optimization of the abencor system to extract olive oil from irrigated orchards

Research Article

Optimization of the Abencor system to extract olive oil fromirrigated orchards

Eric Ben-David1,2, Zohar Kerem2, Isaac Zipori1, Sebastian Weissbein1, Loai Basheer2,

Amnon Bustan1 and Arnon Dag1

1 Gilat Research Center, Agricultural Research Organization, M. P. Negev, Israel2 Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture,

Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel

Studying the composition of olive oil requires cold-press olive oil extraction. One of the most

common laboratorial mills is the Abencor system. However, its operation protocol was formulated

decades ago for Spanish olive varieties from traditionally rain-fed orchards. We modified this protocol

for use with ‘‘Barnea’’ and ‘‘Picual’’ olives from irrigated orchards that are characterized by high

water content. Independent effects of malaxation time, temperature, water addition and talc

addition on extraction efficiency, and major quality indices of virgin olive oil were studied.

Overall, addition of talc to the fruit paste was the most significant treatment in terms of yield and

quality of the oil although its effect was cultivar dependent. Improved oil yield was particularly significant

for ‘‘Picual.’’ Extended malaxation time was also effective in improving oil extractability. Addition of

talc generally improved oil-quality parameters, while water addition had the opposite effect. Yet,

quality parameters remained within the extra virgin level. Temperature increments reduced oil

quality. The need to adapt a modified protocol for use with fruits from irrigated orchards that will

facilitate critical comparison of results obtained from different agronomic theses and different

laboratories is highlighted. It is recommended that each laboratory develops an appropriate protocol

for the operation of the Abencor system in accordance to the characteristics of the olive fruit they are

working with.

Practical applications: Abencor system serves as the major laboratorial mill world-wide. Those

mills allow the researchers to characterize olive oil in accordance to the treatments received by

the trees. This cannot be done in commercial mills. The system operation protocol was established

decades ago for fruits from rain-fed orchards. In the past decade there was a rapid increase in the use of

irrigation in olive orchards and therefore it is crucial to optimize the operation protocol for fruit with

relatively high water content. In the current work we have evaluated the influence of a series of

technological parameters (i.e., talc and water addition, malaxation time, and temperature) on the

extraction efficiency and quality indices of olive oil. This allowed us to present a modified

protocol for the Abencor system operation suitable for olive fruit of irrigated orchards that will facilitate

a reliable representation of the influence of different treatments on the yield and characteristics of the

olive oil.

Keywords: Abencor / Irrigation / Malaxation / Protocol / Virgin olive oil

Received: February 17, 2010 / Revised: June 1, 2010 / Accepted: June 25, 2010

DOI: 10.1002/ejlt.201000056

1 Introduction

Olive (Olea europaea L.) oil is a basic constituent of the

Mediterranean diet [1]. Its consumption has significantly

increased in recent years as a result of its nutritional value

Correspondence: Dr. Arnon Dag, Gilat Research Center, Agricultural

Research Organization, M. P. Negev, 85280 Israel

E-mail: [email protected]

Fax: 972-8-9926485

Abbreviation: FA, free acidity

1158 Eur. J. Lipid Sci. Technol. 2010, 112, 1158–1165

� 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheimwww.ejlst.com

and recognized benefits for human health [2–4]. To meet the

increased demand, irrigation has been introduced to

traditionally rain-fed olive oil orchards and the plantation

of irrigated high-density orchards has intensified [5–6].

These trends have led to a substantial increase in the pro-

duction of olive oil [7–9].

Several studies have demonstrated the effects of irrigation

on oil quality [6–15]. Other factors, genetic, and agronomic,

such as fertilization, cultivar, cultivation technique, date and

method of harvest, transportation and storage of fruits, and

method of oil extraction, have all been reported to influence

the composition and organoleptic characteristics of virgin

olive oil [16–18].

Virgin olive oil production, unlike that of other vegetable

oils, is a mechanical process that consists of crushing, malax-

ation, and oil separation [18, 19]. Retaining the olive flavor

and aroma attributes throughout this process is of prime

importance with respect to the oil’s organoleptic, nutritional,

and oxidative-resistance properties [20]. Unfortunately, the

study of the relations between cultivation practices, yield,

and quality of oil in industrial olive mills is limited by the

continuous mode of operation, the requirement of large

amounts of fruit due to the size of the machinery, and the

lack of homogeneity among those fruits [18]. Consequently,

the development of laboratory-scale mills such as the

Abencor system have facilitated research into the effects of

various agronomic practices on quality indices of olive oil [14,

19–25] and yield [26–28] of olive oil. The Abencor system is

advantageous due to its batchmode of operation, the reduced

amount of fruit needed for statistically reliable results and its

convenient control of the operation parameters [21].

However, the recommended operation conditions of the

Abencor system were formulated several decades ago for

use with Spanish varieties of olives, cultivated in traditionally

rain-fed orchards [21]. The flesh of these fruit contains

considerably less water (�40%) than that of varieties grown

under intensively irrigated conditions in modern orchards

(�60% water). In addition to other parameters, the

water content of the raw material hence the olive paste

is a dominant factor determining the efficiency of the

extraction process and other oil quality parameters. There

is therefore a clear need to define major principles

for a flexible though standard Abencor protocol thus

providing necessary tools for the evaluation of oil yield

and quality from diverse origins (irrigated vs. rain-fed

groves, cultivars, etc.) on the laboratory scale. Noteworthy,

any attempts to relate lab- to industrial-scale of olive oil

yield and quality should be done with caution due to differ-

ences between the systems in the oxygen control, heat

exchange as well as in other parameters [29, 30]. Here

we demonstrate how the adjustment of the Abencor

laboratory scale system to the use with olive fruit of two

cultivars (‘‘Barnea’’ and ‘‘Picual’’) produced in commercial

irrigated orchards facilitates the oil production efficiency

while retaining optimal oil quality.

2 Materials and methods

2.1 Oil extraction

Olive fruits were obtained from a commercially irrigated

orchard in the southern part of Israel in the Negev Desert.

The average annual rainfall in that area is around 100 mm.

Plants were distanced 3 m � 7 m. Due to the high evapo-

transpiration and low rainfall, total amount of water supplied

to the trees is ca. 1000 mm/year.

Fruits from two cultivars, ‘‘Barnea’’ and ‘‘Picual,’’ were

mechanically harvested using trunk-shakers, on January 23,

2007 and January 28, 2008, respectively. The degree of ripe-

ness, estimated by fruit color according to Uceda and Frıas

[31], was within the acceptable range for harvest in Israel [3.79

in ‘‘Barnea’’ (2007) and 3.61 in ‘‘Picual’’ (2008)]. Average

water content in the crude pastes was 59 and 68% in ‘‘Barnea’’

and ‘‘Picual,’’ respectively. Percentage of stone in the pulp was

15.4 and 12.4% ‘‘Barnea’’ and ‘‘Picual,’’ respectively.

For each treatment, four 1.0-kg replicates were randomly

sampled from the harvested fruits. Oil was extracted using an

Abencor system small-quantity mill, simulating commercial

oil-extraction systems (MC2 Ingenierıa Sistemas, Seville,

Spain). The olives were crushed with an Abencor hammer

mill equipped with a 4-mm sieve and 700 g paste were proc-

essed using the Abencor system’s malaxer and centrifuge.

The recommended conditions specified by Abencor’s

operation protocol were used as the baseline [21]. Three treat-

ments: malaxation temperature (25, 30, 35, and 40 8C),

malaxation time (30, 60, 90, and 120 min), and amount of

water added to the paste (0, 100, 150, 225, and 300 cm3) were

evaluated with and without talc addition. In ‘‘Barnea’’, the

effect of malaxation temperature was tested only with talc

addition. Fixed conditions were applied according to the

Mc2 Ingenieria Sistemas’s suggested protocol: temperature

of the paste was fixed at 35 8C when studying malaxation

time and water addition; malaxation time was fixed at

30 min when studying temperature and water addition, and

water addition was fixed at 300 cm3 water per 700 g paste in

the malaxation time and temperature treatments. The talc

treatment consisted of adding 40 g of talc (Talcoliva,

Bonar Leon, Spain) to the paste. Water was added 20 min

after the start of malaxation in accordance with Martinez et al.

[21]. Extracted oil percentage was determined according to

the formula [21]:

Oil percentage ð%Þ ¼ cm3 of obtained oil � 0:915

weight of the paste

� �� 100

2.2 Oil analysis

Determination of free acidity (FA) and peroxide values was

carried out following the analytical methods described in ISO

(International Organization for Standardization) 660 and

Eur. J. Lipid Sci. Technol. 2010, 112, 1158–1165 Optimization of the Abencor system to extract olive 1159

� 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com

3960, respectively. FA, given as percentage of oleic acid, was

determined by titration of a solution of oil in ethanol–diethyl

ether (1:1 v/v) with an ethanolic solution of 0.01 N KOH.

Phenolphthalein solution in ethanol (1% w/v) was used as an

indicator. Peroxide value, expressed as milliequivalents of

active oxygen per kilogram oil (meq O2 kg), was determined

by sodium thiosulfate titration (0.01 N) of free iodine from a

mixture of oil and iso-octane:acetic acid (2:3 v/v) left to react

with potassium iodide solution in the dark for 1 min. Starch

solution (1% w/v) was used as an indicator.

Phenolic compounds were isolated from a solution of oil

in hexane by double-extraction with methanol–water (60:40

v/v). Total phenols, expressed as tyrosol equivalents (mg/kg),

were determined with a UV–Visible spectrophotometer

(Beckman Coulter, Inc. Fullerton, CA) at 735 nm using

Folin–Ciocalteu reagent according to Gutfinger [32].

2.3 Statistical analysis

Data were analyzed using JMP 5.0 software (SAS institute,

Inc., Cary, NC). Effect of the various treatments on oil yield

and quality were examined by ANOVA, and whenever the F

statistics was significant, differences between treatments were

determined using Tukey–Kramer honestly significant differ-

ence test (at p � 0.05). Due to the low extraction efficiency of

‘‘Picual’’ samples without talc addition, replicates were

merged and the statistical significance of their quality indices

was not evaluated.

3 Results and discussion

3.1 Duration of malaxation

The duration of malaxation has a major influence on the

yield of extracted oil as well as on the oil’s quality properties

[25, 33–36]. Malaxation time has been shown to relate posi-

tively to the total content of volatiles in virgin olive oil, and

negatively to total phenol concentration [18, 36]. In the

current study, the effect of malaxation time, with and without

addition of talc, on the yield and properties of olive oil was

evaluated in ‘‘Barnea’’ and ‘‘Picual’’ oils (Tables 1 and 2).

Results of factorial ANOVA indicated that the independent

effect of malaxation time on the percentage of oil extracted

was highly significant in ‘‘Barnea’’ and ‘‘Picual’’ samples,

while the added talc only had a substantial effect on

‘‘Picual’’ (Table 1). Increased malaxation time, without talc

addition, resulted in a significant increase in the percentage of

extracted oil, concomitant with a substantial effect on its

quality parameters (Table 2). Increased levels of extracted

oil concurrent with increased malaxation time have also been

noted by Di Giovacchino et al. [34]. Increasing the malax-

ation time of ‘‘Barnea’’ samples from 30 to 90 min, without

added talc, almost doubled the oil yield: 92 g/kg of pasteas

compared to 174 g/kg of paste. However, in ‘‘Barnea’’

samples with added talc, the samemalaxation time increment

corresponded with only a modest increase in the yield of

extracted oil (from 128 to 159 g/kg of paste). On the contrary,

the addition of talc had a remarkable positive effect on the

yield of oil extracted from ‘‘Picual’’ fruits, 135 to 179 g/kg of

paste compared with 19 to 84 g/kg of paste, where no talc was

included. The combination of talc addition with the longest

malaxation time, 120 min, led to the highest yield (179 g/kg

of paste). The independent effects of malaxation time and

talc addition on the yield of oil from ‘‘Picual’’ were highly

significant (p<0.0001; Table 1).

The operation of the original Abencor protocol with high

water content fruit (68% in fruit flesh) from irrigated

‘‘Picual’’ orchards yielded extremely low oil levels that are

also sub-representative in terms of their quality indices, and

are potentially far from economical in a commercial mill. Our

Table 1. Combined effect of Abencor operating conditions (temperature, malaxation time, and amount of water added), with and without talc

addition, on olive-oil extraction efficiency and quality parameters

Oil percentage (%) ‘‘Barnea’’

‘‘Picual’’ ‘‘Barnea’’ Acidity (%)

Peroxide value

(meq O2 kg/oil)

Polyphenol

concentration (mg/kg)

Talc �� NS ��

Malaxation time ��

Talc � malaxation time NS ��

Talc ��

Amount of water ��

Talc � amount of water �� NS

Temp ��

Talc ��

Talc � Temp ��

One way ANOVA and post-hoc Tukey–Kramer multiple comparison test were conducted individually for different parameters. NS ¼ not

significant;� p � 0.05; �� p � 0.01; �� p � 0.001.

1160 E. Ben-David et al. Eur. J. Lipid Sci. Technol. 2010, 112, 1158–1165


results suggest that addition of talc and increasing the

duration of malaxation are indispensible for that type of fruit.

In commercial mills, the addition of talc to the centrifugal

decanter has been shown to improve its efficiency and to

increase the oil yield [34, 37, 38]. Conversely, in fruits with

lower water content such as ‘‘Barnea’’ (59%), practical

extraction efficiency may be achieved without the addition

of talc. Still, the extension of the malaxation time significantly

improved the efficiency of oil extraction as compared with the

original Abencor protocol.

Water content in the fruit flesh is a significant parameter

of difference between the two cultivars hence the

adjustments required for the Abencor protocol. Talc, func-

tioning as a water absorber, modifies the ‘‘difficult paste’’ of

high water content fruit thus smoothing the extraction

process.

Factorial ANOVA revealed that the independent effects

of malaxation time, talc addition, and their interaction on the

oil composition of the ‘‘Barnea’’ samples were statistically

significant (Table 1). In ‘‘Picual’’ samples, the combined

effect of a long malaxation time (120 min) and talc addition

produced the highest FA values (Table 2). Surprisingly,

reduced FA levels in ‘‘Barnea’’ samples were associated with

a malaxation time increment from 30 to 90 min in samples

without talc (Table 2). Addition of talc led to lower peroxide

values in ‘‘Barnea’’ and ‘‘Picual’’ oils relative to the no-talc

treatments, particularly at long malaxation time (Table 2).

These results may again demonstrate the uniqueness of

results achieved using olive fruits from irrigated orchards,

when compared to other studies that did not find any sig-

nificant association between malaxation times ranging from

15 to 90 min or talc addition and oil quality parameters [34,

38]. The effect of talc addition on oil properties was highly

significant, while malaxation time induced only mild changes

in the oil’s composition (Table 1). Malaxation time corre-

lated negatively to polyphenol content in ‘‘Picual’’ oils, but

surprisingly, showed an opposite trend in ‘‘Barnea’’ oils,

irrespective of the talc treatment (Table 2). Increased poly-

phenol content in ‘‘Barnea’’ oils was associated with a 30–

60 min malaxation time increment while in ‘‘Picual’’ oils,

polyphenol content decreased when malaxation time was

raised above 60 min. Factorial ANOVA revealed significant

effects of malaxation time, talc addition, and their interaction

on ‘‘Barnea’’ oil polyphenol content (Table 1). Increased

malaxation time has been reported to decrease polyphenol

content by up to 20% in commercial mills [36, 25] and by up

to 60% in a small laboratory apparatus, as compared with

commercial mills [36]. A similar trend was found in the

present study for ‘‘Picual’’ but not for ‘‘Barnea.’’ Talc

addition does not significantly influence polyphenol content

according to Cert et al. [38]. Our results suggest, however,

that polyphenol levels in oils from the two tested cultivars are

significantly, albeit inconsistently, influenced by the addition

of talc. Nevertheless in general, all of the oils produced in the

present study were rated extra virgin in terms of peroxide and

FA values. All the differences even when statistically signifi-

cant remained within the extra virgin quality level and there-

fore, had only minor practical relevance.

3.2 Water addition

The addition of water to the paste during malaxation to

improve oil extractability was suggested several decades

ago by Martinez et al. [21]. Their recommended protocol

specified the addition of two portions of boiling water, the

first (300 cm3) after 20 min of malaxation, and the second

Table 2. Influence of malaxation time and talc addition on percentage of extracted oil, oil acidity, oil peroxide value, and oil polyphenol

concentrationa)

Treatment

Malaxation

time (min)

Oil percentage

(%)

FA (expressed

as % oleic acid)

Peroxide value

(meq O2 kg/oil)

Polyphenols

content (mg/kg)

No talc (‘‘Barnea’’) 30 9.20b 0.52a 13.94b 36c

60 15.11a 0.43ab 13.66b 60bc

90 17.42a 0.36b 20.01a 107ab

Talc (‘‘Barnea’’) 30 12.81ab 0.32b 12.55bc 83bc

60 14.62a 0.32b 10.35c 152a

90 15.93a 0.35b 11.17bc 153a

No talc (‘‘Picual’’) 30 1.87A 0.29 4.76 239

60 3.52AB 0.30 3.00 238

90 3.25AB 0.38 5.21 199

120 8.38B 0.51 7.19 121

Talc (‘‘Picual’’) 30 13.47C 0.38A 5.21A 199A

60 15.28C 0.34A 3.79A 224A

90 15.44CD 0.39A 3.28A 90B

120 17.91D 0.69B 4.87A 65B

a) Values are means of four replicates. Different letters indicate significant differences between treatments, p � 0.05.



(100 cm3) after the first centrifugation. They further

suggested the addition of talc to the paste to improve oil

extractability in the system [21]. However, the addition of

water to olive paste, typically associated with a ‘‘three-phase’’

decanter, has been reported to be negatively related to total

phenol and o-diphenol contents compared with the ‘‘two-

phase’’ decanter, which uses less water [39]. Our results, in

agreement with previous studies, demonstrated a significant

increase in oil extractability following the addition of talc;

conversely, we found reduced oil extractability associated

with water addition treatments of �150 cm3 and no talc

addition in both cultivars (Table 3). Factorial ANOVA tests

revealed high significance of the effects of talc and water

addition and their interaction on oil extractability in both

cultivars (Table 1). In light of the negative effect of water

addition during malaxation on oil extractability, it is

suggested that this practice be avoided for fruits from irri-

gated orchards as they already contain considerable water

levels.

Water addition had a significant effect on the quality

indices of the ‘‘Barnea’’ oils (Table 3). FA was significantly

reduced in treatments that included talc addition (0.29–

0.39%) as compared to those without talc (0.46–0.61%).

Interestingly, increasing the amounts of added water in pastes

with added talc was associated with a slight increase in acidity

values for both cultivars. Peroxide values for ‘‘Picual’’ were

approximately one-third those of ‘‘Barnea’’ and did not

respond to the amount of added water (Table 3). In

‘‘Barnea’’, however, peroxide values were significantly higher

for treatments that included a higher amount of water (150–

225 cm3) and talc addition and lowest for the oil treated with

150 cm3 of water without talc addition. Factorial ANOVA

results suggested that the effects of talc and water additions

and their interaction significantly influence the acidity and

peroxide values of the ‘‘Barnea’’ oils (Table 1). Increasing the

levels of added water led to a significant decrease in poly-

phenol content in ‘‘Barnea’’ oils. Conversely, the polyphenol

content in ‘‘Picual’’ oils increased significantly when the

water level was increased to 300 cm3 (Table 3). Addition

of 300 cm3, according to Abencor’s protocol, to ‘‘Barnea’’

oils without talc led to very low levels of polyphenols. The

highest polyphenol levels were found in ‘‘Barnea’’ oils with

added talc and the lowest amount of added water (100 cm3),

in agreement with previous reports [34, 36]. It has been

suggested that phenols of a hydrophilic nature decrease as

a function of the amount of water added [40]. Again, most of

the changes in quality parameter due to the addition of water

were within the range of extra virgin olive oil level. Practically

therefore, where no significant advantage occurs, water

addition to the paste of irrigated olive fruit should be avoided.

3.3 Temperature

Olive paste kneading can be improved by heating, which

reduces the oil’s viscosity, helping the oil drops coalesce

and leading to more readily extractable oil from the vegetable

tissue [25]. Unfortunately, increasing the malaxation

temperature degrades overall oil quality as the more volatile

Table 3. Influence of water and talc addition on percentage of extracted oil, oil acidity, oil peroxide value, and oil polyphenol concentrationa)

Treatment

Water

addition (cm3)

Oil percentage

(%)

Acidity

(% oleic acid)

Peroxide value

(meq O2 kg/oil)

Polyphenols

content (mg/kg)

No talc (‘‘Barnea’’) 100 13.80b 0.61a 14.21abc 216a

150 12.65b 0.46b 12.97c 124bc

225 9.36c 0.50ab 13.24bc 105c

300y 9.20 0.52 13.94 36

Talc (‘‘Barnea’’) 0y 18.40 0.32 13.25 276

100 17.09a 0.30c 13.25bc 237a

150 16.10a 0.29c 15.73ab 178ab

225 16.26a 0.39bc 16.56a 144bc

No talc (‘‘Picual’’) 0 9.69A 0.21 2.94 125

100 9.04A 0.23 3.57 159

150 8.71A 0.24 3.28 260

225 2.96B 0.20 4.00 292

300 1.87B 0.17 4.08 136

Talc (‘‘Picual’’) 0 13.96C 0.21A 5.66A 129A

100 12.81C 0.15A 4.47A 115A

150 14.29C 0.26A 4.98A 129A

225 14.46C 0.32A 4.81A 105A

300 13.47C 0.38A 5.21A 199B


y Statistical data analysis was not performed.



aromas are lost, the rate of oil oxidation is increased and the

polyphenol content decreases [41–43]. Talc addition can be

used to improve the efficiency of the oil extraction by enabling

a reduction in both mixing time and temperature [38]. In the

present study, factorial ANOVA revealed significant effects of

temperature and talc addition and their interaction on oil

yield of ‘‘Picual’’ (Table 1). Increasing malaxation tempera-

ture from 25 to 40 8C did not improve oil yield in samples

without talc, irrespective of cultivar type. However, in

‘‘Picual’’ samples with added talc, the temperature increment

produced a significant effect, increasing the oil yield by 44%

from 106.8 of paste to 154.4 g/kg paste (Table 4). This effect

was already reflected by the 28% rise in oil yield when

temperature was increased from 20 to 40 8C at a fixed malax-

ation time of 60 min [25].

Changes in malaxation temperature had a significant

effect on the quality-related analytical indices considered

(Table 4). Initial assessment of the effect of malaxation

temperature on ‘‘Barnea’’ oil samples without added talc

demonstrated a decrease in polyphenol level when the

temperature was raised from 25 to 40 8C (Table 4). The

influence ofmalaxation temperature on oil quality was further

evaluated in ‘‘Picual’’ oil samples with talc addition

(Table 4). Likewise, raising the temperature from 25 to

40 8C reduced the level of polyphenols in ‘‘Picual’’ oils while

concomitantly inducing an increase in FA and peroxide val-

ues (Table 4).

4 Conclusions

The major difference between fruit of traditional rain-fed

and irrigated oil olive trees is in the water content of the fruit

flesh, about 40% versus 60%, respectively. In the original

Abencor method, which was developed for rain-fed olives,

water addition was required to improve oil extraction [21],

while for irrigated olives, the removal of excess water from

the paste is essential to achieve considerable efficiency of

the extraction process, much closer to levels obtained by

commercial mills. In the present study, we modified the

traditional, laboratory-scale Abencor method and attempted

to adjust it to fruit of irrigated olive orchards. The addition of

talc in order to absorb excess water, smooth the malaxation

process and consequently improve the oil yield is the main

technical adjustment required. The addition of water

should be avoided. The malaxation time should be

extended according to the water characteristics of the raw

material. These modifications increase the oil yield without

significant practical changes in the oil quality parameters.

Increased temperature may contribute to the efficiency of

the extraction process, yet it might affect quality parameters

such as the polyphenols content and therefore should

not exceed 35 8C. Different cultivars may require ad hoc

fine-tuning of the technological parameters. Differences in

the varieties response may relate to differences in their

respective average water content, percentage of stone in

the fruit, and flesh consistency. The work with an adjusted

cultivar dependent protocol suitable for fruit of irrigated

orchards will facilitate reliable representation of the influence

of different treatments on the yield and characteristics of the

olive oil.

The authors have declared no conflict of interest.

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Table 4. Influence ofmalaxation temperature and talc addition on percentage of extracted oil, oil acidity, oil peroxide value, and oil polyphenol

concentrationa)

Treatment

Temperature

(8C)

Oil percentage

(%)

Acidity

(% oleic acid)

Peroxide value

(meq O2 kg/oil)

Polyphenols

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No talc (‘‘Barnea’’) 25 10.51a 0.45ab 12.97a 75a

30 9.53a 0.37a 13.94a 30b

35 9.20a 0.48b 13.94a 36b

40 9.20a 0.36a 14.63a 18b

No talc (‘‘Picual’’) 25 1.54A 0.59 8.15 109

30 2.96A 0.22 3.17 107

35 1.87A 0.17 4.08 136

40 1.48A

Talc (‘‘Picual’’) 25 10.68B 0.29A 4.76A 239A

30 11.83BC 0.30A 3.00A 238A

35 13.47BC 0.38AB 5.21A 199A

40 15.44C 0.51B 7.19A 121B




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optimization of the abencor system to extract olive oil from irrigated orchards

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