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Postharvest Biology and Technology 86 (2013) 100–106

Contents lists available at SciVerse ScienceDirect

Postharvest Biology and Technology

journa l h om epa ge : www.elsev ier .com/ locate /postharvbio

able olive cultivar susceptibility to impact bruising

rancisco Jiménez-Jiméneza, Sergio Castro-Garcíaa,∗, Gregorio L. Blanco-Roldána,ouise Fergusonb,1, Uriel A. Rosac, Jesús A. Gil-Ribesa

Department of Rural Engineering, E.T.S.I. Agrónomos y Montes, University of Cordoba, Campus de Rabanales, Ctra. Nacional IV Km 396, Cordoba, SpainDepartment of Plant Sciences, University of California Davis, 1 Shields Ave, Davis, CA 95616, United StatesAgriculture Division, Trimble Navigation Limited, 935 Stewart Drive, Sunnyvale, CA 94085, United States

r t i c l e i n f o

rticle history:eceived 27 January 2012ccepted 11 June 2013

eywords:

a b s t r a c t

Developing mechanical harvesting for table olives will require decreasing fruit damage during harvestand postharvest handling, transport and storage. The susceptibility to bruising and its development overtime were studied in three table olive varieties, cv. ‘Manzanilla’, ‘Gordal Sevillana’ and ‘Hojiblanca’. Bruis-ing was produced with controlled energy impacts of 56, 26, 13 mJ. A strong correlation (r2 = 0.77–0.90)

ruit injuryechanical harvesting

ostharvest handlinglea europaeais–Nir spectroscopyruit quality

between bruise volume and impact energy was demonstrated. Bruise susceptibility was higher in theManzanilla variety, followed by Hojiblanca and Gordal Sevillana cultivars. Bruise time evolution wasevaluated using a spectrophotometer for visible and near infrared regions. A bruise index was developedusing different wavelengths, 545, 670 and 800 nm. Most darkening due to the browning process hap-pened within 1 h, was exponential and dependent on impact energy level. The discoloration was greatestin the Manzanilla, followed by Hojiblanca and Gordal Sevillana olives.

. Introduction

Table olives (Olea europaea L.) are the second largest olive prod-ct in the world with approximately 2.2 million tons of tablelives produced annually (IOOC, 2011). In spite of its high cost,arvesting is still done by hand. These steadily increasing hand har-est costs severely decrease table olive production net economiceturn. Therefore, most table olive producing countries are tryingo develop mechanical harvesting (Ferguson et al., 2010).

Spanish-style green olive processing is among the three mostommon processing methods (Rejano et al., 2010). For greenrocessing the olives are harvested physiologically immatureIOOC, 2004). Unripe table olives have a high fruit removal forceKouraba et al., 2004). The mechanical harvesting force requiredor fruit removal produces bruising (Ferguson, 2006; Segovia-Bravot al., 2011).

Most mechanical impact damage occurs during harvesting,andling and transportation. This damage reduces fruit quality

s external appearance is the most important criterion in qual-ty determination of fresh olives when delivered to the processorRejano, 1999; Barreiro et al., 2004; Riquelme et al., 2008). When

∗ Corresponding author. Tel.: +34 9 57218548; fax: +34 9 57218550.E-mail addresses: g52jijif@uco.es (F. Jiménez-Jiménez), scastro@uco.es

S. Castro-García), ir3blrog@uco.es (G.L. Blanco-Roldán), ferguson@ucdavis.eduL. Ferguson), uriel rosa@trimble.com (U.A. Rosa), gilribes@uco.es (J.A. Gil-Ribes).

1 Tel.: +1 530 752 0507; fax: +1 530 752 8502.

925-5214/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.postharvbio.2013.06.024

© 2013 Elsevier B.V. All rights reserved.

the force is sufficient for fruit removal it often results in fruit bruis-ing (Van Linden et al., 2006). Bruises consist of a rupture to cellulartissue that releases intracellular fluid leading to oxidation of pheno-lic compounds. In time, depending on the characteristics of impact,the affected skin darkens and stands out from the rest of the olivegreen color (Ben-Shalom et al., 1978; Segovia-Bravo et al., 2009).In processing, olives receive an alkaline treatment in a dilute lyesolution (NaOH), a washing step and then are fermented in brine(NaCl) (Garrido-Fernández et al., 1997). Once processed, green olivecolor varies from green to straw-yellow (IOOC, 2004), and bruisesare obvious.

To reduce bruising during harvesting and postharvest hand-ling it would be helpful to know differential susceptibility amongthe olive cultivars and the specific energy levels that produce thedamage (Bajema and Hyde, 1998). Bruise susceptibility depends onvariety, texture, maturity stage, water content, firmness, tempera-ture, size, shape and the internal fruit factors of cell wall, strengthand elasticity, cell shape and internal structure (Mohsenin, 1986;Van Linden et al., 2006).

The small size of the olive fruit limits the options for studyingthe effects of impact energy. Test systems based on fruit electron-ics (Ortiz et al., 2011) or instrumented pendulums (Van Zeebroecket al., 2003; Opara, 2007) have been widely used in larger fruits, butthey are not applicable to olives. However, the drop test method,

where the impact is localized to one side of the fruit and impactenergy is known is suitable for olives. This method has been usedand described in apples (Lewis et al., 2007), pears (Menesatti andPaglia, 2001), oranges (Ortiz et al., 2011), apricots (De Martino

Biology and Technology 86 (2013) 100–106 101

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F. Jiménez-Jiménez et al. / Postharvest

t al., 2006), peaches (Schulte and Timm, 1994) and strawberriesFerreira et al., 2008).

To determine bruise susceptibility, bruise size must be mea-ured. (Saracoglu et al., 2011). The relationship between bruise sizend impact energy can be obtained by measuring bruise volume,nd relating the bruised surface area to the depth of penetrationnto the fruit pulp. (Schoorl and Holt, 1980; Bollen et al., 1999).

Once bruising is produced, most research focuses on deter-ining what postharvest treatments prevent further fruit damage.ultiple studies suggest immediate postharvest immersion in cold

cidic or antioxidants solutions prevents the bruised area fromrowning during postharvest handling (Segovia-Bravo et al., 2011).hese postharvest operations will be successful if applied beforehe bruise reaction takes place. Therefore, determination of theruise time evolution is a key factor for determining how to applyostharvest treatments for maintaining fresh olive fruit quality.

Spectroscopy is a nondestructive technique for fruit and veg-table parameter determination related to fruit quality (Nicolait al., 2007). These techniques can detect surface bruises at par-icular wavelengths of the spectrum using process models and

ultivariate analysis (Xing et al., 2004; Pholpho et al., 2011). How-ver, there are no models for assessing olive fruit bruising and itsvolution over time. For apples, the bruise index model most widelysed contains reflectance values at three wavelengths. Chivkunovat al. (2001) developed an index to estimate bruising in apples basedn differences in response to different spectrum wavelengths (550,00 and 800 nm).

The objective of this study is to determine olive bruise suscepti-ility (mm3 J−1) by measuring energy absorbed by the fruit duringrop impact and the bruise volume produced while simultaneouslyetermining the time required for the bruise to evolve using visi-le and near-infrared spectroscopy. Once an index relating impactorce to bruising is developed it can be used by the industry toetermine how to reduce and prevent bruising during harvestingnd postharvest operations.

. Materials and methods

The cultivars evaluated in this study are the three most impor-ant international table olive varieties (Rejano et al., 2010), Oleauropaea L. cv. ‘Manzanilla’, ‘Gordal Sevillana’ and ‘Hojiblanca’. Theruit were harvested from different commercial plantations in therovince of Seville and Cordoba in southern Spain (latitude 37.8◦Nnd longitude 5.0◦W). The fruit were hand picked at the appropri-te stage for fresh green olive processing at 21–25 weeks after fullloom, of uniform size and color, and free of defects or mechan-

cal damage. The drop tests were conducted at a controlled roomemperature of 24–25 ◦C within 2 h of harvesting.

An impact device was designed to cause controlled and repro-ucible impact on the fruit by dropping the olives onto a metallate of 1.8 kg (Fig. 1). The fruit were randomly assigned to three

mpact level treatments; high (56 ± 8 mJ), medium (26 ± 3 mJ) andow impact energy level (13 ± 1 mJ) by dropping the fruit from theifferent heights given in Table 2. The drop heights were selectedased on the average fruit mass of the three different cultivars tobtain similar impact energy levels.

Impact parameters were recorded with a piezoelectric load cellPCB 208C02) attached to a metal surface. The load cell signal wasonditioned and analyzed by a dynamic signal analyzer (OROS 25,C-Pack II) set up with a total sampling time of 0.1845 ms and aandwidth of 2 kHz. The impact was characterized by the impact

nergy, impact force and contact time.

Impact energy (Ei) was determined according to Eq. (1), whered is the potential energy of the fruit as determined by drop (Hd)eight and fruit mass (Mf) and Er is the potential energy achieved

Fig. 1. Drop test apparatus and camera set-up.

by the fruit in the rebound height (Hr). Hr was determined using adigital video camera (JVC, MG330HE) that recorded 25 frames persecond and used a background calibration wall.

Ei = Ed − Er = Mfg(Hd − Hr) (1)

A total of 30 fruit for each variety and their correspondingimpact energy levels were used to determine fruit characteristicsand bruise damage after impact. Only fruit with the impact on thestem to stylar axis were selected to avoid the areas near the pit endwhere the impact contact area is reduced and bruise size thereforeincreased.

Basic data consisting of: fruit mass (Mf), stone mass (Ms), axialfruit length (Lf), axial stone length (Ls), maximal fruit diameter (Df)and maximal stone diameter (Ds) were determined for every olive.The fruit index, FI (Lf/Df), the stone index, SI (Ls/Ds) and the flesh-to-stone ratio (Mf/Ms) were calculated.

Bruise susceptibility (mm3 mJ−1) was defined as the ratio ofbruise volume (BV (mm3)) to the Ei (mJ). Bruise area (BA) andBV were determined by Lewis et al.‘s procedure (2007). The outerbruise area of each fruit was assumed to be an elliptical surfacewith two main axes (w1 and w2) according to Eq. (2). BV was deter-mined based on the main axis of the elliptical surface and the bruisedepth (d) according to Eq. (3). The two main bruise axes and thebruise depth were measured by the same evaluator using a digitalcaliper (±0.01 mm). Two BV and BA measurements per fruit wereperformed to eliminate possible errors.

BA = �

4w1w2 (2)

BV = �d

24(3w1w2 + 4d2) (3)

Bruise time evolution was determined with a spectrometer forthe visible and infrared region (Ocean Optics S2000-TR) with arange of 530–1500 nm. The spectrometer probe was placed in aholder to maintain a constant distance from the fruit and the light

102 F. Jiménez-Jiménez et al. / Postharvest Biology and Technology 86 (2013) 100–106

Table 1Table olive fruit parameters of the Manzanilla, Gordal Sevillana and Hojiblanca.

Parameters Manzanilla Gordal Sevillana Hojiblanca

Fruit length, Lf (mm) 23.3 ± 1.0 a 33.3 ± 2.0 b 23.3 ± 1.0 aFruit diameter, Df (mm) 19.6 ± 0.8 a 25.6 ± 1.1 b 19.0 ± 0.8 aFruit index, Lf/Df 1.2 ± 0.1 a 1.3 ± 0.1 b 1.2 ± 0.1 aFruit mass, Mf (g) 5.1 ± 0.5 a 11.7 ± 1.5 b 4.7 ± 0.6 aStone length, Ls (mm) 14.3 ± 0.9 a 22.4 ± 1.8 c 16.6 ± 1.1 bStone diameter, Ds (mm) 8.9 ± 0.4 a 11.4 ± 1,0 c 9.4 ± 0.6 bStone index, Ls/Ds 1.6 ± 0.1 a 2.0 ± 0.2 c 1.8 ± 0.1 bStone mass, Ms (g) 0.8 ± 0.1 a 1.7 ± 0.3 c 1.0 ± 0.2 bFlesh-to-stone ratio (Mf/Ms) 6.7 ± 0.9 b 6.9 ± 0.8 b 5.1 ± 1.2 a

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he post hoc test of Duncan’s multiple variability was applied. Mean and standardeviation for the samples (N = 30) are presented. Different letters in the same row

ndicate significant differences among varieties (p < 0.01).

robe to record only diffused light and to mitigate the effects of lab-ratory light effects. A 100 W tungsten halogen lamp was used as aight source. The surface reflectance of the fruit was analyzed as thealibrated reflectance (R), according to Eq. (4). R was obtained fromhe reflectance of the sample (R0). The reference spectrum (Rref)as determined using a known material (SRM 990 Labsphere Spec-

ralon Inc.). A correction of the spectrum was obtained by turninghe light source off and covering the probe (Rdark).

= R0 − Rdark

Rref − Rdark(4)

Two fruit reflectance spectra were taken both before and aftermpact in the bruise zone at the four evaluation times (1, 3, 8 and4 h after impact). The measured spectra were pre-processed usinghe software for multivariate calibration program, The Unscram-ler, version 6.11 (CAMO ASA, Trondheim, Norway). The originalesolution was reduced by the averaging method to reduce thenfluence of noise until a resolution of 1 nm was obtained. Thexistence of a bruise on the olive fruit was determined throughhe computation of a bruise reflectance index (BRI) presenting theeflectance obtained at different wavelengths using Chivkunovat al.’s procedure (2001) as modified by Solovchenko et al. (2010).he BRI was determined based on the difference in reflectance athe wavelength value at 545 nm (R545) and the value at 670 nmR670), multiplied by the reflectance at 800 nm (R800), accordingo Eq. (5).

RI (%) = [1 − (R545 − R670) R800]100 (5)

All data were subjected to statistical analysis using the analysisf variance (ANOVA) test. Duncan’s multiple range test was per-ormed to determine the significance effects of impact energy levelnd variety on bruise volume.

. Results and discussion

.1. Fruit parameters

The geometric properties of Manzanilla, Gordal Sevillana andojiblanca varieties are presented in Table 1. Significant differ-nces were observed among the fruit characteristics of the differentarieties (p < 0.05). Fruit size (length, diameter) and hence weightas much greater for the Gordal Sevillana variety which had aean mass of 11.7 g, whereas mass was similar for the Manzanilla

nd Hojiblanca varieties with means of 5.1 and 4.8 g, respectively.he main characteristics that differentiated the Manzanilla culti-ar from the Hojiblanca cultivar were the pit size, fruit mass, and

he flesh-to-pit ratio. The flesh-to-pit ratio was similar for Gordalevillana and Manzanilla varieties with mean values of 6.9 and 6.7espectively, whereas this value was 4.9 for the Hojiblanca vari-ty. These results agree with those of Rapoport et al., 2011 and

Fig. 2. Impact force and contact time relative to impact energy level (high = 56 ±8 mJ,medium = 26 ± 3 mJ and low = 13 ± 1 mJ) and variety (Manzanilla, Gordal Sevillanaand Hojiblanca).

Rejano (1999), where mass values of the Manzanilla, Gordal Sevil-lana, and Hojiblanca cultivars were 2.1–4.9, 11.2 and 1.4–4.3 g,respectively. These authors reported greater values for the flesh-to-pit ratio for Gordal Sevillana (6.4 g) and Manzanilla varieties(5.1–7.6 g) versus the Hojiblanca variety, which was usually lower(5.1–6.7 g).

3.2. Impact parameters

Different drop heights facilitated obtaining similar Ei levels inthe fruits. High, medium and low levels of impact energy, withmean values of 56, 26 and 13 mJ, respectively were obtained. Table 2summarizes the important parameters of the impacts for each fruitvariety and impact energy. The Gordal Sevillana variety absorbedthe least amount of energy upon impact (67–72%) followed by theHojiblanca (72–76%) and Manzanilla varieties (72–77%), which hadsimilar absorbed energy values.

Fig. 2 shows the mean impact force and contact time valuesfor the three levels of impact energy. Higher impact energy levelsresulted in higher impact forces. However, fruit contact time dur-ing impact was not related to the potential energy during the drop

F. Jiménez-Jiménez et al. / Postharvest Biology and Technology 86 (2013) 100–106 103

Table 2Effect of impacts relative to variety (M = Manzanilla; G = Gordal Sevillana; H = Hojiblanca) and impact energy level.

Impact energy level Olive variety Drop height (m) Fruit mass (g) Energy (mJ)

Potential Rebound Impact

High(56 ± 8 mJ)

M 1.50 5.1 ± 0.6 a 75 ± 9 ab 17 ± 2 b 58 ± 7 aG 0.66 12.1 ± 1.7 b 78 ± 11 b 23 ± 3 c 56 ± 8 aH 1.50 4.8 ± 0.7 a 70 ± 10 a 13 ± 2 a 53 ± 9 a

Medium(26 ± 3 mJ)

M 0.75 5.1 ± 0.4 a 38 ± 3 b 10 ± 1 b 28 ± 2 aG 0.33 11.5 ± 1.4 b 37 ± 5 b 11 ± 1 c 26 ± 3 aH 0.75 4.7 ± 0.5 a 33 ± 4 a 8 ± 1 a 25 ± 3 a

Low(13 ± 1 mJ)

M 0.38 5.0 ± 0.5 a 18 ± 2 a 5 ± 1 b 13 ± 2 aG 0.16 11.5 ± 1.5 b 18 ± 2 a 6 ± 1 b 12 ± 1 aH 0.38 4.7 ± 0.6 a 18 ± 2 a 4 ± 1 a 13 ± 2 a

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Earlier reports suggest fruits with a higher pit to fruit index hadlower bruise volumes. That is, fruit with more elongated pits andcurvature ratios had lower damage levels. This suggests pits playan important role in bruising. It has been hypothesized that stones

he post hoc test of Duncan’s multiple variability was applied. Mean and standard dignificant differences among varieties (p < 0.01).

Pearson, p = 0.333), although this value varied depending on theariety. The Hojiblanca variety had the lowest contact time (0.9 ms)ollowed by the Manzanilla (1.1 ms) and Gordal Sevillana (1.3 ms)arieties. Consistent with earlier reports, fruit with shorter contactimes have a higher firmness, which reduces the risk of develop-ng bruises (Van Linden et al., 2006). Several researchers have alsobserved increased damage in softer fruits (Van Zeebroeck et al.,007). As fruit firmness is related to fruit ripeness, mature fruitsith longer contact times are therefore more susceptible to fruitamage (Wang et al., 2009). In this study, all varieties were col-

ected at the same ripeness stage, so the different contact times mayorrespond with the differences in firmness among the varieties.

.3. Factors determining the levels of bruising

Table 3 presents the factors of bruise size (depth, area and vol-me) on variety and impact energy. Upon impact with the steelurface, the olive’s bruise was similar in shape to an ellipsoid asas suggested by Saracoglu et al. (2011). Other authors have con-

idered the shape of the bruise of the olive to be spherical like theruises that occurs in pears and apples (Blahovec and Paprstein,005; Opara, 2007).

The analysis of variance revealed that bruise volume for theame level of impact energy was significantly different (p < 0.05)mong the three varieties. High and medium levels of impactnergy caused greater bruise volumes and bruise areas for the Man-anilla variety. These values were similar to the ones obtained inordal Sevillana variety and two times greater than those obtained

n Hojiblanca variety.According to the International Olive Council Trade Standard for

able Olives (IOOC, 2004), bruising is described as olives with marksn the skin that represent more than 9 mm2 in surface and that mayr may not penetrate the flesh. Using this information, it can beetermined what drop height would exceed the damage thresholdo cause this kind of bruising. In this study, the 9 mm2 threshold wasonsistently exceeded. Particularly, for the Manzanilla and Hoji-lanca varieties at drop heights of more than 0.38 m and 0.16 m forhe Gordal Sevillana variety.

Although data are not shown here, drop test results demon-trated that there was a high correlation between the impact energynd bruise volume for each variety (r2 = 0.90–0.77), There was a lin-ar relationship between the two parameters. As drop heights andruit masses increased, impact energy also increased and produced

ore fruit damage. Similar results have been well demonstratedn other fruits (Zarifneshat et al., 2010; Van Linden et al., 2006).aracoglu et al. (2011) also reported a bruise volume increase with

rop height for table olives of Memecik and Domat varieties. Inhis case, olives were dropped on three different impact surfaces,teel, wood and plastic, with the steel surface producing the high-st bruise volumes and areas. Once this method has been used to

on for the samples (N = 30) are presented. Different letters in the same row indicate

determine the forces, drop heights and surfaces that will minimizebruising from impact olive producers can integrate these parame-ters into their harvesting and postharvest handling practices

3.4. Bruise susceptibility

Bruise volume is not only a function of impact energy and fruitvariety, other properties, texture, maturity stage, water content,fruit shape, temperature, firmness, and size, are important in fruitdamage (Van Linden et al., 2006). The effect of the flesh-to-pit ratioand the pit index were significant at the 1% probability level. TheGordal Sevillana and Manzanilla varieties with higher flesh-to-pitratios had more bruise damage than the Hojiblanca variety with alower flesh-to-pit ratio. Eq. (6) shows the final model having impactenergy, flesh and pit ratio (Mf/Ms) and the stone index (SI) as theindependent variables. For this model, the plot of predicted bruisevolume by the model versus bruise volume measured is depicted inFig. 3. A good fit was observed between the measured and predictedbruise volume (r2 = 0.764).

BV = −36.55 + 3786Ei + 18.6Mf

Ms− 42.8SI (6)

Fig. 4 shows bruise susceptibility (mm3 J−1) 24 h after impact inthe fruit relative to impact energy and olive variety. This bruisesusceptibility index has been reported by other authors (Opara,2007).

Fig. 3. Measured bruise volume versus bruise volume predicted (mm3).

104 F. Jiménez-Jiménez et al. / Postharvest Biology and Technology 86 (2013) 100–106

Table 3Bruise size characteristics of each olive variety and impact energy (M = Manzanilla; G = Gordal Sevillana; H = Hojiblanca) and impact energy level.

Impact energy level Olive variety Bruise area (mm2) Bruise depth (mm) Bruise volume (mm3)

High(56 ± 8 mJ)

M 77.9 ± 9.1 b 5.1 ± 0.4 c 235.0 ± 36.4 cG 78.7 ± 11.9 b 4.6 ± 0.5 b 266.6 ± 45.6 bH 45.7 ± 8.0 a 3.9 ± 0.4 a 122.9 ± 25.3 a

Medium(26 ± 3 mJ)

M 52.0 ± 6.2 b 4.3 ± 0.4 c 154.6 ± 24.7 cG 48.1 ± 7.9 b 3.8 ± 0.5 b 120.7 ± 21.0 bH 26.4 ± 6.9 a 3.4 ± 0.2 a 50.5 ± 16.7 a

Low(13 ± 1 mJ)

M 28.9 ± 4.5 b 3.7 ± 0.4 b 81.4 ± 17.1 cG 31.6 ± 7.8 b 2.6 ± 0.5 a 50.5 ± 16,7 bH 21.1 ± 6.2 a 2.8 ± 0.4 a 21.1 ± 7.6 a

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he post hoc test of Duncan’s multiple variability was applied. Mean and standard dignificant differences among varieties (p < 0.01).

ith lower curvature indexes increase the force of an impact andherefore increase bruise damage. A similar effect has been demon-trated in fruit without pits. Zarifneshat et al. (2010) demonstratedhat apples with low curvature radiuses had higher bruise volumeshan those with higher curvature radiuses (at the contact area).an Zeebroeck et al. (2007) also reported that tomatoes with smalladiuses of curvature absorb more energy compared to those with

larger radius of curvature. However, other authors claim just thepposite (Blahovec and Paprstein, 2005). A study on the role ofruit shape and other factors affecting bruising in 22 pear vari-ties reported that more elongated fruit were more susceptible toruising.

The impact of the fruit against a metal surface does not representhe most common conditions found during mechanical harvestingf olives. The fruit removal system components (Castro-Garciat al., 2009) or even the different shock absorbing surfaces useduring fruit interception (Ortiz et al., 2011) have a great influencen the energy absorbed by the fruits. However, using a metalurface under laboratory conditions, it has been demonstratedhat contact time does not depend on the energy level of impact,ut on the fruit properties (Wang et al., 2009) and thus variety.herefore, the Hojiblanca variety, with the lower contact time andess flesh-to-stone ratio, was demonstrated in this study to be the

able olive variety most resistant to impact damage. The lowerusceptibility to bruising presented by Hojiblanca compared tohat of other varieties may be due to its greater fruit firmness,

ig. 4. Bruise susceptibility (mm3 J−1) of the olives within 24 h depending onhe cultivar and the impact energy level (high = 56 ± 8 mJ, medium = 26 ± 3 mJ andow = 13 ± 1 mJ). A post hoc test of Duncan’s multiple variability was applied. Meannd standard deviation values are shown (N = 30) for each variety and energy levelpplied to the olives. Different letters for the same energy level indicate significantifferences among varieties (p < 0.05).

on for the samples (N = 30) are presented. Different letters in the same row indicate

that resulted in lower deformation of the flesh and a lower bruisevolume (Zarifneshat et al., 2010) and its smaller flesh-to-pit ratio(Rejano, 1999). This variety presented a stiffer response uponimpact than other varieties. The current mechanical harvestingsystems shake the trunk of the tree or connect directly with thecanopy using picking heads to remove the fruit (Pezzi and Capraraet al., 2009, Ferguson et al., 2010). An increase of kinetic energytakes place during fruit removal as a consequence of the potentialenergy that exists due to the position of the fruit on the tree. TheGordal Sevillana variety has a size and weight twice as high as theother varieties studied (Rejano, 1999). These factors increase therisk of bruising of this variety during mechanical harvesting.

3.5. Bruise time evolution

The BRI used in this study detects changes in the visible spec-trum by measuring the color change of the bruised area. Mechanicaldamage produces bruises which “brown”. Fruit browning is theresult of the oxidation of polyphenols by the enzyme polyphenoloxidase resulting in pigmentation, or browning, of the affected area(Segovia-Bravo et al., 2009). This browning leads to an increasein light absorption at 545 nm where chlorophyll has weak lightabsorption (Ben-Shalom et al., 1978). By contrast, regions wherechlorophyll absorption is high are less sensitive to browning.Chlorophyll is the most prevalent pigment in immature tableolives. Thus reflectance measurement at 670 nm is an effective

way to account for the amount of chlorophyll present in the olive(Barreiro et al., 2004). The subtraction of the reflectance valuesof 670 nm and 545 nm produces a bruise reflectance index that issensitive to the browning process and that minimizes the variation

Fig. 5. Example of the mean values of multiplied scatter correction (MSC)reflectance depending on the time after impact for Manzanilla cultivar impactedwith high level of energy (58 ± 7 mJ).

F. Jiménez-Jiménez et al. / Postharvest Biolog

Fig. 6. Mean values and standard deviation (N = 30/treatment) of BRI(1 − ((R545 − R670) * R800)) of the table olives cultivars (Gordal Sevillana, Man-za

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Ferguson, L., Rosa, U.A., Castro-Garcia, S., Lee, S.M., Guinard, J.X., Burns, J., Krueger,

anilla and Hojiblanca), impact energy level (high = 56 ± 8 mJ, medium = 26 ± 3 mJnd low = 13 ± 1 mJ) and the time after impact.

n the chlorophyll content (Solovchenko et al., 2010). In addition,he region near 800 nm was where the major differences betweenruised and non-bruised table olives were observed (Fig. 5). Bydding the reflectance at 800 nm in Eq. (5), sensitivity to the BRIor green table olives was improved. Other authors have usedear-infrared spectroscopy to determine the bruising in apples,uch as the ‘Golden Delicious’, suggesting that the region between45 and 905 nm is the most useful region for detecting bruise timevolution (Xing et al., 2006).

BRI measurement of the table olives at different times aftermpact demonstrated bruise time evolution. Fig. 6 shows the BRI

alues obtained from the fruit for each variety evaluated at differentmpact energy levels. The bruise time evolution showed an expo-ential rise with an asymptotic trend in all cases (r2 = 0.65–0.96)

y and Technology 86 (2013) 100–106 105

except for the Gordal variety at low energy level impacts where norise was observed. Similarly, other authors (Ingle and Hyde, 1968)report that the reaction follows a logarithmic trend with a highspeed rise during the first hours and ending at a maximum value.

The browning process in Manzanilla and Hojiblanca varietieswas faster than in Gordal Sevillana variety. Approximately 80% and75% of the increase in BRI for Manzanilla and Hojiblanca varietiesrespectively were achieved within an hour after impact. In thesetwo varieties the maximum in BRI was reached 3 h after impact. TheGordal Sevillana variety demonstrated slower BRI growth with val-ues of BRI ranging from 0% for the low impact energy level and 80%for the medium impact energy level 3 h after impact. The increasewas different for each variety and impact energy level. Manzanillaolives had the greatest increase of BRI followed by Hojiblanca andGordal Sevillana. For example, the increase of BRI in Manzanillafruit was roughly twice that obtained in the other two varieties.

4. Conclusion

These results demonstrate that the development of mechani-cal damage from impact (bruising) in the three table olive cultivarsstudied was directly related to the impact energy level and the timeafter impact. The important table olive cultivars respond very dif-ferently to impact bruising depending on fruit characteristics. TheHojiblanca cultivar was the most resistant to bruising. For the samelevel of energy, bruising volume in Hojiblanca was 50–60% less thanthat produced in the Manzanilla or Gordal Sevillana cultivars. Bruisesusceptibility of Manzanilla cultivar was slightly lower than that ofthe Gordal Sevillana cultivar at the same energy level. However,the larger size and mass of the Gordal Sevillana cultivar makes itmore susceptible to bruising from impact. Bruise time evolutionfollowed an exponential increase with a maximum achieved 3 hafter the impact and approximately 75% of the fruit discolorationof the damaged fruit was generated within an hour after impact.

Acknowledgements

The authors acknowledge the financial support from the ‘Orga-nización Interprofesional de Aceituna de Mesa’ (INTERACEITUNA).The authors also acknowledge the financial support of the RegionalGovernment of Andalusia (2008–00048; project PI45120) for theresearch methodology and instrumentation used.

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