95 10.61 111.02 2.30

12 0.300 4.29 6.85 0.133 5.20 1.242 0.930 2.50 5.29 75.60 10.02 112.70 2.90Storage period (SP) ** ** ns ** ** ns ** ** ** ns * ns **Treatment (T) ** ** **b nsc ** ns * ** ** ns * * **T � SP ** ** ns *a ** * ns ** ** * * ns **

a*: p < 0.05; b**: p < 0.01; cns: not significant, n ¼ 3.Scale of external appearance: 1e9: � 1e4: poor, � 5: marketable, 7e8: good, 9: excellent; Scale of taste-flavor: 1e5: 1: very poor, 2: poor, 3: mild, 4: good, 5: excellent.

d NaClO: Sodium hypochlorite.e HO: Hazelnut oil.f GO: Gaseous ozone.

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purity of color (chroma), was also calculated [C* ¼ ((a*)2 þ (b*)2)1/2]and expressed numerically. Also, fruit flesh color was representedas color difference ½DE*ab ¼ ððL*2 � L*1Þ2 þ ða*2 � a*1Þ2 þ ðb*2 � b*1Þ2Þ1=2�in Table 2. Weight loss was expressed as the percentage of loss ofweight with respect to the initial weight. The soluble solid content(SSC) was measured using a digital refractometer (Atago PocketPAL-1, Tokyo, Japan) and SSC was expressed as percentage of sol-uble solids per 100 g fresh weight. Titratable acidity (TA) wasdetermined by a digital pH meter (Hanna Instruments HI 9231,Italy) and titrimeter (Isolab Digitrate, Germany), and expressed aspercentage of grams of malic acid equivalent per 100 g freshweightand pH was measured by a digital pH meter (Hanna Instruments HI9231, Italy). For respiration measurements, the static systemdescribed by Saltveit (2004) was used. Respiration rate andethylene production were determined by gas chromatography.Samples were put in a gas tight glass jars at room temperature atharvest date and three-day intervals during storage. Gas samplewas taken from the jars at the end of the 4 h. Measurements weremade in split/splitless (S/SL) of inlet in split mode with gas sam-pling valve with 1-mL gas sample by using fused silica capilarcolumn (GS-GASPRO, 30 m � 0.32 mm I.D., U.S.A), with thermalconductivity detector (TCD) for respiration rate measurements andflame ionization detector (FID) for ethylene production measure-ments by Agilent GC-6890N (U.S.A and Canada) model gas chro-matography (GC) and Chemstation A.09.03 [1417] software. Carriergas flow was 1.7 mL/min in stable flow mode. The temperature ofthe oven, TCD and FID detectors were 40 �C (isothermal), 250 �Cand 250 �C, respectively (Dilmaçünal, 2009, p. 188).

2.4. Microbial enumeration

In order to determine the number of microorganisms, 25 g ofmelon sample was added into 225 mL of 1 g/100 mL phosphate-

buffered saline (PBS) and homogenized in a stomacher (BagMixer400, USA) for thirty seconds. After homogenization, samples wereserially diluted in sterile PBS. After dilutions were made, 0.1 mLsample from each dilution was plated on proper media plates intriplicate. Plate count agar (PCA, Merck, Germany) was used for thedetermination of total aerobic bacteria. The plates were incubatedat 30 �C for 24e48 h (Maturin & Peeler, 2001; Anonymous, 2014d).Yeasts and molds were counted on Malt Extract Agar (MEA, Merck,Germany). The pH of MEA plates was adjusted to 3.5 and 50 mg/Lchloramphenicol was added to suppress undesired bacterialgrowth. PDA plates were incubated at 25 �C for 48e72 h (Thomas,Stack, Mislivec, Koch & Bandler, 2001; Anonymous, 2012). Afterincubation, plates were counted and data was analyzed.

2.5. Sensorial attributes

External appearance of fresh-cut melons was evaluated using ascale of 1e9: � 1e4: poor,� 5: marketable, 7e8: good, 9: excellent.Taste and flavor of melon slices were evaluated using a scale of 1e5:1: very poor, 2: poor, 3: mild, 4: good, 5: excellent. Translucencywas evaluated by counting deteriorated melon slices and expressedas a percentage of the total number of slices. The analyses wereconducted by a panel of 15 (age range of 30, 8 women and 7 men)trained judges. They were trained before the sensorial analyses atpostharvest physiology laboratory for the evaluation of the sensoryquality characteristics of fruits.

2.6. Experimental design and statistical analyses

The experiment followed a completely randomized design with3 replication and each package was regarded as a replication. Thedifferences between the mean of the groups was determined byTukey. All analyses were performed using the Minitab® 15 statistics

T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151 1149

software (Minitab Inc. USA). Microbial counts were first subjectedto logarithmic conversion. The analysis of covariance was used todecide whether significant differences (p < 0.05) existed amongtreatments.

3. Results and discussion

3.1. Microbial enumeration

The effect of storage period and treatments on the number ofmicroorganisms was statistically significant (p < 0.05). GO wasdetermined to be the most effective treatment for the inhibition ofboth bacteria and fungi in fresh-cut melon samples during storage.Its effect on yeasts and molds was significantly above other treat-ments. While GO totally inhibited the growth of yeasts and molds,the number of bacteria increased to serious numbers during 12 daystorage. Although, NaClO limited the growth of yeasts and molds,the level of inhibition was not comparable to that of GO. Thetreatment prevented the growth of bacteria at initial period. On theother hand the total number of bacteria increased to highernumbers after 3 days showing that NaClO treatment affected onlybacterial cells in vegetative forms but not bacterial spores. Afterinitial period spores germinated and became vegetative again. Thenumber of yeasts and molds were 4.13 log cfu/g after 12 days.Inhibitory effect of HO on both bacteria and fungi was astonishing.It was determined that degree of inhibition was better whencompared to NaClO treatment (Table 1). Microbial quality of fresh-cut melons during storage is depended on some factors such asgenotype, maturity, soluble solid content, packaging material andstorage temperature (Roller& Seedhar, 2002; Saftner, Bai, Abbott,&Lee, 2003). Maximum required microbial limit set by Turkish leg-islations (Anonymous, 2012) for mesophilic aerobic bacterialgrowth (107 cfu/g) was not exceeded in this study after 12 days ofstorage at 5 �C by all experimental groups except control group(Table 1). Saftner, Abbott, Lester, and Vinyard (2006) reported thatmicrobial population tended to increase in stored melons after 2days and a rapid increase was found after 5 days of storage. Theefficacy of decontamination methods is reflected in the microbio-logical reduction obtained and, even more important, in themaintenance of this reduction during storage (Abadias et al., 2011).GO treatment was determined to be the most effective method forthe inhibition of both bacteria and fungi in fresh-cut melon samplesduring storage. Its effect on yeasts and molds was significantlyabove of the other applications. While GO totally inhibited thegrowth of yeasts and molds, the number of bacteria increased toserious numbers on day 12 of storage. Similar inhibitory effect ofedible alginates on fungi was also reported by Raybaudi-Massilia,Mosqueda-Melgar, and Martin-Belloso (2008). However the effectof alginates on bacterial species was not that strong. Aguayo,Allende, and Art�es (2003) stated that the number of bacteria after14 days of storage in modified atmosphere packaged melons weremore than 107 cfu/g. The number of yeasts recorded in their studywas similar to our findings. Inhibitory effect of HO on both bacteriaand fungi was better when compared to NaClO. It can be explainedby strong binding and coating effect of HO. The oil forms a layer onthe surface of melon slices which prevents accession of microbialcells to nutrients. The coating effect may also limit the oxygenintake of aerobic microorganisms. Being a common food withoutany putative effect is another feature of edible oil which can be usedas a coating material for fresh-cut fruits.

3.2. Firmness

The melon slices became softer compared to harvest date in alltreatments with increasing storage period except the GO treatment.

Control group displayed the highest firmness loss (46.43 N/100 N),followed by HO (39.88 N/100 N), and NaClO (21.88 N/100 N)(Table 2). The melon slices treated with HO had a greasy textureespecially in last days of storage. One of the important effects ofozone in cold storage is to slow down the fruit and vegetableripening process (Xu, 1999). Likewise, GO treated melon slices withhigh flesh firmness values also showed low ethylene productionduring cold storage (Table 2). The obtained results are similar to thefindings by Luna-Guzm�an, Cantwell, and Barrett (1999), who re-ported that samples treated with gaseous ozone seemed to holdfirmness better than other treatments throughout 9 days of storage.Selma, Ib�a�nez, Cantwell, et al. (2008) found similar results in coldstorage of melon slices.

3.3. Weight loss

Weight loss of slices was at low values in all treatments at theend of the storage. GO treated slices displayed highest moisture loss(0.30 g/100 g) at day 12 than those of the others, followed by NaClO(0.20 g/100 g). The lowest weight loss (0.01 g/100 g) was obtainedin HO treated slices at day 12. Also, control group displayed lowweight loss (0.03 g/100 g) at the end of the storage (Table 2). Fresh-cut vegetables are highly perishable, because internal tissues areexposed and generally lack skin or cuticle as a protective coveringand the metabolism of the tissue accelerated by the physicaldamage caused by the fresh-cut processing (Watada & Qi, 1999).Also, the fact of presenting a great exposed surface area induces ahigher dehydration, and consequently a high weight loss (Art�es,G�omez, & Art�es-Hern�andez, 2007). Sliced melons of all treat-ments exposed to air during experimental preparation, handling,washing, dipping and packaging, but the slices in GO treatmentexposed to air for longer period than those of the others during thegaseous ozone treatment. Therefore, the weight loss of the sliceswas higher in GO treatment than control, NaClO and HO treat-ments. The HO was covered over all surfaces of melon slices. Themoisture loss of the slices was prevented thanks to this thin layer.Consequently, the lowest weight loss was obtained in HO (0.01 g/100 g) treated slices at day 12. However, the weight loss of HOtreated slices was 0.04 at day 9. The high moisture loss after day 9maybe caused to decrease the water content of the slices andslowed down the decreasing in weight loss at day 12. Also, melonslices in control group showed low weight loss at the end of thestorage. We considered that treated melon slices had to contact toair more than the control group during the treatments. Therefore,the moisture loss of the melon slices in control group displayedlower values than those of the others (Table 2).

3.4. Respiration rate and ethylene production

According to average values, the respiration rate of melon slicesin GO treatment displayed lowest value (0.61 mLCO2/kg h) while thehighest value (1.43 mLCO2/kg h) was obtained in NaClO treatment.The ethylene production of the melon slices showed lowest value(0.98 mL/kg h) in HO treatment followed by GO (1.04 mL/kg h) andNaClO (1.33 mL/kg h) treatments, while control group displayed thehighest value (1.55 mL/kg h) according to average values (Table 2).Among the different plant hormones which are involved in fruitdevelopment, ethylene has the main role during melon fruit soft-ening (Nu~nez-Palenius, 2005, p. 215). Luna-Guzm�an et al. (1999)reported that an increasing in respiration rate after day 6 couldbe due to microbial growth. Likewise, according to average values,control group had the highest values of ethylene production(Table 2) with highest level of microbial spoilage at the end of thestorage (Table 1).

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3.5. Titratable acidity and pH

During storage, a little fluctuation in titratable acidity (TA) andpH values were found in all treatments. In general, TA values tend todecrease and pH values tend to increase compared to initial valuesto the end of the storage. On the contrary of the general manner, areverse tendency was obtained in TA and pH values of all treat-ments during storage. The TA values were increased and pH valueswere decreased compared to initial values at the end of the storage(Table 2). In general, an increase in pH and a decrease in TA valuesare observed; however, in some cases a reverse tendency isobserved during the last days of storage (Aguayo et al., 2003). Thereverse tendency in TA and pH values of the melon slices foundduring storage (Table 2) was probably due to microbial growth(Aguayo et al., 2003).

3.6. Soluble solid content

While the soluble solid contents of the melon slices showed anincrease in control and HO treatments, a reduction was found inNaClO and GO treatments compared to initial values. HO treatedslices were displayed the highest value (8.58 g/100 g) while thelowest value (6.33 g/100 g) was obtained in NaClO treatment(Table 2). Beaulieu, Ingber, and Lea (2011) found roughly 15% sol-uble solids loss in melon cubes and thin-slices. Similar to ourfindings, Silveira, Aguayo, and Art�es (2010) found a reduction andchanges in the levels of soluble solid contents with storage timeand the researchers based upon this case to influencing of thisparameter by the kind of sanitizer. Likewise the soluble solid con-tents of the melon slices displayed a reduction in GO and NaClOtreatments while an increase was found in control and HO treat-ment compared to initial values (Table 2).

3.7. Flesh color

No tissue browning was observed, but yellow color of samplesdisplayed differences depending on treatments throughout storage.Black spot was observed at high levels at day 12 in control groupand this caused to a darkening in yellow color of slices. The melonslices in control group were less bright, duller and displayed darkyellow color than the other treatments. GO treated slices werebrighter, more vivid and displayed light yellow color than HO,NaClO and control. A very obvious color difference (DE) wasdetermined in control group (Table 2). Color of fresh-cut produce isprobably the main quality attribute considered by consumers.Research in the past few years has focused on the prevention ofdiscoloration (Art�es et al., 2007). No tissue browning was observedand yellow color of samples was kept stable throughout storage inall treatments except control. GO treated slices were appearedmore vivid and bright at day 12 than those of the others (Table 2).The obtained results are similar to the findings by Selma, Ib�a�nez,Cantwell, et al. (2008), who reported that gaseous ozone treat-ment notably affected the color of fresh-cut melon during storage.

3.8. Sensorial attributes

From the sensory quality point of view, melon slices in GOtreatment were found marketable in day 12 when the externalappearance (5.29 points) and taste and flavor (2.50 points) weretaken into account together (Table 2). However, according to mi-crobial enumeration results (Table 1), it can be suggested that GOtreated slices were marketable for 9 days with good quality. At day9, the external appearances of the slices in control and NaClOtreatment were still acceptable (4.75 and 5.83 points, respectively)from the consumer point of view. However, the taste and flavor

values of the samples were significantly decreased after day 6 andevaluated as poor at day 9. HO treated slices lost their marketablequality at day 9 (3.83 points) and taste and flavor was evaluated aspoor (2.33 points) at the same day. So, the melon slices in control,NaClO and HO treatments were found marketable with goodquality for 6 days (Table 2). Neither browning of tissues nor blackspot was observed in all treatments except control group duringstorage. Control group showed high level of black spot at day 12.Translucency was not observed in all treatments for 6 days ofstorage. However, with the prolonged storage life, a slight increasein translucency was observed at day 9 in control (14.3 slices/100slices), NaClO (22.2 slices/100 slices) and HO treatments (25 slices/100 slices). At day 12, translucency was observed in all treatmentsexcept GO. Translucency was observed at high levels in NaClO(23.15 slices/100 slices) and HO (27.38 slices/100 slices) treatmentsand being more evident in samples of control group (33.76 slices/100 slices) at the end of the storage (datawere not given). Very littleamount of juice leakage was observed in NaClO treatment whilecontrol and HO treated slices showed much juice leakage at day 12.The integrity of the slices treated with GO preserved better than theothers and no juice leakage was observed during storage.

The shelf-life of fresh-cut products tends to be very short andeven few days of its extension could represent a remarkableadvantage for the companies operating in the sector (Manzoccoet al., 2011). Delay of spoilage and improvement of sensorial attri-butes of fresh-cut fruit and vegetables, may also be interesting froma commercial point of view (Ayala-Zavala, Gonz�alez-Aguilar, & Del-Toro-S�anchez, 2009). Sensory and microbiological quality of the GOtreated samples were at acceptable quality during 9 days of storage(Tables 1 and 2). The obtained results are similar to the findings bySelma, Ib�a�nez, Cantwell, et al. (2008), who reported that the fresh-cut melon samples treated with ozone maintained a good visualquality, aroma and firmness. The ozone treatment was found to bebetter than the chlorine and other organic acid treatments inmaintaining the sensory quality of fresh-cut green lettuce (Yadav,2010). In our research, a greasy texture and slight off-odor wasperceived in the HO treated slices. The chemical reactivity of nat-ural antimicrobial agents with fresh fruits and vegetables andpackagematrix, could significantly affect the sensorial properties ofproduce (Ayala-Zavala et al., 2009). Next to firmness, the high rateof translucency compared to intact fruit is also an important qualityissue for fresh-cut melon. Tissue water soaking or translucency andjuice leakage are major factors limiting the longevity and quality offresh-cut fruits (Guo et al., 2011). Translucency as a symptom ofsenescence and that all treatments that accelerate ripening, such ashigh temperatures of storage, prolonged storage time, unwashedcut melon, air atmosphere, using blunt blade for cutting, kind of cut(cylinders compared to trapezoid sections), also increase trans-lucency (Aguayo et al., 2003). Oms-Oliu, Soliva-Fortuny, and Mar-tín-Belloso (2007) reported that translucency may be aconsequence of an advanced stage of ripeness, treatments thataccelerate ripening or high storage temperatures. Cold storagecombined with gaseous ozone andmodified atmosphere packagingslowed down the ripening process of the slices during the storage.So, the translucency was successfully prevented by GO treatmentduring cold storage. It was possible that translucency symptomswere also caused by other factors such as sugar content (Guo et al.,2011). Likewise, high level of sugar content (Table 2) with high levelof translucency was observed in control and HO treatment at theend of the storage.

4. Conclusion

It was shownwith this research that GO treatment was themosteffective method and HOwas as effective as sodium hypochlorite in

T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151 1151

reducing microbial populations and preserving the quality of fresh-cut melon during cold storage.

References

Abadias, M., Alegre, I., Usall, J., Torres, R., & Vi�nas, I. (2011). Evaluation of alternativesanitizers to chlorine disinfection for reducing foodborne pathogens in fresh-cut apple. Postharvest Biology and Technology, 59, 289e297.

Aguayo, E., Allende, A., & Art�es, F. (2003). Keeping quality and safety of minimallyfresh processed melon. European Food Research and Technology, 216, 494e499.

Amaro, A. L., Beaulieu, J. C., Grimm, C. C., Stein, R. E., & Almeida, D. P. F. (2012). Effectof oxygen on aroma volatiles and quality of fresh-cut cantaloupe and honeydewmelons. Food Chemistry, 130, 49e57.

Anonymous. (2012). Turkish national standards. Microbiology section. Generalguidelines for enumeration of yeasts and molds. Colony counting technique at25 �C. Ankara: Turkish Standards Institute. TS 6580-ISO 7954.

Anonymous. (2014d). Turkish National Standards. Microbiology Section. Food andanimal feed. General guidelines for enumeration of mesophillic aerobic bacteria.Colony counting technique at 30 �C. Ankara: Turkish Standards Institute. TS 7703EN ISO 4833.

Anonymous. (2014a). Food and Agriculture Organization of the United Nations.FAOSTAT-Agriculture. http://www.fao.org/waicent/portal/statistics_en.asp,06.08.2014.

Anonymous. (2014c). Strong oxidizers present alternatives to chlorine washes.FreshCUT Magazine. http://freshcut.com/index.php/magazine/article/1224.Great American Media Services. 06.08.2014.

Anonymous. (2014b). Kırka�gaç kavunları. Dünyada ve Ülkemizde kavunun yeri. http://www.kirkagackavunlari.com/dunyadakavununyeri.asp, 06.08.2014.

Art�es, F., G�omez, P. A., & Art�es-Hern�andez, F. (2007). Physical, physiological andmicrobial deterioration of minimally fresh processed fruits and vegetables. FoodScience and Technology International, 13(3), 177e188.

Ayala-Zavala, J. F., Gonz�alez-Aguilar, G. A., & Del-Toro-S�anchez, L. (2009). Enhancingsafety and aroma appealing of fresh-cut fruits and vegetables using the anti-microbial and aromatic power of essential oils. Journal of Food Science, 74(7),84e91.

Beaulieu, J. C., Ingber, B. F., & Lea, J. M. (2011). Physiological, volatile, and SEMsurface effects resulting from cutting and dipping treatments in cantaloupe.Journal of Food Science, 76(7), 415e422.

Dilmaçünal, T. (2009). Normal and controlled atmosphere storage of some applecultivars grown in organic and conventional farming conditions (PhD thesis).Süleyman Demirel University (in Turkish).

Guo, Q., Cheng, L., Wang, J., Che, F., Zhang, P., & Wu, B. (2011). Quality characteristicsof fresh-cut ‘Hami’ melon treated with 1-methylcyclopropene. African Journal ofBiotechnology, 10(79), 18200e18209.

Luna-Guzm�an, I., Cantwell, M., & Barrett, D. M. (1999). Fresh-cut cantaloupe: effectsof CaCl2 dips and heat treatments on firmness and metabolic activity. Post-harvest Biology and Technology, 17, 201e213.

Manzocco, L., Pieve, S. D., & Maifreni, M. (2011). Impact of UV-C light on safety andquality of fresh-cut melon. Innovative Food Science and Emerging Technologies,12, 13e17.

Maturin, L., & Peeler, J. T. (2001). Aerobic plate count. Bacteriological analyticalmanual (8th edition). chapter 3.

Nu~nez-Palenius, H. G. (2005). Transformation of ‘Galia’ melon to improve fruit quality.A dissertation presented to the graduate school of the University of Florida in

partial fulfillment of the requirements for the degree of doctor of philosophy.University of Florida.

Oms-Oliu, G., Soliva-Fortuny, R., & Martín-Belloso, O. (2007). Effect of ripeness onthe shelf-life of fresh-cut melon preserved by modified atmosphere packaging.European Food Research and Technology, 225, 301e311.

Raybaudi-Massilia, R., Mosqueda-Melgar, J., & Martin-Belloso, O. (2008). Ediblealginate-based coating as carrier of antimicrobials to improve shelf-life andsafety of fresh-cut melon. International Journal of Food Microbiology, 121,313e327.

Roller, S., & Seedhar, P. (2002). Carvacrol and cinnamic acid inhibit microbial growthin fresh- cut melon and kiwifruit at 4 and 8 �C. Letters in Applied Microbiology,35, 390e394.

Saftner, R., Bai, J., Abbott, J. A., & Lee, Y. S. (2003). Sanitary dips with calcium pro-pionate, calcium chloride, or a calcium amino acid chelate maintain quality andshelf stability of fresh-cut honeydew chunks. Postharvest Biology and Technol-ogy, 29, 257e269.

Saftner, R., Abbott, J. A., Lester, G., & Vinyard, B. (2006). Sensory and analyticalcomparison of orange-fleshed honeydew to cantaloupe and green-fleshedhoneydew for fresh-cut chunks. Postharvest Biology and Technology, 42,150e160.

Saltveit, M. E. (2004). Respiratory metabolism. In The commercial storage of fruits,vegetables, and florist and nursery stocks. Agriculture handbook number 66http://usna.usda.gov/hb66/019respiration.pdf (viewed on 2nd April 2013).

Selma, M. V., Ib�a�nez, A. M., Allende, A., Cantwell, M., & Suslow, T. (2008). Effect ofgaseous ozone and hot water on microbial and sensory quality of cantaloupeand potential transference of Escherichia coli O157:H7 during cutting. FoodMicrobiology, 25, 162e168.

Selma, M. V., Ib�a�nez, A. M., Cantwell, M., & Suslow, T. (2008b). Reduction by gaseousozone of Salmonella and microbial flora associated with fresh-cut cantaloupe.Food Microbiology, 25, 558e565.

Sensoy, S., Büyükalaca, S., & Abak, K. (2007). Evaluation of genetic diversity inTurkish melons (Cucumis melo L.) based on phenotypic characters and RAPDmarkers. Genetic Resources and Crop Evolution, 54, 1351e1365. http://dx.doi.org/10.1007/s10722-006-9120-6.

Silveira, A. C., Conesa, A., Aguayo, E., & Art�es, F. (2008). Alternative sanitizers tochlorine for use on fresh-cut “Galia” (Cucumis melo var. catalupensis) melon.Journal of Food Science, 73(9), 405e411.

Silveira, A. C., Aguayo, E., & Art�es, F. (2010). Emerging sanitizers and clean roompackaging for improving the microbial quality of fresh-cut ‘Galia’ melon. FoodControl, 21, 863e871.

Thomas, V., Stack, M. E., Mislivec, P. B., Koch, A., & Bandler, R. (2001). Yeasts, moldsand mycotoxins. Bacteriological analytical manual (8th edition). chapter 18.

Xu, L. (1999). Use of ozone to improve the safety of fresh fruits and vegetables. FoodTechnology, 53(10), 58e63.

Watada, A. E., & Qi, L. (1999). Quality control of minimally-processed vegetables. InJ. M. Lee, K. C. Gross, A. E. Watada, & S. K. Lee (Eds.), Acta Horticulturae: Vol. 483.Proc. Int. Symp. on Quality of fresh and fermented vegetables (pp. 209e220).

Yadav, L. (2010). The effect of ozone on the growth and development of selected foodspoilage fungi. ISBN-10:1-59942-352-9, ISBN-13: 978-1-59942-352-4. Dis-sertation.com, Boca Raton, Florida, U.S.A http://www.bookpump.com/dps/pdf-b/9423529b.pdf.

Yıldırım, O., Halloran, N., Çavuso�glu, S., & Sengül, N. (2009). Effects of differentirrigation programs on the growth, yield, and fruit quality of drip-irrigatedmelon. Turkish Journal of Agriculture and Forestry, 33, 243e255.