Quality Changes of Extra Virgin Olive Oil Packaged in Coloured Polyethylene Terephthalate Bottles...

Quality Changes of Extra Virgin Olive Oil Packaged in ColouredQ1Polyethylene Terephthalate Bottles Stored Under Different

Lighting Conditions

By Valeria Rizzo,1 Luisa Torri,2 Fabio Licciardello,1 Luciano Piergiovanni3

and Giuseppe Muratore1*

1DiSPA - Department of Agricultural and Food Productions, University of Catania, Via Santa Sofia, 98, 95123Catania, Italy

2University of Gastronomic Sciences, Piazza Vittorio Emanuele 9, 12060 Bra, Italy3DEFENS - Department of Food, Environmental and Nutritional Sciences, University of Milan, Via Celoria,

2, 20133 Milano, Italy

Q2In this paper, the influence of light storage and the exposure on quality parameters of a monovarietal extravirgin olive oil packaged in polyethylene terephthalate (PET) bottles were investigated. Coloured PETbottles (clear, green, orange, white and blue) were stored under different artificial lighting conditions inorder to simulate the market environment (one fluorescent cool white lamp) and to perform an acceleratedtest (four fluorescent cool white lamps); storage in the dark was considered as a control. Total peroxidevalue, polyphenols, chlorophyll and carotenoids contents were, among the ones tested, the quality indexesmost affected by lighting and were useful to investigate the bottle colour influence. Concerning the globalquality of olive oil, under one fluorescent lamp, the best performances were obtained using blue and whitePET bottles; whereas under accelerated conditions, the differences in the protection efficacy offered by thedifferently coloured bottles were reduced. Copyright © 2013 John Wiley & Sons, Ltd.

Received 5 October 2012; Revised 4 June 2013; Accepted 21 June 2013

KEY WORDS: extra virgin olive oil; PET bottles; lighting; shelf life; colour influences; accelerated shelf life test

INTRODUCTION

Extra virgin olive oil (EVOO) is obtained from olives solely by mechanical or other physical means,having a typical characteristic, the presence of natural antioxidant components that can keep it longerthan the other vegetable oils, which are generally submitted to refining processes. It is considered thebest quality olive oil for its sensorial characteristics, stability and bio-active compounds content.The importance of EVOO is well known because it is one of the principal component of the

Mediterranean diet, appreciated for the health benefits that have been demonstrated to be related tothe protection against chronic and degenerative diseases, different tumours and ageing.1

The necessity to preserve the characteristic aroma, taste, colour and nutritive properties focused theattention of the olive oil industry on possible innovations that are able to keep the product without anyloss of these positive attributes. In fact, similarly to other products that are produced in a limitedperiod, but consumed throughout the year, it must be stored and the storage as well as the packagingconditions play an important role in determining its shelf life.2,3

* Correspondence to: Giuseppe Muratore, DiSPA - Department of Agricultural and Food Productions, Universityof Catania, Via Santa Sofia, 98, 95123 Catania, Italy.E-mail: [email protected]

PACKAGING TECHNOLOGY AND SCIENCEPackag. Technol. Sci. (2013)

Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/pts.2044

Copyright © 2013 John Wiley & Sons, Ltd.

Journal Code Article ID Dispatch: 09.07.13 CE: Ada, Emma JaneP T S 2 0 4 4 No. of Pages: 13 ME:

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At the same time, consumers are increasingly demanding that high food quality can be maintainedduring the period between purchase and consumption and used to consider glass bottles as an addedvalue to EVOO, assuming the pair ‘glass-quality’.Glass containers are generally preferred to plastic for bottling virgin olive oil because they help to

prevent the permeation of oxygen molecules into the bottle, slowing down the rate of autoxidationof unsaturated fatty acids compared with their plastic counterparts.4

Nowadays, olive oil is mainly packaged in glass bottles, whereas seed oil is already present on themarket in clear or coloured polyethylene or polyester plastic bottles. Looking at the environmentalimpacts connected to agricultural and industrial manufacturers and to waste production, it is moreand more important to focus on the optimisation of packaging that is able to protect goods, saving theirqualitative characteristics and extending their shelf lives.Considering price, fragility and weight of glass containers as compared with mechanical resistance,

cost and lightness of polyethylene terephtalate (PET) bottles, and taking also into account the hugechance of tailoring their performance, it is reasonable to look at PET as a valid alternative to glassbottles also for traditional products such as EVOO. Actually, many PET bottles – different for theircolour, size and shape – are available, but they are used mainly for water, seed oils, milk, fruit juicesand soft drinks.As reported by Sacchi et al., PET satisfies many important requirements with respect to glass

bottles, with the only exception for oxygen exchange; therefore, they studied the oxidation processof EVOO in glass, PET and PET loaded with oxygen scavengers.5

Previous studies compared also the stability of other commercial vegetable oils packaged in PET,polyvinylchloride, polypropylene and polystyrene.6

Other authors considered the variation of shelf life and the quality of oil packaged in glass, PET andpolyvinylchloride under different storage temperatures (15°C, 30°C and 40°C) and lighting conditions(dark and fluorescent light, 40W).7–9

Quality of EVOO packaged in glass under light and in the darkness was also monitored overstorage.10 Morello et al.11 studied the changes in virgin olive oil contained in amber-coloured glassbottles, whereas Riahi and Marzouk12 used dark glass bottles stored in the dark and clear glass bottlesunder daylight and non-stop artificial lamps. Also, other authors13,2 investigated the changes inqualitative parameters of virgin olive oil packaged in clear glass during the shelf life and the effectof storage time and container type (clear PET bottle, PET bottle covered with aluminium foil, glass,tin and Tetra-brik®). The possibility of substituting glass bottles with innovative materials as PETcoated with high barrier resin and including an ‘oxygen scavenger’ was studied by Gambacorta et al.14

Among the natural antioxidants, phenolic compounds, tocopherols and carotenoids were studied byseveral authors. In particular, Aparicio et al.15 assessed that the role of each of those compounds on thestability of olive oil accounted for 30%, 11% and 6%, respectively. The stability of packaged EVOO,referred to as the attitude to preserve qualitative and nutritional characteristics during storage, dependson several features such as chemical and physical characteristics of the plastic used, in particular, itsoxygen permeability, oxygen present in the package headspace and dissolved in the product, storagetime and temperature, lighting conditions but also the amount of antioxidants in the original olive oil.Because oil colour, flavour and nutrients could be influenced by lighting conditions used in the retail

shops, the optimization of packaging conditions is a necessary step to preserve them from the produc-tion to the consumption. The aim of this work was to monitor the changes of qualitative parameters inEVOO packaged in differently coloured PET bottles stored under light and in the dark in order toevaluate their potential for a shelf-life extension.

MATERIALS AND METHODS

Characterization of polyethylene terephthalate bottles

Polyethylene terephthalate bottles (600ml) in five different colours: clear, green, orange (transparentplastic), white and blue (opaque plastic) with an oxygen transmission rate (measured at 21°C,atmospheric pressure and 50% relative humidity) of 0.032ml/pk/day, were kindly supplied by PET

2 V. RIZZO ET AL.

Copyright © 2013 John Wiley & Sons, Ltd. Packag. Technol. Sci. 2013DOI: 10.1002/pts

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Engineering SRL (San Vendemiano, TV, Italy). Bottles were characterized in terms of light transmis-sion properties according to the American Society for Testing and Materials D 1003-00 officialmethod16 using a spectrophotometer [ultraviolet/visible (UV/Vis) spectrophotometer equipped witha 150mm integrating sphere (Lambda 650 model, Perkin Elmer Inc., USA)]. The measurements werecarried out on a flat piece of packaging material. Illuminance and irradiance were measured on plasticsamples exposed to a fluorescent cool white lamp ( Q4Osram Lumilux 36W/840) by a digital handlephoto-radiometer ( Q5Delta OHM HD 2102.2) equipped with probes for the measurements of illuminance(lux) (400–800 nm ) and irradiance in the extended visible (400–1050 nm ), UVA (315–400 nm ) andUVB (280–315 nm ) regions (W/m2). Light-shielding effect offered by the packaging materials,expressed as percentage of irradiance, was calculated as follows:

Light shielding ¼ Isample=Iairx100

where Isample, irradiance recorded in the presence of sample; and Iair, irradiance recorded in the absenceof sample.

Sampling

Fresh EVOO produced in Sicily, from the Tonda Iblea olive variety, was purchased by a localproducer. All the following analyses were carried out as soon as the EVOO arrived in the laboratory,and then it was dispensed into the previously described PET bottles. Bottles were full-filled (610mlwith 7ml of headspace), then hermetically sealed and stored horizontally for 4months at room temper-ature. Data loggers (Smart Reader SR04) were used to verify the real temperature. During storage, thesamples were divided into three series and exposed to different lighting conditions: (a) under constantillumination produced by one fluorescent cool white lamp (Osram Lumilux 36W/840) in order tosimulate the retailers conditions; (b) under constant illumination produced by four fluorescent coolwhite lamps in order to perform an accelerated test; (c) in the dark; and (d) as reference. In the firsttwo cases, lamps were placed 30 cm above samples. For each selected lighting condition, illuminance(lux) and UVA and UVB irradiance (W/m2) were measured under real storage conditions at the levelof the samples. In particular, 1 lamp values were 2671 ± 9 lux, 101.4�3 ± 0.1 and 10.71�3 ± 0.03W/m2,whereas values under 4 lamps were 9028 ± 16 lux, 284.5�3 ± 0.6 and 31.53�3 ± 0.06W/m2,respectively.Overall, 180 bottles were considered, 60 bottles per each storage conditions; sampling and analyses

were carried out in duplicate on two different bottles for each bottle colour, using always unopenedbottles.Extra virgin olive oil was stored at room temperature 23 ± 2°C and analysed at 0, 20, 40, 60, 80, 100

and 120 days after packaging.

Analytical indexes

The acidity, the peroxide value (PV) and the spectroscopic indexes in the UV region (K232, K270 andK316) were determined according to the Q6European Union (EU) official methods ( Q7Regulations EuropeanEconomic Community (EEC)/2568/9117 and following modifications EEC 656/95, EEC 2472/97 andEEC 1989/200318 of the EU Commission). The Shimadzu spectrophotometer (UV-2401 PC, Kyoto,Japan) was previously calibrated with KCrO4 0.02% in KOH 0.05N solution as described in the sameregulations.Results of acidity and PVs were expressed as oleic acid per 100 g of oil and as milliequivalents

(mEq) of active oxygen per kilogram of oil according to American Oil Chemists' Society methods.19

All analyses were carried out in duplicate, using chemicals (Sigma-Aldrich, Milan, Italy) and solventsof analytical grade (J. T. Baker, Deventer, Holland).

Colour

Oil colour was measured according to the Q8International Commission on Illumination L*, a*, b* scaleby using a handle colorimeter (chromameter) (NR-3000, Nippon Denshoku Ind. Co. Ltd, Japan)

3CHANGES IN EXTRA VIRGIN OLIVE OIL PACKAGED IN COLOURED POLYETHYLENE TEREPHTHALATE BOTTLES


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appropriately calibrated with a standard white tile ( Q9EU certificated) with the following parameters:X= 83.47, Y= 84.43 and Z= 95.16 under illuminant C/2°, (daylight source). Briefly, 4ml of EVOOwere placed in a clear PET petri dishes (Ø = 3.5 cm) and positioned on a white sheet of paper.

Pigment content

The chlorophylls ‘a’ and ‘b’ were assessed measuring the absorbance at 670 nm and 470 nm, respec-tively. Sample (7.5 g) was dissolved in cyclohexane (25ml).11 β-carotene was monitored at 449 nmas described by Caponio et al.10 (0.25 g of EVOO were dissolved in 5ml of UV-hexane). Results wereexpressed as milligrams of chlorophyll ‘a’ and milligrams of β-carotene per 100 g of oil, using thecalibration curves of both standards solutions.

Bitter index

The bitter index (K225) was evaluated by the extraction of the bitter components passed over a C18column (Waters Sep-Pak cartridges) previously activated with methanol (6ml) and washed withhexane (6ml). Each sample, 1.0 ± 0.01 g of EVOO dissolved in 4ml of hexane, was passed throughthe column. After elution, 10ml of hexane were passed to eliminate the fat, and the retainedcompounds were eluted with 25ml of methanol/water (1 : 1). The absorbance of the extract was mea-sured at 225 nm against methanol/water (1 : 1) in a 1 cm UV-cuvette.20 Results were expressed asabsorbance at 225 nm.

Total polyphenols

The total polyphenols analysis was performed as reported by Gutfinger.21 Briefly, 10ml of EVOO wasdissolved in 50ml hexane, and the solution was extracted successively three times with 20ml ofmethanol : water (40 : 60 v/v) solution. The mixture was shaken each time for 2min, and the lower partof the extractive mixture was decanted directly in a volumetric flask of 100ml Q10then brought to finalvolume with distilled water. The total content of phenolic compound was assessed by the colorimetricFolin-Ciocalteu method at 725 nm on 10ml of the hydrophilic extract. Gallic acid served as thestandard for preparing the calibration curve.

Statistical analysis

Results are presented as mean value ± SD. All data were submitted to one-way ANOVA, and post-hoccomparison of means was performed by the Duncan test (p< 0.05) through the statistical packageSPSS® Statistics 13.0 (Armonk, NY, USA). Moreover, the three-dimensional principal componentanalysis was applied to the three-dimensional matrices (bottle colour vs analitycal indices vs storagetime) using the Q11UNSCRAMBLER software, version 9.2. PCA is a procedure that permits useful informa-tion to be extracted from the data, exploration of the data structure and relationships between objectsand global correlation of the variables. The data obtained from the analytical indices were also

Figure 1. Light shielding (%) of polyethylene terephthalate bottles.

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analysed by cluster analysis (CA) using the MINITAB software, release 14.12.0. CA performs agglom-erative hierarchical clustering of objects based on distance measures of dissimilarity or similarity. Thehierarchy of clusters can be represented by a binary tree, called ‘a dendrogram’. A final partition, i.e.the cluster assignment of each object, is obtained by cutting the tree at a specified level.

RESULTS AND DISCUSSION

Light barrier properties of polyethylene

The light barrier offered by PET bottles was studied in terms of light transmittance and shielding in theUV/Vis regions.Figure F11 shows the light shielding expressed as percentage. Generally, as expected, the transparent

bottles (clear, orange and green) offered a much lower protection against light than the opaque ones(white and blue) when illuminance and irradiance in the visible and UVA regions were considered.In particular, the shielding effect increased of in the following order: clear (<10%), orange

Figure 2. Light transmittance (%) spectra of polyethylene terephthalate bottles.

Table 1. Time course of chlorophylls in extra virgin olive oil packaged in polyethylene terephthalate bottlesas affected by lighting and bottle colour.

Darkness Clear Green

Time (days) 1 lamp 4 lamps 1 lamp

Chlorophyll 670 nm (mg/100 g oil)

0 19.47 ± 2.54 aB 19.47 ± 2.54 a

B 19.47 ± 2.54 aB 19.47 ± 2.54 a

B

20 8.31 ± 0.19 dA 0.98 ± 0.00 ab

A 0.49 ± 0.01 aA 2.45 ± 1.39 c

A

40 8.61 ± 0.02 dA 0.54 ± 0.28 a

A 0.42 ± 0.03 aA 0.42 ± 0.10 a

A

60 8.33 ± 0.27 eA 0.82 ± 0.02 c

A 0.46 ± 0.04 abcA 0.20 ± 0.07 ab

A

80 8.37 ± 0.03 eA 0.32 ± 0.04 abc

A 0.21 ± 0.26 abA 0.10 ± 0.01 a

A

100 8.14 ± 0.10 dA 0.21 ± 0.09 a

A 0.28 ± 0.09 aA 0.11 ± 0.00 a

A

120 8.10 ± 0.37 dA 0.15 ± 0.08 ab

A 0.36 ± 0.05 abcA 0.08 ± 0.05 a

A


0 29.39 ± 2.13 aA 29.39 ± 2.13 a

C 29.39 ± 2.13 aD 29.39 ± 2.13 a

C

20 28.91 ± 0.48 eA 23.53 ± 1.07 a

AB 25.62 ± 0.42 bCD 27.10 ± 0.03 bcd

BC

40 28.67 ± 0.20 cdA 26.31 ± 0.34 abc

BC 23.80 ± 0.32 aBC 25.86 ± 0.30 abc

B

60 28.62 ± 0.61 fA 25.35 ± 0.39 cde

B 24.38 ± 2.11 bcdeBC 24.70 ± 0.18 bcde

B

80 28.45 ± 0.48 dA 24.73 ± 0.40 bc

B 21.15 ± 0.55 aAB 23.59 ± 0.31 b

AB

100 27.81 ± 0.14 dA 24.68 ± 0.10 c

B 18.02 ± 0.68 aA 23.88 ± 1.43 bc

AB

120 27.51 ± 1.45 eA 20.97 ± 0.12 cd

A 18.06 ± 0.60 aA 20.91 ± 0.21 bcd

A

Different subscript letters in lines show significant differences (p≤ 0.05) among treatments (bottle colour × lightingcondition). Different superscript letter in columns show significant differences (p≤ 0.05) among storage times.



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(12–24%), green (25–40%), white (62–68%) and blue (83–96%) bottles for the illuminance and Visirradiance parameters. A similar trend was noticed for the UVA irradiance except for the white samplethat, unexpectedly, offered a higher light shielding than the blue sample. Regarding the irradiance inthe UVB region, minor differences in shielding effect were observed (close to 70% for all five plasticcolours analysed). This result is not surprising because it is well known that PET screens UVB radia-tions22 as it is shown in Figure F22. Indeed, the spectra presented clearly show the absence of lighttransmittance for all samples from 200 to 320 nm and until 400 nm for white plastic only. Moreover,the white sample confirms smallest light transmittance (20–38%) with an increase at 400 nm and a tinyslope to 800 nm. From 320 to 360, an increased light transmittance was observed for the clear, orangeand green plastics that continued to 460 nm for blue plastic. The clear sample presented almostcomplete light transmittance (85–90%) from 400 to 780 nm according to Mestdagh et al.22, whereasa similar light transmittance was recorded for the orange and green samples in the range of 590–780 nm and 740–780 nm, respectively. The main differences between the orange and green sampleswere observed in the 400–460 nm and 600–700 nm regions corresponding to the blue and red coloursof the visible light spectrum. The blue sample showed a first peak of light transmittance (70%) from450 to 460 nm and the second one (85–90%) from 700 to 800 nm.

Quality changes of extra virgin olive oil

For all samples used in this study, the values of the quality parameters were below the upper limitsestablished by the European Regulation EEC/2568/9117 and following modifications EEC 656/95,EEC 2472/97 and EEC 1989/200318, which established the characteristics of different olive oils andgave quality and authenticity criteria for a correct olive oil commercial classification. Results of theanalytical measurements are reported in Tables T11 and T22.

Analytical indexes

The acidity of fresh EVOO was 0.33%, slightly increasing during storage up to 0.51% in the clearbottle under 1 fluorescent lamp and in the blue bottle under 4 lamps (data not reported) confirmingno significant difference between the two storage conditions according to Caponio et al.10 and Riahiand Marzouk.12

The PV, a measure of primary oxidation and oil, showed an initial value of 15.90 ± 0.13mEqO2/kg(Table 2). This parameter did not increase significantly and had the same constant trend for storage inthe dark and under 1 lamp.

Table 1. Continued

Green Orange White

4 lamps 1 lamp 4 lamps 1 lamp


19.47 ± 2.54 aB 19.47 ± 2.54 a

B 19.47 ± 2.54 aB 19.47 ± 2.54 a

B

0.38 ± 0.03 aA 0.95 ± 0.03 ab

A 0.49 ± 0.00 aA 2.94 ± 0.00 c

A

0.26 ± 0.09 aA 1.45 ± 1.15 a

A 0.52 ± 0.03 aA 2.92 ± 0.73 b

A

0.10 ± 0.04 aA 0.66 ± 0.10 bc

A 0.47 ± 0.02 abcA 0.83 ± 0.01 c

A

0.13 ± 0.03 aA 0.53 ± 0.02 bc

A 0.05 ± 0.07 aA 0.58 ± 0.05 c

A

0.11 ± 0.03 aA 0.29 ± 0.03 a

A 0.30 ± 0.01 aA 0.52 ± 0.01 ab

A

0.12 ± 0.04 abA 0.05 ± 0.00 a

A 0.43 ± 0.02 abcA 0.51 ± 0.03 bc

A


29.39 ± 2.13 aE 29.39 ± 2.13 a

C 29.39 ± 2.13 aE 29.39 ± 2.13 a

C

25.62 ± 0.42 bD 27.53 ± 0.05 de

BC 25.93 ± 0.02 bcD 27.40 ± 0.45 cde

BC

23.43 ± 0.25 aCD 27.42 ± 2.51 bcd

BC 24.54 ± 0.08 abCD 29.88 ± 1.48 d

C

21.65 ± 0.31 aBC 25.98 ± 0.68 e

ABC 22.78 ± 0.11 abBC 25.65 ± 0.28 de

AB

20.21 ± 0.07 aAB 24.24 ± 0.69 bc

AB 20.82 ± 0.77 aAB 24.67 ± 0.23 bc

AB

18.41 ± 0.03 aA 23.40 ± 0.95 bc

AB 19.57 ± 0.48 aA 23.96 ± 0.09 bc

AB

18.65 ± 0.36 abA 21.97 ± 0.64 d

A 19.13 ± 0.53 abcA 22.13 ± 0.86 d

A

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The time course for PVs suggests an initial increase and a successive decrement of values. Maxi-mum values were observed around 40–60 days of storage for samples submitted to 1 fluorescent lampand after 20–40 days for samples exposed to 4 fluorescent lamps. Indeed, it seems that the exposure toa higher light intensity accelerated the oxidative processes; however, peroxides are intermediatereactive species that are converted into secondary oxidation products, and this justifies their reductionduring the successive stages of the shelf-life test. It is noteworthy that for samples subjected to 1fluorescent lamp, the PVs remained at significantly higher (p< 0.05) levels compared with thecorresponding samples under 4 lamps; this observation suggests that the exposure to a high radiantintensity resulted in a rapid degradation of peroxides in favour of secondary oxidation compounds.This result was not unexpected and was in agreement with what already observed in EVOO stored in

PET bottles with and without oxygen scavenger,23 in olive oil stored in PET bottles2 and in EVOOfrom whole and de-stoned fruits.24 It seems to indicate that in PET bottles, in the first stage ofoxidation, the rate of hydroperoxides production through the oxidation of unsaturated fatty acids ishigher than the rate of their consumption, leading to a decrease in PV; this result suggests a possiblerole of PET polymer in promoting the peroxides consumption that should be better investigated. Aspreviously mentioned, PVs of samples stored in the dark were higher than for those stored under light,confirming that light increases the rate at which hydroperoxides break down.23

Storage under different conditions did not appear to have a significant effect on the spectrophoto-metric indexes K270 and K316 having a starting value of 0.31 ± 0.01 and 0.06 ± 0.01, respectively,and remains quite stable. Our findings are in agreement with those of Caponio et al.10 and Bosque-Sendra et al.25 The only exception was for K232, which decreased from the initial value of3.01 ± 0.04 to 0.31 ± 0.27 after 80 days of storage.

Colour

Colour is one of the major attributes that affect the consumer's perception of the quality of virgin oliveoil. Oil colour variations due to different varieties, to processes and to stage of ripeness are directlyrelated to pigment content and are generally expressed by the International Commission on Illumina-tion a* and b* values.26 Extraction processes and environmental factors may be more important thangenetic factors in influencing the pigments content (chlorophyll and carotenoids) responsible for theEVOO colour. For its characterisation, we did not observe a specific trend, all samples were compara-ble and no significant change related to lighting or bottle colour was detected (data not shown).

Table 1. Continued

White Blue

4 lamps 1 lamp 4 lamps


19.47 ± 2.54 aB 19.47 ± 2.54 a

E 19.47 ± 2.54 aB

0.46 ± 0.04 aA 8.16 ± 0.23 d

D 1.96 ± 0.00 bcA

0.69 ± 0.07 aA 6.98 ± 0.17 c

CD 0.88 ± 0.00 aA

0.51 ± 0.11 abcA 6.05 ± 0.36 d

CD 0.73 ± 0.08 cA

0.37 ± 0.03 abcA 4.03 ± 0.20 d

BC 0.39 ± 0.06 abcA

0.83 ± 0.01 bA 2.58 ± 0.36 c

AB 19.46 ± 0.20 aA

0.58 ± 0.06 cA 0.51 ± 0.04 bc

A 0.61 ± 0.10 cA


29.39 ± 2.13 aD 29.39 ± 2.13 a

D 29.39 ± 2.13 aE

25.68 ± 0.33 bC 28.79 ± 0.55 e

CD 26.83 ± 0.40 bcdDE

24.10 ± 0.19 aBC 26.50 ± 0.40 abc

BCD 24.24 ± 0.08 aCD

22.92 ± 0.08 abcABC 26.54 ± 0.41 ef

BCD 23.33 ± 0.33 abcdBC

21.26 ± 0.52 aAB 25.55 ± 0.54 c

BC 20.68 ± 0.01 aAB

21.99 ± 0.47 bAB 23.93 ± 0.13 bc

AB 19.46 ± 0.20 aA

20.61 ± 0.09 bcdA 22.21 ± 0.83 d

A 20.34 ± 0.29 bcdA



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Pigments content

The starting amounts of chlorophylls, 19.47 ± 2.54mg of chlorophyll ‘a’ per 100 g of oil, sharplydropped during the first 20 days for all samples. Chlorophylls as measured at 670 nm (Table 1) wererapidly degraded; only in samples stored in the dark and in blue bottles lightened with 1 fluorescentlamp, such pigments were preserved at significantly higher (p< 0.05) levels than the other samples;at a lower extent, white and transparent-green bottles exerted a protective effect until 40 and 20 daysof storage. Samples stored under 4 lamps showed minimum chlorophylls levels after 20 daysirrespective of the bottle colour, with the only exception of blue PET, which maintained 1.96mg/100 g oil until 20 days of storage; in any case, for samples whose pigments were not completelydegraded after 20 days, the exposure at 4 lamps determined chlorophylls contents significantly lowercompared with the correspondent samples subject to 1 lamp.For what concerns chlorophylls determined at 470 nm, the exposure to 1 and 4 fluorescent lamps

caused a reduction in the range of 30% and 40%, respectively, after 120 days of storage, with signif-icant differences (p< 0.05) between the two lighting conditions, whereas for samples maintained inthe dark, the chlorophylls loss amounted to about 12%. Among the samples exposed to light, thosebottled in blue and white PET showed the closest data to the control stored in the dark.Chlorophylls contents decreased quickly owing to their role as photosensitisers. As confirmed by

Riahi and Marzouk12, the degradation of chlorophylls affects oil stability. These pigments play a dou-ble function showing a pro-oxidant power under light exposure, not proportional to their amount, andan antioxidant power as regards the auto-oxidation process when in the dark, ability related with theirquantity.

Table 2. Time course of carotenoids, peroxide value and polyphenols in extra virgin olive oil packaged inpolyethylene terephthalate bottles as affected by lighting and bottle colour.

Darkness Clear Green

Time (days) 1 lamp 4 lamps 1 lamp

Carotenoid 449 nm (β-carotene mg/100 g oil)0 8.56 ± 0.95 a

A 8.56 ± 0.95 aC 8.56 ± 0.95 a

B 8.56 ± 0.95 aC

20 8.49 ± 0.45 aA 6.53 ± 0.44 a

AB 7.55 ± 0.69 aB 7.83 ± 1.02 a

C

40 8.79 ± 0.27 eA 7.78 ± 0.36 cde

BC 7.18 ± 0.24 abcdB 7.38 ± 0.25 bcd

BC

60 8.53 ± 0.25 gA 5.59 ± 0.16 bc

A 4.52 ± 0.23 aA 6.79 ± 0.07 e

ABC

80 7.67 ± 0.21 eA 5.70 ± 0.03 bcd

A 4.57 ± 0.48 abA 5.74 ± 0.05 bcd

AB

100 7.36 ± 0.23 cA 5.38 ± 0.30 b

A 4.67 ± 0.40 aA 5.53 ± 0.07 b

AB

120 7.10 ± 1.32 dA 6.23 ± 0.02 cd

A 3.54 ± 0.15 aA 5.30 ± 0.11 bc

A

Peroxide value (mEqO2/kg)0 15.90 ± 0.13 a

AB 15.90 ± 0.13 aD 15.90 ± 0.13 a

E 15.90 ± 0.13 aB

20 16.14 ± 0.54 bB 12.06 ± 1.29 ab

A 14.56 ± 0.63 abD 15.94 ± 1.17 b

B

40 14.48 ± 0.13 efAB 14.62 ± 0.50 ef

CD 12.57 ± 0.42 cC 16.60 ± 0.37 g

B

60 10.77 ± 3.07 abA 13.60 ± 0.40 bc

ABC 12.39 ± 0.58 abcC 15.20 ± 0.57 cd

AB

80 15.55 ± 0.07 gAB 15.68 ± 0.21 g

D 8.06 ± 0.08 aA 15.80 ± 0.27 g

B

100 16.98 ± 0.02 gB 12.40 ± 0.28 d

AB 7.80 ± 0.15 aA 16.40 ± 0.27 g

B

120 16.02 ± 2.22 fB 14.34 ± 0.27 ef

BCD 9.45 ± 0.17 bcB 13.75 ± 0.48 def

A

Polyphenols 725 nm (gallic acid mg/kg oil)0 445.10 ± 2.10 a

A 445.10 ± 2.10 aD 445.10 ± 2.10 a

C 445.10 ± 2.10 aE

20 392.25 ± 22.10 gA 281.23 ± 1.97 cd

BC 267.82 ± 5.53 bcB 212.91 ± 6.37 a

B

40 374.79 ± 64.76 eA 302.95 ± 13.1 cde

C 230.25 ± 2.38 abcA 304.12 ± 15.6 cde

D

60 313.87 ± 117.06 aA 257.27 ± 7.55 a

B 268.68 ± 9.84 aB 271.26 ± 13.9 a

C

80 301.26 ± 26.15 aA 257.61 ± 20.9 a

B 234.45 ± 2.38 aA 270.53 ± 1.87 a

C

100 294.54 ± 64.18 eA 293.67 ± 8.27 e

BC 207.33 ± 3.83 abcA 235.31 ± 8.94 bcde

B

120 316.90 ± 33.40 fA 197.61 ± 5.53 bcde

A 214.94 ± 18.7 cdeA 173.60 ± 1.87 abc

A

Different subscript letters in lines show significant differences (p≤ 0.05) among treatments (bottle colour × lightingcondition). Different superscript letter in columns show significant differences (p≤ 0.05) among storage times.

(Continues)

8 V. RIZZO ET AL.


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No significant difference in the total carotenoids content was observed among the different treat-ments until 20 days of storage (Table 2); after that, samples subjected to 4 lamps lighting showed sig-nificantly lower values compared with the correspondent samples stored under 1 lamp. Among bottleslighted with 1 lamp, no significant difference was observed, with the only exception of clear PET bot-tles which showed, between 40 and 60 days of storage, a significant reduction (p< 0.05) of carotenoidscompared with samples bottled in differently coloured PET. Samples subjected to 4 fluorescent lampsdid not show a significant effect of the bottle colour on the total carotenoids content (Table 2). Asreported in the literature11,24, their contents decreased less than the chlorophylls.Comparing the evolution over time of the carotenoids content in the samples, it is possible to notice

that, under both 1 lamp and 4 lamps, orange bottles better preserved the pigments compared with greenones. Light barrier properties of the plastic samples might be useful to explain the differences in pig-ment content evolutions observed between EVOO samples stored in green and orange bottles. Indeed,even if orange bottles showed lower total light shielding in the UV/Vis region (Figure 1), the transmit-tance at the wavelengths corresponding to carotenoids and chlorophylls absorption, respectively 449and 470 nm, were higher for the green bottles than for the orange ones (Figure 2). This observationsuggests that, in order to preserve the pigments naturally present in EVOO, it is better to choosecoloured PET bottles that reduce the transmission of the specific absorption wavelengths of caroten-oids and chlorophylls rather than generically reduce the transmission of the visible light.

Bitter index

Bitter index is an important parameter to take into account because sensory quality plays a key role inorienting the consumers' preference27 and it was monitored to assess the effect of storage in relation to

Table 2. Continued

Green Orange White

4 lamps 1 lamp 4 lamps 1 lamp

Carotenoid 449 nm (β-carotene mg/100 g oil)

8.56 ± 0.95 aD 8.56 ± 0.95 a

C 8.56 ± 0.95 aC 8.56 ± 0.95 a

C

7.16 ± 0.31 aCD 7.26 ± 0.25 a

ABC 6.41 ± 0.60 aB 7.39 ± 1.64 a

ABC

6.25 ± 0.46 abBC 8.09 ± 0.50 cde

C 5.98 ± 0.00 aB 8.42 ± 0.54 de

BC

5.11 ± 0.44 bAB 7.78 ± 0.11 f

BC 5.64 ± 0.05 bcB 6.50 ± 0.11 de

ABC

4.63 ± 0.63 abAB 6.95 ± 0.91 de

ABC 4.04 ± 0.05 aA 6.15 ± 0.01 cd

ABC

4.09 ± 0.20 aA 5.74 ± 0.06 b

A 5.74 ± 0.30 bB 5.74 ± 0.18 b

AB

4.21 ± 0.10 abA 5.86 ± 0.05 cd

AB 3.33 ± 0.23 aA 5.55 ± 0.07 c

A

Peroxide value (mEqO2/kg)

15.90 ± 0.13 aE 15.90 ± 0.13 a

C 15.90 ± 0.13 aB 15.90 ± 0.13 a

D

14.56 ± 0.63 abA 15.24 ± 0.67 ab

BC 10.66 ± 4.61 abAB 11.47 ± 0.44 ab

A

12.57 ± 0.42 cDE 13.17 ± 0.51 cd

A 12.04 ± 0.06 bcAB 14.14 ± 0.19 de

C

12.39 ± 0.58 abcD 14.81 ± 0.28 cd

BC 11.23 ± 0.04 abAB 12.52 ± 0.22 abc

B

8.06 ± 0.08 aB 13.37 ± 0.17 e

A 11.78 ± 0.33 cAB 12.62 ± 0.22 d

B

7.80 ± 0.15 aC 15.07 ± 0.13 f

BC 8.99 ± 0.03 bA 13.16 ± 0.16 e

B

9.45 ± 0.17 bcBC 14.34 ± 0.35 ef

AB 6.72 ± 0.03 aA 13.24 ± 0.14 de

B

Polyphenols 725 nm (gallic acid mg/kg oil)

445.10 ± 2.10 aE 445.10 ± 2.10 a

E 445.10 ± 2.10 aE 445.10 ± 2.10 a

C

248.87 ± 3.75 bB 410.57 ± 4.75 g

D 359.69 ± 2.88 fD 295.28 ± 21.8 de

AB

347.08 ± 7.69 deD 176.71 ± 2.04 a

A 357.41 ± 4.53 deD 329.36 ± 35.7 de

B

261.32 ± 3.54 aBC 206.36 ± 10.0 a

B 250.30 ± 4.57 aB 301.85 ± 5.70 a

B

306.25 ± 34.5 aCD 259.33 ± 3.68 a

C 289.91 ± 23.2 aC 304.40 ± 5.66 a

B

218.20 ± 9.10 abcdB 271.07 ± 15.4 cde

C 158.08 ± 4.89 aA 284.25 ± 3.85 de

AB

166.43 ± 8.98 abA 170.61 ± 1.76 abc

A 150.08 ± 3.08 aA 240.94 ± 3.91 e

A



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the sensorial quality. The bitter index of fresh EVOO from Tonda Iblea was 0.72 ± 0.022, correspond-ing to a very high bitterness, considered a distinctive characteristic of EVOO, and it showed a progres-sive decrease during both storage conditions with a loss of that positive attribute to a mean value of0.14 ± 0.04. In fact, following the ranges indicated by previous studies,20 for values of absorbancelower or equal to 0.140, the intensity of bitterness can be classified as ‘imperceptible bitterness’. Fora value of Abs K225 of 0.250, the bitter index could be considered a medium bitter value; whereas avalue higher than 0.360 corresponds to an oil having high or extremely high bitterness. Only underthe effect of the 1 fluorescence lamp lighting, the white bottle kept the value closest to the fresh (datanot shown).

Total polyphenols

The content of total polyphenols was 445.10 ± 2.10mg of gallic acid in 1 kg of fresh EVOO (Table 2).As expected, the polyphenols content decreased during storage in both lighting conditions; however,white and blue bottles were able to keep the highest concentrations of these compounds. Total poly-phenols decrease is due to decomposition and oxidation processes.11

The total polyphenols value in EVOO stored in the dark decreased sharply until 60 days of storage,then remaining constant until 120 days. Interestingly, the light intensity (1 or 4 fluorescent lamps) didnot significantly affect the level of total polyphenols, whereas samples stored in the dark alwaysshowed significantly higher (p< 0.05) values.One of the most peculiar characteristics of olive oil is its greater resistance to oxidation stress with

respect to other commercial vegetable oils. This peculiarity is known to be due to the high percentageof natural antioxidant molecules, especially polyphenols, as well as to other compounds known to pos-sess high antioxidant capacity.28 Bitter index value and total phenols followed the same pattern;

Table 2. Continued

White Blue

4 lamps 1 lamp 4 lamps

Carotenoid 449 nm (β-carotene mg/100 g oil)

8.56 ± 0.95 aC 8.56 ± 0.95 a

B 8.56 ± 0.95 aC

6.84 ± 1.21 aBC 8.63 ± 0.49 a

B 8.27 ± 0.39 aC

6.84 ± 0.12 abcBC 8.80 ± 0.36 e

B 7.55 ± 0.64 bcdeC

5.94 ± 0.06 cdAB 7.57 ± 0.07 f

B 5.90 ± 0.08 cdB

5.24 ± 0.08 abcAB 5.72 ± 0.04 bcd

A 4.33 ± 0.04 aAB

5.57 ± 0.04 bAB 5.51 ± 0.11 b

A 5.61 ± 0.05 bB

4.03 ± 0.01 abA 5.86 ± 0.09 cd

A 3.34 ± 0.05 aA

Peroxide value (mEqO2/kg)

15.90 ± 0.13 aD 15.90 ± 0.13 a

CD 15.90 ± 0.13 aB

13.19 ± 1.23 abC 14.57 ± 0.04 ab

BC 10.96 ± 2.95 abA

8.18 ± 0.06 aA 13.17 ± 0.54 cd

B 11.17 ± 0.24 bA

9.94 ± 0.09 aB 17.13 ± 0.42 d

D 9.20 ± 0.05 aA

8.00 ± 0.00 aA 14.61 ± 0.41 f

BC 8.66 ± 0.21 aA

7.40 ± 0.11 aA 14.57 ± 0.45 f

BC 8.60 ± 0.18 bA

7.14 ± 0.06 abA 11.42 ± 0.63 cd

A 7.58 ± 0.37 abA

Polyphenols 725 nm (gallic acid mg/kg oil)

445.10 ± 2.10 aB 445.10 ± 2.10 a

D 445.10 ± 2.10 aD

385.64 ± 3.92 gB 310.43 ± 7.62 e

C 257.80 ± 5.69 bcC

378.43 ± 13.3 eB 291.56 ± 11.2 bcd

BC 221.45 ± 6.55 abB

231.63 ± 2.07 aA 280.13 ± 3.39 a

ABC 240.75 ± 1.77 aBC

266.15 ± 47.2 aA 274.65 ± 24.2 a

ABC 249.09 ± 12.1 aBC

247.76 ± 8.52 bcdeA 259.26 ± 13.1 bcde

AB 188.53 ± 5.52 abA

226.95 ± 11.2 deA 238.93 ± 0.38 e

A 191.77 ± 14.4 abcdA

10 V. RIZZO ET AL.


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indeed, it is generally accepted that the phenolic fraction of EVOO is mainly responsible for the bitterattribute.11

Statistical analysis

In order to better explore and visualize the obtained results, a three-way analysis was applied to thethree-dimensional analytical data matrix (bottle colour vs analytical indices vs storage time). The plotsfrom the 3D-PCA are presented in Figure F33. The loading plot (Figure 3a) shows that the quality indicesmost affected by lighting and useful to investigate the bottle colour influence, were PV, polyphenols,chlorophylls and carotenoid contents, whereas changes in acidity, bitter index, absorption coefficientsand colour parameters (L = lightness; C = chroma) provided weak information in storage conditiondiscrimination. The score plot (Figure 3b) shows a good discrimination among different packagingand illumination conditions. The reference storage condition (darkness) is clearly isolated in the upperright part of the graph and a neat separation between the retailer (1 lamp) and accelerated (4 lamps)light conditions is evident. Because the oil stored in the dark was affected by the lowest loss of quality,the relative position of storage conditions in the plot reveals that the accelerated light conditioninduced higher quality changes in the samples than the retailer light condition. Regarding the colour

-4

-3

-2

-1

0

1

2

3

4

-4 -2 0 2 4 6 8

Risultati PCA 3D, X-expl: 37%,10% Y-expl: 10%,10%

D

C1

G1

O1

W1B1

C4 G4

O4

W4

B4

PC1

PC2 Scores

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6

RESULT1, X-expl: 37%,10% Y-expl: 10%,10%

0

20

40

60 80100

120

Chlor670

Chlor470

Carotenoids

K232

K270

K316

Acidity

PV

BI

Polyphenols

LC

PC1

PC2 X1-loading Weights and X2-loading Weights

(a)

(b)

Figure 3. Loading (a) and score (b) plots obtained by the three-way analysis (D = darkness; C = clear;O = orange; G = green; W=white; B = blue; 1 = one lamp; 4 = four lamps) (numbers in the loading plot

identify the storage time expressed in days.



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of the packaging materials, it is possible to notice that blue and white bottles allowed to better preserveEVOO quality in comparison with the performances offered by the clear, orange and green bottlesunder the illumination produced by 1 fluorescent lamp. This result could be well explained by thehigher light barrier offered by these two plastic materials. As previously mentioned and reported inFigure 1, the white and blue materials were characterized by the highest light shielding both in thevisible and UVA regions. Focusing on the accelerated conditions, only the white bottles provided adifferent protection performance whereas the other four bottle colours did not play a diversified roleagainst the light damage induced by the accelerated condition. This result suggests that under thestressed illumination condition, the differences in protection efficacy offered by the differentlycoloured PET bottles were reduced.All analytical data (average scores) were also elaborated by CA (Ward and the square Euclidian

distance methods) in order to investigate the similarities among EVOO samples. CA identified threemain groups of samples characterized by low (1), medium (2) and high (3) quality changes (Table T33).Overall, CA results (Table 3) pointed out that EVOO samples stored for 80–120 days under retailerlight conditions had similar characteristics to those kept for 40–60 days under accelerated lightconditions, whereas the degradation observed in samples after 80 days under 4 lamps was not achievedby samples stored under 1 lamp neither after 120 days.Generally, under the best storage conditions of darkness and low controlled temperature (0–8°C),

the critical physical–chemical parameters of the olive oil in glass bottling are stable at least during2 years with light variability.25 It is well known how edible oils are subject to oxidative rancidity whenexposed to illumination and packaged in plastic, which poses some problems of shelf-life stability;however, our preliminary tests and the excellent performance of PET could encourage the increasein the use of such material.Our study was conducted in order to identify the changes in EVOO quality characteristics due to

packaging in coloured PET bottles and subject to lighting stress. Concerning the global quality of oliveoil, the best performances were obtained using blue and white PET bottles stored under one fluorescentlamp. Results suggest that quadrupling the light source causes the doubling of EVOO degradationintensity. The present study highlights that EVOO can be conveniently packaged in PET bottles andgives a clear indication for retailers to adequately consider the lighting conditions to preserve the shelflife of olive oil. Further studies could provide helpful information to design accelerated shelf-life testsor less-expensive modelling studies.

REFERENCES

1. Servili M, Selvaggini R, Esposto S, et al. Health and sensory properties of virgin olive oil hydrophilic phenols:agronomic and technological aspects of production that affect their occurrence in the oil. Journal of Chromatography.A 2004; 1054: 113-127.

2. Mendez AI, Falqué E. Effect of storage time and container type on the quality of extra-virgin olive oil. Food Control 2007;18: 521-529.

Table 3. Groups of samples identified by the cluster analysis (numbers in the table are referred to the storagetime expressed in days).

Lightingcondition

Bottlecolour

Sample group 1 (lowquality changes)

Sample group 2 (mediumquality changes)

Sample group 3 (highquality changes)

1 lamp Clear 40 20, 60, 80, 100, 120Green 20, 40, 60 80, 100, 120Orange 20, 40, 60 80, 100, 120White 20, 40 60, 80, 100, 120Blue 20, 40, 60 80, 100, 120

4 lamps Clear 20 40, 60 80, 100, 120Green 40 20, 60 80, 100, 120Orange 20, 40 60 80, 100, 120White 20, 40 60 80, 100, 120Blue 20 40, 60 80, 100, 120

12 V. RIZZO ET AL.


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3. Piergiovanni L, Limbo S. Packaging and shelf life of vegetable oils. In Food Packaging and Shelf Life: A Practical Guide,Robertson G (ed.). CRC Press (Publ.), 2009; 17. Q13

4. Del Nobile MA, Ambrosino ML, Sacchi R, Masi P. Design of plastic bottles for packaging of virgin olive oil. Journal ofFood Science 2003; 68: 170-175.

5. Sacchi R, Savarese M, Del Regno A, et al. Shelf life of vegetable oils bottled in different scavenging polyethyleneterephthalate (PET) containers. Packaging Technology and Science 2008; 21: 269-277. DOI: 10.1002/pts.801.

6. Tawfik MS, Huyghebaert A. Interaction of packaging materials and vegetable oils: oil stability. Food Chemistry 1999;64: 451-459.

7. Kanavouras A, Hernandez-Munoz P, Coutelieris FA. Shelf life predictions for packaged olive oil using flavor compounds asmarkers. European Food Research and Technology 2004; 219: 190–198.

8. Coutelieris FA, Kanavouras A. Experimental and theoretical investigation of packaged olive oil: development of a qualityindicator based on mathematical predictions. Journal of Food Engineering 2006; 73: 85–92.

9. Kanavouras A, Coutelieris FA. Shelf-life predictions for packaged olive oil based on simulations. Food Chemistry 2006;96: 48–55.

10. Caponio F, Bilancia MT, Pasqualone A, Sikorska E, Gomes T. Influence of the exposure to light on extra virgin olive oilquality during storage. European Food Research and Technology 2005; 221: 92-98.

11. Morello JR, Motilva MJ, Tovar MJ, Romero MP. Changes in commercial virgin olive oil (cv Arbequina) during storage,with special emphasis on the phenolic fraction. Food Chemistry 2004; 85: 357-364.

12. Riahi J, Marzouk B. Effets de la lumière sur la qualité et la stabilité de quelques huiles végétales. Note préliminaire. LaRivista Italiana delle Sostanze Grasse 2000; LXXVII: 25-30.

13. Okogeri O, Tasioula-Margari M. Changes occurring in phenolic compounds and r-tocopherol of virgin olive oil during stor-age. Journal of Agricultural and Food Chemistry 2002; 50: 1077-1080.

14. Gambacorta G, Del Nobile MA, Tamagnone P, et al. Shelf-life of extra virgin olive oil stored in packages with differentoxygen barrier properties. Italian Journal of Food Science 2004; 16: 417-428.

15. Aparicio R, Roda L, Albi MA, Gutierrez F. Effect of various compounds on virgin olive oil stability measured by Rancimat.Journal of Agricultural and Food Chemistry 1999; 47: 4150-4155.

16. ASTM D 1003-00 Official method, 2000.17. Regulation EEC/2568/91. Official Journal of the European Communities 1991.18. Regulation EEC/1989/03. Official Journal of the European Communities 2003.19. AOCS official methods of analyses, 1993.20. Gutierrez Rosales F, Perdiguero S, Gutierrez R, Olias JM. Evaluation of the bitter taste in virgin olive oil. Journal of Amer-

ican Oil Chemistry Society 1992; 69: 394-395.21. Gutfinger T. Polyphenols in olive oils. Journal of American Oil Chemistry Society 1981: 966-968.22. Mestdagh F, De Meulenaer B, De Clippeleer J, Devlieghere F, Huyghebaert A. Protective influence of several packaging

materials on light oxidation of milk. Journal of Dairy Science 2005; 88: 499–510.23. Cecchi T, Passamonti P, Cecchi P. Study of the quality of extra virgin olive oil stored in PET bottles with or without an ox-

ygen scavenger. Food Chemistry 2010; 120: 730-735.24. Del Caro A, Vacca V, Poiana M, Fenu P, Piga A. Influence of technology, storage and exposure on components of extra

virgin olive oil (Bosana cv) from whole and de-stoned fruits. Food Chemistry 2006; 98: 311-316.25. Bosque-Sendra JM, de la Mata-Espinosa P, Cuadros-Rodriguez L, Gonzales-Casado A, Rodriguez-Garcia FP, Garcia-To-

ledo H.; stability for olive oil control materials. Food Chemistry 2011; 125: 1418-1422.26. Minguez-Mosquera MI, Rejano-Navarro L, Gandul-Rojas B, Sanchez-Gomez AH, Garrido-Fernandez J. Color-pigment cor-

relation in virgin olive oil. Journal of American Oil Chemistry Society 1991; 68: 332-336.27. Artajo LS, Romero MP, Morello JR, Motilva MJ. Enrichment of refined olive oil with phenolic compounds: evaluations

of their antioxidant activity and their effect on the bitter index. Journal of Agricultural and Food Chemistry 2006; 54:6079-6088.

28. Amati L, Campanella L, Dragone R, et al. New investigation of the isothermal oxidation of extra virgin olive oil: determi-nation of free radicals, total polyphenols, total antioxidant capacity, and kinetic data. Journal of Agricultural and FoodChemistry 2008; 56: 8287-8295.



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Quality Changes of Extra Virgin Olive Oil Packaged in Coloured Polyethylene Terephthalate Bottles...

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