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Postharvest Biology and Technology 25 (2002) 109115

Preprocessing storage conditions for green Conservolea andChondrolia table olives

G.D. Nanos a,*, A.K. Kiritsakis b, E.M. Sfakiotakis c

a Department of Agriculture, Laboratory of Pomology, Uni6ersity of Thessaly, Fitoko Str., 38446, Volos, Greeceb Department of Food Technology, Technological Educational Institute of Thessaloniki, 54101, Sindos, Greece

c Laboratory of Pomology, Department of Agriculture, Aristot. Uni6ersity of Thessaloniki, 54006, Thessaloniki, Greece

Received 13 November 2000; accepted 20 August 2001

Abstract

Green olives (Olea europaea L. cvs. Conservolea and Chondrolia ), destined for Spanish-style processing, were

harvested at the beginning and the end of commercial harvest period and stored at 5 and 7.5 C in air or various

controlled atmospheres. Olive quality was measured periodically and included mass loss, skin color, flesh firmness and

chilling injury symptoms, mainly internal browning. Larger samples of Conservolea olives were commercially

processed with the Spanish method after storage for objective quality determination and taste panel evaluation. Mass

loss of fresh olives during storage was generally low and no fruit decay was encountered. Fresh Chondrolia green

olives were very sensitive to chilling injury. They lost their capacity to develop skin color and ripen after 24 weeks

of cold storage with excessive internal browning, resulting in pitting and external discoloration. Fresh Conservoleagreen olives developed skin color, especially at 7.5 C, and after storage in air, 2 or 5 kPa CO2. Fruit stored at 2 kPa

O2 in the presence or not of high CO2 retained their green color for more than 2 months. Conservolea olives slightly

softened during storage but with longer storage, in parallel with chilling injury development, a rehardening of the fruit

flesh was measured, possibly an additional chilling injury symptom. Storage at 5 C and combinations of 2 kPa O2and 2 or 5 kPa CO2 increased susceptibility to chilling injury, although fruit successfully retained skin green color.

Objective and subjective quality evaluation of processed Conservolea olives gave similar differences between

treatments. Abnormal flavor seemed to be an additional result of chilling injury. In conclusion, Conservolea green

olives can be stored up to 37 days at 5 C in air or for up to 22 days at 7.5 C and 2 kPa O2 plus 5 kPa CO2. 2002

Elsevier Science B.V. All rights reserved.

Keywords: Olea europaea ; Olive; Quality; Cold storage; Controlled atmosphere; Low O2; High CO2; Chilling

www.elsevier.com/locate/postharvbio

1. Introduction

A number of olive cultivars are being cultivated

in Greece for processing as table olives. Fruit are

harvested mature-green or black depending on the

cultivar and processing method. The most com-

* Corresponding author. Tel.: +30-421-93181; fax: +30-

421-93161.

E-mail address: [email protected] (G.D. Nanos).

0925-5214/02/$ - see front matter 2002 Elsevier Science B.V. All rights reserved.

PII: S 0 9 2 5 - 5 2 1 4 ( 0 1 ) 0 0 1 6 4 - 8
mailto:[email protected]


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G.D. Nanos et al. /Posthar6est Biology and Technology 25 (2002) 109115110

mon processing methods for green olives are the

Spanish and Castel-Vetrano ones. Most of the

Greek olives processed with the above methods

belong to the Conservolea (Amfissis) and

Chondrolia cultivars. The quality of the pro-

cessed product depends on the skin color and

flesh firmness of the raw product at the time of

processing. Thus the harvesting period of greenolives is short followed by storage in brine before

final processing. The disposal of brine requires

wastewater treatment, while the effect of brine

on final product quality has not been measured.

In addition, only fresh olives can be processed

with the Castel-Vetrano method. Therefore, the

green olive processing industry is interested in

the use of an alternative to the above preprocess-

ing storage method for fresh green olives.

There is a limited number of reports on olive

storage without brine, most of which concernolives destined for Californian-style processing or

for oil extraction (ripe green or colored fruit). It

was found that there is a great deal of variation

on storability between cultivars even when grown

in the same area. Mature-green olives are chilling

sensitive when kept long enough at temperatures

below 5 C, while fruit of some cultivars can be

damaged at temperatures as high as 10 C

(Maxie, 1963, 1964). The main chilling injury

symptoms of olives include internal browning of

the flesh around the pit, pitting appearing as dull

skin color and, progressively, external browning

(Kader et al., 1989; Kader, 1996).

Controlled atmospheres have been successfully

used in addition to low temperature to extend

the storage life of various fruits and vegetables

(Kader, 1986). Reduced O2, increased CO2 levels

or their combinations in the storage room atmo-

sphere can inhibit chlorophyll degradation, color

development and loss of flesh firmness in various

commodities. Atmospheric manipulation is useful

to delay the above physiological changes espe-

cially for chilling sensitive crops, as these cannot

be stored for a long time at low temperatures. In

addition, controlled atmosphere storage has been

found to delay the appearance or, often, aggra-

vate physiological disorders, like chilling injury,

depending on the commodity (Kader, 1986).

Mission and Manzanillo mature green olives

grown in California and Gordal and Picual

olives grown in Spain have benefited from con-

trolled atmosphere storage at 5 C (Woskow and

Maxie, 1965; Kader et al., 1989; Garcia and

Streif, 1991; Castellano et al., 1993). Since those

olives were destined for Californian-style process-

ing or oil extraction, they were harvested mature

and skin color was not of importance.The objective of this study was to evaluate the

effects of controlled atmospheres during low

temperature storage on olive fruit chilling sensi-

tivity and quality, mainly skin color and flesh

firmness, for the two most important table olive

Greek cultivars. This would allow an extension

of the processing period with the Spanish

method for fresh green olives.

2. Material and methods

Conservolea and Chondrolia green olives

(Olea europaea L.) were harvested from commer-

cial farms in Volos, Central Greece and Thessa-

loniki, Northern Greece, respectively, at the

beginning and end of the commercial harvest

period in 1994 (22 September and 7 October)

and 1995 (3 October and 17 October). In all

harvests two trees per replicate were used and

the fruit were sorted next day for defects and

color.

In 1994, each 10-fruit replicate was kept in

netted bags and all replicates were placed ran-

domly in 400 L sealed metal chambers connected

to a CO2 and O2 analyzer and a computer auto-

matically controlling the atmospheric composi-

tion of each chamber (90.2%). Around 95%

(92%) relative humidity in the chambers was

achieved with good air circulation using fans and

free water in trays. In the 5 C or 7.5 C room,

individual chambers were set at atmospheric con-

ditions shown for each year in Table 1 (balance

N2). In 1995, we decided to use only the above

storage conditions for the following reasons: (a)

CO2 could build up due to olive respiration and

it would be expensive to remove it from commer-

cial storage rooms; and (b) combinations of low

O2 and high CO2 kept green skin color for a

long period in 1994.


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G.D. Nanos et al. /Posthar6est Biology and Technology 25 (2002) 109115 111

Table 1

Atmospheric conditions (kPa) in individual chambers used in

green olive fruit storage (balance N2)

19951994

At 7.5 CAt 5 C At 5 C At 7.5 C

O2O2 CO2CO2 O2 CO2 O2 CO2

2121 00 21 0 21 0

2 0 20 02 2 5

219 19 2 2 5

517 17 5

2 222

2 5 2 5

Three 10-fruit replicates were used for each

cultivar, harvest, combination of temperature and

atmospheric conditions and storage period. Anal-

ysis of variance was performed in relation to

cultivar, duration of storage and treatment and

LSDs at the 5% level were calculated (SPSS 8.0,

Chicago, IL).

In 1995, additional two 3-kg samples ofConservolea olives per treatment and storage

period were also stored for quality evaluation

after processing. After each storage period, sam-

ples of adequate quality (green skin color and

minor or no chilling injury symptoms) were com-

mercially processed with the Spanish method.

Processed olives were evaluated for skin color and

flesh firmness as the fresh ones. In addition, a

taste panel of 13 trained members (olive process-

ing industry personnel and the authors) evaluated

all fruit samples for color, crispness and flavor ona scale ranging from worst (1) to best (4) in

comparison to each other and commercial high

quality fruit samples. Means and standard devia-

tions were calculated.

3. Results and discussion

Green Chondrolia olives lost slightly more

mass during storage than Conservolea olives

(Table 3). This may be due to high chilling injury

or anatomical features of the epidermis of Chon-

drolia olives, as it was previously reported that

chilling accelerates water loss for many commodi-

ties (Kays, 1997). Olive mass loss increased with

storage temperature and duration for both culti-

vars tested (Table 3). Olives stored in air lost

more mass than those kept in controlled atmo-

sphere (pooled data for both cultivars, 1st harvest

and longest storage duration. 3.8% at 5 C and

5% at 7.5 C in air vs 1.7% at 5 C and 2.2% at

7.5 C in controlled atmosphere). Similar results

were previously found for other commodities

(Kader, 1986). It must be mentioned that

throughout the storage experiments no rotten

fruit were found, as we used relatively immature

fruit compared to olive fruit used previously

which showed significant fungal growth after cold

storage for 50 days (Castellano et al., 1993).

Quality was evaluated on three 10-fruit repli-

cates before storage and after the duration in

storage shown in Table 2 for both years. Quality

evaluation included mass loss, skin color measure-ments with a Minolta colorimeter (model CR-200,

Minolta Camera Co., Japan) and flesh firmness

with a Chatillon penetrometer equipped with a 3

mm diameter plunger (J. Chatillon and Sons,

NY). Flesh firmness measurements were taken

after careful removal of skin and penetration of

the flesh for about 2 mm (flesh width ranged from

45 mm). Calculations of Chroma (C*, departure

from gray towards pure color) and hue angle (h,

true color) were performed according to McGuire

(1992). Chilling injury incidence was always evalu-ated by a trained judge. Pitting and internal

browning were evaluated separately on individual

fruit and calculated as follows: 0, no fruit with

symptoms; 1, from 1 to 30% of fruit injured; 2,

from 30 to 50% of fruit injured; 3, more than 50%

of fruit injured. Samples from categories 0 and 1

were considered marketable.

Table 2

Days in storage after which quality evaluation was performed

for each year and harvest of Conservolea and Chondrolia

green olives

1994 1995

1st harvest 2nd harvest 1st harvest 2nd harvest

14 222833

3554 43 50

5877 63


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Table 3

Mass losses of Conservolea and Chondrolia green olives

harvested on 22 September (1st harvest) and 7 October 1994

(2nd harvest) and stored for the duration shown at 5 or 7.5 C

HarvestCultivar Duration Mass loss (%)

(days)

Storage at 5 C1stConservolea 33 1.4

54 1.7

77 2.3

2nd 14 0.5

35 0.9

58 1.4

1stChondrolia 33 1.5

54 1.8

77 2.6

14 1.12nd

35 1.2

58 1.9

Storage at 7.5 C

Conservolea 331st 2.0

54 2.5

77 3.2

2nd 14 1.0

35 1.4

58 2.3

Chondrolia 1st 33 2.2

54 2.5

77 3.3

2nd 14 1.0

35 1.5

58 2.4

Significance

Temperature ***

Cultivar *

Harvest ***

Duration in ***

storage

Combinations of temperature and atmospheric conditions

were taken as replicates because there were no differences

between them (n=18)

* Significant at P50.05.

*** Significant at P50.001.

developed red color faster than low O2 stored

fruit (Fig. 1). Skin color remained green in

Conservolea olives stored in combinations of

low O2 and high CO2. Similar results were found

with the changes in a* and h color indices (data

not shown). Red color development is detrimental

for these fruit as only green fruit can be processed

with the Spanish method.

Skin C* values of Chondrolia green olives

also decreased during storage (Fig. 2). However,

this decrease was mostly the result of advanced

chilling injury, and not due to normal red color

development. Chilling injury initially appeared as

flesh browning, and then developed in pitting and

brownblack areas of the skin following extensive

flesh damage. At 5 C, skin injury developed

mainly after prolonged storage in high CO2 alone

or in combination with low O2 (Fig. 2A). Con-trolled atmosphere treatments clearly intensified

chilling injury symptoms (depicted as skin color

Fig. 1. Changes in skin C* values of Conservolea olives

harvested on 22 September 1994 and stored at 5 (A) and

7.5 C (B) in air, 2 kPa O2, 2 kPa CO2, 5 kPa CO2 and their

combinations for 0, 33, 54 and 77 days. Each data point

represents the mean of three 10-fruit replicates. Overall

LSD0.05=6.2.

Red skin color appeared faster at 7.5 C than

at 5 C in Conservolea olives, as shown by the

decreasing C* values measured (Fig. 1). Red color

development progressed with storage especially

after 45 days at 5 C or before 30 days at 7.5 C.

Conservolea olives stored in air or high CO2


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Fig. 2. Changes in skin C* values of Chondrolia olives

harvested on 22 September 1994 and stored at 5 (A) and

7.5 C (B) in air, 2 kPa O2, 2 kPa CO2, 5 kPa CO2 and their

combinations for 0, 33, 54 and 77 days. Each data point

represents the mean of three 10-fruit replicates. Overall

LSD0.05=4.5.

this flesh firmness increase could be due to in-

creased mass losses. In our study, mass losses

were very low in general and treatments with the

higher mass losses were the least affected by chill-

ing injury (Tables 3 and 4). In addition, we used a

penetrometer instead of other methods used previ-

ously. Olives kept at 7.5 C were softer than the

ones kept at 5 C (Fig. 3). Controlled atmosphere

treatments generally resulted in the highest rise in

flesh firmness after prolonged storage (Fig. 3).

Chondrolia olives developed more internal

browning (main chilling injury symptom) during

storage than Conservolea olives (Table 4).

Chondrolia olives also developed pitting and

skin injury, making this cultivar unsuitable for

storage due to its high chilling sensitivity. For

both cultivars, storage of fruit at 5 C resulted in

higher internal browning incidence than storage at

7.5 C, while internal browning incidence in-

creased with time in storage (Table 4). Chon-

drolia olives developed unacceptable internal

Fig. 3. Changes in flesh firmness (N) of Conservolea (A) and

Chondrolia (B) olives harvested on 17 October 1995 and

stored at 5 and 7.5 C in air, 2 kPa O2 or 2 kPa O2 plus 5 kPa

CO2 for 0, 22 and 50 days. Each data point represents the

mean of three 10-fruit replicates. LSD at 5% level for each

cultivar is shown.

changes) of Chondrolia olives. At 7.5 C, redskin color developed in the presence of air or high

CO2 rendering these fruit unsuitable for process-

ing (Fig. 2B). Low O2 treatments delayed red

color appearance at 7.5 C.

Late harvested green olives were softer than

early harvested ones (data not shown). This dif-

ference may be unimportant as processing may

reharden the fruit. In general, flesh firmness de-

creased with storage, but late in storage, when

chilling injury developed, the fruit of most treat-

ments became significantly harder (Fig. 3). Thistrend was found in both years, cultivars and

harvests and it could be an additional characteris-

tic chilling injury symptom of olives not recorded

before. Significant increase in flesh firmness of

Gordal mill olives after prolonged cold storage

was also observed but not discussed (Garcia and

Streif, 1991). They did not report mass losses, so


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Table 4

Development of internal browning in Conservolea and Chondrolia olives harvested 22 September 1994 and stored at 5 C and

7.5 C in air, 2 kPa O2, 2 kPa CO2, 5 kPa CO2 and their combinations for 54 and 77 days

2 kPaO2 2 kPaCO2 5 kPaCO2Air 2+2 2+5

Storage at 5 C

Conservolea

54 days 0 1 1 1 1 02 1 2 277 days 21

Chondrolia

254 days 2 3 3 3 3

3 3 3 377 days 33

Storage at 7.5 C

Conservolea

0 1 01 154 days 0

77 days 01 1 1 2 3

Chondrolia

254 days 2 2 1 2 3

2 1 2 377 days 32

Chilling injury was evaluated as: 0, no fruit with symptoms; 1, from 1 to 30% of fruit injured; 2, from 30 to 50% of fruit injured;3, more than 50% of fruit injured. Each data point represents the mean of 30 fruit.

browning in less than 30 days at 5 C and less

than 54 days at 7.5 C. Internal browning inci-

dence was without commercial significance for

Conservolea olives up to 54 days at 5 C and

after more than 54 days at 7.5 C (Table 4).

During 1995, Conservolea olives processed

with the Spanish method had lower skin L* (5%),

a* (59%), C* (17%) and h (12%) values and

higher flesh firmness (38%) than fresh olives (data

not shown). Thus, it can be concluded that pro-

cessing substantially changes the major subjective

quality indices of green olives. Processed olive

flesh firmness did not show substantial differences

between treatments (data not shown). It seems

that flesh firmness of the final processed product

is the result of preprocessing storage conditions,

chilling injury and processing itself, and merits

further studying.

Taste panel evaluation similarly showed that

prolonged storage, in general, resulted in poor

color processed product (Table 5). Flesh texture

(crispness) was acceptable for fruit from all treat-

ments. Finally, extended storage that resulted in

chilling injury (especially storage at 5 C and

controlled atmospheres) or ripening negatively

affected processed fruit flavor. This loss of flavor

may be another symptom of olive chilling

injury common to chilling sensitive commodities.

The 5 C storage temperature used in our ex-

periments is the one previously found as the best

for olive storage (Kader et al., 1989). Tempera-

tures above 5 C can also be used, but ripening,

mainly green color loss, must be delayed with

controlled atmospheres. Low O2 with or without

high CO2 delayed ripening changes for our culti-vars but aggravated chilling injury symptoms. In

fact, controlled atmospheres have been shown to

delay or aggravate chilling injury for various com-

modities (Wang, 1982; Kader, 1986). Low O2storage seems to act synergistically with low tem-

perature to aggravate chilling injury in mature-

green olives in USA, Spain and Greece (Kader et

al., 1989; Castellano et al., 1993; Olias and Gar-

cia, 1997). High CO2 storage in our experiments

did not delay ripening and may actually have

accelerated green color loss of olive skin.Chilling injury of green olives appeared as the

typical previously observed symptoms (Kader,

1996). Thus, Chondrolia olives are unsuitable for

preprocessing storage for more than 1520 days,

although treatments to delay chilling injury could

be further investigated. The flesh firmness in-

crease, which was observed with chilling in our


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Table 5

Taste panel evaluation for color, crispness (texture) and flavor of processed Conservolea olives after preprocessing storage of fresh

fruit for the duration and conditions shown

Temperature/atmosphere (C/kPaO2+kPaCO2) Color CrispnessHarvest date FlavorDays

5/2+5 2October 3 443 1

October 3 43 7.5/2+5 4 4 3

5/21+0 3October 17 322 45/2+5 322 3October 17 2

22October 17 7.5/21+0 3 2 2

7.5/2+5 4October 17 322 4

5/21+0 337 4October 17 3

37October 17 5/2+5 4 2 2

37October 17 7.5/2+5 1 3 2

Each data point represents the mean of 13 individual judge evaluations. Evaluation was conducted on a scale of four from worst

(1) to best (4) in comparison to each other and commercial high quality fruit samples.

experiments and measured with a penetrometer,

could be another novel symptom. The loss of

flavor found in chilled olives is also a typicalsecondary effect of chilling injury. The two cul-

tivars used in our study with different chilling

sensitivity could be a useful system for future

work on the understanding of chilling injury

mechanisms.

Conservolea green olives used in our experi-

ments, when harvested early or late, had similar

quality and chilling sensitivity. Late harvested

olives are practically more suitable for storage,

as processing equipment and personnel can be

used for an additional period when freshly har-

vested green olives are not available.

Limiting factors in Conservolea green olive

storage were chilling injury appearance (internal

browning of fresh fruit and loss of taste of pro-

cessed product) and loss of green skin color.

Softening of fresh olives does not seem of im-

portance as processing results in partial fruit

flesh hardening. Finally, the best storage condi-

tions for Conservolea green olives are for up

to 37 days at 5 C in air or for up to 22 days

at 7.5 C i n 2 k P a O2 plus 5 kPa CO2. Of

course, storage in air is cheaper and should be

used commercially in combination with good

ventilation, so CO2 does not accumulate in stor-

age rooms.

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